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C8 solid-phase extraction of the pyrethroid insecticide fenvalerate and the chloroacetanilide herbicide metazachlor from pond water
the Science of the Total Environment A~ t.Je~amomJJc.sm~ ~ S ~ * , t a ~ m m ~ ¢ ~
ELSEVIER
The Science of the Total Environment 156 (1994) 67-75
C s solid-phase extraction of the pyrethroid insecticide fenvalerate and the chloroacetanilide herbicide metazachlor from pond water Per Woin Laboratory of Chemical Ecology and Ecotoxicology, Department of Ecology, Universityof Lund, S-223 62 Lund, Sweden Received 22 March 1993; accepted 20 March 1994
Abstract A method was developed for the simultaneous extraction of the pyrethroid insecticide fenvalerate and the chloroacetanilide herbicide metazachlor from water using a solid-phase C8 column. After elution from the C8 column, the concentrated eluate was analysed using a capillary gas chromatographequipped with an electron-capture detector. The method was used to confirm residues of the compoundsin spiked tap water, pond water and river water. The recoveryrates were high (84% for the fenvalerate and 101% for the metazachlor) and there was no need for clean-up. Keywords: Solid-phaseextraction; Fenvalerate; Metazachlor; Pond water
1. Introduction The development of quick, simple and inexpensive methods for the determination of different pollutants in the environment has always been important to ecotoxicologists. However, as the number of pollutants in circulation has increased, the need for such methods has grown. One major advance in this area has been the development of pre-manufactured solid phase extraction (SPE) columns. Solid-phase extraction has been used extensively for removing non-polar organic chemicals from water [1-6]. In this procedure, a water sample containing the chemical compound of interest is passed through a column containing a sorbent having high affinity for non-polar com-
pounds. The target compound is bound by the column sorbent, the water is discarded and the compound is then eluted from the column and determined by appropriate methods. The use of SPE as a means for sample collection has many benefits, particularly when extraction is carried out in the field. For example, samples (SPE cartridges) transported to the laboratory are of much smaller size and weight, potential adsorption to sampling materials is eliminated, samples are easier to store in the laboratory and both the use of solvents and the time required for extraction are reduced markedly compared with liquid-liquid extraction. Many ponds and natural waters are surrounded by arable land and are thus subject to possible
0048-9697/94/$07.00 © 1994 Elsevier Science BV. All rights reserved. SSDI 0048-9697(94)04198-V
P. Woin / Sci. Total Environ. 156 (1994) 67-75
68
contamination by various pesticides [7-9]. A sampling and extraction method covering a wide range of compounds differing considerably in their physical and chemical properties should therefore be of great benefit to the control and regulation of pesticides and to related research. The pesticides considered in the present study represent two groups of agricultural chemicals used worldwide. One, the insecticide fenvalerate, is a nonpersistent pyrethroid; the other, the herbicide metazachlor, is typical of the large chloroacetanilide group. Fenvalerate (water solubility = 2-20 /xg 1 1, log Pow = 4.1) and metazachlor (water solubility = 20 mg 1-', log Pow = 2.1) were found appropriate for the study largely because of the difference in their polarity. Although methods for determining fenvalerate and other insecticides in water are well represented in the literature, few simple methods for determining herbicides have been reported and none of them concern metazachlor. The importance of being able to determine a broad spectrum of pesticides, including metazachlor, in natural waters has been focused on in our laboratory. The investigation has been aimed, accordingly, at developing a simple and reliable method for the simultaneous determination of fenvalerate, metazachlor and related compounds in pond water.
2. Materials and methods
High-purity pesticides (Pestanal®) to provide external GC-standards were obtained from Riedel-de Haen. Commercially available emulsifiable concentrate formulations of fenvalerate (Sumicidin 10FW, Dupont, 100 g 1-1 ) and metazachlor (Butisan S, BASF, 500 g 1-1) served as test substances. All the organic solvents were of residue analysis grade. Bonded-phase cartridges of C 8 (300 mg sorbent) were PrepSep® from Allied Fisher Scientific. The SPE-columns were cleaned before use by passing 6 ml methanol, 6 ml n-hexane and 4 ml ethyl acetate through them. Prior to sampling, the cartridges were preconditioned with 4 ml of methanol, followed by 4 ml of deionized water. Known amounts of Sumicidin 10FW and Butisan S were shaken vigorously in 961 ml of tap water to create a standard solution of 3.55/zg 1-1 fenvalerate and 11.92 /xg 1-1 metazachlor. Seven samples of this solution (67-264 ml, Table 1) were passed through preconditioned SPE-columns by drawing the solution directly from the bottle with a vacuum pump. Different volumes were extracted in order to simulate conditions in the field, where the SPE-columns may become clogged by seston. A hand-driven vacuum pump was connected to the submersed SPE-column via
Table 1 Recovery of fenvalerate (3.55 /zg 1-1) and metazachlor (11.92 /zg 1 1) from spiked tap-water Sample identity
Volume extracted
Nominal (ng M)
Detected (ng M)
Nominal (ng F)
Detected (ng F)
SPE1 SPE2 SPE3 SPE4 SPE5 SPE6 SPE7
67 ml 85 ml 264 ml 173 ml 97 ml 152 ml 123 ml
799 1013 3147 2062 1156 1812 1466
1042 1007 2991 2228 1102 1828 1335
238 301 936 613 344 539 436
150 235 834 504 299 458 373
Total M e a n + S.D.
