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Screening analysis of volatile organic contaminants in commercial inorganic coagulants used for drinking water treatment
Journal of Environmental Management 91 (2009) 142–148
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Screening analysis of volatile organic contaminants in commercial inorganic coagulants used for drinking water treatment Michael Petri a, Jia-Qian Jiang b, *, Matthias Maier b a b
¨ berlingen, Germany ¨ ßenmu ¨ hle 1, D-88662 U Zweckverband Bodensee-Wasserversorgung, Betriebs- und Forschungslabor, Su Faculty of Engineering and Physical Science (C5), University of Surrey, Guildford, Surrey GU2 7XH, UK
a r t i c l e i n f o
a b s t r a c t
Article history: Received 30 December 2008 Received in revised form 15 July 2009 Accepted 28 July 2009 Available online 31 August 2009
A method for quality screening is suggested to detect volatile impurities in inorganic coagulants that are used for drinking water treatment. Static headspace gas chromatography with mass spectrometry detection (HS–GCMS) is sensitive and selective to detect volatiles in low concentrations. This study has discovered that volatile organic impurities are detectable in ferric and aluminium-based coagulants which are used for drinking water treatment. For ferric chloride, 2-propanol was detected at a level of 17–24 mg ml1, acetone at 0.7–1.7 mg ml1, 1,1,1-trichloroacetone at 0.02–0.04 mg ml1, trichloromethane at 0.01–0.02 mg ml1 and toluene at 0.01–0.12 mg ml1. For ferric chloride sulfate, acetone was detected at a level of 0.12 mg ml1, 1,1,1-trichloroacetone at 0.06–0.08 mg ml1, trichloromethane at 0.13–0.23 mg ml1, bromodichloromethane at 0.04–0.06 mg ml1 and dibromochloromethane at 0.04–0.05 mg ml1. For aluminium hydroxide chloride, only trichloromethane was detectable, but below the method detection limits (MDL). Although the concentrations of these impurities in commercial coagulants are low, this observation is important and should have impact on water industries for them to pay attention to the chemicals they are using for drinking water production. Ó 2009 Elsevier Ltd. All rights reserved.
Keywords: Coagulation Coagulants Drinking water treatment Mass spectrometry Static headspace gas chromatography Volatile organic contaminants
1. Introduction Although a potential for natural, accidental or intentional contamination of raw water sources and drinking water has always existed, the effort for developing and implementing contamination warning systems (CWSs) for drinking water security has been intensified significantly by homeland security after the attack on the 11th of September, 2001. Several publications reviewed the progress in developing CWS for source and drinking water (Gullick et al., 2003; Hasan et al., 2004; States et al., 2004; USEPA, 2005) and described the state-of-art technologies for detection of chemical, microbiological and radiochemical contaminations. Recent research projects on CWSs are mainly focused on detection of intentional contamination with hazardous compounds like biological or chemical warfare agents and radiological compounds in raw and drinking water that produce adverse health effects or poisoning after an acute exposure. Although warfare agents are extremely toxic and have to have high priority in development of a CWS other drinking water pollutants should also be taken into account such as intentional and non-intentional contamination with easy-to-get
* Corresponding author. Tel.: þ44 1483 686609; fax: þ44 1483 450984. E-mail address: [email protected] (J.-Q. Jiang). 0301-4797/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.jenvman.2009.07.015
chemicals for household, gardening, cleaning, construction and painting. Even if most of these industrial and common household chemicals have a much lower toxicity than warfare agents, any pollution of raw or drinking water is a possible threat to the public health and endangers the confidence in the water supply. An effective CWS consider all aspects of possible contamination paths in the drinking water supply. Therefore it should include not only physical protection of treatment plants and distribution systems but also repeated monitoring of raw water and drinking water and used treatment chemicals. Coagulation is a process commonly used in drinking water treatment to remove colour, natural organic matter, turbidity and other soluble organic and inorganic compounds from the raw water. In the process small particles and colloids are agglomerated to larger particles which can be removed by a subsequent clarification process, whereas natural organic matter and soluble compounds are removed by adsorption onto the surface of the flocs and then separated from water (Jiang, 2001). Common inorganic coagulants that are used in large amounts in drinking water treatment are aluminium sulfate, ferric sulfate or ferric chloride. Coagulants could be possible contamination sources in drinking water treatment because the coagulants are normally controlled by the manufacturer only on the basis of product specifications and standardized monitoring programs for selected metals such as As,
M. Petri et al. / Journal of Environmental Management 91 (2009) 142–148
Cd, Cr, Hg, Ni, Pb, Sb and Se or adsorbable organic halogen (AOX) (CEN, 2004a–h). Other monitoring programs to control the amount of organic compounds in coagulants are not standardized or common. But it is necessary to detect intentional or unintentional contamination caused by production, storage and transportation. The aim of the present study was to develop a rapid and reliable screening method for the surveillance of solvents and volatiles in coagulants after transport to the water treatment plant and before usage in the treatment process. Rapid screening methods are assessed as to be more qualitative than quantitative but they can provide a binary yes/no-response to indicate that an analyte is detectable in the sample or not (Valca´rcel et al., 1999). When the concentration of an analyte in the sample is above a defined threshold, a conventional quantification procedure should be triggered for confirmation and accurate quantification. Static headspace gas chromatography with mass spectrometry detection (HS–GCMS) is an appropriate method for a screening analysis of volatile compounds. HS–GCMS is sensitive and selective enough to detect volatiles in low concentrations and has a high degree of automation for practical routine analysis (Kolb and Ettre, 2006). With a mass spectrometer as a detector, the identification of unknown compounds is possible and false-positive misidentification can be reduced. The results demonstrate that the static HS–GCMS method is applicable for a rapid and accurate qualitative and quantitative screening approach to detect volatile organic contaminants in coagulants used in drinking water treatment. 2. Materials and methods 2.1. Chemicals To set up the screening method, a set of 45 volatile organic compounds were chosen as targeted chemicals which could be present in the coagulants used for the drinking water treatment. A gasoline organic stock solution and 1,1,1-trichloroacetone (EPA GRO-Mix in methanol) were purchased from Supelco (Steinheim, Germany). Stock solutions of acetate (8260B acetate Mix in methanol), ketones (VOA calibration mix #1 in methanol:water (90:10)), halocarbon (VOA purgeable halocarbon mix #1 in methanol) and oxygenate (oxygenates in methanol) were purchased from Restek (Bad Homburg, Germany). Stock solutions of trihalomethane mixture (THM-511 in methanol) and carbon tetrachloride (HC-040 in methanol) were purchased from Ultra Scientific (North Kingstown, USA). Acetone and 2-propanol for organic residue analysis were provided by Mallinckrodt J.T. Baker (Griesheim, Germany) and methanol in P&T-quality was from LGC-Promochem (Wesel, Germany). Ferric chloride hexahydrate in analytical quality was from Fluka (Steinheim, Germany) and hydrochloric acid 30% suprapur was from Merck (Darmstadt, Germany). Ultra-pure water was made with Milipore Elix-3 and Milli-Q Gradient A10 (Molsheim, Germany). 2.2. Ferric and aluminium-based coagulants Various types of ferric and aluminium coagulants were used for the screening analysis. All of them were in liquid and commercially available in Germany. They were ferric chloride (with 14% Fe, pH < 1, density at 20 C, 1.43 g ml1), aluminium hydroxide chloride (with 12% Al, pH 3.8, density at 20 C, 1.34 g ml1), aluminium sulfate (with 4.3% Al, pH 2.5, density at 20 C, 1.3 g ml1), aluminium hydroxide chloride sulfate (with 5.6% Al, pH 2.2, density at 20 C, 1.20 g ml1) and sodium aluminate (with 10% Al, pH 14, density at 20 C, 1.5 g ml1). Ferric chloride and all aluminium coagulants were purchased from BK Giluini GmbH (Ludwigshafen, Germany). Ferric chloride sulfate (with 12% Fe, pH < 1, density at
143
20 C, 1.52 g ml1) was purchased from Kronos ecochem (Leverkusen, Germany). The used coagulants were allowed to use in drinking water treatment according to the German Drinking Water Directive (TrinkwV, 2001; UBA, 2009) and the standardized product specifications (CEN, 2004a–h). For matrix simulation a ferric chloride solution was prepared and used for calibration. 150 g of iron ferric chloride hexahydrate were dissolved in 30 ml 30% hydrochloric acid and 70 ml ultra-pure water. The solution has a density of 1.38 g ml1 and an iron concentration of 166 mg ml1 solution. In every analytical sequence a sample of the ferric chloride solution was analysed as a blank sample to make sure, that no target analytes or non-target compounds were detectable.
