A review of applications of luminescence to monitoring of chemical contaminants in the environment

Chemosphere, Vol. 28, No.

Pergamon 0045-6535(94)E0105-3

10, pp. 1819-1857, 1994 Elsevier Science Ltd Printed in Great Britain 0045-6535/94 $7.00+0.00

A Review of Applications of Luminescence to Monitoring of Chemical Contaminants in the Environment Spencer M. Steinberg Department of Chemistry University of Nevada, Las Vegas, NV, 89154-1017 Edward J. Poziomek Harry Reid Center for Environmental Studies University of Nevada, Las Vegas, NV, 89154-4009 William H. Engelmann United States Environmental Protection Agency Environmental Monitoring Systems Laboratory Las Vegas, NV 89193-3478 (Received in USA 12 December 1993; accepted 3 March 1994)

ABSTRACT The recent analytical literature on the application of luminescence techniques to the measurement of various classes of environmentally significant chemicals has been reviewed. Luminescent spectroscopy based methods are compared to other current techniques. Also, examples of recently developed applications of luminescence to environmental monitoring are provided. The advantages and disadvantages of luminescence measurements for field screening measurements are discussed. INTRODUCTION Luminescence (fluorescence and phosphorescence) has a long history in analytical chemistry.

Molecular fluorescence and phosphorescence can be measured for very low

concentrations of many compounds and are inherently more sensitive than other spectroscopies such as UV/Vis, Raman, infrared (IR), and nuclear magnetic resonance (NMR). Because of these properties fluorescence and phosphorescence are attractive for application to environmental monitoring. Because many important classes of organic pollutants are fluorescent, luminescence measurements have been utilized for environmental applications. Workers in the field have also been encouraged by the ease of implementing fluorescence and phosphorescence spectroscopies. Luminescence methods have been employed as rapid screening methods for organic pollutants. Utility has been especially apparent for rapid screening of environmental samples. For example, Gammage et al. (1991, 1988) discussed the screening of groundwater samples for petroleum hydrocarbons using synchronous fluorescence, Vo-Dinh et al. (1978) applied synchronous scanning methods to the analysis of polynuclear aromatic hydrocarbons

1819

1820 (PAH) originating from coal conversion processes, while Taylor and Patterson (1987) analyzed aromatic compounds in fuel oil. Potential applications of molecular spectroscopy for hazardous waste site screening were reviewed by Eastwood and Lidberg (1986), Eastwood and Vo-Dinh (1991), and Eastwood et al. (1991).

The potential of applying molecular spectroscopy to field screening was extensively

discussed.

Advantages are that the immediate results obtained during a field investigation can

be utilized to guide exploratory excavations and can potentially reduce the number of samples to be sent to an analytical laboratory for more expensive conventional analysis.

Dudelzak et

al. (1991) have pointed out the potential of using lasers and luminescence spectroscopy for

remote sensing in the environment. Because of simplicity, the use of spectroscopic measurements could greatly benefit efforts to map the extent of contamination in the environment. In the mapping of a contaminant plume, an abundance of moderately accurate field data could be more beneficial than a small amount of accurate laboratory data. Rapid field analysis can greatly assist in field operations when realtime decisions are required regarding drilling or trenching. In this article, we have reviewed the literature from 1980-1993, regarding the application of luminescence spectroscopy to monitoring several environmentally important classes of compounds. Also, we discuss the various implementations of luminescence spectroscopy and the advantages and disadvantages of this general analytical approach.

A discussion of field

applications and competitive technologies is included as well. LUMINESCENCE TECHNIQUES Fluorescence spectra are composed of both excitation and emission components which should in principle give this spectroscopic approach a great potential for selective analysis. However, because both excitation and emission bands are normally broad with very little fine structure, it is difficult to use these to develop both sensitive and selective analytical methods. Therefore,

most fluorescence-based methods

require the addition

of separation

and

chromatography to obtain analytically useful selectivity.

Thus, in many applications

luminescence analysis is at best a semi-quantitative method.

However, luminescence has a

multi-dimensional character which can be manipulated to produce additional selectivity.

This

multi-dimensional character of luminescence measurements was recently reviewed by Warner et al. (1985), who discussed at least nine parameters that can be modulated to achieve additional

selectivity with luminescence measurements.

In addition to specific excitation and emission

1821 measurements, selectivity can be enhanced for fluorescence by utilizing matrix effects (micelles, surfaces, heavy atoms), temperature effects (Shpol'skii effect), fluorescence and phosphorescence lifetime filtering, and synchronous scanning.

Selectivity can also be obtained by coupling

fluorescence measurements to column or thin-layer chromatography (TLC). Matrix effects in phosphorimetry were recently reviewed by Hurtubise (1983 and 1989). Fluorescent lifetime filtering can be used to selectively measure luminescence from a specific set of chromophores. These methods were recently reviewed by McGown (1989). This method has been utilized for resolution of mixtures of various compounds which are of environmental interest. For example, McGown and Bright (1985), and Millican and McGown (1989), utilized phase resolution (time filtering) for resolution of a two-component mixture. Nithipatikom and McGown used both phase resolution and synchronous scanning for determination of up to four-component mixtures of polynuclear aromatic hydrocarbons (PAHs). Several approaches have been described.

The simplest is to collect the fluorescence signal at

an optimum time after an excitation pulse. Compounds with short fluorescence half-lives will then have a minimum interference with the fluorescence signal. Another approach is to use a frequency domain filtering mechanism. In this approach the excitation source is modulated at an optimum frequency. This results in the fluorescence signal becoming modulated at the same frequency but phase-shifted from the excitation modulation. The phase shift is a function of the modulation frequency and the fluorescence half-life. The AC part of the fluorescence signal is then multiplied by another function of the same mathematical form. The detector phase angle in this function can be adjusted to filter the resulting AC fluorescence signal to optimize detection of a signal with a narrow range of half-lives. This method has been discussed in detail by McGown and Millican (1988). Normal fluorescence spectra are obtained at a single excitation frequency while scanning the emission frequency, or by monitoring a single emission and scanning the excitation frequency. Because of the broad poorly structured appearance of most fluorescent and phosphorescent excitation and emission spectra (at ambient temperatures), it is difficult to take advantage of the potential sensitivity of fluorescence spectroscopy. Conventional spectra are obtained at constant excitation wavelength (emission spectra) or constant emission (excitation). In the synchronous mode, both excitation and emission are scanned simultaneously. The result is a more structured (narrow) spectra. There is also a greater probability of spectroscopically isolating a single chromophore. However, when both the excitation and emission wavelengths

1822 are scanned simultaneously with a constant difference in excitation and emission wavelengths, fluorescent spectra can be greatly simplified and are often only a single peak. In 1979, VoDinh et al. reviewed the potential applications of synchronous spectroscopy (and second derivative spectroscopy) for trace organic analysis. They indicated that the combination of synchronous scanning with the second derivative method could provide increased spectroscopic resolution in complex matrices.

Vo-Dinh (1983) pointed out the potential for utilizing a

synchronous scanning instrument for examining surface contamination during environmental monitoring and industrial hygiene operations or surveys.

Eastwood et al. (1993) recently

presented an evaluation of a portable field scanning UV-Vis spectrofluorometer for monitoring oils in the environment. Alaire et aL (1993) also reviewed the potential for application of this type of instrument to various environmental matrices. Stevenson and Vo-Dinh (1993) examined the use of laser excited synchronous spectroscopy. The authors have discussed the utility of synchronous scanning and pointed out the potential sensitivity of laser based instruments. Using a laser excitation source these investigators were able to reach a limit of detection (LOD) of 1(921 moles for several PAHs. Most synchronous scanning has been performed with a constant wavelength difference between excitation and emission. Cabaniss (1991), on the other hand, has pointed out the potential superiority of constant energy difference synchronous scanning in obtaining spectral resolution and addresses a modified scanning method where the difference in excitation and emission is varied in a controlled way (variable angle). Cabaniss points out that variable angle measurements may be potentially more useful than constant wavelength or constant energy difference modes for analysis of complex matrices. As noted above, fluorescence and phosphorescence spectra normally are broad and poorly structured and thus difficult to interpret in terms of individual chemical structures.

However,

by utilizing more than one parameter, data that are more analytically useful can sometimes be obtained. Research is underway on a number of fiber optic based chemical sensors for environmental monitoring. Some of these sensors utilize fluorimetric designs.

Chudyk and

Pohling (1988) discussed field screening for aromatic organic compounds with an instrument that uses laser-induced fluorescence and fiber optics. Kenny et al. (1988) discussed multicomponent analysis with a fiber optic based instrument.

Walt (1993) has recently reviewed some of the

research activity and applications in this area.

Some of these fiber optic sensors utilize

fluorimetry, diffusion released reagents (for pH), or membrane bound reagents (polarity sensitive

1823 chromophores), giving several examples. Walt (1993) also has presented a design for a fielddeployable dedicated fiber optic based fluorescence spectrophotometer.

This unit has the

potential of using fiber optic sensors (for groundwater or hazardous waste monitoring) and employs a single fiber optic design for both excitation and emission. As noted above, fiber optics have been utilized by Kenny et al. (1988) and Lieberman et aL (1991) for analysis of volatile aromatics and petroleum. Fiber optics have been evaluated for use with the Fujiwara reaction as a means of monitoring volatile halocarbons (Angel et al., 1987).

TARGET ANALYTES Important Classes: Chemical compounds that could be potentially screened with luminescence measurements can be classified as follows: compounds that are intrinsically fluorescent, compounds that can form fluorescent derivatives, and compounds that can modulate the fluorescence of another compound. Applications of luminescence spectroscopy to all three classes can be found in the literature. Compounds that possess intrinsic fluorescence are compounds that have delocalized electrons held in a rigid molecular framework. Most of the fluorescent compounds contain ring structures.

The most important classes of compounds are: polynuclear aromatic hydrocarbons

(PAHs), aromatics, phenols, dyes, some pesticides, humic acids, lanthanides, and actinides. As noted above, many of these compounds have environmental significance. Many important classes of compounds can be chemically reacted to form luminescent derivatives.

These derivatives

have in many cases been exploited for use in conjunction with thin layer and liquid chromatographic separations. Many of these derivatives form rapidly and are highly fluorescent, and thus could likely be adapted to field applications. Some of the types of analytes that could be potentially monitored using luminescence are: volatile aromatics including benzene, toluene, ethylbenzene, and xylenes; polychlorinated biphenyls (PCBs) including the AroclorsTM; PAHs; phthalates; phenols; some pesticides; several main group elements such as selenium, tin, and aluminum; actinides and lanthanides; ammonia and various other amines; sulfides and mercaptans. established methods exist.

For some of these compounds, other well

However, field applications utilizing fluorescence could serve as

useful adjuncts to existing methods for these compounds, through the potential of enhanced selectivity and sensitivity.

Some specific classes of compounds where luminescence methods

have been used are as discussed below.

1824 Because the list of potential applications of the luminescence spectroscopy is quite long, we have divided the potential analytes into classes:

Class 1 - immediately applicable and

important applications; Class 2 - applicable but not as important as Class 1; Class 3 -applicable but not the best technology for the specific analytes; and Class 4 - implementation may require considerable sample preparation or some chemistry to be performed in the field (See Table I). A more detailed discussion of the potential applications of luminescence technology is provided in the sections that follow.

Claases of E n v y / a l l y

Chu,s I :

TABLE I Important Compounds that can be Measured by Lmnlnelccnce Spc~lrmcopy

Immediately applicable end hnpotlant Ilppli~tiom.

Compound Clam

Commeot8

Polynuclear Aromatic Hydmcarbons

Priority pollutants,' highly fluoreace,o,t.

Crude Oil

Hislory of applicationof Imnineacence.

Petrolemn ProductJ Chum 2:

Cla~ 3:

CI~, 4:

Applicablebut not as important u CI~, 1.

Applicabl©lint not the best ~:hnology for ~ e .pecific analyt~,

Implementatioamay rcqmr¢ considerable sample preparation or some chemist,T to be pcrfonnc~l in the field.

Polychlorinated Biphenyls

Alternative field me~ods e x i .

pealcldes

Some pe,ticlde, are I w t .

Volatile Aromatics

May not be bat tectmololly--but could be mote coavmlent.