961 ml
11 455
11533
3408
Bottle
surface
--
41
11 455
11574
Recovery (% M)
Recovery (% F)
130.4 99.4 95.0 108.1 95.3 100.9 91.1
63.0 78.1 89.1 82.2 86.9 85.0 85.6
2853
100.7 102.9 + 13.3
83.7 81.4 + 8.9
--
384
--
--
3408
3237
101.0
95.0
T h e c o m p o u n d s were extracted from the water in C s SPE-columns and from the inner surface of the bottle using 4 × 10 ml tea-butyl methyl ether:n-hexane (5:5, v/v). M, metazachlor; F, fenvalerate.
P. Woin / Sci. Total Environ. 156 (1994) 67-75
a filtering bottle and silicone tubing. The extracted water, collected in the filtering bottle, was quantified in a measuring cylinder. Following extraction, the columns were dried for 10 min by drawing air through them. The compounds were eluted from the SPE-columns with 4 ml ethyl acetate. The eluate was evaporated to ~ 1 ml and was transferred to autosampler vials. To determine the amounts of fenvalerate and metazachlor adsorbed onto the glass surfaces, the empty standard solution bottle was rinsed with 4 × 10 ml ten-butyl methyl ether:n-hexane (1:1, v/v). The resulting solution was evaporated to dryness and was redissolved in ethyl acetate, that was then transferred to autosampler vials. The compounds were determined using a Varian 3500 gas chromatograph equipped with an EC detector and a splitless injection system operated at 290°C and 220°C, respectively. Following injection, the J & W DB-5 capillary fused-silica column (30m × 0.3mm i.d.) was kept at ll0°C for 3 min. It was programmed to then increase at 20°C min- 1 to 270°C and was kept there for 10 min. The carrier gas was hydrogen which had a flow rate of 2.5 ml min -1. To test the method under field conditions, the SPE-columns were used to extract fenvalerate and metazachlor from natural pond water (without prior filtration) kept in mesocosms. Apart from the water, the mesocosms contained 1 m 3 unpolluted eutrophic lake sediment and different fresh water plants. All the natural components contained a natural composition of organisms (algae, zooplankton, benthos, etc.). Three of the mesocosms were continuously supplied with fenvalerate for 2 weeks and three of them were continuously supplied with metazachlor for 1 week. All the mesocosms were static (no inflow or outflow), the water being recirculated. Solutions of the compounds were introduced slowly by being pumped into the recirculation tubes of each mesocosm by a multi-channel peristaltic pump. To test the application of the method to other types of natural waters, water samples (500 ml) were taken from a clear-water duck-pond and from a eutrophic river of high turbidity. These two water samples were fortified with realistic
69
concentrations [8] of fenvalerate and metazachlor. The main purpose for this test was to investigate possible interferences that might be found in other water matrices. In addition, tandem-coupled SPE-columns were used to confirm that no breakthrough of the compounds occurred. Some 200-300 ml of the water were passed through the columns, an elution volume of 2 ml being obtained, providing extracts of ~ 1.5 ml that were transferred directly to autosampler vials. 3. Results and discussion
Fenvalerate and metazachlor were isolated and concentrated in a rapid and efficient manner using the C a solid-phase extraction procedure described here. Excellent recoveries were obtained on a total basis, the amounts adsorbed on the glass being included (Table 1). Almost all of the compounds added to the water (101% of the metazachlor applied and 95% of fenvalerate) were recovered. The SPE-columns collected 100% of the metazachlor and 83.7% of the fenvalerate. The extraction step for these compounds is reliable and the technique may also be useful for the extraction of the related acetanilides and pyrethroids at concentrations one could expect to find in natural waters. Most studies concerning the separation of non-polar and semi-polar pesticides from natural waters have used ClS as a sorbent [1,2,4,5]. However, as the high recovery of fenvalerate and metazachlor in this study suggest, C 8 may be almost as effective as ClS as a pesticide sorbent. Hinckley and Bidleman [3], also using C s as the sorbent, reported high recovery rates (85-115%) from a collection of organochlorine, organophosphate and pyrethroid insecticides (including fenvalerate) that were extracted from spiked deionized water, as well as from sea water. They also found the breakthrough of the pesticides to be low (0-13%). Recovery rates of 80-100% for the extraction by C 8 of carbaryl and malathion from pond and well water have also been reported [6]. Because of the tendency of hydrophobic compounds to adhere or adsorb to surfaces, extraction from the empty standard solution bottle was included in the study. Fenvalerate and pyrethroids
P. Woin / Sci. Total Enuiron. 156 (1994)67-75
70
are known generally to adsorb strongly onto glass and plastic materials [10]. In the present study, however, only 11.3% of the fenvalerate was found to adhere to the surfaces of the glass bottle (Table 1.). This low adsorption, compared with what has been reported elsewhere [3,11,12], may be due to the fact that the fenvalerate was applied to the water in an emulsifiable formulation. It is also possible that the time (~ 1 h) between preparation of the water solution and sampling was too short for adsorption to develop since the latter is a time-dependent phenomenon. Other workers have found the adsorption of fenvalerate to surfaces to be 54% for glass bottles and 28% for glass-fiber filters [3], 60-90% for a glass diluter system [11] and 8.6% for BOD bottles [12]. Sharom and Solomon [10] found the adsorption of permethrin (same chemical family as fenvalerate) to glass to be as high as 70% and that of polyethylene and PVC to be as high as 100% after 96 h of agitation. Particulate bounded fenvalerate collected on glass-fiber filters (GFF) before extraction with C 8 have been found to constitute up to 77% of the total amount of fenvalerate found in
tidal creek water [3]. The choice of sampling strategy is of great importance, therefore, for the accurate determination of pesticides in water. Use of traditional methods (collecting water in bottles) may thus lead to large reductions in the amounts of key compounds due to the adsorption and degradation that occur during transportation and storage. With the use of the SPE method, both dissolved compounds and those bound to particles in the water are collected efficiently and the cartridges can be easily stored in a freezer. The recovery of a specific compound is governed by many factors, such as volatility, water solubility and log Pow. The present method was optimized to the determination of fenvalerate and metazachlor in neutral natural waters having a low content of particulate matter. Because of the differing properties of the two compounds, one can assume that the method is applicable to a wide spectrum of pesticides, to pyrethroids and chloroacetanilides in particular. The results from the application of the method to real environmental water (pond-water) are illustrated in Figs. 1 (fenvalerate) and 2 (meta-
100 [] DetectedHi O
10
[] Nominal Hi -"43
il
* DetectedVIed
l
<> Nominal Med A
0,1
• DetectedLo ----A
A Nominal Lo
[]
0,01
L.