2.3. Preparation of standards and samples For overview screening, a standard solution of 45 analytes listed in Table 1 was made from the stock solution mixtures and diluted to a concentration between 5 and 15 mg ml1 with methanol depending on the concentration in the purchased stock solution mixtures. The calibration standard for overview screening was
Table 1 Retention time and qualifier-ion from SIR or extracted from TIC for overview screening of volatile compounds in aqueous samples. Peak no Name
CAS no
RT [min] Qualifier-ion
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45
67-64-1 75-35-4 107-83-5 75-09-2 1634-04-4 156-60-5 108-20-3 75-34-3 637-92-3 78-93-3 141-78-6 67-66-3 71-55-6 540-84-1 56-23-5 142-82-5 994-05-8 108-21-4 71-43-2 107-06-2 79-01-6 919-94-8 78-87-5 109-60-4 75-27-4 110-75-8 108-10-1 10061-01-5 108-88-3 10061-02-6 79-00-5 591-78-6 127-18-4 123-86-4 124-48-1 108-90-7 100-41-4 108-38-3 95-47-6 628-63-7 75-25-2 95-63-6 541-73-1 106-46-7 95-50-1
6.36 6.48 7.24 7.99 8.56 8.95 10.30 10.70 12.10 12.90 13.68 14.00 15.66 15.7 16.70 17.10 17.15 17.30 17.60 17.70 20.37 20.67 21.29 22.01 22.39 24.17 24.40 25.08 26.04 27.58 28.25 28.58 29.41 29.82 30.56 33.55 33.89 34.28 36.41 36.89 38.28 43.90 45.98 46.52 48.00
Acetone 1,1-Dichloroethylene 2-Methylpentane Methylene chloride Methyl tert-butyl ether (MTBE) Trans-1,2-dichloroethylene Diisopropyl ether (DIPE) 1,1-Dichloroethane Ethyl tert-butyl ether (ETBE) 2-Butanone (MEK) Ethyl acetate Trichloromethane 1,1,1-Trichloroethane 2,2,4-Trimethylpentane Carbon tetrachloride n-Heptane tert-Amyl methyl ether (TAME) Isopropyl acetate Benzene 1,2-Dichloroethane Trichlorethylene tert-Amyl ethyl ether (TAEE) 1,2-Dichloropropane Propyl acetate Bromodichloromethane 2-Chloroethyl vinyl ether 2-Methyl-2-pentanone (MIBK) cis-1,3-Dichloropropylene Toluene trans-1,3-Dichloropopylene 1,1,2-Trichloroethane 2-Hexanone Tetrachloroethene Butyl acetate Dibromochloromethane Chlorobenzene Ethylbenzene m-Xylene o-Xylene n-Amyl acetate Tribromomethane 1,2,4-Trimethylbenzene 1,4-Dichlorobenzene 1,3-Dichlorobenzene 1,2-Dichlorobenzene
43 (SIR) 61 43 (SIR) 49 73 (SIR) 61 45 63 59 (SIR) 43 (SIR) 43 (SIR) 83 (SIR) 97 43 (SIR) 117 43 (SIR) 43 (SIR) 43 (SIR) 78 (SIR) 62 (SIR) 130 43 (SIR) 63 43 (SIR) 83 (SIR) 43 (SIR) 43 (SIR) 75 91 75 97 43 (SIR) 129 (SIR) 43 (SIR) 129 (SIR) 112 106 91 91 43 (SIR) 173 (SIR) 105 146 146 146
144
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prepared in 10 ml ultra-pure water in a headspace vial by injecting 20 ml of the standard solution under the surface of 10 ml ultra-pure water. For quantification of identified volatiles in coagulants a second calibration stock solution was made in methanol with neat compounds and stock solution mixtures. The calibration stock solution contained 2-propanol (3.9 mg ml1), acetone (0.25 mg ml1), 1,1,1-trichloroacetone (0.020 mg ml1), trichloromethane (0.004 mg ml1), bromodichloromethane (0.004 mg ml1), dibromochloromethane (0.004 mg ml1), tribromomethane (0.004 mg ml1), carbon tetrachloride (0.002 mg ml1), benzene (0.002 mg ml1), toluene (0.006 mg ml1), ethylbenzene (0.004 mg ml1), m-xylene (0.004 mg ml1), o-xylene (0.004 mg ml1) and 1,2,4-trimethylbenzene (0.004 mg ml1). The calibration curves were used to quantify the concentration of the compounds in coagulants. The calibration standards for quantification were prepared in 5 ml ferric chloride solution for matrix simulation and diluted to 10 ml with ultrapure water in the headspace vials before injecting 2.5, 5.0, 10, 15 and 20 ml of the calibration stock solution under the surface of the solution. The calibration range of each compound is given in Table 2. For analysing the coagulants 5 ml or an aliquot of the coagulant was placed in a 20 ml head-space vial and diluted to 10 ml with ultra-pure water. The vial was closed with a PTFE-coated silicon septum and aluminium crimp cap.
2.4. Static headspace gas chromatograph–mass spectrometry method Blanks, calibration standards for overview screening and for quantification and samples were analysed with the same static HS– GCMS method. The analysis was performed with a TurboMatrix 40 headspace sampler coupled to an AutosystemXL gas chromatograph (Perkin–Elmer, Rodgau-Ju¨gesheim, Germany). The samples were heated at 80 C for 30 min and shaken constantly. After thermostatting the headspace needle (thermostatted to 90 C) was inserted into the headspace of the sample vial. The vial was pressurerised to 131 kPa within 2 min (balanced-pressure system (Kolb, 1999)). The sample was injected to the GC with a sampling time of 0.12 min (injection volume was 9.1 ml) and transferred to the GC through a transfer line at 130 C. Helium (99.9995%, Linde, Stuttgart, Germany) was used as a transfer and carrier gas with a column head pressure of 131 kPa. The gas chromatographic separation was performed with a VOCOL capillary column (60 m 0.32 mm 1.8 mm, Supelco, Steinheim, Germany). The column oven temperature program was: initial temperature of 35 C, initial time 10 min, increased at a rate of 3 C min1 to 120 C, hold for 5 min, increased at 10 C min1 to 200 C and hold for 10 min. The total chromatographic run time
was 61.33 min. The column head pressure was 145 kPa with a velocity of 100 cm s1. The capillary column was coupled to the mass spectrometer directly into the ion source and heated to 180 C in the transfer section. The mass spectrometer was a single quadrupole (TurboMass, Perkin–Elmer, Rodgau-Ju¨gesheim, Germany). It was operated by electron impact ionisation with a voltage of 70 eV. The temperature of the ion source was 180 C. After a solvent delay of 3 min, the analyses were performed in full scan mode (TIC) and in single ion recording mode (SIR) simultaneously. The full scan mode was used for identification and confirmation of detected compounds in the samples. The m/z range was 41–200 Da, with a scan time of 0.50 s. The compounds were identified by comparison of the experimental mass spectra with a mass spectra library (NIST/EPA/NIH Mass Spectral Library, version 2.0d). To enhance the detection limit for quantification nine single ion recording groups were additionally used, each acquired with 0.100 ms for inter channel delay and a span of 0.70 Da. The first SIR function was from 5.0 to 40.0 min and formed by the characteristic ion m/z 43 for C2H3Oþ in methyl ethers, acetates, methyl-ketones and C2Hþ 7 from hydrocarbons. The second SIR function (5.0–9.0 min) contained the ion m/z 45 for 2-propanol. The third SIM function (8.0–10.0 min) contained the ion m/z 73 for methyl tert-butyl-ether (MTBE) and the fourth (11.0–13.0 min) contained the ion m/z 59 for ethyl tert-butyl-ether (ETBE). The fifth SIR function (13.0–16.0 min) was made with the ion m/z 83 for trichloromethane, the sixth SIR function (16.0–19.0 min) with the ions m/z 62 for 1,2-dichloroethane and m/z 78 for benzene, the seventh SIR function (21.0–24.0 min) with the ion m/z 83 for bromodichloromethane, the eighth SIR function (28.0–31.0 min) with ion m/z 129 for dibromochloromethane. The last SIR function (37.0–40.0 min) contained the ion m/z 173 for tribromomethane. 2.5. Calibration curves and method detection limit Calibration curves for quantification were calculated from peak areas by using the quantifier ion of specified SIR or were extracted from the TIC. Since the 5-point calibration for quantification was not linear in the lower working range quadratic calibration curves were used for quantification. The method detection limits (MDLs) of the quantified compounds given in Table 2 were defined according to the ‘‘Definition and Procedure for the Determination of the Method Detection Limit’’ from the USEPA (2007) with seven replicates in diluted ferric chloride solution for matrix simulation containing the lowest calibration standard level. The MDL was calculated by multiplying the sample standard deviation of the replicates in the final method reporting units with the Student’s t value appropriate for a 99% confidence level and with n 1 degrees of freedom. 3. Results and discussion
Table 2 Calibration range and MDLs for quantification of detected compounds in iron coagulants in order of retention time. Peak no Name
CAS no
MDL RT Calibration [min] range [mg ml1] [mg ml1]
46 1 12 15 19 25 29 35 47 37 41
67-63-0 67-64-1 67-66-3 56-23-5 71-43-2 75-27-4 108-88-3 124-48-1 918-00-3 100-41-4 75-25-2
5.87 6.36 14.00 16.70 17.60 22.39 26.04 30.56 33.41 33.89 38.28
2-Propanol Acetone Trichloromethane Carbon tetrachloride Benzene Bromodichloromethane Toluene Dibromochloromethane 1,1,1-Trichloroacetone Ethylbenzene Tribromomethane
1.96–15.7 0.13–1.01 0.02–0.16 0.01–0.08 0.01–0.08 0.02–0.16 0.03–0.24 0.02–0.16 0.01–0.08 0.02–0.08 0.02–0.16
0.50 0.05 0.01 0.008 0.005 0.01 0.02 0.02 0.005 0.02 0.02
3.1. Calibration for overview screening Static HS–GCMS allows the determination of 45 different volatiles in aqueous samples such as halogenated hydrocarbons, trihalomethanes, ketones, acetic esters, fuel ether oxygenates and monoarometic compounds in gasoline like benzene and its monomethyl-, dimethyl-, trimethyl- and monoethyl-derivates. Under the described conditions, m-xylene and p-xylene were coeluted completely and cannot be quantified separately, so that p-xylene was quantified and expressed in terms of m-xylene. Fig. 1 shows a total ion chromatogram (TIC) in which 45 analytes (assigned in Table 1) were spiked into a water sample in a concentration range from 0.01 mg ml1 to 0.03 mg ml1. To improve the detection power for several analytes, a single ion recording (SIR) was used, which
M. Petri et al. / Journal of Environmental Management 91 (2009) 142–148 700
1: Scan EI+ TIC 5.87e6
29
100
145
38
3 13,14
21
39 33
%
37 1,2
6 4
12 7 8
5
16,17 18,19
11
22 23
9
43
44
45
25
24
10
42
36
15
20
28
30
26,27
31 32 34
40 35
41
12
Time
6.50
11.50
16.50
21.50
26.50
31.50
36.50
41.50
46.50
Fig. 1. Total ion chromatogram of calibration standard for overview screening with 45 volatiles in a concentration level at 0.010 mg ml1 to 0.030 mg ml1. For peak identification see Table 1.
