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Bull. Environ. Contam. Toxicol. (1997) 59:171-178 1997 Springer-Verlag New York Inc
New Method for Analysis of Pyrethroid
Insecticides: Esfenvalerate, cis-Permethrin, and trans-
Permethrin, in Surface Waters Using Solid-Phase Extraction
and Gas Chromatography
Department of Environmental Toxicology, University of California, Davis, California 95616,USA
Received: 4 February 1997/Accepted: 13 May 1997
Synthetic pyrethroids are used widely to control many common pests, including
, on crops such as almonds, corn, garlic, and
tomatoes (Meister, 1996). During the last 15 years, the use of synthetic pyrethroidinsecticides, such as esfenvalerate and permethrin, has increased substantially,because of their potent insecticidal properties and low mammalian and avian toxicity(Ecobichon, 1996). In California, two commonly used pyrethroid insecticides areesfenvalerate or Asana®, cis
-permethrin, and trans
-permethrin. From 1990through 1994, over 330,000 and 1.3 million lb of esfenvalerate and permethrin,
respectively, were applied on various crops throughout California (Pesticide Use
Many aquatic organisms (fish, amphibians, macroinvertebrates, andmicroinvertebrates) are highly susceptible to pyrethroid intoxication, andapplications typically occurring throughout the spring and summer months coincidewith the spawning period of several fish species in California (Moyle, 1976).
Esfenvalerate has exhibited detrimental effects to aquatic organisms, by reducingand/or eliminating test populations of crustaceans, chironomids, juvenile bluegills,and larval cyrinids at exposure levels of 1 ppb (Lozano, 1992). Permethrin,applied as a mixture of cis-
isomers, has also been shown to adverselyimpact aquatic species, giving a LC (48 hr) of 5.4 ppb and 1.8 ppb for rainbow
trout and bluegill sunfish, respectively (Kidd and James, 1995).
Since certain pyrethroids have been shown to enter the aquatic environment fromagricultural runoff or drift from aerial or ground-based spraying (Tanner, 1996),applications may pose a serious threat to fish populations by direct exposure ofyoung fish, which tend to be less tolerant to pesticides (Kumaraguru, 1981), andindirectly by the reduction of sensitive invertebrate populations serving as prey foryoung fish (Kreutzweiser, 1987). Therefore, it is important to develop a sensitiveand selective method for determining these pesticides to monitor their possiblecontaminations in a surface water.
In the present study, a fast, selective, and sensitive method of esfenvalerate, cis-
permethrin, and trans
-permethrin analysis in surface waters using solid-phaseextraction (SPE) and gas chromatography (GC) with electrolytic conductivitydetection (ELCD) was developed.
E s f e n v a l e r a t e [ ( S ) α -cyano-3-phenoxybenzyl (S)-2-(4-chlorphenyl)-3-methylbutyrate] was purchased from DuPont (Wilmington, DE). cis-
Permethrin [3-phenoxybenzyl (lRS)-cis
- a n d -trans
-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane carboxylate] were obtained from the EPA (Research TrianglePark, NC).
Surface waters (3 L) were collected from Putah Creek (South of UC Davis, DavisCA), Sacromento River (West of Sacramento Municiple airport, Sacromento, CA),Clear Lake (Konocti Marina, Kelseyville, CA), and Lake Tahoe (Near Elk Point,
South Lake Tahoe, NV) in 4 L amber glass jugs. They were preserved on ice at thesampling site, through transit, and then stored in a 4°C refrigerator. Observedappearance and pH of the surface water samples were shown in Table 1.
Observed appearance and pH of water samples.
Safety precautions were necessary to handle esfenvalerate because it is combustibleat 66°C and can produce hydrogen cyanide. Proper protective clothing were wornwhen working with the compound.
A mixed stock solution of esfenvalerate, cis
-permethrin, and trans
-permethrin wasprepared by dissolving 25.0 mg of each compound in acetone (J. T. Baker Inc.,Phillipsburg, NJ) in a 25 mL volumetric flask and then the volume of a solutionwas adjusted to give a final concentration of 1 mg/mL concentration. Fortification
standards of 100 µg/mL and 10 µg/mL solutions were prepared by transferring 1
mL of the stock solution into a 10 and 100 mL of acetone in volumetric flasks,respectively. The lowest fortification standard solution (1 µg/mL) was made byadding a 1 mL of the fortification solution (10 µg/mL) into 10 mL of acetone in avolumetric flask.