0,001 13-aug
I
I
I
I
I
I
20-aug
27-aug
3-sep
10-sep
17-sep
24-sep
Date Fig. 1. Detected and nominal concentrations of fenvalerate in natural pond-water mesocosms supplied with 20 (Hi), 2 (Med) and 0.2 (Lo) ~g 1-l during a 2-week exposure period.
P. Woin / Sci. Total Environ. 156 (1994) 67-75
zachlor). The most striking difference between the two compounds, is the difference in the nominal versus the detected concentrations involved. These differences between fenvalerate and metazachlor are presumably due, however, to their differing solubility in water. The fenvalerate concentrations detected (Fig. 1) never reached > 20% of the nominal ones, and when the addition of fenvalerate ceased the concentration dropped rapidly. In the case of metazachlor (Fig. 2), the amount detected closely followed the supply, the concentration detected never being < 60% of the theoretical concentration. The drop in concentration after exposure ceased was also much slower. The low concentration of fenvalerate and its rapid decrease are most likely due to that substance's high affinity for surfaces and particulate matter [3,10,11,12]. It is thus extracted from the water column continuously by particles, plankton, macrophytes and sediment. Within the time scale involved (13 Aug-24 Sept), degradation probably played only a minor role [13,14]. The testing of duck-pond and river water indi-
M
71
cated no detectable breakthrough of the two compounds. However, in cases in which large quantities of water which have a high content of DOC (dissolved organic carbon) are C 8 extracted, great care must be taken to eliminate the risk of breakthrough of the compounds of interest. With large water volumes the sorbent may become saturated, resulting in increased breakthrough. DOC, with which many hydrophobic substances form stable complexes [12], also increases the risk of sizeable breakthroughs occurring. A breakthrough of 36% has been documented for fenvalerate extracted (500 mg C 8) from 1 1 of river water containing 17-20 mg DOC 1-1 [3]. However, under the circumstances described in the present paper, the risk for breakthrough of the two compounds is probably negligible. GC interference from compounds other than the target one usually represents a problem when samples that have not been subjected to a clean-up procedure are analyzed. In the present study there was no need for clean-up, as can be seen in the chromatograms (Figs. 3 and 4). The application of
!
I-----
• DetectedHi r~ Nominal Hi
100
• DetectedMed O Nominal Med
10 ¢9
• DetectedLo A
A Nominal Lo
L..._~
0,1 13-aug
20-aug
27-aug
3-sep
10-sep
17-sep
24-sep
Date Fig. 2, Detected and nominal concentrations of metazachlor in natural pond-water mesocosms supplied with 600 (Hi), 30 (Med) and 1.5 (Lo) /xg 1 1 during a 1-week exposure period.
72
P. Woin / Sci. Total En~iron. 156 (1994) 67-75
External GC-standard Metazachlor
Fenvalerate
i
Spiked tap-water
3
~:
~
,,
i
I
Spiked pond-water (mesoeosms)
i
;
I
I
i
i
I
l
I
I
I
i
73
P. Woin / Sci. Total Environ. 156 (1994) 67-75
Spiked pond-water
Fenvalerate Metazachlor
I
i
I
!
I
I
~[
I
I
I
I
I
I
I
Spiked fiver-water
Metazachlor
Fig. 4. ECD chromatograms of real environmental waters supplied with realistic concentrations of fenvalerate and metazachlor. The pond-water containing 0.69/xg metazachlor and 1.03 ~g fenvalerate 1-I was taken from a eutrophic clear-water duck-pond. The river-water containing 0.60 /xg metazachlor and 1.55 /~g fenvalerate 1-1 was taken from an eutrophic lowland stream containing large amounts of suspended materials. GC conditions as in Fig. 3. the m e t h o d described to p o n d a n d river w a t e r (Fig. 4) w o u l d p r e s u m a b l y provide a c o n v e n i e n t q u a n t i f i c a t i o n of m e t a z a c h l o r a n d fenvalerate d o w n to 50 ng 1-1 a n d 10 ng 1-1, respectively. F o r all the samples tested (tap water, p o n d water,
river w a t e r a n d lake s e d i m e n t (the latter n o t p r e s e n t e d h e r e ) there were n o peaks i n t e r f e r i n g with fenvalerate, as f e n v a l e r a t e had a relatively long r e t e n t i o n time o n the DB-5 c o l u m n (Figs. 3 a n d 4). F o r m e t a z a c h l o r t h e r e were n o peaks that
Fig. 3. Electron capture detector (ECD) chromatograms of an external standard (metazachlor 0.255 ng /xl-I, fenvalerate 0.194 ng /~l-1), C s-extracted spiked tap-water (metazachlor 11.92 /~g 1-1, fenvalerate 3.55 ~g 1-1) and Cs-extracted spiked pond-water (metazachlor 2/xg 1-1 , without the presence of fenvalerate). One tzl was injected in all cases. The two peaks for fenvalerate show a separation in two diastereoisomers. GC operating conditions: EC detector heated at 290°C; splitless injection at 220°C. The J&W DB-5 capillary fused-silica column (30m × 0.3mm i.d.) was held at ll0°C for 3 min following injection. It was programmed to increase then at 20°C min-1 to 270°C, and was kept there for 10 min. The carrier gas was hydrogen having a flow rate of 2.5 ml min-l.