can be run simultaneously with the full scan mode. Therefore a simultaneous acquisition of TIC and SIR increases the certainty in compound detection and decreases the uncertainty in compound identification and misinterpretation. For the SIR, the recorded ion masses (m/z) should be specific for a functional group like m/z 43 for ethers, esters, ketones and hydrocarbons, or for one compound, like m/z 78 for benzene. The described screening procedure for volatiles with static HS–GCMS provides a reliable binary yes/noresponse to indicate if a target analyte is detectable in the sample or not (Valca´rcel et al., 1999). Therefore the calibration routine for an overview screening procedure can be minimized to a simple twopoint calibration with a blank and one standard. The simplified calibration can be used as system check and for a rough estimation of the amount of a detected target analyte. This simplified overview screening approach increases the sample throughput and provides a rapid response for immediate decision making. In a case of a contamination, the static HS–GCMS method can rapidly screen samples of raw water, treated drinking water and incoming or used treatment chemicals. 3.2. Ether cleavage, hydrolysis and saponification of esters in coagulants In samples with a neutral pH all 45 volatiles (see Table 1) can be determined with static HS–GCMS when the samples were heated for 30 min at 80 C before headspace injection. Liquid ferric and aluminium coagulants have a pH that is near or below 2. Sodium ´ Reilly et al. (2001) and Lin et al. (2003) aluminate has a pH of 14. O showed that fuel ether oxygenates such as MTBE, ETBE and TAME hydrolyze at pH near 2 during sample heating at 80 C. When the analytes were spiked in a ferric chloride solution for matrix simulation, the fuel ether oxygenates, acetic esters and xylenes were observed to be hydrolyzed. A cleavage of ethers under acidic conditions causes the instability of ethers and is forced with heating (McMurry, 1992). The acetic acid esters were also hydrolyzed in solutions with hydrochloric acid, because the esterification of a carboxylic acid with an alcohol is a reversible reaction and catalyzed by strong acids (McMurry, 1992). When the volatiles listed in Table 1 were spiked in an alkaline sodium aluminate solution only the acetic esters were hydrolyzed by saponification
with hydroxide ion. The fuel ether oxygenates remained stable in strong alkaline solutions. The breakdown of m- and o-xylene in iron coagulants has not been eludicated yet, since the monoaromatic compounds are normally stable in aqueous acids. An influence of ferric ions seems to be rather probable and should be investigated more in detail. 3.3. Volatiles in coagulants For ferric chloride the following target analytes were detected, acetone (1), trichloromethane (12), toluene (29), ethylbenzene (37) (see Fig. 2). For ferric chloride sulfate the following were detected, acetone (1), trichloromethane (12), bromodichloromethane (25) and dibromochloromethane (35) (see Fig. 3). The identification of these compounds was confirmed by comparison of the experimental mass spectra with the NIST/EPA/NIH mass spectra library. Non-target compounds were detected with retention time of 5.87 min (TIC, SIR m/z 43 and 45) and 33.42 min (TIC, SIR m/z 43) in ferric chloride and with a retention time of 25,74 min (TIC, SIR m/z 43, see Fig. 4) and 33.43 min (TIC, SIR m/z 43) in ferric chloride sulfate. Two of unknown compounds in ferric chloride could be identified as 2-propanol (retention time 5.87 min, assigned peak number 46) and 1,1,1-trichloroacetone (retention time 33.42, assigned peak number 47) by analysing reference compounds that were suggested by the mass spectra library. One unknown compound detected in ferric chloride sulfate with a retention time of 25.74 min (mass spectra see Fig. 4) has not been identified yet. The mass spectra of the unknown compound (Fig. 4) show an insignificant fragmentation and are not very informative for an unambiguous interpretation. The base peak m/z 43 can be formed by C2H3Oþ from methyl ethers, acetates, methyl-ketones or by C2Hþ 7 from hydrocarbons. The small peaks at m/z 77 and 105 could be an indication for aromatic structures in the compound but their intensities are too low for regarding them as a significant indication. The elucidation of this unknown impurity detectable in ferric chloride sulfate is challenging, due to the insufficient information available from the mass spectra. After the identification and confirmation, a stock standard solution was made for an accurate calibration and quantification. Table 2 shows the calibration range, based on the potential
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755 100
46
1: Scan EI+ TIC 1.44e7
12
%
SIR No. 6 m/z 83 1 29
47 37
0
Time 6.51
11.51
16.51
21.51
26.51
31.51
36.51
41.51
46.51
Fig. 2. Determination of volatiles in ferric chloride. TIC and SIR (SIR No 6: m/z 83) from a 5 ml sample with two non-target analytes, that could be identified as 2-propanol (46) and 1,1,1-trichloracetone (peak 47).
acetone at 0.7–1.7 mg ml1, 1,1,1-trichloroacetone at 0.02– 0.04 mg ml1, trichloromethane at 0.01–0.02 mg ml1 and toluene at 0.01–0.12 mg ml1. In samples of ferric chloride sulfate, acetone was detected at a level of 0.12 mg ml1, 1,1,1-trichloroacetone at 0.06– 0.08 mg ml1, trichloromethane at 0.13–0.23 mg ml1, bromodichloromethane at 0.04–0.06 mg ml1 and dibromochloromethane at 0.04–0.05 mg ml1. In aluminium coagulants, trichloromethane was detected in aluminium hydroxide chloride only but below the MDL. The detection of halogenated volatile organic compounds in ferric coagulants can be explained by the production process. Dissolved ferrous chloride or ferrous sulfate is normally treated with chlorine gas to be oxidized to the corresponding ferric chloride or ferric chloride sulfate. The used raw materials are of technical quality, so that possible organic contaminations are oxidized and chlorinated by chlorine gas. The 2-propanol that
concentration of the target compounds in the coagulant, and the MDLs of each detected compound. For matrix simulation, the calibration standards were made in a ferric chloride solution. This was necessary to adjust the matrix of the calibration standard to the coagulant sample, so that the influence of the matrix during static headspace extraction is minimized (Kolb and Ettre, 2006). In addition, Koch and Vo¨lker (1996) described that halogenated acetones can only be analysed when the sample is acidified, or they will decompose to acetic acid and their corresponding halogenated methanes. Therefore, 1,1,1-trichloroacetone can only be analysed in samples with a pH < 2 but not in aqueous samples like raw or drinking water or in alkali coagulants such as sodium aluminate without pH-adjustment. Table 3 shows the results of volatile contaminations in commercial iron and aluminium coagulants. In the ferric chloride coagulant, 2-propanol was detected at a level of 17–24 mg ml1,
759
25
100
1: Scan EI+ TIC 7.14e6
35
SIR No. 8 m/z 83 SIR No. 9 m/z 129 %
12
unknown
47
0
Time 6.51
11.51
16.51
21.51
26.51
31.51
36.51
41.51
46.51
Fig. 3. Determination of volatiles in ferric chloride sulfate. TIC and SIR (SIR No 8: m/z 83 and SIR No 9: m/z 129) from a 5 ml sample with two non-target analytes. One of them could be identified as 1,1,1-trichloroacetone (peak 47). The second compound with a retention time of 25.74 min (mass spectra see Fig. 4) has not been identified yet.