Tnmsunmlc* (e.$. U r t ~ u m )

Requirm mine ohemi~y much m dilution with appropriate medium.

Phenols

Not many fietaalternativese x i t .

H~unic and Fulvic Acids

Not comldered s pollutam and not ro.ti~ly ,creencd.

Aluminmn

Routine. but not tmually itmdyzed i~ the flckl.

AmiJ~esand A n i l i n ~

Non-specific and would require field derivatizatlon.

Me~atptamt(sulfide) Aldehyde~ Orgmllc A c k l l pH

Impntct/cal - unk~s indicatorswere incon~o~ted into an ot~'od©.

Metals: Se, Sn, Cr

Requires significantchemi~:y.

1825 Polvnuclear Aromatic Hydrocarbons (PAHS): The PAHs represent a very important class of environmental contaminants. The analysis of these compounds represents the most important application of luminescence spectroscopy.

PAHs are produced during petroleum

formation or during incomplete combustion of organic materials, and thus may occur in combustion of wood, coal, gasoline, and oil. As a result, PAHs are widely distributed in the environment

including water, sediment, and soil.

PAHs and their metabolites may be

mutagenic or carcinogenic. For this reason there has been much interest in quantifying them in the environment. PAHs are responsible for much of the luminescent properties of'petroleum. Many of these compounds have intense fluorescence in the visible light frequencies (see below). Heterocyclic PAHs are considered priority pollutants and also exhibit fluorescence in the visible wavelengths.

Examples of fluorescent heterocycle are quinoline, acridine, and carbazole.

Because of their intense and innate fluorescence and phosphorescence, much research has been performed on the use of fluorimetry as a way to rapidly analyze PAHs in environmental samples. Direct quantitation of PAHs in environmental matrixes has been explored as well as the adjunct use of solid surfaces, sensitizers, and micelles. Various researchers have noted that sample environment can have a profound influence on the fluorescence and phosphorescent properties of a compound. Weinberger and Cline Love (1983) studied the effects of colloidal and microcrystalline states of the spectroluminescent properties of PAHs. Generally speaking, phosphorescence is only apparent for PAHs in solution at low temperatures (77°K). However, Bower and Winefordner (1978) studied the effects of sample environment on the room temperature fluorescence of PAHs. They found that a "heavy atom effect" could lead to a significant enhancement of PAH signals. This effect was studied on a sodium acetate and filter paper support. Compounds were spotted on the solid support, and phosphorescence was measured directly on the paper.

Scypinski and Cline Love (1984)

examined room temperature phosphorescence of PAHs in cyclodextrins. Cyclodextrins form inclusion complexes with many compounds.

These authors found that when PAHs were

incorporated into a cyclodextrin in the presence of a heavy atom species (ethylene dibromide), their phosphorescence was strongly enhanced. PAHs were analyzed in aqueous solutions containing the cyclodextrins. Blysak et al. (1989) studied multidimensional phosphorescence analysis in cyclodextrin solvent extraction systems. These authors emphasized the stereoselective nature of cyclodextrin enhanced fluorescence, which can be exploited for separation and analysis. Similarly enhanced fluorescence has been observed in the presence of micelles by

1826 Weijun and Changsong (1993). Tucker et al. (1993) investigated the fluorescence emission and tluenching behavior of selected acenaphthylene derivatives in various organic non-electrolytes. They noted that these compounds could serve as polarity probes for many of the solvents and that fluorescent intensity was very low in aromatic solvents.

These authors point out the

necessity of considering this type of information in identifying PAHs in complex samples. VoDinh and Martinez (1981) were able to directly determine ten selected PAHs in a coal liquification product using synchronous scanning methods. This study also demonstrated the use of room temperature phosphorimetry on a filter paper substrate. Vo-Dinh and Alak (1987), Alak and Vo-Dinh (1988), and Alak et al. (1989) investigated the enhancement of room temperature phosphorescence of anthracene on cyclodextrin-treated filter paper.

Heavy atoms were also

added to enhance phosphorescence. This treatment was found to enhance the analytical utility of solid-phase phosphorescence.

The use of synchronous scanning in conjunction with this

treatment was also examined. Alak et al. (1989) also measured enhanced phosphorescence for p-aminobenzoic acid and dibenzofuran. Bello and Hurtubise (1986) utilized room temperature luminescence in an ~-cyclodextrin and NaCI mixture to measure both fluorescence and phosphorescence of various PAHs and substituted PAHs. Sensitivities as low as 0.2 ng were reported. Inman and Winefordner (1982) have discussed the use of constant-energy synchronous fluorescence for analysis of PAHs. They noted considerable improvement in spectral selectivity when constant energy difference scanning was used instead of constant wavelength difference. Vo-Dinh and White (1986) utilized sensitive fluorescence spectrometry for enhanced detection of various PAHs. Filter papers treated with the PAH extract and anthracene (sensitizer) could be analyzed using a field portable spectrophotometer. The authors noted that this method had a great potential for use with environmental samples. In a similar application Aaron et al. (1990) utilized both thallium(1) and sodium dodecylsulfate to enhance the phosphorescence of purine derivatives on filter paper. Carr and Harris (1988) studied the detection of PAHs following concentration on alkylated silica adsorbents.

The implication of this work is that compounds could be

concentrated from solution using the "reversed phase" sorbent and then quantified by fluorescence. Poziomek et al. (1991) and Eastwood et al. (1993) utilized a solid phase C18 membrane extractant in a "dip-stick" mode in order to concentrate anthracene from aqueous solutions.

The fluorescence of anthracene was then measured on the membrane with no

additional sample manipulation. This type of procedure has the potential of being utilized for

1827 diffusive sampling and analysis of groundwater in monitoring wells.

Many of these "filter

paper" or "solid sorbent" methods could be conveniently implemented in the field. Schuresko (1980) discussed the necessity of monitoring PAH exposure of workers and the need for discriminating between PAHs and other fluorescent substances.

This reference

includes a discussion of the development of a portable fluorimetric monitor for detecting surface contamination by PAHs. This instrument is portable and battery operated so that quantitative measurements can be obtained both indoors and outdoors throughout a facility. Bjorseth and Bescher (1986) discussed PAHs in the work atmosphere and reviewed analytical methods available for monitoring. These authors have noted the potential of synchronous fluorescence, second derivative spectroscopy and room temperature phosphorescence measurements for realtime monitoring of worker exposure.

Baudot et al. (1991) investigated the application of

synchronous fluorescence spectroscopy to occupational health. These workers have provided synchronous spectra for fifty different PAHs. They also demonstrated the ability to quantify ten different PAHs in a mixture of compounds that was utilized for HPLC separation. The method was applied to an extract of PAHs collected from air by filtration on a glass fiber filter. Screening for PAHs was accomplished after extraction in about 2.5 minutes.

Abbott et aL

(1986) discussed synchronous luminescence screening for PAHs in environmental samples collected at a coal gasification process development unit. PAHs were collected from air and water by sorption onto XAD-2

TM

resin.

Solid samples were directly extracted with

dichloromethane. The analytes were extracted from the resin with dichloromethane and then analyzed without further processing. The synchronous scanning method provided an estimate of PAH content that was well correlated to GC/MS measurements.

Yao et al. (1993) used

synchronous scanning in conjunction with HPLC separations for identification and quantitation of compounds that were not completely resolved by the chromatography. Mellone (1990) discussed fingerprinting of PAHs in environmental materials by laserexcited fluorescence spectrometry. Environmental samples were heated in a graphite furnace and the PAHs were analyzed in the vapor phase. Lin et al. (1991) utilized synchronous scan fluorimetry for analysis of anthracene derivatives in supersonic jets. The supersonic jet cools the sample to several degrees Kelvin so that a sharp line spectra is obtained. This method could be utilized for analysis of environmental samples. The device can be coupled to chromatographic separations.

Jandris and Force (1983) determined PAHs in the vapor phase by laser-induced

fluorescence. Niessner et al. (1991) utilized time-resolved fluorescence for detection of PAHs

1828 in particulate form (as crystals or on NaCI particles).

Bolton and Winefordner (1983) used

laser-excited fluorescence line narrowing for analysis of six PAHs. This method entails specific excitation of a subset of species occupying similar lattice sites in a solid sample. Sample cooling is also used in conjunction with this method. There has been interest in employing time resolution for spectroscopic identification of PAHs.

Inman et al. (1990) discussed the development of a pulsed-laser, fiber optic based

fluorimeter for determination of fluorescence decay times of PAHs in seawater. Bark and Force (1991) utilized time-resolved fluorescence in a Shpol'skii matrix for characterizing mixtures of PAHs. Other studies have stressed the utility of low temperatures for resolving the fluorescence signals of mixtures of PAHs. One approach based on Shpol'skii spectroscopy involves cooling the sample to 10-70°K, in an alkane solvent, in order to obtain well resolved emission spectra. Laser-excited Shpol'skii spectroscopy was reviewed in 1984 by D'Silva and Fassel. Yang et al. (1981a,b) utilized Shpol'skii spectroscopy for analysis of benzo(a)pyrene and perylene in liquid fuels. These authors pointed out that deuterated analogues of the analyte compounds could be utilized as internal standards. Lai et al. (1982) reported spectra in Shpol'skii matrices at 77°K for eleven PAHs. Limits of detection in the ppb range were reported. Wittenberg et aL (1985) used Shpol'skii matrices at 10°K for analysis of PAHs from environmental samples including smoke and highway runoff.

Application of the Shpol'skii effect to PAHs in environmental

samples was also discussed by Garrigues and Ewald (1985, 1987) and Garrigues et al. (1985). These authors utilized a preliminary liquid chromatography separation to isolate PAHs. Colmsjo (1987) used cryogenic-temperature fluorescence spectroscopy of a group of PAHs of molecular weight 378.

Twenty compounds were studied, and the sensitivity of the method is clearly

sufficient for nine well resolved spectra to be recorded in a single sample. MacDonald et al. (1988) utilized site-selection in fluorescent spectrometry of PAHs in vapor deposited argon matrices.

Bark and Force (1990) studied the analysis of PAHs that were thermally desorbed

from particulate matter and then condensed from the vapor phase into a low-temperature matrix for laser Shpol'skii spectroscopy. selectivity.

These workers also utilized time resolution to improve

Hofstraat et al. (1991) reviewed applications of Shpol'skii spectroscopy to marine

environmental analysis of PAHs.

Examples of applications to PAHs in suspended matter,

sediments, and biotic samples were provided. Quantitative results were obtained without sample cleanup even in complex biological matrices.

The method was also used to demonstrate the

1829 presence of interfering compounds in HPLC chromatograms.

Ariese et al. (1990) utilized

Shpol'skii spectroscopy for direct analysis of PAHs in tern and mussel samples. Interference resulted principally from the formation of a poor Shpol'skii matrix due to the presence of fatty components in the crude extracts of the samples. This effect required dilution of the sample or cleanup (silica gel chromatography) prior to analysis.

However, several PAHs could be

determined without any sample treatment. Detection limits were in the range of 10-100 ng for most of these methods. Kicinski et al. (1989) described the use of HPLC analysis with time-programmed fluorescence detection for determination of PAHs in environmental samples.

PAHs in water

samples were concentrated using solid-phase extraction and then eluted with a small volume of dichloromethane. The eluant was evaporated to dryness, reconstituted in acetonitrile, and then analyzed. Sediments and other solids were rapidly extracted using toluene with the assistance of ultrasound.

The toluene extract was evaporated to dryness and the sample reconstituted in

acetonitrile and analyzed. The fluorescence detector was time-programmed to provide optimum excitation and emission for all of the target analytes.

Nunez and Centrich (1990) reported a

method for the determination of PAHs in water after solvent extraction (petroleum ether and diethyl ether). PAHs were separated by reversed-phase HPLC and detected with a fluorescence detector at fixed excitation and emission. Detection limits were in the low ppb range. These authors also reported that PAHs on air filters could be rapidly recovered through extraction and analyzed using HPLC.

Lopez-Garcia et al. (1992) studied the determination of PAHs in

environmental samples (water, sediment, coal washings) using HPLC with fluorescence detection. These authors were able to separate and quantify 16 PAHs that have been listed as hazardous materials by the EPA.

Coal washing and water samples were extracted with

dichloromethane, concentrated by evaporation to dryness, and then reconstituted in acetonitrile, which was then analyzed with no further sample preparation or cleanup.