74
P. Woin / Sci. Total Environ. 156 (1994) 67-75
disturbed quantification when extracts of the water matrices that were tested were analyzed (Figs. 3 and 4). However, when extracts from matrices other than the ones tested are analyzed (e.g. sediments, organisms, water with a high content of particulate matters and phytoplankton) cleanup could well be necessary, e.g. by the use of Florisil. The most valuable features of the method described appear to be its simplicity and its high recovery of the two different types of pesticides. The method is one that should be useful for the direct extraction in the field of a wide range of pesticides found in neutral (pH 6-10) natural waters. Very few methods described in the literature cover a broad range of pesticides of quite differing chemical and physical properties, and none provides for extraction of the herbicide metazachlor. The sorbents used are most frequently C18, with methanol, acetonitril, acetone, ethyl ether, hexane and methylene chloride, pure or in various combinations, serving as elution agents. The excellent method developmental work of Junk and Richard [2], which concerns the extraction of a range of different pesticides (including substances closely related to metazachlor) and the use of ethyl acetate as the elution agent, provides the only method directly comparable with the present method. In their method, however, C~8 is used as the sorbent. The application of both types of methods to environmental waters of various types should be investigated further. In environmental research there is often a need to determine concentrations of different pesticides in surface waters and in ground water so as to illuminate potential effects on organisms. In most aquatic environments the organisms are exposed not only to the pure water soluble fractions of pesticides but also to pesticides bound to particulate matter and to organisms. Organisms can, through food intake, respiration and direct contact with the bound fraction of pesticides be affected by them. For pesticides such as fenvalerate, with low water solubility and high affinity for particulate matter, it is important that this bound fraction is measured, since a major part of the substance present in the water column tends to
be of this form. In combination with a G F F coupled to the front of the SPE-column, particulate bound fractions can easily be separated from the water-solved fraction. The paper describes an extraction method that can be used directly in the field. It allows both dissolved and particulate bound fractions of pesticides in water to be extracted. The method was also tested on real environmental waters with good results. Therefore, the direct extraction of water in the field through the use of SPE-columns represents an excellent method for the determination of 'real-life' exposure concentrations.
Acknowledgements I wish to thank Professor Anders SiSdergren for comments on this paper and the Swedish Environmental Protection Agency, Crafoordska Stiftelsen and Gyllenstiernska Krapperupsstiftelsen for financial support.
References 1 M.J.M. Wells and J.L. Michael, Reversed-phase solidphase extraction for aqueous environmental sample preparation in herbicide residue analysis, J. Chromatogr. Sci., 25 (1987) 345-350. 2 G.A. Junk and J.J. Richard, Organics in water: solid phase extraction on a small scale, Anal. Chem., 60 (1988) 451-454. 3 D.A. Hinckley and T.F. Bidleman, Analysis of pesticides in seawater after enrichment onto C8 bonded-phase cartridges, Environ. Sci. Technol., 23 (1989) 995-1000. 4 D.M. Swineford and A.A. Belisle, Analysis of trifluralin, methyl paraoxon, methyl parathion, fenvalerate and 2,4-D dimethylamine in pond water using solid-phase extraction, Environ. Toxicol. Chem., 8 (1989) 465-468. 5 E.J. Durhan, M.T. Lukasewyczand J.R. Amato, Extraction and concentration of non-polar organic toxicants from effluents using solid phase extraction, Environ. Toxicol. Chem., 9 (1990) 463-466. 6 D.W. Beyers, C.A. Carlson and J.D. Tessari, Solid-phase extraction of carbaryl and malathion from pond and well water, Environ. Toxicol. Chem., 10 (1991) 1425-1429. 7 C.E. Grue, L.R. Deweese, P. Mineau, G.A. Swanson, J.R. Foster, P.M. Arnold, J.N. Huckins, P.J. Sheehan, W.K. Marshall and A.P. Ludden, Potential impacts of agricultural chemicals on water-fowl and other wildlife inhabiting prairie wetlands: an evaluation of research needs and approaches, in R.E. McCabe (Ed.), Trans. 51st North American Wildlife and Natural Resource Conference,
P. Woin /Sci. Total Environ. 156 (1994) 67-75
8
9
10
11
Wildlife Management Institute, Washington, DC, 1986, pp. 357-383. J. Kreuger and N. Brink, Losses of pesticides from arable land, V~ixtskyddsrapporter (Swedish University of Agricultural Sciences), Jordbruk, 49 (1988) 50-61. R.P. Richards and D.B. Baker, Pesticide concentration patterns in agricultural drainage networks in the Lake Erie basin, Environ. Toxicol. Chem., 12 (1993) 13-26. M.S. Sharom and K.R. Solomon, Adsorption and desorption of permethrin and other pesticides on glass and plastic materials used in bioassay procedures, Can. J. Fish. Aquat. Sci., 38 (1981) 199-204. W.P. Schoor and C.L. McKenney Jr., Determination of
75
fenvalerate in flowing-seawater exposure studies. Bull. Environ. Contam. Toxicol., 30 (1983) 84-92. 12 K.E. Day, Effects of dissolved organic carbon on accumulation and acute toxicity of fenvalerate, deltamethrin and cyhalothrin to Daphnia magna (Straus), Environ. Toxicol. Chem., 10 (1991) 91-101. 13 W.E. Cotham Jr. and T.F. Bidleman, Degradation of malathion, endosulfan and fenvalerate in seawater and seawater/sediment microcosms J. Agric. Food Chem., 37 (1989) 824-828. 14 World Health Organization, Environmental Health Criteria 95, Fenvalerate, WHO, Geneva, 1990, pp. 41-42.