M. Petri et al. / Journal of Environmental Management 91 (2009) 142–148
147
759 1525 (25.743) 100
1: Scan EI+ 4.77e5
43
%
42 44
0 40
53
61 64
79 86 90 97 72 77
60
80
105 112
100
122
120
126
141
152
140
156 163
160
176 183
188
180
197
200
m/z
Fig. 4. Mass spectra of an unknown compound in ferric chloride sulfate coagulant with a retention time of 25.74 min (chromatogram see Fig. 3). The largest m/z- peaks are 43 (100.0% BPI (base peak intensity)), m/z: 42 (12.5% BPI), m/z: 105 (6.4% BPI), m/z: 61 (3.2% BPI), m/z: 62 (2.7% BPI) and m/z 77 (2.5% BPI).
was detected in ferric chloride is probably oxidized to acetone, which is subsequently chlorinated to 1,1,1-trichloroacetone. The formation of trihalomethane can be explained with the haloform reaction of halogenated methyl-ketones groups in various organic compounds. Including bromide in the ferrous solution leads to the mixture of chlorine and bromine containing trihalomethanes since bromide is oxidized by chlorine to bromine. The detection of toluene and ethylbenzene in ferric chloride cannot been explained. Because there are no chlorinated monoaromatic compounds detectable in ferric chloride, a contamination during storage and/or transportation of the coagulant is probable. 3.4. The VOC’s concentration level in the coagulated water The concentration levels of the detected VOC contaminants in the analysed ferric coagulants are very low so that there will be no harmful effect on the quality of drinking water. For drinking water treatment the maximum addition of coagulants is regulated in Germany by the Drinking Water Directive (TrinkwV, 2001). The
Federal Environment Agency is responsible for having a record of all coagulants currently permitted for drinking water treatment and their maximum addition. This record is supplemented and published regularly by the Federal Office. For ferric chloride the maximum addition is 12 mg iron per litre water and for ferric chloride sulfate the maximum addition is 6 mg iron per litre water (UBA, 2009). The detected volatiles, 2-propanol, acetone, 1,1,1-trichloracetone and toluene, are not regulated by the Drinking Water Directive (TrinkwV, 2001). In the treated drinking water, 2-propanol and acetone can react with chlorine to halogenated disinfection by-products. 2-Propanol and acetone can easily be removed by rapid or slow sand filtration. The detectable trihalomethanes are regulated and must not exceed a sum concentration of 50 mg l1 after treatment and disinfection (TrinkwV, 2001). For a maximum addition of ferric coagulant the possible sum concentrations of trihalomethanes is 1.2 mg l1 for ferric chloride and 11.2 mg l1 for ferric chloride sulfate which do not exceed the regulated trihalomethanes sum concentration of 50 mg l1 in Germany or the guideline values from WHO for drinking water (WHO, 2008) (see Table 3).
Table 3 Amount of volatiles in the commercially available ferric and aluminium coagulants. Inorganic coagulant
Peak no
Analyte
Concentration in coagulants [mg ml1]
Possible concentration for the maximum addition of coagulanta [mg l1]a
Ferric chloride
46 1 12 47 29 37
2-Propanol Acetone Trichloromethane 1,1,1-Trichloracetone Toluene Ethylbenzene
17–24 0.7–1.7 <0.01–0.02 0.02–0.04 <0.02–0.12 <0.02
1440 102 1.2 2.4 7.2
Ferric chloride sulfate
1 12 25 35 47
Acetone Trichloromethane Bromodichloromethane Dibromochloromethane 1,1,1-Trichloroacetone
0.12 0.13–0.23 0.04–0.06 0.04–0.05 0.06–0.08
Aluminium hydroxide chloride
12
Trichloromethane
<0.01
Aluminium sulfate
No volatiles detected
Aluminium hydroxide chloride sulfate
No volatiles detected
Sodium aluminate
No volatiles detected
a
3.9 7.6 2.0 1.6 2.6
The calculated concentration of volatiles in water after addition of the maximum amount of coagulant is listed in the Federal Environment Agency. For ferric chloride the permitted maximum addition is 12 mg iron per litre water. For ferric chloride sulfate the permitted maximum addition is 6 mg iron per litre water (UBA, 2009).
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4. Conclusion The described static HS–GCMS method has been successfully applied in screening for volatile organic compounds in coagulants. A simplified overview screening approach with a 2-point calibration increases the sample throughput and provides a rapid binary yes/no-response for immediate decision making. In the case of a suspected contamination, the static HS–GCMS method can be used to rapidly screening of raw water, different treatment steps, treated drinking water and incoming or used treatment chemicals. Several volatiles such as trichloromethane, bromodichloromethane, dibromochloromethane and 1,1,1-trichloroacetone were detected in sub-mg ml1 range in ferric chloride and ferric chloride sulfate, which are produced by oxidation of ferrous chloride or ferrous sulfate with chlorine. In ferric chloride, 2-propanol and traces of toluene and ethylbenzene were detected, too. Volatile organic contaminations were not detected or their concentrations were below the MDL in aluminium coagulants. Ethers and acetates cannot be analysed in acidic coagulants because they decompose by hydrolysis just as acetates in alkali coagulants. This work shows clear differences in the pattern of volatile contaminations in commercially iron and aluminium-based coagulants depending on the used raw materials and production process. The study reported in this paper has discovered volatile organic contamination in ferric and aluminium-based coagulants which are used for drinking water treatment. Although the concentration of the detected volatile compounds in aluminium and iron coagulants are very low, a more intensive surveillance and monitoring of coagulants should be conducted by the coagulant manufacturer and waterworks especially when using them for drinking water treatment. Further investigations for semiand non-volatile organic contaminations in coagulants should be carried out. For incoming treatment chemicals, a routine screening procedure should be implemented to detect potential intended or non-intended chemical contaminations.
References CEN, 2004a. Chemicals Used for Treatment of Water Intended for Human Consumption – Aluminium Sulfate. European Committee for Standardization, Brussel. EN 878. CEN, 2004b. Chemicals Used for Treatment of Water Intended for Human Consumption – Aluminium Chloride, Aluminium Chloride Hydroxide and Aluminium Chloride Hydroxide Sulfate (Monomeric). European Committee for Standardization, Brussel. EN 881. CEN, 2004c. Chemicals Used for Treatment of Water Intended for Human Consumption – Sodium Aluminate. European Committee for Standardization, Brussel. EN 882.
CEN, 2004d. Chemicals Used for Treatment of Water Intended for Human Consumption – Polyaluminium Chloride Hydroxide and Polyaluminium Chloride Hydroxide Sulfate. European Committee for Standardization, Brussel. EN 883. CEN, 2004e. Chemicals Used for Treatment of Water Intended for Human Consumption – Iron(III) Chloride. European Committee for Standardization, Brussel. EN 888. CEN, 2004f. Chemicals Used for Treatment of Water Intended for Human Consumption – Iron(II)Sulfate. European Committee for Standardization, Brussel. EN 889. CEN, 2004g. Chemicals Used for Treatment of Water Intended for Human Consumption – Iron(III)Sulfate Liquid. European Committee for Standardization, Brussel. EN 890. CEN, 2004h. Chemicals Used for Treatment of Water Intended for Human Consumption – Iron(II)Chloride Sulfate. European Committee for Standardization, Brussel. EN 891. Gullick, R.W., Grayman, W.M., Deininger, R.A., Males, R.M., 2003. Design of early warning systems for source waters. Journal of the American Water Works Association 95 (11), 58–72. Hasan, J., States, S., Deininger, R., 2004. Safeguarding the security of public water supplies using early warning systems: a brief review. Journal of Contemporary Water Research and Education 129, 27–33. Jiang, J.Q., 2001. Development of coagulation theory and pre-polymerized coagulants for water treatment. Separation & Purification Methods 30 (1), 127–141. Koch, J., Vo¨lker, P., 1996. Zur Bildung von Artefakten und deren Vermeidung bei der Bestimmung leichtflu¨chtiger Halogenkohlenwasserstoffen in Wasser mittels Headspace-Gaschromatographie unter den Bedingungen der DIN 38407 (DEV¨ berho¨hte Trihalogenmethanbefunde in gechlortem SchwimmF5). Teil II: U badbeckenwasser. Acta hydrochimica et hydrobiologica 24, 179–184. Kolb, B., 1999. Headspace sampling with capillary column. Journal of Chromatography A 842, 163–205. Kolb, B., Ettre, L.S., 2006. Static Headspace-Gas Chromatography: Theory and Practice, second ed. Wiley-Interscience, Hoboken. Lin, Z., Wilson, J.T., Fine, D.F., 2003. Avoiding hydrolysis of fuel ether oxygenates during headspace analysis. Environmental Science and Technology 37, 4994–5000. McMurry, J., 1992. Organic Chemistry, third ed. Brooks/Cole Publishing Company, Pacific Grove. ´ Reilly, K., Moir, M., Taylor, C., Hyman, M., 2001. Hydroylis of tert-butyl methyl O ether (MTBE) in dilute aqueous acid. Environmental Science and Technology 35, 3954–3961. States, S., Newberry, J., Wichtermann, J., Kuchta, J., Scheuring, M., Casson, L., 2004. Rapid analytical techniques for drinking water security investigations. Journal of the American Water Works Association 96 (1), 52–64. TrinkwV, 2001. Trinkwasserverordnung 2001 – Verordnung u¨ber die Qualita¨t von Wasser fu¨r den menschlichen Gebrauch. Bundesgesetzblatt 21. Mai 2001 Teil I 24, 959–980. UBA, 2009. Liste der zugelassenen Aufbereitungsstoffe und Desinfektionsverfahren gema¨ß x11 der Trinkwasserverordnung 2001. Umweltbundesamt Stand Juni 2009. Available from. http://www.umweltbundesamt.de/wasser/themen/downloads/ trinkwasser/trink11.pdf. USEPA, 2005. Technologies and Techniques for Early Warning Systems to Monitor and Evaluate Drinking Water Quality: A State-of-Art Review. US Environmental Protection Agency. EPA-600/R-05/156. USEPA, 2007. Definition and Procedure for the Determination of the Method Detection Limit – Revision 1.11, Code of Federal Regulations 40 CFR Chapter I Appendix B to part 136, 343–346. Valca´rcel, M., Ca´rdenas, S., Gallego, M., 1999. Sample screening systems in analytical chemistry. Trends in Analytical Chemistry 18, 685–694. WHO, 2008. Recommendations. Incorporating 1st and 2nd addenda. In: Guidelines for Drinking-Water Quality, third ed., vol. 1. Available from. http://www.who. int/water-sanitation-health/dwq/fulltext.pdf.