Solid samples were

extracted ultrasonically in a mixture of hexane and acetone. After concentration the samples were "cleaned-up" by normal phase chromatography on silica gel/alumina and then analyzed by HPLC. Numerous methods for separation of PAHs by TLC have been published. For example, Butler et al. 0985) discussed the determination for PAHs in environmental samples using high performance TLC in conjunction with fluorescence scanning densitometry. conditions for a variety of PAHs were reported.

Fluorescence

TLC could be used in the laboratory or the

1830 field in conjunction with luminescence for rapid analysis of PAHs. TLC on silica gel could be used as a rapid "group separation" to isolate or purify a fluorescent target analyte from interfering or quenching compounds, or a derivatizing agent. Brumly and Brownrigg (1991) have described the applicability of TLC chromatography to field screening of polyaromatic nitrogen compounds and PAHs. Commercially available silica gel plates could be used for screening up to 40 different samples simultaneously.

Rapid group separations were achieved using a 70:30

hexane:methylene chloride solvent system. Petroleum Hydrocarbon Monitoring: Oil spills (such as from the Exxon Valdez), release of crude oil during the recent conflict in the Persian Gulf, and problems of groundwater contamination by underground fuel tanks have underscored the needs for reliable measurements of petroleum contamination.

Kinnicutt et al. (1991) discussed the use of fluorescence for

screening various sediments, water, and biological samples for petroleum hydrocarbons after a fuel spill in Antarctica. Freeze-dried samples were extracted with dichloromethane and then screened for fluorescence, which was related to petroleum hydrocarbon contamination. Samples that fluoresced were then analyzed for detailed petroleum compound distribution using GC/MS. Similarly, Theis et al. (1991) described the screening of total petroleum hydrocarbons at a manufactured gas plant using fluorescence.

The estimated concentrations obtained by

fluorescence analysis were in good agreement with laboratory analysis. ASTM (1988) has published a standard method practice for determining various fluorescent compounds in water. Similarly, ASTM (1990) has published a standard method for the analysis of petroleum in water which utilizes the innate fluorescent properties of various components of petroleum (D3650-90). In addition, ASTM has published several procedures for oil spill identification that utilize the fluorescent characteristics of a particular crude oil (D365090). Bentz (1976) reviewed oil spill identification technology including fiuorimetry, IR, TLC, GC, and MS. Also, Eastwood (1981) reviewed the use of luminescence in oil identification. Ostgaard (1984) also reviewed the application of fluorescence to the determination

of

environmental pollutants, including oil. Fingerprinting of crude oils can be performed using an instrument capable of scanning both excitation and emission over the spectral range of 220-600 nm. Oil samples are diluted in cyclohexane and the fluorescence properties of the sample measured directly. Similarly, petroleum hydrocarbons can be extracted from a water sample and then quantified using fluorescence measurements. Other sampling methods may involve the use of hydrophobic resins or extraction disks. Similarly, solvent extracts could be spotted onto a

1831 filter paper or TLC plate and the fluorescence measured using a fiber optic probe. For example, Vo-Dinh and White (1986) have discussed using a "stethoscope" fiber optic probe for analysis of PAHs spotted onto a filter paper along with a sensitizer. Emission spectra of most petroleum products are broad and lack significant fine structure. This limits the utility of fluorescence spectra for identification of petroleum products and crude oils.

Fortier and Eastwood (1978) utilized fluorescence spectroflourimetry at 77°K to

"fingerprint" fuel oils. The low temperature spectra were found to have significantly more fine structure, and thus provide a greater ability to discriminate fuel oil types. John and Soutar (1976) published a study of the identification of crude oil by synchronous excitation spectrofluorimetry. It was found that the use of the synchronous scanning mode produces spectra with more fine structure.

Low temperature measurements (Shpol'skii) have been utilized in

addition to the scanning techniques.

Files et al. (1987) have discussed the use of synchronous

scanning and for fingerprinting of gasoline and crude oil. It was indicated that individual PAHs could be identified using either low temperature measurements or synchronous scanning methods. Morel et al. (1991) utilized synchronous scanning spectrofluorimetry and Shpol'skii matrix spectrofluorimetry in combination with a number of chromatographic measurements for characterization of petroleum derived compounds in the environment.

While the authors

indicated that no single method is a panacea, they did note that synchronous scanning provided information on the relative concentrations of PAHs with various numbers of rings and did permit some fingerprinting of the oil samples.

The synchronous spectra also seemed to provide an

index of weathering and photodecomposition of oil. ASTM (1990) also noted that fluorescence signatures could be altered by "weathering."

Thus, the fluorescence or phosphorescence

signatures should also be able to serve as a useful indicator of oil decomposition or biodegradation through field measurements. Polychlorinated Biphenyls (PCBs): PCBs were at one time widely utilized as transformer dielectrics, lubricants, heat transfer media, and flame retardants.

As a result of poor disposal

practices, these compounds now widely contaminate the environment. PCBs do fluoresce and phosphorescence and, as a result, there are several literature reports for the screening of these compounds using luminescence spectroscopy. Brownrigg and Horning (1976) published an early study of PCB measurements in the presence of DDT. DDT and PCBs are difficult to separate using gas chromatography (with an electron capture detector). These authors also performed some recovery studies from water and a natural river water and allude to the difficulty in

1832 extracting these compounds in the presence of humic and fulvic acids.

Khasawneh and

Winefordner (1988) discussed the use of room temperature fluorescence and low temperature phosphorescence for determination of biphenyls and polychlorinated biphenyls. The sensitivity of the method was apparently quite good (ng/mL range), although it was not possible to separate specific congeners. Vo-Dinh et aL (1991) also described rapid screening of PCBs using room temperature phosphorescence. Fenia et aL (1985) reported on the fluorescence characteristics of PCB isomers in cyclodextrin media. Cyclodextrins form inclusion complexes with PCBs. Fluorescence intensity of PCBs is enhanced using the complexes. The stability of the complex is a function of isomeric substitution.

These investigators noted that, using the inclusion

complexes, it was possible to achieve isomeric separation.

A1-Haddad et al. (1989) utilized

fluorescence to quantify PCBs in the trichlorethylene (TCE) solvent used to rinse transformers. Heavy atom quenching, by the wash solvent, was minimized by dilution of the TCE with hexane. The authors discussed application of this method to field screening using a simple filter fluorimeter. Watts et al. (1992) investigated the use of room temperature phosphorescence for analyzing PCBs. Several phosphorescence enhancing agents (cyclodextrins, sodium dodecyl stilfate, fumed silica, and thallium) were also investigated. These authors also utilized synchronous scanning and second derivatives to improve the resolution of phosphorescence spectra. Detection limits in the range of 7.5 to 620 ppb were reported for various AroclorsTM. Results from several soil extracts were also reported. Pal et al. (1992) found that sodium lauryl sulfate/thallium acetate treated filter paper was a useful substrate for phosphorescence analysis of PCBs.

Detection limits for various AroclorsTM in the low ppm range were reported.

Detection of polybrominated biphenyls should be similar to the PCBs; however, the heavy atom effect may tend to promote phosphorescence. Pesticides: Suet al. (1984) utilized room temperature phosphorimetry for direct analysis of six pesticides after their sorption onto ion exchange paper. The authors discussed heavy atom enhancement of the room temperature fluorescence for the various pesticides measured. Limits of

detection

for phenothiazine,

1-naphthol,

Warfarin",

AsulamTM, CarbarylTM, and

napthaleneacedic acid are reported to be in the low ppm range. The detection limit of these compounds in water could be lowered by using a simple field concentration method. Files and Winefordner (1987) demonstrated the feasibility of using constant energy synchronous scanning spectrophotometry and low temperature luminescence (77°K) for analysis of Carbaryr-', naphthol, and carbofuran. Although 11o environmental (real world) samples were examined in

1833 this study, the indication is that detection limits should be in the low ppb range for all three of these compounds. Vilchez et al. (1993) isolated and concentrated the fungicide 2-phenylphenol onto QAE SephadexTM and then measured the compound by solid-phase florescence on the solid after packing the sorbent into a conventional cuvette. A similar approach was used by Capitan et al. (1993) for analysis of thiabendazole residues in water.

Shivhare et al. (1991) analyzed the herbicides 2,4-D and 2,4-T by first decomposing the analytes in H2SO4 to yield formaldehyde as a decomposition product. The formaldehyde was then reacted with 6-amino-1-napthol-3-sulfonic acid (J acid) to yield a fluorescent product which could be quantified spectroscopically. Other examples of a decomposition derivatization method follow. Carbamate pesticides decompose in strong base to yield methyl amine and phenols. The methyl amine can be analyzed by reaction with o-phthalaldehyde and mercaptoethanol to yield a highly fluorescent iso-indole derivative.

This method has been employed by de Kok et al.

(1992) for analysis of N-methylcarbamates in surface water.

This method was employed for

post-column detection after separation of the pesticides and their metabolites by HPLC.; however, the approach could be utilized for analysis of total carbamates after isolation by cartridge extraction from surface water. Stab et al. (1992) measured the concentration of several organotin pesticides after post column conversion and formation of a morin complex. The method required photodecomposition of the pesticide, but in principle could be adapted to field screening. Phenols: Phenols are associated with creosote which is also listed as a hazardous waste and fluoresce without derivatization.

Several useful fluorescent derivatives do exist and can be

used in conjunction with chromatographic separations (Lawrence and Frei, 1976). Phenols are used as wood preservatives and pesticides and have a wide distribution in the environment. The EPA has published a colorimetric method for phenols (EPA 420.1). However, recommended procedures for low concentrations may be difficult to implement in the field.

Prucell et al.

(1985) published a synchronous scanning fluorescence spectroscopy method for analysis of phenolic compounds in aqueous samples. Synchronous scanning was performed with a constant excitation-emission offset of 3 nm. The spectral results were further resolved using derivative spectroscopy. Chudyk et al. (1985) discussed the application of laser-induced fluorescence and fiber optics to monitor several phenols in groundwater. Volatile Aromatic Hydrocarbons: This is an extremely important pollutant class that is associated with hazardous waste and fuel. Much of the activity regarding "Leaking Underground

1834 Storage Tanks (LUST)" have centered around the monitoring or remediation of these compounds. Most aromatic compounds have some fluorescence; however, the analytical utility of the fluorescence spectra may be limited by low UV adsorption and quantum yields. Benzene is an important organic compound that is only weakly fluorescent. However, when the benzene ring is substituted with electron releasing moieties, the fluorescence may be increased.

For

example, phenols and aromatic amines exhibit fluorescence with 1-10 % quantum efficiency (380285nm). There is a dramatic increase in fluorescence upon addition of a fused benzene ring (naphthalene), as will be discussed later. These compounds are easy to detect using field GC or an organic vapor analyzer such as a photoionization detector (PID) or flame ionization detector (FID). These methods are mature, having already been reasonably well established as field screening approaches (Spitler, 1992).

However, by using synchronous scanning, the

luminescence monitoring could still be very useful for routine monitoring of drinking water wells where other potentially fluorescent organic compounds (humic and fulvic acids for example) might be expected in low abundance. For example, Kenny et al. (1989) and Taylor et al. (1991) discussed a field portable instrument that utilized laser-induced fluorescence for gasoline and phenolic compounds in groundwater.

This instrument was capable of generating excitation

emission matrices (EEM) which could be used for fingerprinting petroleum contamination. Compounds that Form Fluorescent Derivatives: Compounds that can be decomposed to fluorescent products or that can be derivatized can also be analyzed by fluorescence. Several examples of pesticides that fall into this category were reviewed above. These types of analytes will include many compounds such as amines, mercaptans, metals, and organic acids. Many of these derivatives have been analyzed in conjunction with HPLC or TLC (Lawrence and Frei, 1976). However, many of the derivatives discussed by Lawrence and Frei (1976) for use with liquid chromatography (LC) could be easily synthesized under field conditions and utilized for screening applications. Guilbault (1973) presented a list of organic acids that can by analyzed by fluorescence after reaction (condensation)

with another reagent.

For example, many hydroxy and

dicarboxylic acids condense with resorcinol to yield fluorescent products, a-keto acids can be condensed with o-phenylene diamine to form highly florescent products. Steinberg (1982 and -1985) has utilized these derivatives in an HPLC-based fluorescent method for analysis of seawater, rain, fogs, and mists.