ELSEVIER
The Science of the Total Environment 156 (1994) 67-75
C s solid-phase extraction of the pyrethroid insecticide fenvalerate and the chloroacetanilide herbicide metazachlor from pond water Per Woin Laboratory of Chemical Ecology and Ecotoxicology, Department of Ecology, Universityof Lund, S-223 62 Lund, Sweden Received 22 March 1993; accepted 20 March 1994
Abstract A method was developed for the simultaneous extraction of the pyrethroid insecticide fenvalerate and the chloroacetanilide herbicide metazachlor from water using a solid-phase C8 column. After elution from the C8 column, the concentrated eluate was analysed using a capillary gas chromatographequipped with an electron-capture detector. The method was used to confirm residues of the compoundsin spiked tap water, pond water and river water. The recoveryrates were high (84% for the fenvalerate and 101% for the metazachlor) and there was no need for clean-up. Keywords: Solid-phaseextraction; Fenvalerate; Metazachlor; Pond water
1. Introduction The development of quick, simple and inexpensive methods for the determination of different pollutants in the environment has always been important to ecotoxicologists. However, as the number of pollutants in circulation has increased, the need for such methods has grown. One major advance in this area has been the development of pre-manufactured solid phase extraction (SPE) columns. Solid-phase extraction has been used extensively for removing non-polar organic chemicals from water [1-6]. In this procedure, a water sample containing the chemical compound of interest is passed through a column containing a sorbent having high affinity for non-polar com-
pounds. The target compound is bound by the column sorbent, the water is discarded and the compound is then eluted from the column and determined by appropriate methods. The use of SPE as a means for sample collection has many benefits, particularly when extraction is carried out in the field. For example, samples (SPE cartridges) transported to the laboratory are of much smaller size and weight, potential adsorption to sampling materials is eliminated, samples are easier to store in the laboratory and both the use of solvents and the time required for extraction are reduced markedly compared with liquid-liquid extraction. Many ponds and natural waters are surrounded by arable land and are thus subject to possible
0048-9697/94/$07.00 © 1994 Elsevier Science BV. All rights reserved. SSDI 0048-9697(94)04198-V
P. Woin / Sci. Total Environ. 156 (1994) 67-75
68
contamination by various pesticides [7-9]. A sampling and extraction method covering a wide range of compounds differing considerably in their physical and chemical properties should therefore be of great benefit to the control and regulation of pesticides and to related research. The pesticides considered in the present study represent two groups of agricultural chemicals used worldwide. One, the insecticide fenvalerate, is a nonpersistent pyrethroid; the other, the herbicide metazachlor, is typical of the large chloroacetanilide group. Fenvalerate (water solubility = 2-20 /xg 1 1, log Pow = 4.1) and metazachlor (water solubility = 20 mg 1-', log Pow = 2.1) were found appropriate for the study largely because of the difference in their polarity. Although methods for determining fenvalerate and other insecticides in water are well represented in the literature, few simple methods for determining herbicides have been reported and none of them concern metazachlor. The importance of being able to determine a broad spectrum of pesticides, including metazachlor, in natural waters has been focused on in our laboratory. The investigation has been aimed, accordingly, at developing a simple and reliable method for the simultaneous determination of fenvalerate, metazachlor and related compounds in pond water.
2. Materials and methods
High-purity pesticides (Pestanal®) to provide external GC-standards were obtained from Riedel-de Haen. Commercially available emulsifiable concentrate formulations of fenvalerate (Sumicidin 10FW, Dupont, 100 g 1-1 ) and metazachlor (Butisan S, BASF, 500 g 1-1) served as test substances. All the organic solvents were of residue analysis grade. Bonded-phase cartridges of C 8 (300 mg sorbent) were PrepSep® from Allied Fisher Scientific. The SPE-columns were cleaned before use by passing 6 ml methanol, 6 ml n-hexane and 4 ml ethyl acetate through them. Prior to sampling, the cartridges were preconditioned with 4 ml of methanol, followed by 4 ml of deionized water. Known amounts of Sumicidin 10FW and Butisan S were shaken vigorously in 961 ml of tap water to create a standard solution of 3.55/zg 1-1 fenvalerate and 11.92 /xg 1-1 metazachlor. Seven samples of this solution (67-264 ml, Table 1) were passed through preconditioned SPE-columns by drawing the solution directly from the bottle with a vacuum pump. Different volumes were extracted in order to simulate conditions in the field, where the SPE-columns may become clogged by seston. A hand-driven vacuum pump was connected to the submersed SPE-column via
Table 1 Recovery of fenvalerate (3.55 /zg 1-1) and metazachlor (11.92 /zg 1 1) from spiked tap-water Sample identity
Volume extracted
Nominal (ng M)
Detected (ng M)
Nominal (ng F)
Detected (ng F)
SPE1 SPE2 SPE3 SPE4 SPE5 SPE6 SPE7
67 ml 85 ml 264 ml 173 ml 97 ml 152 ml 123 ml
799 1013 3147 2062 1156 1812 1466
1042 1007 2991 2228 1102 1828 1335
238 301 936 613 344 539 436
150 235 834 504 299 458 373
Total M e a n + S.D.
961 ml
11 455
11533
3408
Bottle
surface
--
41
11 455
11574
Recovery (% M)
Recovery (% F)
130.4 99.4 95.0 108.1 95.3 100.9 91.1
63.0 78.1 89.1 82.2 86.9 85.0 85.6
2853
100.7 102.9 + 13.3
83.7 81.4 + 8.9
--
384
--
--
3408
3237
101.0
95.0
T h e c o m p o u n d s were extracted from the water in C s SPE-columns and from the inner surface of the bottle using 4 × 10 ml tea-butyl methyl ether:n-hexane (5:5, v/v). M, metazachlor; F, fenvalerate.