Contents lists available at ScienceDirect
Journal of Environmental Management journal homepage: www.elsevier.com/locate/jenvman
Screening analysis of volatile organic contaminants in commercial inorganic coagulants used for drinking water treatment Michael Petri a, Jia-Qian Jiang b, *, Matthias Maier b a b
¨ berlingen, Germany ¨ ßenmu ¨ hle 1, D-88662 U Zweckverband Bodensee-Wasserversorgung, Betriebs- und Forschungslabor, Su Faculty of Engineering and Physical Science (C5), University of Surrey, Guildford, Surrey GU2 7XH, UK
a r t i c l e i n f o
a b s t r a c t
Article history: Received 30 December 2008 Received in revised form 15 July 2009 Accepted 28 July 2009 Available online 31 August 2009
A method for quality screening is suggested to detect volatile impurities in inorganic coagulants that are used for drinking water treatment. Static headspace gas chromatography with mass spectrometry detection (HS–GCMS) is sensitive and selective to detect volatiles in low concentrations. This study has discovered that volatile organic impurities are detectable in ferric and aluminium-based coagulants which are used for drinking water treatment. For ferric chloride, 2-propanol was detected at a level of 17–24 mg ml1, acetone at 0.7–1.7 mg ml1, 1,1,1-trichloroacetone at 0.02–0.04 mg ml1, trichloromethane at 0.01–0.02 mg ml1 and toluene at 0.01–0.12 mg ml1. For ferric chloride sulfate, acetone was detected at a level of 0.12 mg ml1, 1,1,1-trichloroacetone at 0.06–0.08 mg ml1, trichloromethane at 0.13–0.23 mg ml1, bromodichloromethane at 0.04–0.06 mg ml1 and dibromochloromethane at 0.04–0.05 mg ml1. For aluminium hydroxide chloride, only trichloromethane was detectable, but below the method detection limits (MDL). Although the concentrations of these impurities in commercial coagulants are low, this observation is important and should have impact on water industries for them to pay attention to the chemicals they are using for drinking water production. Ó 2009 Elsevier Ltd. All rights reserved.
Keywords: Coagulation Coagulants Drinking water treatment Mass spectrometry Static headspace gas chromatography Volatile organic contaminants
1. Introduction Although a potential for natural, accidental or intentional contamination of raw water sources and drinking water has always existed, the effort for developing and implementing contamination warning systems (CWSs) for drinking water security has been intensified significantly by homeland security after the attack on the 11th of September, 2001. Several publications reviewed the progress in developing CWS for source and drinking water (Gullick et al., 2003; Hasan et al., 2004; States et al., 2004; USEPA, 2005) and described the state-of-art technologies for detection of chemical, microbiological and radiochemical contaminations. Recent research projects on CWSs are mainly focused on detection of intentional contamination with hazardous compounds like biological or chemical warfare agents and radiological compounds in raw and drinking water that produce adverse health effects or poisoning after an acute exposure. Although warfare agents are extremely toxic and have to have high priority in development of a CWS other drinking water pollutants should also be taken into account such as intentional and non-intentional contamination with easy-to-get
* Corresponding author. Tel.: þ44 1483 686609; fax: þ44 1483 450984. E-mail address: [email protected] (J.-Q. Jiang). 0301-4797/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.jenvman.2009.07.015
chemicals for household, gardening, cleaning, construction and painting. Even if most of these industrial and common household chemicals have a much lower toxicity than warfare agents, any pollution of raw or drinking water is a possible threat to the public health and endangers the confidence in the water supply. An effective CWS consider all aspects of possible contamination paths in the drinking water supply. Therefore it should include not only physical protection of treatment plants and distribution systems but also repeated monitoring of raw water and drinking water and used treatment chemicals. Coagulation is a process commonly used in drinking water treatment to remove colour, natural organic matter, turbidity and other soluble organic and inorganic compounds from the raw water. In the process small particles and colloids are agglomerated to larger particles which can be removed by a subsequent clarification process, whereas natural organic matter and soluble compounds are removed by adsorption onto the surface of the flocs and then separated from water (Jiang, 2001). Common inorganic coagulants that are used in large amounts in drinking water treatment are aluminium sulfate, ferric sulfate or ferric chloride. Coagulants could be possible contamination sources in drinking water treatment because the coagulants are normally controlled by the manufacturer only on the basis of product specifications and standardized monitoring programs for selected metals such as As,
M. Petri et al. / Journal of Environmental Management 91 (2009) 142–148
Cd, Cr, Hg, Ni, Pb, Sb and Se or adsorbable organic halogen (AOX) (CEN, 2004a–h). Other monitoring programs to control the amount of organic compounds in coagulants are not standardized or common. But it is necessary to detect intentional or unintentional contamination caused by production, storage and transportation. The aim of the present study was to develop a rapid and reliable screening method for the surveillance of solvents and volatiles in coagulants after transport to the water treatment plant and before usage in the treatment process. Rapid screening methods are assessed as to be more qualitative than quantitative but they can provide a binary yes/no-response to indicate that an analyte is detectable in the sample or not (Valca´rcel et al., 1999). When the concentration of an analyte in the sample is above a defined threshold, a conventional quantification procedure should be triggered for confirmation and accurate quantification. Static headspace gas chromatography with mass spectrometry detection (HS–GCMS) is an appropriate method for a screening analysis of volatile compounds. HS–GCMS is sensitive and selective enough to detect volatiles in low concentrations and has a high degree of automation for practical routine analysis (Kolb and Ettre, 2006). With a mass spectrometer as a detector, the identification of unknown compounds is possible and false-positive misidentification can be reduced. The results demonstrate that the static HS–GCMS method is applicable for a rapid and accurate qualitative and quantitative screening approach to detect volatile organic contaminants in coagulants used in drinking water treatment. 2. Materials and methods 2.1. Chemicals To set up the screening method, a set of 45 volatile organic compounds were chosen as targeted chemicals which could be present in the coagulants used for the drinking water treatment. A gasoline organic stock solution and 1,1,1-trichloroacetone (EPA GRO-Mix in methanol) were purchased from Supelco (Steinheim, Germany). Stock solutions of acetate (8260B acetate Mix in methanol), ketones (VOA calibration mix #1 in methanol:water (90:10)), halocarbon (VOA purgeable halocarbon mix #1 in methanol) and oxygenate (oxygenates in methanol) were purchased from Restek (Bad Homburg, Germany). Stock solutions of trihalomethane mixture (THM-511 in methanol) and carbon tetrachloride (HC-040 in methanol) were purchased from Ultra Scientific (North Kingstown, USA). Acetone and 2-propanol for organic residue analysis were provided by Mallinckrodt J.T. Baker (Griesheim, Germany) and methanol in P&T-quality was from LGC-Promochem (Wesel, Germany). Ferric chloride hexahydrate in analytical quality was from Fluka (Steinheim, Germany) and hydrochloric acid 30% suprapur was from Merck (Darmstadt, Germany). Ultra-pure water was made with Milipore Elix-3 and Milli-Q Gradient A10 (Molsheim, Germany). 2.2. Ferric and aluminium-based coagulants Various types of ferric and aluminium coagulants were used for the screening analysis. All of them were in liquid and commercially available in Germany. They were ferric chloride (with 14% Fe, pH < 1, density at 20 C, 1.43 g ml1), aluminium hydroxide chloride (with 12% Al, pH 3.8, density at 20 C, 1.34 g ml1), aluminium sulfate (with 4.3% Al, pH 2.5, density at 20 C, 1.3 g ml1), aluminium hydroxide chloride sulfate (with 5.6% Al, pH 2.2, density at 20 C, 1.20 g ml1) and sodium aluminate (with 10% Al, pH 14, density at 20 C, 1.5 g ml1). Ferric chloride and all aluminium coagulants were purchased from BK Giluini GmbH (Ludwigshafen, Germany). Ferric chloride sulfate (with 12% Fe, pH < 1, density at
143
20 C, 1.52 g ml1) was purchased from Kronos ecochem (Leverkusen, Germany). The used coagulants were allowed to use in drinking water treatment according to the German Drinking Water Directive (TrinkwV, 2001; UBA, 2009) and the standardized product specifications (CEN, 2004a–h). For matrix simulation a ferric chloride solution was prepared and used for calibration. 150 g of iron ferric chloride hexahydrate were dissolved in 30 ml 30% hydrochloric acid and 70 ml ultra-pure water. The solution has a density of 1.38 g ml1 and an iron concentration of 166 mg ml1 solution. In every analytical sequence a sample of the ferric chloride solution was analysed as a blank sample to make sure, that no target analytes or non-target compounds were detectable.