Compounds that yield acids such as pyruvic, glyoxylic, or

oxalic upon hydrolysis can also be analyzed using these methods. Ammonia and various other

1835 amines can be analyzed as fluorescent isoindole derivatives (Lawrence and Frei, 1976; Goyal et al.

1988).

These derivatives can also be separated by HPLC.

Other fluorescent amine

derivatives exist and are commonly used in conjunction with a chromatographic separation for identification of the individual compounds (Beale et al. 1988). These amines appear on various toxic compound lists and also can be decomposition products of various pesticides. Therefore, there should be some interest in monitoring these compounds in agricultural runoff, soil and produce. Anilines are decomposition products of pesticides and are common pollutants associated with the dye industry. Anilines do possess intrinsic weak fluorescence which could be enhanced in the solid phase (Sarkar and Kastha, 1992). These compounds could be analyzed as isoindole derivatives. Mercaptans are listed as hazardous chemicals and can also be analyzed as isoindole derivatives (Lawrence and Frei, 1976). The derivatives can be separated chromatographically for speciation of individual mercaptans. Schreurs et aL (1990) used 4-maleimidylsalicylic acid to derivatize mercaptans for HPLC analysis and post-column detection by fluorescence. These authors also found that the chromatographic separation provided inadequate resolution of analytes and therefore utilized post-column synchronous scanning in addition to the chromatographic separation. Several volatile chlorinated compounds react with alkaline pyridine to form fluorescent products. This reaction is known as the Fujiwara reaction and was reviewed by Angel et al. (1987) and discussed by Milanovich et al. (1991) for possible application to environmental monitoring with fiber optic probes. Derivatives of 2-diphenylacetyl-l,3-indandione-l-hydrazone are highly fluorescent; the use of this reagent and its closely related analogues have been proposed for identification of various classes of organic analytes (Mosher et al. 1968). These include aldehydes, ketones, orthoesters, esters, primary amines, secondary amines, alcohols, anhydrides, hydrazone, substituted hydrazines, acid hydrazides, and alkylating agents. Compounds that Quench, Enhance, or Shift Fluorescence Peaks: Many compounds can be detected indirectly using luminescence techniques. Some petroleum hydrocarbons, oxygen, and pH have been monitored indirectly using fluorescent optrodes. Barnard and Walt (1991) have immobilized the dye, Nile Red, at the end of an optical fiber and have used the shift in the fluorescence emission maxima of the fluorophore as a measure of gasoline vapor. The device

1836 senses petroleum vapors by the effect the compounds have on the "polarity" of the chromophore environment. Jain and Seitz (1990) used a similar effect for the detection of nitroaromatics using a fiber optic probe and the quenching behavior of a fluorescent dye. Luo and Walt (1989) have discussed a pH sensor based on the pH sensitivity of fluorescent indicator dyes that are continuously delivered to the end of a fiber optic. Recently, Szmacinki and Lakowicz (1993) have discussed the effect of pH on the fluorescence lifetimes of several dyes and the use of this effect as a pH monitor. Lee et al. have utilized the quenching behavior of dicyanoplatinum (II) complexes as a sensor for oxygen in air.

Warner et al. (1989) have discussed the general

approach for development of fluorescent cation detectors. Chemical sensors that are based on immobilized indicators and fiber optics have recently been reviewed by Seitz (1988). A novel application of fluorescence for detection of specific classes of bacteria was discussed by Nakamura et al. (1990). These authors linked a fluorescein dye and a bacterial magnetic particle to a monoclonal antibody for indirect detection of Escherichia coli. When the dye-antibody-magnetic particle conjugate was mixed with a sample, the E. coli were precipitated under the influence of a magnetic field and quantified by a decrease in fluorescence of the sample.

The authors noted that this technology should be suitable for clinical, food, and

environmental samples. Poziomek and coworkers (Mosher et al., 1968) discovered that 2-diphenylacetyl-l,3indandione-l-p-dimethylamino-benzaldazine undergoes fluorescence enhancement in the solidstate in the presence of a variety of compounds (e.g., fungicides, pesticides, amino acids, uhydroxy esters, and aliphatics).

The same group (Ashman et al., 1985) showed that the

fluorescence enhancement is associated with the ability of analytes that have minimum absolute lengths of 7.2 /t~ and appropriate pi-pi type charge transfer or lipophilic groups to form molecular complexes with the indandione benzaldazine. A structure-fluorescence enhancement (decision tree) model for predicting fluorescence activity was defined. Dissolved Orzanic Carbon and Humic Acids: Humic acids are important components of natural waters and represent an important, if not dominant, fraction of the total organic carbon content of natural waters.

Humic and fulvic acids are known to affect the sorption of

pollutants onto soils and sediments (Chou et al., 1986). During water treatment (chlorination), humic substances decompose to form various volatile chlorinated hydrocarbons such as chloroform (Christman et al., 1983). In most natural waters, these humic substances account for a majority of the total dissolved carbon. Because of the potential impact of humic substances

1837 on water quality, there is considerable interest in quantitation of these molecules. An additional important implication for humic and fulvic acids is that they can have profound effect on the fluorescence of other (pollutan0 compounds in natural waters (see references below). Because of this interaction and the fact that humic substances may contribute background fluorescence, the presence of these polyelectrolytes could represent an impediment to the application of luminescence to detection of some compound classes in environmental samples. Humic materials are highly aromatic organic polyelectrolytes.

The maximum

fluorescence intensity of most humic materials in natural waters is 420-500 nm with an excitation of 330-360 rim. From studies of fluorescence decay rates there appears to be several different fluorescent moieties in most humic materials (Cabaniss, 1992). The fluorescence of humic acids can generally be correlated to the organic carbon content of water.

Since a majority of the

dissolved organic carbon in natural waters is humic in nature, fluorescence measurements should correlate with dissolved organic carbon. Organic carbon content of water is a useful index of eutrophication which may result from phosphate or nitrate loading of natural waters. Goldberg and Weiner (1992) have discussed how fluorescence can be used to fingerprint water bodies, trace circulation patterns in lakes, and follow the movement of agricultural pollution. The study of water mixing is an important activity in oceanography, and in limnology and groundwater hydrology. The advective movement of water masses is a major mechanism for the transport of various environmental pollutants.

Thus, determination of water mixing is an important

activity in pollution monitoring, abatement, and emergency response.

As noted above, the

fluorescent signature of natural organic compounds has been used to trace movement of water masses.

Chudyk et al. (1985) utilized a fiber optic based (25m) instrument for monitoring

phenols and humic materials in groundwater. individual species could not be determined.

Phenolic compounds were detected, although

Humic acid could be differentiated from phenols.

Another interesting application of luminescence spectroscopy is the characterization of the hydrodynamic properties of large molecules. The size and shape of humic materials have profound implications as to their effects on mediating the migration of organic and inorganic species in groundwater. Fluorescence depolarization measurements have been used to measure the size of humic materials, as well as biological macromolecules (Goldberg and Negomir, 1989). Fluorescence depolarization measurements provide a means of monitoring the rotation of a chromophore in solution. Rates of rotation are a function of the hydrodynamic radius of the molecule. Although there is considerable environmental interest in this type of measurement,

1838 it would be difficult to foresee a need for field measurements of the hydrodynamic properties of molecules. The fluorescent properties of humic acids have been monitored as an indicator of metal binding. The quenching of fluorescence by various metallic species can be used as a measure of metal binding and to characterize the active site heterogeneity of the humic molecule (Cabaniss, 1992).

This type of measurement has been used in laboratory studies of humic

materials; however, there is a possibility that it could be utilized as a field monitor of heavy metal contamination.

If fluorescent properties of humic materials in soil or water can be

correlated with metal ion concentrations, then it may be possible to use field monitoring or screening of fluorescence as a guide to heavy metal contamination. Humic materials can be fingerprinted by synchronous fluorescence. Because fluorescence spectra of humic materials tend to be rather featureless, the synchronous scanning procedure has been found to be useful for deriving more useful data for differentiating sources of organic matter (Cabaniss, 1991a). Thus, different contributions to the dissolved organic carbon (DOC) could be potentially monitored by measuring the fluorescent properties of the humic materials. Another potential application would be to gauge the impact of municipal or Sewer runoff on various water supplies during floods or waste water plant malfunctions.

Application of

synchronous scanning methods to humic materials was recently reviewed by Cabaniss (1991b), Goldberg and Weiner (1992), and Goldberg and Negomir (1989). As noted above, humic acids have important implications for environmental fate and transport. The solubility of many contaminants such as PAHs and pesticides is apparently much higher in the presence of humic acids (Chou et al., 1986). The general thought is that these pollutant compounds become extensively associated with humic materials in a micelle-like interaction. There are several important implications of this type of interaction. Association with the humic may lead to fluorescent quenching.

Puchalski et al. (1992) investigated the

fluorescence behavior of 1-naphthol and DefenzoquatTM with a humic acid.

Backhus and

Gschwend (1992) investigated the potential role of hu,nic colloids in the transport of PAHs by utilizing the quenching properties of humic acids. Although there are mechanistic uncertainties regarding the quenching, a severe reduction of the fluorescent signal was observed above 3 ppm organic carbon (as humic acid). Association with the humic acid may make analyte extraction difficult and thus decrease the effectiveness of preconcentration. For example, ifa concentration method based on solid-phase extraction is selected, humic and fulvic acids may reduce extraction

1839 efficiency. Surfactants are another class of DOC that may enhance transport of anthropogenic pollutants.

Because of this interaction we mention their determination in this section.

Anthropogenic surfactants can also be analyzed using fluorescence detection. Castles et al. (1989) analyzed linear alkylbenzenes using HPLC separation and fluorescence detection. Similarly, Field et al. dialkyltetralinesulfonates

(1992) have studied the fate of alkylbenzenesulfonates and in sewage-contaminated groundwater using HPLC and fluorescence

detection. Metals: There is intense environmental interest in monitoring trace metals and various heavy metals and main group metals in the environment. Although a few of the actinides are fluorescent, most elements require some derivatization or chelation for luminescence analysis. Selenium has attracted attention as a contaminant from semiconductor manufacturing. Tin-based pesticides have been utilized in the past in oil-based and latex paints. preservatives are utilized in PVC manufacturing. monitored in water supplies.

Tin

Organotin compounds are toxic and are

One important application of luminescence spectroscopy is

elucidating the environmental chemistry of aluminum. Soluble aluminum concentrations have important environmental consequences. Concentrations of aluminum increase in acidified waters as a result of enhanced leaching of aluminosilicate rocks. Aluminum is thought to be important for fish diseases and has been implicated in Alzheimer's disease. speciation of aluminum appear to be an indicator of acid rain.

The concentration and

Vilchez et al. (1993) have

discussed the analysis of trace amounts of aluminum by reaction with salicylidene-o-amino phenol to form a fluorescent complex that could be adsorbed onto a dextran cation exchange gel and then analyzed by conventional fluorimetry. Saarl and Seitz (1983) utilized immobilized morin as a fluorescence sensor for determination of aluminum. The sensor was placed at the end of a bifurcated fiber optic for determination of aluminum concentration in solution. Takayangagi and Wong (1983) discussed the fluorimetric determination of Se(IV) and total selenium in natural waters after forming a fluorescent 4,5-benzopiazselenol derivative by reaction of 2,3-diaminonaphthalene with Se(IV). Earlier works used this derivative for sensitive analysis of selenium in water (Raile, 1972; Rankin, 1973) and soils and sediments (Hemsted et aL, 1972). Nagy et al. (1990) discussed a general procedure for the analysis of metals in solution using an intermolecular luminescence quenched spin-labeled reagent.

Although such reagents

1840 have not been applied to field screening studies, there is a potential for their future use in monitoring of heavy metal contamination in the environment.