P. Woin / Sci. Total Environ. 156 (1994) 67-75
a filtering bottle and silicone tubing. The extracted water, collected in the filtering bottle, was quantified in a measuring cylinder. Following extraction, the columns were dried for 10 min by drawing air through them. The compounds were eluted from the SPE-columns with 4 ml ethyl acetate. The eluate was evaporated to ~ 1 ml and was transferred to autosampler vials. To determine the amounts of fenvalerate and metazachlor adsorbed onto the glass surfaces, the empty standard solution bottle was rinsed with 4 × 10 ml ten-butyl methyl ether:n-hexane (1:1, v/v). The resulting solution was evaporated to dryness and was redissolved in ethyl acetate, that was then transferred to autosampler vials. The compounds were determined using a Varian 3500 gas chromatograph equipped with an EC detector and a splitless injection system operated at 290°C and 220°C, respectively. Following injection, the J & W DB-5 capillary fused-silica column (30m × 0.3mm i.d.) was kept at ll0°C for 3 min. It was programmed to then increase at 20°C min- 1 to 270°C and was kept there for 10 min. The carrier gas was hydrogen which had a flow rate of 2.5 ml min -1. To test the method under field conditions, the SPE-columns were used to extract fenvalerate and metazachlor from natural pond water (without prior filtration) kept in mesocosms. Apart from the water, the mesocosms contained 1 m 3 unpolluted eutrophic lake sediment and different fresh water plants. All the natural components contained a natural composition of organisms (algae, zooplankton, benthos, etc.). Three of the mesocosms were continuously supplied with fenvalerate for 2 weeks and three of them were continuously supplied with metazachlor for 1 week. All the mesocosms were static (no inflow or outflow), the water being recirculated. Solutions of the compounds were introduced slowly by being pumped into the recirculation tubes of each mesocosm by a multi-channel peristaltic pump. To test the application of the method to other types of natural waters, water samples (500 ml) were taken from a clear-water duck-pond and from a eutrophic river of high turbidity. These two water samples were fortified with realistic
69
concentrations [8] of fenvalerate and metazachlor. The main purpose for this test was to investigate possible interferences that might be found in other water matrices. In addition, tandem-coupled SPE-columns were used to confirm that no breakthrough of the compounds occurred. Some 200-300 ml of the water were passed through the columns, an elution volume of 2 ml being obtained, providing extracts of ~ 1.5 ml that were transferred directly to autosampler vials. 3. Results and discussion
Fenvalerate and metazachlor were isolated and concentrated in a rapid and efficient manner using the C a solid-phase extraction procedure described here. Excellent recoveries were obtained on a total basis, the amounts adsorbed on the glass being included (Table 1). Almost all of the compounds added to the water (101% of the metazachlor applied and 95% of fenvalerate) were recovered. The SPE-columns collected 100% of the metazachlor and 83.7% of the fenvalerate. The extraction step for these compounds is reliable and the technique may also be useful for the extraction of the related acetanilides and pyrethroids at concentrations one could expect to find in natural waters. Most studies concerning the separation of non-polar and semi-polar pesticides from natural waters have used ClS as a sorbent [1,2,4,5]. However, as the high recovery of fenvalerate and metazachlor in this study suggest, C 8 may be almost as effective as ClS as a pesticide sorbent. Hinckley and Bidleman [3], also using C s as the sorbent, reported high recovery rates (85-115%) from a collection of organochlorine, organophosphate and pyrethroid insecticides (including fenvalerate) that were extracted from spiked deionized water, as well as from sea water. They also found the breakthrough of the pesticides to be low (0-13%). Recovery rates of 80-100% for the extraction by C 8 of carbaryl and malathion from pond and well water have also been reported [6]. Because of the tendency of hydrophobic compounds to adhere or adsorb to surfaces, extraction from the empty standard solution bottle was included in the study. Fenvalerate and pyrethroids
P. Woin / Sci. Total Enuiron. 156 (1994)67-75
70
are known generally to adsorb strongly onto glass and plastic materials [10]. In the present study, however, only 11.3% of the fenvalerate was found to adhere to the surfaces of the glass bottle (Table 1.). This low adsorption, compared with what has been reported elsewhere [3,11,12], may be due to the fact that the fenvalerate was applied to the water in an emulsifiable formulation. It is also possible that the time (~ 1 h) between preparation of the water solution and sampling was too short for adsorption to develop since the latter is a time-dependent phenomenon. Other workers have found the adsorption of fenvalerate to surfaces to be 54% for glass bottles and 28% for glass-fiber filters [3], 60-90% for a glass diluter system [11] and 8.6% for BOD bottles [12]. Sharom and Solomon [10] found the adsorption of permethrin (same chemical family as fenvalerate) to glass to be as high as 70% and that of polyethylene and PVC to be as high as 100% after 96 h of agitation. Particulate bounded fenvalerate collected on glass-fiber filters (GFF) before extraction with C 8 have been found to constitute up to 77% of the total amount of fenvalerate found in
tidal creek water [3]. The choice of sampling strategy is of great importance, therefore, for the accurate determination of pesticides in water. Use of traditional methods (collecting water in bottles) may thus lead to large reductions in the amounts of key compounds due to the adsorption and degradation that occur during transportation and storage. With the use of the SPE method, both dissolved compounds and those bound to particles in the water are collected efficiently and the cartridges can be easily stored in a freezer. The recovery of a specific compound is governed by many factors, such as volatility, water solubility and log Pow. The present method was optimized to the determination of fenvalerate and metazachlor in neutral natural waters having a low content of particulate matter. Because of the differing properties of the two compounds, one can assume that the method is applicable to a wide spectrum of pesticides, to pyrethroids and chloroacetanilides in particular. The results from the application of the method to real environmental water (pond-water) are illustrated in Figs. 1 (fenvalerate) and 2 (meta-
100 [] DetectedHi O
10
[] Nominal Hi -"43
il
* DetectedVIed
l
<> Nominal Med A
0,1
• DetectedLo ----A
A Nominal Lo
[]
0,01
L.