After water samples were equilibrated to room temperature, they were thoroughlymixed by shaking the 4 L jug for 5 min. Into a 125 mL erlenmeyer flask, 100 mLof water sample, fortification solution (if necessary), and 10 g of NaCl was added.
The mixture was homogenized for 5 min with a gyrotory shaker (New Brunswick
Scientific Company, New Brunswick, NJ). Samples were loaded into an attached
75 mL reservoir and passed through a C solid phase extraction (SPE) cartridges
(Mega Bond-Elut®, 6 cc-l g, steel fritted, Varian, Harbor City, CA). The
cartridges were conditioned by pulling through two column volumes each ofmethanol and deionized water with a vacuum manifold (Varian, Harbor City, CA)prior to use. In addition, the sample flask was rinsed with deionized water (10 mL)and the rinsate was loaded onto the cartridge. After all water was passed through,the cartridge was removed from the manifold, placed into a 15 mL graduated
centrifuge tube, and eluted with 6 mL ethyl acetate twice using a centrifuge
(International Equipment Company, Needham Heights, MA).
Analysis of ethyl acetate extracts was conducted with a Hewlett-Packard Model5890A GC (Hewlett-Packard, Avondale, PA) equipped with a O.I. Model 4420electrolytic conductivity detector (O.I. Corporation, College Station, TX) and a 15m x 0.53 mm i.d. (d =1.5 µm) Rtx-1® bonded phase fused silica megabore
column (Restek Corporation, Bellefonte, PA). The injector and detector wereoperated at 250 and 280°C respectively. A Hewlett-Packard Model 6890 SeriesAutoinjector was used to inject 3 µL (set for fast injection) of samples in splitlessmode. The oven temperature was programmed from 200°C to to 250°C at 5°
C/min and held for 1 min. Helium was used as both carrier (20 mL/min) and make-up (10 mL/min) gas, and hydrogen was used as the detector gas (83 mL/min).
Quantitation was performed by manually drawing baselines for each peak of interestand measuring the peak heights with Turbochrom® v4.1 software (Perkin ElmerCorporation, Norwalk, CT). Four point standard curves were used at thebeginning and end of each set of samples with standards interspersed between
replicate sample injections to ensure a linear response over the range of 100-800pg/µL. The average of the standards was used to generate the standard curve forquantitation. Detection limits of qualitative and quantitative analysis were 30 pg and
300 pg for each pesticide, respectively.
Standard samples for the GC calibration curve were prepared by placing a 200 µLaliquot of the 100 µg/mL fortification solution into volumetric flasks containing aminimum amount of ethyl acetate and then the volume of the samples were broughtup to 25, 50, 100, and 200 mL with ethyl acetate, resulting in 800, 400, 200, and
In order to examine the stability of a sample during storage, the water samplesfrom Putah Creek and Sacramento River (100 mL) were placed into 250 mLsilanized amber bottles. The water samples were fortified with the pesticides at the
100 ppb level, and then stored in a 4°C refrigerator. Two replicates from each
water sample were extracted and analyzed after 0, 1,2,4, and 8 days
Advantages of combined SPE and ELCD method provides speed, simplicity, and
sensitivity for determination of halogenated compounds, such as esfenvalerate and
permethrin. Figure 1 shows a typical gas chromatogram of an ethyl acetate extractfrom a Lake Tahoe water fortified 1 ppb each of esfenvalerate, cis-,
Table 2 shows results from method validation spikes of esfenvalerate and cis-
-petmethrin in deionized water. The permethrin recoveries were comparable tothe recoveries conducted using a liquid-liquid extraction (Smith, 1983). Theesfenvalerate recoveries were also consistent with those from agricultural runoffwater tested using various elution patterns and C SPE packing sizes (Wells et al.,
1994). Both methods described above use GC with electron capture detection
(ECD) for quantification of the pesticides.