Valcarel and Grases (1983)

reviewed fluorimetric reaction rate methods (enzymatic and non-enzymatic) that could be used for inorganic analysis. Sanchez et al. (1983) have discussed indirect metal analysis by using the rate of bromate oxidation of benzyl 2-pyridylketone 2-pyridylhydrazone (BKHKP) to yield a fluorescent product. The complexing of the BKHKP by metals decreases the reaction rate and can be used to measure metal concentrations. However, these methods would probably be difficult to implement with a field instrument since normally stopped flow systems are required. Pal et al. (1989) published a direct fluorimetric method for the analysis of Cr(VI) and total Cr ions in several different matrices. The method is based on the oxidation of the nonfluorescent reagent, 2-(o~-pyridyl)-thioquinaldinamide, by Cr(VI) to form an intensely fluorescent product. The reaction is complete within five minutes and has a range of 2 ng/ml to 0.8 #g/ml. The method appears robust in that over sixty different cations, anions, and complexing agents were found not to interfere.

The method is specific for Cr(VI), although total chromium can

be measured after oxidation of Cr(lll) to Cr(VI) with permanganate. Actinides and Lanthanides:

Lanthanides and actinides can be found at trace levels

throughout the environment and extensively contaminate nuclear weapons production facilities. Sensitive fluorescence and phosphorescence methods do exist for a number of these elements. Trace levels of uranium in aqueous samples can be analyzed using laser-induced fluorescence (Perry et al., 1981) and laser-induced phosphorescence (Bushaw, 1983). ASTM has published a standard method for analysis of uranium using laser-induced phosphorescence (D5174-91). Several commercial instruments are available for this application (DMW Geophysics Service, Chemchek Instruments). Jing-He et al. (1987) discussed the enhanced luminescence of europium and terbium with a thenoyltrifluoro-acetone/l,10-phenanthroline/surfactant system.

Such

enhancement resulted in a detection limit of 10-13M. Similarly, Ci et al. (1988) reported that the fluorimetric determination of europium (111) with thenoyltrifluoracetone and 4,7-diphenyl1,10-phenanthroline could be enhanced by the presence of gadolinium (III). A detection limit of 1015 g/mL could be achieved. Si et al. (1992) reported that the fluorimetric determination of europium with dibenzoylmethane and diphenylguanidine could be enhanced by the presence of terbium. Tran and Zhang (1990) demonstrated that luminescence detection of rare-earths could be enhanced by energy transfer from a counter-ion such as benzoate to a crown ether lanthanide complex. Enhancement of luminescence by up to 67 times was achieved. Because

1841 of the sensitivity of these methods for europium, chelate labels have been utilized as labels for fluorescence immunoassays. This application was reviewed by Diamandis (1993) and Diamandis and Christopoulos (1990). Beitz et al. (1988) discussed the detection and speciation of transuranium elements (using

f-f sorption bands) in synthetic groundwater via pulsed laser excitation. detected at 8.5 parts per trillion (ppt) using this approach.

Curium (III) was

Beitz (1991) also studied the

fluorescence lifetimes of curium (III) in solution. Thouvenot et al. (1993) used time-resolved laser-induced fuorescence for determination of trace americium in aqueous and solid matrices. In the solid matrices concentrations as low as 10"t°M could be measured, while in solutions the detection limit was about 10"SM. Zhu et aL (1990) simultaneously determined terbium, samarium, and europium in a hexafluoroacetylacetone-trioctylphosphine oxide and in Triton X100". A conventional fluorescence spectrophotometer was used to obtain parts per billion (ppb) detection limits. Moulin et al. (1991) determined curium at 1 ng/L levels in a micellar medium using time-resolved laser-induced fluorescence method. These authors pointed out that with a surfactant media, conventional chelating agents could be utilized without the need of an extraction procedure. Wimmer et al. (1992) reported the direct speciation of curium (III) in three different groundwaters at concentrations as low as 10-SM using time resolved laser fluorescence spectrophotometry.

SPECIFIC ADVANTAGES OF LUMINESCENCE ANALYSIS Specificity or False Positives: False positives could be an important problem for gaining acceptance of a method. A false positive could trigger unnecessary sampling, trenching, or drilling in a remediation scheme. Methods such as GC and GC/MS have the advantage of potentially identifying individual components of a complex mixture, and thus minimizing the potential of a false positive.

Similarly, fluorescence (in synchronous mode) also has the

potential of identifying individual components, while having much greater throughput than GC or GC/MS.

On the other hand, filter fluorometers or infrared monitors cannot perform

speciation with any degree of certainty and are more likely to provide a false indication of the presence of a target analyte. Similarly, electrochemical or colorimetric tests may have a limited ability to speciate.

The immunochemical methods, on the other hand, have the advantage of

very high specificity. In some monitoring situations, however, high selectivity may not be necessary.

In

1842 monitoring the extent of pollution, when the pollution is already well established and/or characterized, non-specific measurements may be more important than detailed information on individual compounds. This would be especially true of a petroleum or sewage spill. In this situation, luminescence monitoring would have a great advantage over GC, GC/MS, and immunochemical based tests if speed and low costs could be achieved. Waste minimization: In principle, luminescence analysis should not generate any waste products or only a minimum of waste. A field operator might be relieved of the burden 'of tracking and handling of waste containers and implementing hazardous waste procedures. However, if organic solvents are required for sample preparation this would not be true. Speed: Luminescence with a fiber optic option has the potential for real-time monitoring. Rapid operations in water could be provided by the combination of a flow cell and a battery operated pump. Conventional laboratory instruments such as GC/MS and HPLC would have considerable slower throughput (15 min to 2 hours) and would not be able to provide data in real time on site.

FIELD APPLICATIONS There are a number of tradeoffs or concerns that can be used to select a method

forfieM

applications. We have selected some key parameters to construct Table II, where alternative methods to the luminescence analysis are compared for several types of compounds (Table 1). We have focused on the following: • Throughput The ability to processes multiple samples and provide estimates of target analyte concentrations in a reasonable amount of time. • Resolution The ability of a method to resolve the various members of a compound class. This may not always be necessary for a field method. • Selectivity The ability of a method to selectively analyze a single compound class. This would reduce the probability of false positives for the compound class of concern. • Simplicity Ease of field operation of the instrument. Methods that require lengthy derivatizations or mixing of reagents would be considered complex.

1843 In Table II, while keeping field applications in mind, judgements, based on personal experience, are made as to the advantages and disadvantages of luminescence methods relative to alternative methods. As noted above, additional field methods (such as immunochemicalbased kits) are constantly being developed and commercialized. Therefore, it is probable that competitive technologies and methods other than the ones given in Table II will appear soon. TABLE II Advantages end Disadvantages of Luminescence Methods versus Alternative Methods for Field Applications

CompOUnd Class

Alternative Method

Polynuclear Aromatics

HPLC

Greater throughput (5 rain versus 25 rain) Simplicity (no solvents or waste) Lower cost

Lower resolution end selectivity.

GC/MS

Greater throughput (5 rain versus 120 mln) Ease of operation Simplicity (no carrier gas) Lower cost

L,ower resolution and selectivity.

UV/Vis

Greeter resolution Sensitivity (10-100X) Greater selectivity (in synchronous mode)

Higher cost.

immunoassay

Sia~licity (fewer numipulations and reagents)

Lower selectivity Higher cost

GC/FID

Greater throughput (5 rain versus 30 rain) Simplicity (no carrier gas)

Lower resolution Lower sensitivity Detection is limited to fluorescent t~O " nlpoflt~,nt$ Higher cost

UV/Vis

Greater resolution and sensitivity.

Higher cost

hnmunoassay

Simplicity (fewer manipulations and reagents).

Lower selectivity Higher cost

lmmunoassay

Sinlplicity (fewer menipulations and reagents).

Lower selectivity Higher cost

GC/ECD

Greater throughput (5 rain versus 120 rain) Ease of operation Simplicity (no carrier gas),

Lower selectivity Higher cost

Colorimetric

Greater sensitivity (10 X) Simplicity (no reagents)

Lower selectivity Greater need for operator training Higher cost

Electrochemical

Greater sensitivity (I 0 X) Simplicity (no reagents)

Lowef selectivity Greater need for operator training Higher cost.

Petroleum

• Polychlorinated Biphenyls

I Advautages of Luminmeeace

I

DL~advantages of Luminese~ce

1844 The

major

advantage

projected

for

the

luminescence

versus

alternative

instruments/kits/methods are greater sample throughput, simplicity, greater selectivity, greater sensitivity, and ease of operation. However, each of these advantages does not apply across the board to every competing technology (see Table II). In some cases, the luminescence offers the advantage of lower cost. This is true when comparison is made to techniques such as GC/MS and HPLC. SUMMARY AND CONCLUSIONS: A review of the literature does indicate that luminescence analysis already serves the environmental community and its role could be expanded further. However, it is also clear that it is not to be a panacea for field or laboratory analysis. A literature survey of the various applications of luminescence techniques showed that implementation of the synchronous scanning would yield improved results in many of the potential applications. The chemical compounds that might be analyzed by luminescence spectroscopy can be classified as follows: compounds that are intrinsically fluorescent, compounds that can form fluorescent derivatives, compounds that can modulate fluorescence of another compound. Applications of luminescence spectroscopy to all three classes can be found in the literature. Examples include: volatile aromatics, including benzene, toluene, ethylbenzene, and xylene; PCBs, including the Aroclors"; PAHs; phthalates; phenols; some pesticides; several main group elements, such as selenium, tin, and aluminum; actinides and lanthanides; ammonia and various other amines; mercaptans and sulfides. For some of these compounds, other well established methods exist. However, field applications utilizing fluorescence could serve as useful adjuncts to existing methods.

Although the luminescence methods may not represent the "best"

technology, they remain versatile, with the capability of screening for multiple analytes. REFERENCES Aaron, J.; Campiglia, A.; Winefordner, J. (1990) Solid-Substrate Room-Temperature Phosphorescence of Purine Derivatives Enhanced by Thallium(I) Ions and a Surface-Active Agent, Analytica Chimica Acta 236, 257-265. Abbott, D.; Moody, R.; Mann, R.; Vo-Dinh, T. (1986) Synchronous Luminescence Screening for Polynuclear Aromatic Compounds in Environmental Samples Collected at a Coal Gasification Process Development Unit, Am. Ind. Hyg. Assoc. J. 47, 379-385. A1-Haddad, A.; Creaser, C.; Homer, R. (1989) Studies Towards a Fluorescence Method for the Determination of Polychlorinated Biphenyls in 1,1,1-Trichloroethane Transformer Washings, Analyst 114, 1125-1127.

1845 Alaire, J.P.; Vo-Dinh, T; Miller, G. Ericson, N, Maddox, S.R.; Watts, W. (1993)Development of a Battery Operated Portable Synchronous Luminescence Spectrofluorometer, Review of Scientific Instruments (in press). Alak, A.; Vo-Dinh, T. (1988) Selective Enhancement of Room Temperature Phosphorescence Using Cyclodextrin-Treated Cellulose Substrate, Anal. Chem. 60, 596-600. Alak, A.M.; Contoline, N.; Vo-Dinh, T. (1989) Studies of Cyclodextrin-Enhanced Room Temperature Phosphorescence, Anal. Chem. Acta 217, 171-176. Angel, S.; Daley, P.; Langry, K.; Kulp, T.; Camins (1987) The Feasibility of Using Fiber Optics for Monitoring Groundwater Contaminants VI. Mechanistic Evaluation of the Fujiwara Reaction for Detection of Organic Chlorides, EPA/600/X-87/467, 42 pp. Arise, F.; Gooijer, C.; Velthorst, N.H.; Hofstraat, J. W. (1990) Shpol'skii Spectrofluorimetric Determination of Polycyclic Aromatic Hydrocarbons in Biota, Anal. Chem. Acta 232,245-251. Ashman, W.P.; Lewis, H.; Poziomek, E.J. (1985) Decision Tree for Chemical Detection Applications, Anal. Chem. August 1985, 1951-1955. ASTM (1990) D3650-90 Standard Test Method for Comparison of Waterborne Petroleum Oils by Fluorescence Analysis, ASTM Standards 11.02, 253-257. ASTM (1988) D4763-88 Standard Practice for Identification of Chemicals in Water by Fluorescence Spectroscopy, ASTM Standards 11.01, 75-80. ASTM (1991) D5174-91 Standard Test Method for Trace Uranium in Water by Pulsed-Laser Phosphorimetry, Annual Book of ASTM Standards, 425-427. Backhus, D.; Gschwend, P. (1990) Fluorescent Polycyclic Aromatic Hydrocarbons as Probes for Studying the Impact of Colloids on Pollutant Transport in Groundwater, Environ. Sci. Technol. 24, 1214-1223. Bark, K.; Force, R. (1991) Analysis of Polynuclear Aromatic Hydrocarbon Mixtures in Various Environments by Time-Resolved Fluorescence Spectroscopy, Talanta 38, 181-188. Bark, K.; Force, R. (1990) Analysis of Polynuclear Aromatic Hydrocarbon Mixtures Desorbed from Particulate Matter in a Low-Temperature Matrix by Shpol'skii Time-Resolved Fluorescence Spectroscopy, Applied Spectroscopy 44, 1373-1380. Barnard, S.;Walt, D. (1991) Fiber-Optic Organic Vapor Sensor, Environ. Sci. Technol, 25, 1301-1304. Baudot, P.; Viriot, M.; Andre, J.; Jezequel, J; Lafontaine, M. (1991) Analysis of Polyaromatic Hydrocarbons by Synchronous Fluorescence Spectrometry: Application to Occupational Health, Analusis 19, 85-97.