0,001 13-aug
I
I
I
I
I
I
20-aug
27-aug
3-sep
10-sep
17-sep
24-sep
Date Fig. 1. Detected and nominal concentrations of fenvalerate in natural pond-water mesocosms supplied with 20 (Hi), 2 (Med) and 0.2 (Lo) ~g 1-l during a 2-week exposure period.
P. Woin / Sci. Total Environ. 156 (1994) 67-75
zachlor). The most striking difference between the two compounds, is the difference in the nominal versus the detected concentrations involved. These differences between fenvalerate and metazachlor are presumably due, however, to their differing solubility in water. The fenvalerate concentrations detected (Fig. 1) never reached > 20% of the nominal ones, and when the addition of fenvalerate ceased the concentration dropped rapidly. In the case of metazachlor (Fig. 2), the amount detected closely followed the supply, the concentration detected never being < 60% of the theoretical concentration. The drop in concentration after exposure ceased was also much slower. The low concentration of fenvalerate and its rapid decrease are most likely due to that substance's high affinity for surfaces and particulate matter [3,10,11,12]. It is thus extracted from the water column continuously by particles, plankton, macrophytes and sediment. Within the time scale involved (13 Aug-24 Sept), degradation probably played only a minor role [13,14]. The testing of duck-pond and river water indi-
M
71
cated no detectable breakthrough of the two compounds. However, in cases in which large quantities of water which have a high content of DOC (dissolved organic carbon) are C 8 extracted, great care must be taken to eliminate the risk of breakthrough of the compounds of interest. With large water volumes the sorbent may become saturated, resulting in increased breakthrough. DOC, with which many hydrophobic substances form stable complexes [12], also increases the risk of sizeable breakthroughs occurring. A breakthrough of 36% has been documented for fenvalerate extracted (500 mg C 8) from 1 1 of river water containing 17-20 mg DOC 1-1 [3]. However, under the circumstances described in the present paper, the risk for breakthrough of the two compounds is probably negligible. GC interference from compounds other than the target one usually represents a problem when samples that have not been subjected to a clean-up procedure are analyzed. In the present study there was no need for clean-up, as can be seen in the chromatograms (Figs. 3 and 4). The application of
!
I-----
• DetectedHi r~ Nominal Hi
100
• DetectedMed O Nominal Med
10 ¢9
• DetectedLo A
A Nominal Lo
L..._~
0,1 13-aug
20-aug
27-aug
3-sep
10-sep
17-sep
24-sep
Date Fig. 2, Detected and nominal concentrations of metazachlor in natural pond-water mesocosms supplied with 600 (Hi), 30 (Med) and 1.5 (Lo) /xg 1 1 during a 1-week exposure period.
72
P. Woin / Sci. Total En~iron. 156 (1994) 67-75
External GC-standard Metazachlor
Fenvalerate
i
Spiked tap-water
3
~:
~
,,
i
I
Spiked pond-water (mesoeosms)
i
;
I
I
i
i
I
l
I
I
I
i
73
P. Woin / Sci. Total Environ. 156 (1994) 67-75
Spiked pond-water
Fenvalerate Metazachlor
I
i
I
!
I
I
~[
I
I
I
I
I
I
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Spiked fiver-water
Metazachlor
Fig. 4. ECD chromatograms of real environmental waters supplied with realistic concentrations of fenvalerate and metazachlor. The pond-water containing 0.69/xg metazachlor and 1.03 ~g fenvalerate 1-I was taken from a eutrophic clear-water duck-pond. The river-water containing 0.60 /xg metazachlor and 1.55 /~g fenvalerate 1-1 was taken from an eutrophic lowland stream containing large amounts of suspended materials. GC conditions as in Fig. 3. the m e t h o d described to p o n d a n d river w a t e r (Fig. 4) w o u l d p r e s u m a b l y provide a c o n v e n i e n t q u a n t i f i c a t i o n of m e t a z a c h l o r a n d fenvalerate d o w n to 50 ng 1-1 a n d 10 ng 1-1, respectively. F o r all the samples tested (tap water, p o n d water,
river w a t e r a n d lake s e d i m e n t (the latter n o t p r e s e n t e d h e r e ) there were n o peaks i n t e r f e r i n g with fenvalerate, as f e n v a l e r a t e had a relatively long r e t e n t i o n time o n the DB-5 c o l u m n (Figs. 3 a n d 4). F o r m e t a z a c h l o r t h e r e were n o peaks that
Fig. 3. Electron capture detector (ECD) chromatograms of an external standard (metazachlor 0.255 ng /xl-I, fenvalerate 0.194 ng /~l-1), C s-extracted spiked tap-water (metazachlor 11.92 /~g 1-1, fenvalerate 3.55 ~g 1-1) and Cs-extracted spiked pond-water (metazachlor 2/xg 1-1 , without the presence of fenvalerate). One tzl was injected in all cases. The two peaks for fenvalerate show a separation in two diastereoisomers. GC operating conditions: EC detector heated at 290°C; splitless injection at 220°C. The J&W DB-5 capillary fused-silica column (30m × 0.3mm i.d.) was held at ll0°C for 3 min following injection. It was programmed to increase then at 20°C min-1 to 270°C, and was kept there for 10 min. The carrier gas was hydrogen having a flow rate of 2.5 ml min-l.