2.3. Preparation of standards and samples For overview screening, a standard solution of 45 analytes listed in Table 1 was made from the stock solution mixtures and diluted to a concentration between 5 and 15 mg ml1 with methanol depending on the concentration in the purchased stock solution mixtures. The calibration standard for overview screening was
Table 1 Retention time and qualifier-ion from SIR or extracted from TIC for overview screening of volatile compounds in aqueous samples. Peak no Name
CAS no
RT [min] Qualifier-ion
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45
67-64-1 75-35-4 107-83-5 75-09-2 1634-04-4 156-60-5 108-20-3 75-34-3 637-92-3 78-93-3 141-78-6 67-66-3 71-55-6 540-84-1 56-23-5 142-82-5 994-05-8 108-21-4 71-43-2 107-06-2 79-01-6 919-94-8 78-87-5 109-60-4 75-27-4 110-75-8 108-10-1 10061-01-5 108-88-3 10061-02-6 79-00-5 591-78-6 127-18-4 123-86-4 124-48-1 108-90-7 100-41-4 108-38-3 95-47-6 628-63-7 75-25-2 95-63-6 541-73-1 106-46-7 95-50-1
6.36 6.48 7.24 7.99 8.56 8.95 10.30 10.70 12.10 12.90 13.68 14.00 15.66 15.7 16.70 17.10 17.15 17.30 17.60 17.70 20.37 20.67 21.29 22.01 22.39 24.17 24.40 25.08 26.04 27.58 28.25 28.58 29.41 29.82 30.56 33.55 33.89 34.28 36.41 36.89 38.28 43.90 45.98 46.52 48.00
Acetone 1,1-Dichloroethylene 2-Methylpentane Methylene chloride Methyl tert-butyl ether (MTBE) Trans-1,2-dichloroethylene Diisopropyl ether (DIPE) 1,1-Dichloroethane Ethyl tert-butyl ether (ETBE) 2-Butanone (MEK) Ethyl acetate Trichloromethane 1,1,1-Trichloroethane 2,2,4-Trimethylpentane Carbon tetrachloride n-Heptane tert-Amyl methyl ether (TAME) Isopropyl acetate Benzene 1,2-Dichloroethane Trichlorethylene tert-Amyl ethyl ether (TAEE) 1,2-Dichloropropane Propyl acetate Bromodichloromethane 2-Chloroethyl vinyl ether 2-Methyl-2-pentanone (MIBK) cis-1,3-Dichloropropylene Toluene trans-1,3-Dichloropopylene 1,1,2-Trichloroethane 2-Hexanone Tetrachloroethene Butyl acetate Dibromochloromethane Chlorobenzene Ethylbenzene m-Xylene o-Xylene n-Amyl acetate Tribromomethane 1,2,4-Trimethylbenzene 1,4-Dichlorobenzene 1,3-Dichlorobenzene 1,2-Dichlorobenzene
43 (SIR) 61 43 (SIR) 49 73 (SIR) 61 45 63 59 (SIR) 43 (SIR) 43 (SIR) 83 (SIR) 97 43 (SIR) 117 43 (SIR) 43 (SIR) 43 (SIR) 78 (SIR) 62 (SIR) 130 43 (SIR) 63 43 (SIR) 83 (SIR) 43 (SIR) 43 (SIR) 75 91 75 97 43 (SIR) 129 (SIR) 43 (SIR) 129 (SIR) 112 106 91 91 43 (SIR) 173 (SIR) 105 146 146 146
144
M. Petri et al. / Journal of Environmental Management 91 (2009) 142–148
prepared in 10 ml ultra-pure water in a headspace vial by injecting 20 ml of the standard solution under the surface of 10 ml ultra-pure water. For quantification of identified volatiles in coagulants a second calibration stock solution was made in methanol with neat compounds and stock solution mixtures. The calibration stock solution contained 2-propanol (3.9 mg ml1), acetone (0.25 mg ml1), 1,1,1-trichloroacetone (0.020 mg ml1), trichloromethane (0.004 mg ml1), bromodichloromethane (0.004 mg ml1), dibromochloromethane (0.004 mg ml1), tribromomethane (0.004 mg ml1), carbon tetrachloride (0.002 mg ml1), benzene (0.002 mg ml1), toluene (0.006 mg ml1), ethylbenzene (0.004 mg ml1), m-xylene (0.004 mg ml1), o-xylene (0.004 mg ml1) and 1,2,4-trimethylbenzene (0.004 mg ml1). The calibration curves were used to quantify the concentration of the compounds in coagulants. The calibration standards for quantification were prepared in 5 ml ferric chloride solution for matrix simulation and diluted to 10 ml with ultrapure water in the headspace vials before injecting 2.5, 5.0, 10, 15 and 20 ml of the calibration stock solution under the surface of the solution. The calibration range of each compound is given in Table 2. For analysing the coagulants 5 ml or an aliquot of the coagulant was placed in a 20 ml head-space vial and diluted to 10 ml with ultra-pure water. The vial was closed with a PTFE-coated silicon septum and aluminium crimp cap.
2.4. Static headspace gas chromatograph–mass spectrometry method Blanks, calibration standards for overview screening and for quantification and samples were analysed with the same static HS– GCMS method. The analysis was performed with a TurboMatrix 40 headspace sampler coupled to an AutosystemXL gas chromatograph (Perkin–Elmer, Rodgau-Ju¨gesheim, Germany). The samples were heated at 80 C for 30 min and shaken constantly. After thermostatting the headspace needle (thermostatted to 90 C) was inserted into the headspace of the sample vial. The vial was pressurerised to 131 kPa within 2 min (balanced-pressure system (Kolb, 1999)). The sample was injected to the GC with a sampling time of 0.12 min (injection volume was 9.1 ml) and transferred to the GC through a transfer line at 130 C. Helium (99.9995%, Linde, Stuttgart, Germany) was used as a transfer and carrier gas with a column head pressure of 131 kPa. The gas chromatographic separation was performed with a VOCOL capillary column (60 m 0.32 mm 1.8 mm, Supelco, Steinheim, Germany). The column oven temperature program was: initial temperature of 35 C, initial time 10 min, increased at a rate of 3 C min1 to 120 C, hold for 5 min, increased at 10 C min1 to 200 C and hold for 10 min. The total chromatographic run time
was 61.33 min. The column head pressure was 145 kPa with a velocity of 100 cm s1. The capillary column was coupled to the mass spectrometer directly into the ion source and heated to 180 C in the transfer section. The mass spectrometer was a single quadrupole (TurboMass, Perkin–Elmer, Rodgau-Ju¨gesheim, Germany). It was operated by electron impact ionisation with a voltage of 70 eV. The temperature of the ion source was 180 C. After a solvent delay of 3 min, the analyses were performed in full scan mode (TIC) and in single ion recording mode (SIR) simultaneously. The full scan mode was used for identification and confirmation of detected compounds in the samples. The m/z range was 41–200 Da, with a scan time of 0.50 s. The compounds were identified by comparison of the experimental mass spectra with a mass spectra library (NIST/EPA/NIH Mass Spectral Library, version 2.0d). To enhance the detection limit for quantification nine single ion recording groups were additionally used, each acquired with 0.100 ms for inter channel delay and a span of 0.70 Da. The first SIR function was from 5.0 to 40.0 min and formed by the characteristic ion m/z 43 for C2H3Oþ in methyl ethers, acetates, methyl-ketones and C2Hþ 7 from hydrocarbons. The second SIR function (5.0–9.0 min) contained the ion m/z 45 for 2-propanol. The third SIM function (8.0–10.0 min) contained the ion m/z 73 for methyl tert-butyl-ether (MTBE) and the fourth (11.0–13.0 min) contained the ion m/z 59 for ethyl tert-butyl-ether (ETBE). The fifth SIR function (13.0–16.0 min) was made with the ion m/z 83 for trichloromethane, the sixth SIR function (16.0–19.0 min) with the ions m/z 62 for 1,2-dichloroethane and m/z 78 for benzene, the seventh SIR function (21.0–24.0 min) with the ion m/z 83 for bromodichloromethane, the eighth SIR function (28.0–31.0 min) with ion m/z 129 for dibromochloromethane. The last SIR function (37.0–40.0 min) contained the ion m/z 173 for tribromomethane. 2.5. Calibration curves and method detection limit Calibration curves for quantification were calculated from peak areas by using the quantifier ion of specified SIR or were extracted from the TIC. Since the 5-point calibration for quantification was not linear in the lower working range quadratic calibration curves were used for quantification. The method detection limits (MDLs) of the quantified compounds given in Table 2 were defined according to the ‘‘Definition and Procedure for the Determination of the Method Detection Limit’’ from the USEPA (2007) with seven replicates in diluted ferric chloride solution for matrix simulation containing the lowest calibration standard level. The MDL was calculated by multiplying the sample standard deviation of the replicates in the final method reporting units with the Student’s t value appropriate for a 99% confidence level and with n 1 degrees of freedom. 3. Results and discussion
Table 2 Calibration range and MDLs for quantification of detected compounds in iron coagulants in order of retention time. Peak no Name
CAS no
MDL RT Calibration [min] range [mg ml1] [mg ml1]
46 1 12 15 19 25 29 35 47 37 41
67-63-0 67-64-1 67-66-3 56-23-5 71-43-2 75-27-4 108-88-3 124-48-1 918-00-3 100-41-4 75-25-2
5.87 6.36 14.00 16.70 17.60 22.39 26.04 30.56 33.41 33.89 38.28
2-Propanol Acetone Trichloromethane Carbon tetrachloride Benzene Bromodichloromethane Toluene Dibromochloromethane 1,1,1-Trichloroacetone Ethylbenzene Tribromomethane
1.96–15.7 0.13–1.01 0.02–0.16 0.01–0.08 0.01–0.08 0.02–0.16 0.03–0.24 0.02–0.16 0.01–0.08 0.02–0.08 0.02–0.16
0.50 0.05 0.01 0.008 0.005 0.01 0.02 0.02 0.005 0.02 0.02
3.1. Calibration for overview screening Static HS–GCMS allows the determination of 45 different volatiles in aqueous samples such as halogenated hydrocarbons, trihalomethanes, ketones, acetic esters, fuel ether oxygenates and monoarometic compounds in gasoline like benzene and its monomethyl-, dimethyl-, trimethyl- and monoethyl-derivates. Under the described conditions, m-xylene and p-xylene were coeluted completely and cannot be quantified separately, so that p-xylene was quantified and expressed in terms of m-xylene. Fig. 1 shows a total ion chromatogram (TIC) in which 45 analytes (assigned in Table 1) were spiked into a water sample in a concentration range from 0.01 mg ml1 to 0.03 mg ml1. To improve the detection power for several analytes, a single ion recording (SIR) was used, which
M. Petri et al. / Journal of Environmental Management 91 (2009) 142–148 700
1: Scan EI+ TIC 5.87e6
29
100
145
38
3 13,14
21
39 33
%
37 1,2
6 4
12 7 8
5
16,17 18,19
11
22 23
9
43
44
45
25
24
10
42
36
15
20
28
30
26,27
31 32 34
40 35
41
12
Time
6.50
11.50
16.50
21.50
26.50
31.50
36.50
41.50
46.50
Fig. 1. Total ion chromatogram of calibration standard for overview screening with 45 volatiles in a concentration level at 0.010 mg ml1 to 0.030 mg ml1. For peak identification see Table 1.