1846 Beale, S.C.; Savage, J.C.; Wiesler, D.; Wiestock, S.M.; Novotny, M. (1988) Fluorescence Reagents for High-Sensitivity Chromatographic Measurements of Primary Amines, Anal. Chem. 60, 1765-1769. Beitz, J.V.; Bowers, D.L.; Doxtander, M.M.; Maroni, V.A.; Reed, D.T. (1988) Detection and Speciation of Transuranium Elements in Synthetic Groundwater via Pulsed-Laser Excitation, Radiochemica Acta 56, 87-93. Bello, J.; Hurtubise, R. (1986) Room-Temperature Luminescence of Several Compounds on a a-Cyclodextrin-NaCl Mixture, Applied Spectroscopy 40, 790-794. Bentz, A.P. (1976) Oil Spill Identification, Anal. Chem. 48, 455A-470A. Bietz, J. (1991) Laser-induced Fluorescence of Cm +3 Complexes in Solution, Radiochemica Acta 59, 35-39. Bjorseth, A; Becher, G. (1986) PAH in Work Atmospheres: Occurrence and Determination, CRC Press, Inc., Boca Raton, F1, 63-101. Blyshak, L.A.; Patonay, G.; Warner, I.M. (1989) Multidimensional Fluorescence Analysis of Cyclodextrin Solvent Extraction System, In "M. Goldberg, ed ~ Luminescence Applications, ACS Symposium Series 383, 167-179. Bolton, D.; Winefordner, J. (1983) Laser-Excited Fluorescence Line-Narrowing: An Analytical Study, Talanta 30, 713-716. Bower, E.; Winefordner, J. (1978) The Effect of Sample Environment on the Room Temperature Phosphorescence of Several Polynuclear Aromatic Hydrocarbons, Anal. Chem. Acta 102, 1-13. Brownrigg, J.; Homing, A. (1974) Identification of PCBs in the Presence of DDT-Type Compounds Using Low Temperature Luminescence, Archives of Environmental Contamination and Toxicology 4, 174-182. Brumley, W.C. ;Brownrigg, C.M. (1991) Applicability of Thin-Layer Chromatography to Field Screening of Nitrogen-Containing Aromatic Compounds, Second International Symposium Field Screening Methods for Hazardous Wastes and Toxic Chemicals, Las Vegas, NV, Symposium Proceedings, 615-619. Bushaw, B.A. (1983) Kinetic Analysis of Laser Induced Phosphorescence in Uranyl Phosphate for Improved Analytical Measurements, Presented at 26th Oak Ridge Conference on Analytical Chemistry in Energy Technology, Knoxville, TN. Oct., 1983, . Butler, H.T.; Coddens, M.; Khatib, S.; Poole, C. (1985) Determination of Polycyclic Aromatic Hydrocarbons in Environmental Samples by High Performance Thin-Layer Chromatography and Fluorescence Scanning Densitometry, J. Chromat. Sci. 23,200-207.

1847 Cabaniss, S. (1991) Synchronous Fluorescence Spectra of Dissolved Organic Matter, In "R.A. Baker, ed" Organic Substances and Sediments in Water, Lewis Publishers, Chelsea. Michigan, 503-519. Cabaniss, S. (1991) Theory of Variable-Angle Synchronous Fluorescence Spectra, Anal. Chem. 63, 1323-1327. Cabaniss, S. (1992) Synchronous Fluorescence Spectra of Metal-fulvic Acid Complexes, Environ. Sci. Technol. 26, 1133-1139. Capitan, F. ;Alonso, E. ;Avidad, R; Capitan-Vallvey, L. F.; Vilchez, J. L. (1993) Determination of Thiabendazole Residues in Waters by Solid-Phase Spectrofluorimetry, Anal. Chem. 65, 13361339. Carr, J.W.; Harris, J. (1988) In Situ Fluorescence Detection of Polycyclic Aromatic Hydrocarbons following Preconcentration of Alkylated Silica Adsorbents, Anal. Chem. 60, 698702. Castles, M.; Moore, B.; Ward, S. (1989)Measurement of Linear Alkylbenzenesulfonates in Aqueous Environmental Matrices by Liquid Chromatography with Fluorescence Detection, Anal. Chem.61, 2534-2540. Chiou, C.T.; Malcolm, R.L.; Brinton, T.I.; Kile, D.E. (1986) Water Solubility Environ. Sci. Technol. 20, 502-508.

Acids,

Christman, R.; Norwood, D.; Millington, D.; Johnson, J. (1983) Identity and yields of Major Halogenated Products of Aquatic Fulvic Acid Chlorination, Environ. Sci. Technol. 17, 625-628. Chudyk, W.; Carrabba, M.; Kenny, J. (1985) Remote Detection of Groundwater Contaminants Using Far-Ultraviolet Laser-Induced Fluorescence, Anal. Chem. 57, 1237-1242. Chudyk, W.; Pohlig, K. (1988) Field Screening for Aromatic Organics Using Laser-Induced Fluorescence and Fiber Optics, First International Symposium Field Screening Methods for Hazardous Wastes and Toxic Chemicals, Las Vegas, NV, Symposium Proceedings, 99-102. Ci, Y,; Lan, Z. (1988) Enhanced Fluorimetric Determination of Europium (III) with Thenoyltrifluoroacetone and 4,7-Diphenyl-1,10-Phenathroline by Gadolinium (Ill), Anal. Lett. 21, 1499-1513. Colmsjo, A. (1987) Cryogenic-Temperature Fluorescence Spectroscopy of Polynuclear Aromatic Hydrocarbons of Molecular Weight 378, Anal. Chem. Acta 197, 71-75. D'Silva, A, Fassel, V. (1984) Laser-Excited Shpol'skii Spectrometry, Anal. Chem. 56, 985A1000A.

1848 de Kok,A. ;Hiemstra, M.; Brinkman, U. A. The. (1992) Low ng/L-level Determination of Twenty N-Methylcarbamate Pesticides and Twelve of their Polar Metabolites in Surface Water via Off-Line Solid-Phase Extraction and High Performance Liquid Chromatography with Post Column Reaction and Fluorescence Detection, J. Chrom. 623, 265-276. Demirigan, J.; Clapper-Gowdy, M.; Tober, M.L. (1993) Identification and Quantification of Volatile Organics in Soils by Use of Fourier Transform Infrared (FTIR) Spectroscopy, Presented at National Symposium on Measuring and Interpreting VOCs in Soils: State of the Art and Research Needs, Las Vegas, NV. Diamandis, E.; Christopoulos, T.K. (1990) Europium Chelate Labels in Time-Resolved Fluorescence Immunoassays and DNA Hybridization Assays, Anal. Chem. 62, 1149A-1157A. Diamandis, E. (1993) Fluorescence Spectroscopy, Anal. Chem. 65, 454R-459R. Dudelzak, A; Babichenko, S; Poryvkina, L.; Saar, K.J. (1991) Total Luminescent Spectroscopy for Remote Laser Diagnostics of Natural Water Conditions, Applied Optics 30, 453-458.

Eastwood, D., Lidberg, R. (1986) Application of Fluorescence and FT-IR Techniques to Screening and Classifying Hazardous Waste Samples, Proceedings of 77th National Conference on Management of Uncontrolled Hazardous Waste Sites, 370-379. Eastwood, D.; Dominguez, M.E.; Lidberg, R. L.; Poziomek, E.J. (1993) A Solid Phase Extraction/Solid State Luminescence Approach for Monitoring PAHs in Water, Draft Manuscript. Eastwood, D. (1981) Use of Luminescence Spectroscopy in Oil Identification, In "E.L Wehry, ed", Modern Fluorescence Spectroscopy 4, Plenum Publishing Corporation, 251-275. Eastwood, D.; Vo-Dinh, T. (1991) Molecular Optical Spectroscopic Techniques for Hazardous Waste Site Screening, EPA/600/4-91/011, 87pp. Eastwood, D.; Lidberg, R.; Zimmermann, J.; Domingues, M.; Vo-Dinh, T.;Alaire, J.; Miller, G. (1993) Evaluation of a Portable Field Scanning Ultraviolet-Visible Spectrofluorometer Using Synchronous Fluorescence for Oils in Environmental Samples, Third International Symposium on Field Screening Methods for Hazardous Waste and Toxic Chemicals, Las Vegas, NV.(In Press). Femia, R.A.; Scypinski, S.; Cline Love, L. (1985) Fluorescence Characteristics of Polychlorinated Biphenyl Isomers in Cyclodextrin Media, Environ. Sci. Technol. 19, 155-159. Field, J.; Barber, L.; Thurman, E.; Moore, B.; Lawrence, D.; Peake, D. (1992) Fate of Alkylbenzenesulfonates and Dialkytetralinesulfonates in Sewage-Contaminated Groundwater, Environ. Sci. Technol. 26, 1140-1148. Files, L. A; Wineforder, J.D. (1987) Feasibility Study of Constant Energy Synchronous Luminescence Spectrometry for Pesticide Determination: Application to Carbaryl, Naphthol, and Carbofuran, J. Agric. Food Chem. 35,471-474.

1849 Files, L.; Moore,M.; Ke~'khoff, M.; Winefordner, J. (1987) Gasoline and Crude Oil Fingerprinting Using Constant Energy Synchronous Luminescence Spectrometry, Microchemical Journal 35, 305-314. Fortier, S.; Eastwood, D. (1978) Identification of Fuel Oils by Low Temperature Luminescence Spectrometry, Anal. Chem. 50, 334-338. Lopez-Garcia, A. ; Blanco-Gonzales, E.; Garcia°Alonso, J.I., Sanz-Medel, A (1992) Determination of some Selected Polycyclic Aromatic Hydrocarbons in Environmental Samples by High-Performance Liquid Chromatography with Fluorescence Detection, Chromatographia 33, 225- 230. Gammage, R.; Haas, J.; Miller, G.; Vo-Dinh, T. (1988) Improved Luminescence Techniques for Screening Aromatic Contaminants in Environmental Samples, First International Symposium Field Screening Methods for Hazardous Wastes and Toxic Chemicals, Las Vegas, NV, Symposium Proceedings, 51-55. Gammage, R.; Haas, J.; Allen, T. (1991) Screening of Groundwater for Aromatics by Synchronous Fluorescence, Second International Symposium Field Screening Methods for Hazardous Wastes and Toxic Chemicals, Las Vegas, NV, Symposium Proceedings, 673-676. Garrigues, P.; Ewald, M. (1987) High Resolution Emission Spectroscopy (Shpol'skii Effect): A New Analytical Technique for the Analysis of Polycyclic Aromatic Hydrocarbons (PAH) in the Environmental Samples, Chemosphere 16, 485-494. Garrigues, P. Ewald, M. (1985) Application of High Resolution Shpol'skii Luminescence Spectroscopy to the Analysis of Polycyclic Aromatic Hydrocarbons (PAH) in the Environmental Samples, Intern. J. Environ. Anal. Chem. 21, 185-197. Garrigues, P.; de Sury, R.; Bellocq, J., Ewald, M. (1985)Analyse de Composes Aromatiques Isomeres par Spectrofluorimetrie haute Resolution darts des Extraits d'Echangtillons Naturels, Analusis 13, 81-86. Goldberg, M.; Negomir, P. (1989) Characterization of Aquatic Humic Acid Fractions by Fluorescence Depolarization Spectroscopy, In "M. Goldberg, ed" Luminescence Applications, ACS Symposium Series 383, 180-232. Goldberg, M.; Weiner, E. (1993) Fluorescence Spectroscopy in Environmental and Hydrological Sciences, In"Otto S. Wolfbeis, ed" Fluorescence Spectroscopy New Methods and Applications, Springer-Verlag, Berlin, 213-241. Goyal, S.; Rains, D.; Huffaker, R. (1988) Determination of Ammonium Ion by Fluorometry or Spectrophotometry after On-Line Derivatization with o-phthalaldehyde, Anal. Chem. 60, 175179. Guibault, G. (1973) Practical Fluorescence: Theory, Methods, Techniques, Marcel Dekker, Inc. New York,Chapter 7, 277-348.