74
P. Woin / Sci. Total Environ. 156 (1994) 67-75
disturbed quantification when extracts of the water matrices that were tested were analyzed (Figs. 3 and 4). However, when extracts from matrices other than the ones tested are analyzed (e.g. sediments, organisms, water with a high content of particulate matters and phytoplankton) cleanup could well be necessary, e.g. by the use of Florisil. The most valuable features of the method described appear to be its simplicity and its high recovery of the two different types of pesticides. The method is one that should be useful for the direct extraction in the field of a wide range of pesticides found in neutral (pH 6-10) natural waters. Very few methods described in the literature cover a broad range of pesticides of quite differing chemical and physical properties, and none provides for extraction of the herbicide metazachlor. The sorbents used are most frequently C18, with methanol, acetonitril, acetone, ethyl ether, hexane and methylene chloride, pure or in various combinations, serving as elution agents. The excellent method developmental work of Junk and Richard [2], which concerns the extraction of a range of different pesticides (including substances closely related to metazachlor) and the use of ethyl acetate as the elution agent, provides the only method directly comparable with the present method. In their method, however, C~8 is used as the sorbent. The application of both types of methods to environmental waters of various types should be investigated further. In environmental research there is often a need to determine concentrations of different pesticides in surface waters and in ground water so as to illuminate potential effects on organisms. In most aquatic environments the organisms are exposed not only to the pure water soluble fractions of pesticides but also to pesticides bound to particulate matter and to organisms. Organisms can, through food intake, respiration and direct contact with the bound fraction of pesticides be affected by them. For pesticides such as fenvalerate, with low water solubility and high affinity for particulate matter, it is important that this bound fraction is measured, since a major part of the substance present in the water column tends to
be of this form. In combination with a G F F coupled to the front of the SPE-column, particulate bound fractions can easily be separated from the water-solved fraction. The paper describes an extraction method that can be used directly in the field. It allows both dissolved and particulate bound fractions of pesticides in water to be extracted. The method was also tested on real environmental waters with good results. Therefore, the direct extraction of water in the field through the use of SPE-columns represents an excellent method for the determination of 'real-life' exposure concentrations.
Acknowledgements I wish to thank Professor Anders SiSdergren for comments on this paper and the Swedish Environmental Protection Agency, Crafoordska Stiftelsen and Gyllenstiernska Krapperupsstiftelsen for financial support.
References 1 M.J.M. Wells and J.L. Michael, Reversed-phase solidphase extraction for aqueous environmental sample preparation in herbicide residue analysis, J. Chromatogr. Sci., 25 (1987) 345-350. 2 G.A. Junk and J.J. Richard, Organics in water: solid phase extraction on a small scale, Anal. Chem., 60 (1988) 451-454. 3 D.A. Hinckley and T.F. Bidleman, Analysis of pesticides in seawater after enrichment onto C8 bonded-phase cartridges, Environ. Sci. Technol., 23 (1989) 995-1000. 4 D.M. Swineford and A.A. Belisle, Analysis of trifluralin, methyl paraoxon, methyl parathion, fenvalerate and 2,4-D dimethylamine in pond water using solid-phase extraction, Environ. Toxicol. Chem., 8 (1989) 465-468. 5 E.J. Durhan, M.T. Lukasewyczand J.R. Amato, Extraction and concentration of non-polar organic toxicants from effluents using solid phase extraction, Environ. Toxicol. Chem., 9 (1990) 463-466. 6 D.W. Beyers, C.A. Carlson and J.D. Tessari, Solid-phase extraction of carbaryl and malathion from pond and well water, Environ. Toxicol. Chem., 10 (1991) 1425-1429. 7 C.E. Grue, L.R. Deweese, P. Mineau, G.A. Swanson, J.R. Foster, P.M. Arnold, J.N. Huckins, P.J. Sheehan, W.K. Marshall and A.P. Ludden, Potential impacts of agricultural chemicals on water-fowl and other wildlife inhabiting prairie wetlands: an evaluation of research needs and approaches, in R.E. McCabe (Ed.), Trans. 51st North American Wildlife and Natural Resource Conference,
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8
9
10
11
Wildlife Management Institute, Washington, DC, 1986, pp. 357-383. J. Kreuger and N. Brink, Losses of pesticides from arable land, V~ixtskyddsrapporter (Swedish University of Agricultural Sciences), Jordbruk, 49 (1988) 50-61. R.P. Richards and D.B. Baker, Pesticide concentration patterns in agricultural drainage networks in the Lake Erie basin, Environ. Toxicol. Chem., 12 (1993) 13-26. M.S. Sharom and K.R. Solomon, Adsorption and desorption of permethrin and other pesticides on glass and plastic materials used in bioassay procedures, Can. J. Fish. Aquat. Sci., 38 (1981) 199-204. W.P. Schoor and C.L. McKenney Jr., Determination of
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fenvalerate in flowing-seawater exposure studies. Bull. Environ. Contam. Toxicol., 30 (1983) 84-92. 12 K.E. Day, Effects of dissolved organic carbon on accumulation and acute toxicity of fenvalerate, deltamethrin and cyhalothrin to Daphnia magna (Straus), Environ. Toxicol. Chem., 10 (1991) 91-101. 13 W.E. Cotham Jr. and T.F. Bidleman, Degradation of malathion, endosulfan and fenvalerate in seawater and seawater/sediment microcosms J. Agric. Food Chem., 37 (1989) 824-828. 14 World Health Organization, Environmental Health Criteria 95, Fenvalerate, WHO, Geneva, 1990, pp. 41-42.