Although environmental water samples varied in pH and appearance (Table l),recoveries (Table 3) were not significantly different from those of deionized water(Table 2). This is somewhat surprising since suspended solid loading varied from
Table 2. Results of recovery tests on esfenvalerate and cis-
a Average of six replicates. b None fortified deionized water. ND: not detected (lessthan 0.5 ppb).
Results of recovery tests on esfenvalerate and cis-
from surface water samples.
a Average of two replicates. b None fortified surface water. ND: not detected (lessthan 0.5 ppb).
A typical gas chromatogram of an ethyl acetate extract from a Lake
Tahoe water fortified 1 ppb each of cis-permethrin (1
at 6.647 min) ,trans-
at 6.799 min), and esfenvalerate (3
at 9.539 min).
Gas chromatogram of an ethyl acetate extract obtained from a deionized
water fortified with 10 ppb each of cis-permethrin (1
at 6.633 min), trans-
at 6.793 min), and esfenvalerate (4
at 9.529 min). The peak at 9.183
min is fenvalerate.
highest to lowest in the order Clear Lake < Putah Creek < Sacramento River < LakeTahoe. Also permethrin and esfenvalerate are highly lipophilic compounds whichmay partition from water to sediments in littoral enclosures (Heinis, 1992; Muir,
1985). Although it is possible that permethrin and esfenvalerate could sorb to
suspended lipophilic particles and be carried through the C packing, no dramatic
loss was shown in the recoveries (Table 3).
While ECD’s sensitivity to halogenated compounds is single picograms over alinear range of two orders of magnitude, it may also respond to other electronaccepting compounds in natural waters, such as aromatics, conjugated carbonyls,and organometallics (Willard et al., 1988). The detection of unwanted compoundsmay interfere determination of the analyte of interest. Alternatively, because ELCDprovides extremely high selectivity for halogenated compounds, in addition to highsensitivity (10 pg) and large linear range (five orders of magitude), comparativelyfewer chromatographic interferences are obtained (Willard et al., 1988).
Additionally, SPE affords rapid sample through put, simultaneous processing of
several samples, and reduced solvent waste compared to conventional liquid-liquidextraction methods.
A storage stability study was conducted to determine the acceptable storage time fornatural water samples suspected of containing esfenvalerate, cis
-permethrin residues. A storage time of 2,4 and 8 days resulted significantlylow recoveries (Table 4). During the storage stability study, ethyl acetate rinsatesfrom the storage bottles revealed no permethrin or esfenvalerate residues,suggesting that the losses were not the result of pesticide adsorbing to the samplecontainer. Eventhough approximately 60% of the permethrin was reportedlyadsorbed on glass within 48 hr (Sharom and Solomon, 1981a). Thus, possible
routes of loss may include physical adsorption on particulates suspended in thewater samples, chemical degradation by oxidative free-radicals such as alkylperoxy
and hydroxyl radicals present in natural waters, or microbial degradation (Sharomand Solomon, 1981b). It is advisable, therefore, that esfenvalerate and permethrinin natural water samples are analyzed within 24 hr.
Results of stability test on esfenvalerate and cis-
It was noted that a second peak eluted near the esfenvalerate peak in the screeningstudies (Wells, 1994). In the present study, a similar peak was found beforeesfenvalerate when the pH of the deionized water sample was adjusted above 8 withNaOH (Figure 2). This peak was later confirmed as fenvalerate, [(RS)-a-cyano-3-phenoxybenzyl (RS)-2-(4-chlorophenyl)-3-methylbutyrate] by GC-mass selectivedetection (Hewlett-Packard Model 5972A MSD coupled to a Hewlett-PackardModel 6890 GC). At no time during the analysis of natural waters did thefenvalerate peak occur and this is most likely due to the neutral to slightly acidic pHof the natural waters.
With increasing analytical demand for determination of pesticides in water in orderto assess their possible hazard to aquatic organisms, the need for development ofmethods with selectivity, speed, and sensitivity have become paramount. The newmethod developed for esfenvalerate and cis-
-permethrin in the present
Acknowledgment. This work was supported, in part, by the California Departmentof Pesticide Regulation, the U.S. EPA (R819658) Center for Ecological HealthResearch at UC Davis, and the USDA IR-4.
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