1850 Hemsted, W.; Sina, M.; Cekicer, S. (1972) A Simplified Method for the Determination of Selenium in Soils and Sediments, Analyst 97, 383-387. Hofstraat, J.W.; van Zeijl, W.; Ariese, F.; Mastenbroek, J.; Gooijer, C.; Velthorst, N.H. (1991) (Laser-Excited) Shpol'skii Fluorimetry: Applications in Marine Environmental Analysis of Polynuclear Aromatic Hydrocarbons, Mar. Chem. 33,301-320. Hurtubis, R.; Ramasamy, S.; Bello, J.; Burrell, G.; Citta, L. (1989) Applications and Interactions in Solid-Surface Luminescence, In "M. Goldberg, ed" Luminescence Applications, ACS Symposium Series 383, 155-166. Hurtubise, R.J. (1983) Phosphorimetry, Anal. Chem. 55,669A-675A. Hurtubise, R.J. (1989)Solid-Surface Luminescence Spectrometry, Anal. Chem. 61,889A-895A. Inman, E.; Winefordner, J. (1982) Constant Energy Synchronous Fluorescence for Analysis of Polynuclear Aromatic Hydrocarbon Mixtures, Anal. Chem. 54, 2018-2022. Inman, S.; Thibado, P.; Theriault, G.; Lieberman, S. (1990) Development of a Pulsed-Laser, Fiber-Optic-Based Fluorimeter: Determination of Fluorescence Decay Times of Polycyclic Aromatic Hydrocarbons in Sea Water, Anal. Chem. Acta 239, 45-51. Jandris, L.; Force, R. (1983) Determination off Polynuclear Aromatic Hydrocarbons in Vapor Phases by Laser Induced Molecular Fluorescence, Anal. Chem. Acta 151, 19-27. Jian, C.; Seitz, W. (1990) Membrane for In Situ Optical Detection of Organic Nitro Compounds based on Fluorescence Quenching, Anal. Chem. Acta 237, 265-271. Jing-He, Y; Gui-Yun, Z.; Bo, W. (1987) Enhanced Luminescence of the Europium/Terbium/Thenoyltrifluoroacetone/1,10-Phenanthroline/Surfactant System, and its Analytical Application, Analytica Chemica Acta 198, 287-292. John, P.; Soutar, I. (1976) Identification of Crude Oils by Synchronous Excitation Spectrofluorimetry, Anal. Chem. 48, 520-523. Johnston, E.P.; Baumann, P.C. (1989) Analysis of Fish Bile with HPLC-Fluorescence to Determine Environmental Exposure to Benzo(a)pyrene, Hydrobiologia 188/189, 561-566. Kennicutt, M.; Sweet, S.; Fraser, W; Stockton, W.; Culver, M. (1991) Grounding of the Bahia Pariaso at Arthur Harbor, Antarctica. 1. Distribution and Fate of Oil Spill Related Hydrocarbons, Environ. Sci. Technol. 25, 509-518. Kenny, J.; Jarvis, G.; Xu, H. (1988) Instrumentation and Methodology for Multicomponent Analysis Using In Situ Laser-Induced Fluorescence, First International Symposium Field Screening Methods for Hazardous Wastes and Toxic Chemicals, Las Vegas, NV, Symposium Proceedings, 133-138.

1851 Kenny, J.; Jarvis, G.; Chudyk, W.; Pohlig, K. (1989) Ground-Water Monitoring Using Remote Laser-Induced Fluorescence, In "M. Goldberg, ed" Luminescence Applications, ACS Symposium Series 383, 233-239. Khasawneh, I.; Windefordner, J. (1988) Room-Temperature Fluorescence and Low-Temperature Phosphorescence Properties of biphenyl and Some Polychlorinated Biphenyls, Microchemical J. 37, 86-92. Kicinski, H.; Adamek, S.; Kettrup (1989) Trace En richmerit and HPLC Analysis of Polycyclic Aromatic Hydrocarbons in Environmental Samples, Using Solid Phase Extraction in Connection with UV/Vis Diode-Array and Fluorescence Detection, Chromatographia 28, 203-208. Kinnicutt, M. (1990) Oil Spillage in Antarctica, Environ. Sci. Technol. 24, 620-624. Lai, E.; Inman, E.; Winefordner, J.D. (1982) Conventional Fluorescence Spectrometry of Polynuclear Aromatic Hydrocarbons in Shpol'skii Matrices at 77K, Talanta 29, 601-608. Lawrence, J.; Frei, R. (1976) Chemical Derivatization in Liquid Chromatography, Journal of Chromatography Library Volume 7, 152-201. Lee, W.; Wong, K; Li, X. (1993) Luminescent Dicyanoplatinum (II) Complexes as Sensors for the Optical Measurement of Oxygen Concentrations, Anal. Chem. 65, 255-258. Lieberman, S.; Theriault, G.; Cooper, S.; Malone, P.; Olsen, R.; Lurk, P. (1991) Rapid, Subsurface, In Situ Field Screening of Petroleum Hydrocarbon Contamination Using Laser Induced Fluorescence over Optical Fibers, Second International Symposium Field Screening Methods for Hazardous Wastes and Toxic Chemicals, Las Vegas, NV, Symposium Proceedings, 57-63. Lin, C.; Fukii, H.; Imasaka, T.; Ishibashi, N. (1991) Synchronous Scan Luminescence Techniques Monitoring Resonance and Non-Resonance Fluorescence in Supersonic Jet Spectrophotometry Applied to Anthracene Derivatives, Anal. Chem. 63, 1433-1440. Lopez-Garcia, A; Blanco-Gonzalez, E.; Garcia-Alonso, J.; Sanz-Medel, A. (1992) Determination of some Selected Polycyclic Aromatic Hydrocarbons in Environmental Samples by High-Performance Liquid Chromatography with Fluorescence Detection, Chromatographia 33, 225-230. Luo, S.; Walt, D. (1989) Fiber-Optic Sensors Based on Reagent Delivery With ControlledRelease Polymers, Anal. Chem. 61, 174-177. MacDonald, B.; Hammons, J.; Gore, R.; Maple, J.; Wehry, E. (1988) Site-Selection Fluorescence Spectrometry of Polycyclic Aromatic Hydrocarbons in Vapor-Deposited Argon Matrices, Applied Spectroscopy 42, 1079-1083. McCreery, R.; Fleischmann, M.; Hendra, P. (1993) Fiber Optic Probe for Remote Raman Spectrometry, Anal. Chem. 55, 146-148.

1852 McGown, L. (1989) Fluorescence Lifetime Filtering, Anal. Chem. 61,839A - 847A. McGown, L.B.; Millican, D. W. (1988) Fluorescence Lifetime Selectivity in Multifrequency Phase-Resolved Fluorescence Spectroscopy, Applied Spectroscopy 42, 1084-1089. McGown, L.; Bright, F. (1985) Simultaneous Two-Component Determinations by Phase Resolved Fluorescence Spectrometry, Analytica Chemica Acta 169, 117-123. Mellone, A.; Smith, B.W.; Winefordner, J.D. (1990) Rapid Screening of Polycyclic Aromatic Hydrocarbons and Fingerprinting of Environmental Materials by Laser-Excited Fluorescence Spectrometry, Talanta 37, 111-118. Milanovich, F.; Daley, P.; Langry, K.; Colston, B.; Brown, S.; Angel, S. (1991) A Fiber Optic Sensor for the Continuous Monitoring of Chlorinated Hydrocarbons, Second International Symposium Field Screening Methods for Hazardous Wastes and Toxic Chemicals, Las Vegas, NV, Symposium Proceedings, 51-56. Millican, D. W.; McGown, L. B. (1989) Fluorescence Lifetime Selectivity in ExcitationEmission Matrices for Qualitative Analysis of a Two-Component System, Anal. Chem. 61,580583. Montgomery, R.E.; Remeta, D.P.; Gruenfeld, M. (1985)Rapid On-site Methods of Chemical Analysis, In (M. Smith, ed) "Contaminated Land", Plenum Publishing, 257-309. Morel, G.; Samhan, O.; Literathy, H.; AI-Hashash, H.;Moulin, L.; Saeed, T.; AI-Matrouk, K.; Martin-Bouyer, M.; Saber, A.; Paturel,L.; Jarosz, J.; Vial, M.; Combet,E.; Fachinger, C.; Suptil, J. (1991) Evaluation of Chromatographic and Spectroscopic Methods for the Analysis of Petroleum-derived Compounds in the Environment, Fresenius J. Anal. Chem. 339, 699-715. Mosher, W. A.; Bechara, I.S.; Poziomek, E.J. (1968) Application of 2-Diphenylacetyl-l,3indandione Chemistry in the Identification of Organic Compounds. Talanta 18, 482-484. Moulin, C; Decambox, P.; Mauchien, P. (1991) Determination of Curium at 0.1 ng/L levels in a Micellar Medium by Time Resolved Laser-Induced Spectrofluorimetry, Analytica Chemica Acta 254, 145-151. Nagy, V.; Bystryak, I.; Kotel'nikov, A.I.; Likhtenshtein, G.l.;Petrukhin, O.; Zolotov, Y.; Volodarskii, L. (1990) Determination of Metals in Solution by Chelate Formation with Intramolecular Luminescence-Quenched Spin-Labelled Reagents, Analyst 115, 839-841. Nakamura, N.; Burgess, J.; Yagiuda, K. ; Sakaguchi, T.; Matsunaga, T. (1993) Detection and Removal of Escherichia Coli Using Fluorescein Isothiocyanate Conjugated Monoclonal Antibody Immobilized on Bacterial Magnetic Particles, Anal. Chem. 65, 2036-2039. Niessner, R; Robers, W.I Krupp, A. (1991) Detection of Particulate Polycyclic Aromatic Hydrocarbons by Laser-Induced time-resolved fluorescence, Fresenius J. Anal. Chem. 341,207213.

1853 Nithipatikom, K.;McGown, L. B. (1986) Multidimensional Data formats for Phase-Resolved Fluorometric Multicomponent Determinations Using Synchronous Excitation and Emission Spectra, Anal. Chem. 58, 2469-2473. Nunez, M.D.; Centrich, F. (1990) Liquid Chromatographic Method with Fluorescence Detection for the Determination of Polycyclic Aromatic Hydrocarbons in Environmental Samples, Analytica Chemica Acta 234, 269-273. Ostgaard, K. (1984) Determination of Environmental Pollutants by Direct Fluorescence Spectroscopy, Ed "J. Lawrence, eds" Determination of Environmental Pollutants by Direct Fluorescence Spectroscopy, Academic Press, Inc., 163-210. Pak, A; Watts, W.; Caraway, J.; Vo-Dinh, T. (1992) Enhanced Room-Temperature Phosphorescence Using Sodium Lauryl Sulfate Treated Solid Substrate, Analusis 20, 149-153. Pal, B.; Charkrabarti, A.; Ahmed, M. (1989) 2-(ot-Pyridyl)-thioquinaldinamide (PTQA)- A Novel Fluorimetric Reagent in Inorganic Trace Analysis. I: The non-extractive, Nonquenching Fluorescent Method for the Determination of Chromium (VI), Mikrochim Acta I, 393-401. Perry, D.; Klainer, S.; Bowman, H.; Milanovich, F.; Hirchfeld, T.; Miller, S. (1981) Detection of Ultratrace Levels of Uranium in Aqueous Samples by Laser-Induced Fluorescence Spectroscopy, Anal. Chem. 53, 1048-1050. Poziomek, E.; Eastwood, D.; Lidberg, R.; Gibson, G. (1991) Solid-Phase Extraction and SolidState Spectroscopy for Monitoring Water Pollution, Anal. Lett. 24, 1913-1921. Puchalski, M.; Morra, M.; yon Wandruszka, R. (1992) Fluorescence Quenching of Synthetic Organic Compounds by Humic Materials, Environ. Sci. Technol. 26, 1787-1792. Purcell, F.; Kaminski, R.; Obenauf, R. (1985) Synchronous-Excitation Fluorescence Applied to Characterization of Phenolic Species, American Society for Testing and Materials Special Technical Publication 863, 81-94. Raihle, J.A. (1972) Fluorometric Determination of Selenium in Effluent Streams with 2,3Diaminonaphthalene, Environ. Science and Technol. 7, 621-622. Rankin, J. (1973) Fluorometric Determination of Selenium in Water Diaminonaphthalene, Environ. Sci. Technol. 7, 823-824.

with 2,3-

Saarl, L.A.; Seitz, W. (1983) Immobilized Morin as Fluorescence Sensor for Determination of Aluminum (Ili), Anal. Chem. 55, 667-670. Sanchez, F.; Navas Diaz, A.; Laserna, J.J, (1983) Kinetic Fluorimetric Determination of Inorganic Species by Bromate Oxidation of Chelating Agent and Complexation with Metal Ions, Anal. Chem. 55,253-256. Sarkar, S.; Kastha, G. (1992) Environmental Effects on the Adsorption and Luminescence Properties of Aromatic Amines: Aniline, Spectrochemica Acta 48A, 1611-1624.