can be run simultaneously with the full scan mode. Therefore a simultaneous acquisition of TIC and SIR increases the certainty in compound detection and decreases the uncertainty in compound identification and misinterpretation. For the SIR, the recorded ion masses (m/z) should be specific for a functional group like m/z 43 for ethers, esters, ketones and hydrocarbons, or for one compound, like m/z 78 for benzene. The described screening procedure for volatiles with static HS–GCMS provides a reliable binary yes/noresponse to indicate if a target analyte is detectable in the sample or not (Valca´rcel et al., 1999). Therefore the calibration routine for an overview screening procedure can be minimized to a simple twopoint calibration with a blank and one standard. The simplified calibration can be used as system check and for a rough estimation of the amount of a detected target analyte. This simplified overview screening approach increases the sample throughput and provides a rapid response for immediate decision making. In a case of a contamination, the static HS–GCMS method can rapidly screen samples of raw water, treated drinking water and incoming or used treatment chemicals. 3.2. Ether cleavage, hydrolysis and saponification of esters in coagulants In samples with a neutral pH all 45 volatiles (see Table 1) can be determined with static HS–GCMS when the samples were heated for 30 min at 80 C before headspace injection. Liquid ferric and aluminium coagulants have a pH that is near or below 2. Sodium ´ Reilly et al. (2001) and Lin et al. (2003) aluminate has a pH of 14. O showed that fuel ether oxygenates such as MTBE, ETBE and TAME hydrolyze at pH near 2 during sample heating at 80 C. When the analytes were spiked in a ferric chloride solution for matrix simulation, the fuel ether oxygenates, acetic esters and xylenes were observed to be hydrolyzed. A cleavage of ethers under acidic conditions causes the instability of ethers and is forced with heating (McMurry, 1992). The acetic acid esters were also hydrolyzed in solutions with hydrochloric acid, because the esterification of a carboxylic acid with an alcohol is a reversible reaction and catalyzed by strong acids (McMurry, 1992). When the volatiles listed in Table 1 were spiked in an alkaline sodium aluminate solution only the acetic esters were hydrolyzed by saponification
with hydroxide ion. The fuel ether oxygenates remained stable in strong alkaline solutions. The breakdown of m- and o-xylene in iron coagulants has not been eludicated yet, since the monoaromatic compounds are normally stable in aqueous acids. An influence of ferric ions seems to be rather probable and should be investigated more in detail. 3.3. Volatiles in coagulants For ferric chloride the following target analytes were detected, acetone (1), trichloromethane (12), toluene (29), ethylbenzene (37) (see Fig. 2). For ferric chloride sulfate the following were detected, acetone (1), trichloromethane (12), bromodichloromethane (25) and dibromochloromethane (35) (see Fig. 3). The identification of these compounds was confirmed by comparison of the experimental mass spectra with the NIST/EPA/NIH mass spectra library. Non-target compounds were detected with retention time of 5.87 min (TIC, SIR m/z 43 and 45) and 33.42 min (TIC, SIR m/z 43) in ferric chloride and with a retention time of 25,74 min (TIC, SIR m/z 43, see Fig. 4) and 33.43 min (TIC, SIR m/z 43) in ferric chloride sulfate. Two of unknown compounds in ferric chloride could be identified as 2-propanol (retention time 5.87 min, assigned peak number 46) and 1,1,1-trichloroacetone (retention time 33.42, assigned peak number 47) by analysing reference compounds that were suggested by the mass spectra library. One unknown compound detected in ferric chloride sulfate with a retention time of 25.74 min (mass spectra see Fig. 4) has not been identified yet. The mass spectra of the unknown compound (Fig. 4) show an insignificant fragmentation and are not very informative for an unambiguous interpretation. The base peak m/z 43 can be formed by C2H3Oþ from methyl ethers, acetates, methyl-ketones or by C2Hþ 7 from hydrocarbons. The small peaks at m/z 77 and 105 could be an indication for aromatic structures in the compound but their intensities are too low for regarding them as a significant indication. The elucidation of this unknown impurity detectable in ferric chloride sulfate is challenging, due to the insufficient information available from the mass spectra. After the identification and confirmation, a stock standard solution was made for an accurate calibration and quantification. Table 2 shows the calibration range, based on the potential
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755 100
46
1: Scan EI+ TIC 1.44e7
12
%
SIR No. 6 m/z 83 1 29
47 37
0
Time 6.51
11.51
16.51
21.51
26.51
31.51
36.51
41.51
46.51
Fig. 2. Determination of volatiles in ferric chloride. TIC and SIR (SIR No 6: m/z 83) from a 5 ml sample with two non-target analytes, that could be identified as 2-propanol (46) and 1,1,1-trichloracetone (peak 47).
acetone at 0.7–1.7 mg ml1, 1,1,1-trichloroacetone at 0.02– 0.04 mg ml1, trichloromethane at 0.01–0.02 mg ml1 and toluene at 0.01–0.12 mg ml1. In samples of ferric chloride sulfate, acetone was detected at a level of 0.12 mg ml1, 1,1,1-trichloroacetone at 0.06– 0.08 mg ml1, trichloromethane at 0.13–0.23 mg ml1, bromodichloromethane at 0.04–0.06 mg ml1 and dibromochloromethane at 0.04–0.05 mg ml1. In aluminium coagulants, trichloromethane was detected in aluminium hydroxide chloride only but below the MDL. The detection of halogenated volatile organic compounds in ferric coagulants can be explained by the production process. Dissolved ferrous chloride or ferrous sulfate is normally treated with chlorine gas to be oxidized to the corresponding ferric chloride or ferric chloride sulfate. The used raw materials are of technical quality, so that possible organic contaminations are oxidized and chlorinated by chlorine gas. The 2-propanol that
concentration of the target compounds in the coagulant, and the MDLs of each detected compound. For matrix simulation, the calibration standards were made in a ferric chloride solution. This was necessary to adjust the matrix of the calibration standard to the coagulant sample, so that the influence of the matrix during static headspace extraction is minimized (Kolb and Ettre, 2006). In addition, Koch and Vo¨lker (1996) described that halogenated acetones can only be analysed when the sample is acidified, or they will decompose to acetic acid and their corresponding halogenated methanes. Therefore, 1,1,1-trichloroacetone can only be analysed in samples with a pH < 2 but not in aqueous samples like raw or drinking water or in alkali coagulants such as sodium aluminate without pH-adjustment. Table 3 shows the results of volatile contaminations in commercial iron and aluminium coagulants. In the ferric chloride coagulant, 2-propanol was detected at a level of 17–24 mg ml1,
759
25
100
1: Scan EI+ TIC 7.14e6
35
SIR No. 8 m/z 83 SIR No. 9 m/z 129 %
12
unknown
47
0
Time 6.51
11.51
16.51
21.51
26.51
31.51
36.51
41.51
46.51
Fig. 3. Determination of volatiles in ferric chloride sulfate. TIC and SIR (SIR No 8: m/z 83 and SIR No 9: m/z 129) from a 5 ml sample with two non-target analytes. One of them could be identified as 1,1,1-trichloroacetone (peak 47). The second compound with a retention time of 25.74 min (mass spectra see Fig. 4) has not been identified yet.