1854 Schreurs, M.I Gooijer, C.; Velthorst, N. (1990) Labeling Reaction for Time-Resolved Luminescence Detection in Liquid Chromatography, Anal. Chem. 62, 2051-2053. Schuresko, D. (1980) Portable Fluorometric Monitor for Detection of Surface Contamination by Polynuclear Aromatic Hydrocarbons, Anal. Chem. 52, 371-373. Scypinski, S.; Cline Love, L. (1984) Room-Temperature Phosphorescence of Polynuclear Aromatic Hydrocarbons in Cyclodextrins, Anal. Chem. 56, 322-327. Seitz, W. (1988) Chemical Sensors Based on Immobilized Indicators and Fiber Optics, CRC Critical Reviews in Analytical Chemistry 19, 135-173. Shivihare, P; Raju, J.; Gupta, V.K. (1991) A New and Improved Reagent for the Spectrophotometric Determination of 2,4-Dichlorophenoxy Acetic Acid in Water, Grain and Plant Materials, Microchemical Journal 43, 204-207. Si, Z.; Zhu, G-Y.; Zhang, B.; Jiang, W. (1992) Enhanced Fluorimetric Determination of Europium with Dibenzoylmethane and Diphenylguanidine by Terbium, Anal. Lett. 25,321-330. Spittler, T. (1992) Protecting Groundwater Supplies with Field GC, Environmental Lab April/May 1992, 38-43. Stab, J. A.; Rozing, M.J.M.; van Hattum, B.; Cofino, W.P.;Brinkman, U.A. The. (1992) Normal-Phase High Performance Liquid Chromatography with UV Irradiation, Morin Complexation and Fluorescence Detection for the Determination of Organotin Pesticides, J. Chrom. 609, 195-203. Steinberg, S.M.; Bada, J.L. (1984) Oxalic, Glyoxalic, and Pyruvic acids in Eastern Pacific Ocean Waters, Journal of Marine Research 42, 697-708. Steinberg, S.M.; Kawamura, K.T.; Kaplan, I.R. (1985) The Determination of a-Keto Acids and Oxalic Acid in Rain, Fog, and Mist by HPLC, Intern. J. Environ. Anal. Chem. 19, 251-260. Stevenson, C.L.; Vo-Dinh, T. (1993) Laser-Excited Synchronous Luminescence Spectroscopy, Applied Spectroscopy 47, 430-435. Stine, G. (1993) Have LC Lab, Will Travel Testing Propellant Stability after Operation Desert Storm, Anal. Chem. 64, 453A-455A. Su, S.Y.; Asafu-Adjaye, E.; Ocak, S. (1984)Room-Temperature Phosphorimetry of Pesticides Using a Luminescence Sampling System, Analyst 109, 1019-1023. Szmacinski, H.; Lakowicz, J.R. (1993) Optical Measurements of pH Using Fluorescence Lifetimes and Phase-Modulation Fluorometry, Anal. Chem. 65, 1668-1674. Takayanagi, K.; Wong, G. (1983) Fluorimetric Determination of Selenium(IV) and Total Selenium in Natural Waters, Analytica Chimica Acta, 148, 263-269.

1855 Taylor, T.; Patterson, H, (1987) Excitation Resolved Synchronous Fluorescence Analysis of Aromatic Compounds in Fuel Oil, Anal. Chem. 59, 2180-2187. Taylor, T.; Xu, H.; Kenny, J. (1991) Laser Fluorescence EEM Instruments for In Situ Groundwater Screening, Second International Symposium Field Screening Methods for Hazardous Wastes and Toxic Chemicals, Las Vegas, NV, Symposium Proceedings, 797-804. Theis, T.; Collins, A.; Monsour, P.; Pavostathis, S.; Theis, C. (1991) Analysis of Total Polyaromatic Hydrocarbon Using Ultraviolet-Fluorescence Spectrometry, Second International Symposium Field Screening Methods for Hazardous Wastes and Toxic Chemicals, Symposium Proceedings, 805-810. Thompson, R.; Lakowicz, J. (1993) Fiber Optic pH Sensor Based on Phase Fluorescence Lifetimes, Anal. Chem. 65, 853-856. Thouvenot, P.; Hubert, S, Moulin, C.; Decabox, P. Mauchien, P. (1993) Americium Trace Determination in Aqueous and Solid Matrices by Time-Resolved Laser-Induced Fluorescence, Radiochemica Acta 61, 15-21. Thurman, E.M.; Meyer, M.; Pomes, M.; Perry, C.A.; Schwab, A. (1990) Enzyme-Linked Immunosorbent Assay Compared with Gas Chromatography/ Mass Spectrometry for the Determination of Triazine Herbicides in Water, Anal. Chem. 62, 2043-2048. Tran, C.; Zhang, W. (1990) Luminescence Detection of Rare-Earth Ions by Energy Transfer from Counteranion to Crown Ether-Lanthanide Ion Complexes, Anal. Chem. 62, 835-840. Tucker, S. A.,;Bates, H. C.; Amszi, V.L.; Acree, W.E.; Lee, H.; Di Raddo, P.; Harvey, R.; Fetzer, J.; Dyker, G. (1993) Spectroscopic Properties of Polycyclic Aromatic Compounds Part II. Fluorescence Emission and Quenching Behavior of Select Acenapthylene Derivatives in Organic Nonelectrolyte Solvents, Anal. Chem. Acta 278, 269-274. Valcarcel, M.; Grases, F. (1983) Fluorimetric Reaction-Rate Methods of Inorganic Analysis: A Review, Talanta 30, 139-143. Vilchez, J.; Navalon, A.; Avidad, R.; Garcia-Lopez, T.; Capitan-Vallvey, L. (1993) Determination of Trace Amounts of Aluminum in Natural Waters by Solid-Phase Spectrofluorimetry, Analyst 118, 303-307. Vo-Dinh, T.; Gammage, R.; Hawthorne, A.; Thornegate, J. (1978) Synchronous Spectroscopy for Analysis of Polynuclear Aromatic Hydrocarbons, Environ. Sci. Technol. 12, 1297-1302 Vo-Dinh, T.; Martinez, P. (1981) Direct Determination of Selected Polynuclear Aromatic Hydrocarbons in a Coal Liquification Product by Synchronous Scanning Luminescence Techniques, Anal. Chem. Acta 125, 13-19. Vo-Dinh, T. (1983) Surface Detection of Contamination: Principles, Applications and Recent Developments, Journal of Environmental Sciences Jan/Feb 1983, 40-43.

1856 Vo-Dinh, T.; Miller, G.; Pal, A.; Watts, W.; Eastwood, D.; Lidberg, R. (1991) Rapid Screening Technique for Polychlorinated Biphenyls (PCBs) using Room Temperature Phosphorescence, Second International Symposium Field Screening Methods for Hazardous Wastes and Toxic Chemicals, Las Vegas, NV, Symposium Proceedings, 819-822. Vo-Dinh, T; Gammage, R.B.; Hawthorne, A.R; Thorngate, J.H. (1979) Recent Advances in Synchronous Luminescence Spectroscopy for Trace Organic Analysis, National Bureau of Standards Special Publication 519, 679-684. Vo-Dinh, T.; White, D.A. (1986) Sensitized Fluorescence Spectrometry Using Solid Organic Substrate, Anal. Chem. 58, 1128-1133. Vo-Dinh, T. ;Alak, A (1987) Enhanced Room-Temperature Phosphorescence of Anthracene on Cyclodextrin-Treated Filter Paper, Applied Spectroscopy 41,963-966. Walt, D.R. (1993) Continuous Monitoring of Groundwater Using Fiber Optic Chemical Sensors, Draft Manuscript. Warner, I.M.; Patanonay, G.; Thomas, M. P. (1985) Multidimensional Luminescence Measurements, Anal. Chem. 57, 463A-474A. Watts, W.; Pal, A.; Ford, L. Miller, G.; Vo-Dinh, T.; Eastwood, D.; Lidberg, R. (1992) Improved Methods for Screening of Polychlorinated Biphenyls (PCBs) Using Room-Temperature Phosphorescence, Applied Spectroscopy 46, 1235-1239. Weijun, J.; Changsong, L. (1993) Luminescence Rule of Polycyclic Aromatic Hydrocarbons in Micelle-Stabilized Room-Temperature Phosphorescence, Anal. Chem. 65, 863-865. Weinberger, R.; Cline Love, L. (1984) Luminescence Properties of Polycyclic Aromatic Hydrocarbons in Colloidal or Microcrystalline Suspensions, Spectrochemica Acta 40A, 49-55. Werner, T.C.;Cummings, J.G.; Seitz, W.R. (1989) General Approach to the Development of Luminescent Cation Detectors, Anal. Chem. 61, 211-215. Wimmer,H.; Kim, J.I.; Klenz, R. (1992) A Direct Speciation of Cm(IlI) in Natural Aquatic Systems by Time-Resolved Laser-Induced Fluorescence Spectroscopy (TRLFS), Radiochimica Acta, 165-170. Wittenberg, M.;Jarosz, J; Paturel, L.; Vial, M.; Martin-Botlyer, M.; (1985) Analyse des Hydrocarbures Aromatiques Polynuclearires dansd l'Environnement par Spectrofluoreimetirie Shpol'skii a 10 K: Methods de Prelevelment et Extraction des Echantillons, Resultants Quantitatifs, Analusis 13,249-260. Yang, Y.; D'Silva,A.; Fassel, V. (1981) Deuterated Analogues as Internal Reference Compounds for the Direct Determination of Benzo(a)pyrene and Perylene in Liquid Fuels by Laser-Excited Shpol'skii Spectrometry, Anal. Chem. 53, 2107-2109.

1857 Yang, Y.;D'Silva, A.; Fassel, V. (1981) Laser-Excited Shpol'skii Spectroscopy for the Selective Excitation and Determination of Polynuclear Aromatic Hydrocarbons, Anal. Chem. 53,894-899. Yao, W.; He, W.; Hu, X.; Cao, X. (1993) Rapid Determination of the Isomers of Polycyclic Aromatic Hydrocarbons With Three Dimensional Fluorescence Spectrum, J. Molecular Structure 294, 279-282. Zhu, G.; Si, Z.;Yang, J.; Ding, J. (1990) Simultaneous Spectrofluorimetric Determination of Terbium, Samarium, and Europium with Hexafluoracetylacetone-Trococtylphosphine Oxide and Triton X-100, Analytica Chimica Acta 231, 157-159. NOTICE The U.S. Environmental Protection Agency (EPA), through its Office of Research and Development (ORD), partially funded and collaborated in the research described here. It has been subjected to the Agency's peer review and has been approved as an EPA publication. The U.S. Government has a non-exclusive, royalty-free license in and to any copyright covering this article.