M. Petri et al. / Journal of Environmental Management 91 (2009) 142–148
147
759 1525 (25.743) 100
1: Scan EI+ 4.77e5
43
%
42 44
0 40
53
61 64
79 86 90 97 72 77
60
80
105 112
100
122
120
126
141
152
140
156 163
160
176 183
188
180
197
200
m/z
Fig. 4. Mass spectra of an unknown compound in ferric chloride sulfate coagulant with a retention time of 25.74 min (chromatogram see Fig. 3). The largest m/z- peaks are 43 (100.0% BPI (base peak intensity)), m/z: 42 (12.5% BPI), m/z: 105 (6.4% BPI), m/z: 61 (3.2% BPI), m/z: 62 (2.7% BPI) and m/z 77 (2.5% BPI).
was detected in ferric chloride is probably oxidized to acetone, which is subsequently chlorinated to 1,1,1-trichloroacetone. The formation of trihalomethane can be explained with the haloform reaction of halogenated methyl-ketones groups in various organic compounds. Including bromide in the ferrous solution leads to the mixture of chlorine and bromine containing trihalomethanes since bromide is oxidized by chlorine to bromine. The detection of toluene and ethylbenzene in ferric chloride cannot been explained. Because there are no chlorinated monoaromatic compounds detectable in ferric chloride, a contamination during storage and/or transportation of the coagulant is probable. 3.4. The VOC’s concentration level in the coagulated water The concentration levels of the detected VOC contaminants in the analysed ferric coagulants are very low so that there will be no harmful effect on the quality of drinking water. For drinking water treatment the maximum addition of coagulants is regulated in Germany by the Drinking Water Directive (TrinkwV, 2001). The
Federal Environment Agency is responsible for having a record of all coagulants currently permitted for drinking water treatment and their maximum addition. This record is supplemented and published regularly by the Federal Office. For ferric chloride the maximum addition is 12 mg iron per litre water and for ferric chloride sulfate the maximum addition is 6 mg iron per litre water (UBA, 2009). The detected volatiles, 2-propanol, acetone, 1,1,1-trichloracetone and toluene, are not regulated by the Drinking Water Directive (TrinkwV, 2001). In the treated drinking water, 2-propanol and acetone can react with chlorine to halogenated disinfection by-products. 2-Propanol and acetone can easily be removed by rapid or slow sand filtration. The detectable trihalomethanes are regulated and must not exceed a sum concentration of 50 mg l1 after treatment and disinfection (TrinkwV, 2001). For a maximum addition of ferric coagulant the possible sum concentrations of trihalomethanes is 1.2 mg l1 for ferric chloride and 11.2 mg l1 for ferric chloride sulfate which do not exceed the regulated trihalomethanes sum concentration of 50 mg l1 in Germany or the guideline values from WHO for drinking water (WHO, 2008) (see Table 3).
Table 3 Amount of volatiles in the commercially available ferric and aluminium coagulants. Inorganic coagulant
Peak no
Analyte
Concentration in coagulants [mg ml1]
Possible concentration for the maximum addition of coagulanta [mg l1]a
Ferric chloride
46 1 12 47 29 37
2-Propanol Acetone Trichloromethane 1,1,1-Trichloracetone Toluene Ethylbenzene
17–24 0.7–1.7 <0.01–0.02 0.02–0.04 <0.02–0.12 <0.02
1440 102 1.2 2.4 7.2
Ferric chloride sulfate
1 12 25 35 47
Acetone Trichloromethane Bromodichloromethane Dibromochloromethane 1,1,1-Trichloroacetone
0.12 0.13–0.23 0.04–0.06 0.04–0.05 0.06–0.08
Aluminium hydroxide chloride
12
Trichloromethane
<0.01
Aluminium sulfate
No volatiles detected
Aluminium hydroxide chloride sulfate
No volatiles detected
Sodium aluminate
No volatiles detected
a
3.9 7.6 2.0 1.6 2.6
The calculated concentration of volatiles in water after addition of the maximum amount of coagulant is listed in the Federal Environment Agency. For ferric chloride the permitted maximum addition is 12 mg iron per litre water. For ferric chloride sulfate the permitted maximum addition is 6 mg iron per litre water (UBA, 2009).
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4. Conclusion The described static HS–GCMS method has been successfully applied in screening for volatile organic compounds in coagulants. A simplified overview screening approach with a 2-point calibration increases the sample throughput and provides a rapid binary yes/no-response for immediate decision making. In the case of a suspected contamination, the static HS–GCMS method can be used to rapidly screening of raw water, different treatment steps, treated drinking water and incoming or used treatment chemicals. Several volatiles such as trichloromethane, bromodichloromethane, dibromochloromethane and 1,1,1-trichloroacetone were detected in sub-mg ml1 range in ferric chloride and ferric chloride sulfate, which are produced by oxidation of ferrous chloride or ferrous sulfate with chlorine. In ferric chloride, 2-propanol and traces of toluene and ethylbenzene were detected, too. Volatile organic contaminations were not detected or their concentrations were below the MDL in aluminium coagulants. Ethers and acetates cannot be analysed in acidic coagulants because they decompose by hydrolysis just as acetates in alkali coagulants. This work shows clear differences in the pattern of volatile contaminations in commercially iron and aluminium-based coagulants depending on the used raw materials and production process. The study reported in this paper has discovered volatile organic contamination in ferric and aluminium-based coagulants which are used for drinking water treatment. Although the concentration of the detected volatile compounds in aluminium and iron coagulants are very low, a more intensive surveillance and monitoring of coagulants should be conducted by the coagulant manufacturer and waterworks especially when using them for drinking water treatment. Further investigations for semiand non-volatile organic contaminations in coagulants should be carried out. For incoming treatment chemicals, a routine screening procedure should be implemented to detect potential intended or non-intended chemical contaminations.
References CEN, 2004a. Chemicals Used for Treatment of Water Intended for Human Consumption – Aluminium Sulfate. European Committee for Standardization, Brussel. EN 878. CEN, 2004b. Chemicals Used for Treatment of Water Intended for Human Consumption – Aluminium Chloride, Aluminium Chloride Hydroxide and Aluminium Chloride Hydroxide Sulfate (Monomeric). European Committee for Standardization, Brussel. EN 881. CEN, 2004c. Chemicals Used for Treatment of Water Intended for Human Consumption – Sodium Aluminate. European Committee for Standardization, Brussel. EN 882.
CEN, 2004d. Chemicals Used for Treatment of Water Intended for Human Consumption – Polyaluminium Chloride Hydroxide and Polyaluminium Chloride Hydroxide Sulfate. European Committee for Standardization, Brussel. EN 883. CEN, 2004e. Chemicals Used for Treatment of Water Intended for Human Consumption – Iron(III) Chloride. European Committee for Standardization, Brussel. EN 888. CEN, 2004f. Chemicals Used for Treatment of Water Intended for Human Consumption – Iron(II)Sulfate. European Committee for Standardization, Brussel. EN 889. CEN, 2004g. Chemicals Used for Treatment of Water Intended for Human Consumption – Iron(III)Sulfate Liquid. European Committee for Standardization, Brussel. EN 890. CEN, 2004h. Chemicals Used for Treatment of Water Intended for Human Consumption – Iron(II)Chloride Sulfate. European Committee for Standardization, Brussel. EN 891. Gullick, R.W., Grayman, W.M., Deininger, R.A., Males, R.M., 2003. Design of early warning systems for source waters. Journal of the American Water Works Association 95 (11), 58–72. Hasan, J., States, S., Deininger, R., 2004. Safeguarding the security of public water supplies using early warning systems: a brief review. Journal of Contemporary Water Research and Education 129, 27–33. Jiang, J.Q., 2001. Development of coagulation theory and pre-polymerized coagulants for water treatment. Separation & Purification Methods 30 (1), 127–141. Koch, J., Vo¨lker, P., 1996. Zur Bildung von Artefakten und deren Vermeidung bei der Bestimmung leichtflu¨chtiger Halogenkohlenwasserstoffen in Wasser mittels Headspace-Gaschromatographie unter den Bedingungen der DIN 38407 (DEV¨ berho¨hte Trihalogenmethanbefunde in gechlortem SchwimmF5). Teil II: U badbeckenwasser. Acta hydrochimica et hydrobiologica 24, 179–184. Kolb, B., 1999. Headspace sampling with capillary column. Journal of Chromatography A 842, 163–205. Kolb, B., Ettre, L.S., 2006. Static Headspace-Gas Chromatography: Theory and Practice, second ed. Wiley-Interscience, Hoboken. Lin, Z., Wilson, J.T., Fine, D.F., 2003. Avoiding hydrolysis of fuel ether oxygenates during headspace analysis. Environmental Science and Technology 37, 4994–5000. McMurry, J., 1992. Organic Chemistry, third ed. Brooks/Cole Publishing Company, Pacific Grove. ´ Reilly, K., Moir, M., Taylor, C., Hyman, M., 2001. Hydroylis of tert-butyl methyl O ether (MTBE) in dilute aqueous acid. Environmental Science and Technology 35, 3954–3961. States, S., Newberry, J., Wichtermann, J., Kuchta, J., Scheuring, M., Casson, L., 2004. Rapid analytical techniques for drinking water security investigations. Journal of the American Water Works Association 96 (1), 52–64. TrinkwV, 2001. Trinkwasserverordnung 2001 – Verordnung u¨ber die Qualita¨t von Wasser fu¨r den menschlichen Gebrauch. Bundesgesetzblatt 21. Mai 2001 Teil I 24, 959–980. UBA, 2009. Liste der zugelassenen Aufbereitungsstoffe und Desinfektionsverfahren gema¨ß x11 der Trinkwasserverordnung 2001. Umweltbundesamt Stand Juni 2009. Available from. http://www.umweltbundesamt.de/wasser/themen/downloads/ trinkwasser/trink11.pdf. USEPA, 2005. Technologies and Techniques for Early Warning Systems to Monitor and Evaluate Drinking Water Quality: A State-of-Art Review. US Environmental Protection Agency. EPA-600/R-05/156. USEPA, 2007. Definition and Procedure for the Determination of the Method Detection Limit – Revision 1.11, Code of Federal Regulations 40 CFR Chapter I Appendix B to part 136, 343–346. Valca´rcel, M., Ca´rdenas, S., Gallego, M., 1999. Sample screening systems in analytical chemistry. Trends in Analytical Chemistry 18, 685–694. WHO, 2008. Recommendations. Incorporating 1st and 2nd addenda. In: Guidelines for Drinking-Water Quality, third ed., vol. 1. Available from. http://www.who. int/water-sanitation-health/dwq/fulltext.pdf.