Article pubs.acs.org/JAFC
Evaluation of Low-Pressure Gas Chromatography−Tandem Mass Spectrometry Method for the Analysis of >140 Pesticides in Fish Yelena Sapozhnikova* Eastern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, 600 East Mermaid Lane, Wyndmoor, Pennsylvania 19038, United States ABSTRACT: A multiresidue method for the analysis of 143 pesticide residues in fish was developed and evaluated using fast, low-pressure gas chromatography/triple-quadrupole tandem mass spectrometry (LP-GC/MS-MS). The method was based on a QuEChERS (quick, easy, cheap, effective, rugged, safe) extraction with acetonitrile and dispersive solid-phase extraction (d-SPE) cleanup with zirconium-based sorbent. The developed method was evaluated at four spiking levels (1, 5, 50, and 100 ng/g) and further validated by analysis of NIST Standard Reference Materials (SRMs) 1974b and 1947 for selected pesticides with certified concentrations. Acceptable recoveries (70−120%) and standard deviations below 20% were achieved for the majority of pesticides from fortified samples. The measured values for both SRMs agreed with certified values (71−115% accuracy, 4−14% relative standard deviations) for all pesticides, except for p,p-DDD + o,p-DDT (45%) and heptachlor (133%) in SRM 1974b and except for mirex (58%) and trans-chlordane (136%) in SRM 1947. The developed method is fast, simple, and inexpensive with detection limits of 0.5−5 ng/g. Residues of dimethoate, hexachlorobenzene, BHC, lindane, nonachlor, chlorpyrifos, trifluralin, p,p-DDE, p,p-DDD, o,p-DDD, o,p-DDT, p,p-DDD, and chlordane were measured in catfish samples from the market. KEYWORDS: pesticide residues, QuEChERS sample preparation, fast gas chromatography/tandem mass spectrometry, catfish analysis
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INTRODUCTION With increasing global trading of agricultural goods, fast and efficient monitoring of imported/exported food is needed to comply with food safety regulations. According to the USDA National Agricultural Statistics Service, 204 million pounds of catfish was imported into the United States during 2011.1 Catfish is a valued source of vitamin D2 and omega-3 fatty acids3 and is one of the 10 top consumed seafood in the United States and other countries.4 However, there is a concern regarding contamination of edible fish tissues with pesticides. Most pesticides are lipophilic and therefore tend to accumulate in sediments and fatty tissues. Because most catfish are bottomfeeders, they can potentially accumulate pesticides from bottom sediments. In fact, some studies have reported findings of persistent pesticides in catfish.5,6 Tolerances have been established for some pesticide residues in fish for consumer’s protection, for example, 2000 ng/g for diuron and 50 ng/g for pendimethalin (crayfish).7 However, for a majority of pesticides in fish, tolerances have not been established, and it is unclear if chronic residual pesticide exposure may cause any potential human health effects. Analysis of multiple pesticides with fast and reliable analytical methods is one of the major tasks in food safety programs. Traditionally, analysis of pesticides in fish includes pressurized fluid extraction, gel permeation chromatography, and solidphase extraction cleanup with conventional gas chromatography (GC) using a 30 m capillary column.8,9 These techniques are time and labor consuming and require large amounts of organic solvents and multiple sample preparation steps. Previously, we reported a method for the analysis of environmental contaminants and 18 selected pesticides in catfish samples10 based on QuEChERS extraction with acetonitrile and dispersive solid-phase extraction (d-SPE) This article not subject to U.S. Copyright. Published 2014 by the American Chemical Society
cleanup with zirconium-based sorbent and fast, low-pressure gas chromatography with tandem mass spectrometry. The goal of the present study was to evaluate the recoveries of 143 pesticides from catfish samples at four spiking levels, so these pesticides can be analyzed along with environmental contaminants providing a high-throughput method for approximately 200 analytes from one sample. We intended to cover a wide range of pesticides in a fast, inexpensive, and simple to use analytical method, with low detection limits, to increase sample throughput and improve the monitoring of chemical contaminants in foods.
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MATERIALS AND METHODS
Pesticide standards were from the U.S. Environmental Protection Agency’s National Pesticide Repository (Fort Meade, MD, USA), Dr. Ehrenstorfer GmbH (Augsburgm, Germany), and Chemservice (West Chester, PA, USA). Atrazine-d5 (ethyl-d5) and fenthion-d6 (o,odimethyl-d6), used as internal standards (ISTDs), were from C/D/N Isotopes (Pointe-Claire, Quebec, Canada). All standards were of ≥98% purity. All solvents were of HPLC grade. Acetonitrile (MeCN) was from Fisher Scientific (Pittsburgh, PA, USA). Anhydrous magnesium sulfate (anh MgSO4), reagent grade, 99.5% purity, was purchased from United Chemical Technologies (UCT) (Bristol, PA, USA). Deionized water of 18.2 Ω was prepared with an E-Pure model D4641 from Barnstead/Thermolyne (Dubuque, IA, USA). ACS grade sodium chloride (NaCl) was obtained from Mallinckrodt (Paris, KY, USA). Supel QuE Z-Sep sorbent was from Supelco (Bellefonte, PA, USA). ZSpecial Issue: 50th North American Chemical Residue Workshop Received: Revised: Accepted: Published: 3684
October 31, 2013 January 2, 2014 January 3, 2014 January 3, 2014 dx.doi.org/10.1021/jf404389e | J. Agric. Food Chem. 2014, 62, 3684−3689
Journal of Agricultural and Food Chemistry
Article
Table 1. Pesticide Retention Times, Lowest Calibrated Level (LCL), Average Recoveries (n = 5), and Standard Deviations (SD) for Fortified Samplesa spiking level alachlor aldrin α-BHC atrazine azinphos-ethyl azinphos-methyl β-BHC + lindane bifenthrin bromophos bromophos-ethyl bromopropylate bupirimate buprofezin cadusafos carbaryl carbofuran carbophenothion chinomethionat chlorfenvinphos chlorothalonil chlorpropham chlorpyrifos chlorpyrifos-methyl cis-chlordane cis-nonachlor cis-permethrin coumaphos cyanophos cyfluthrin cypermethrin cyprodinil δ-BHC + lindane deltamethrin demeton-s-methyl demeton-s-methyl sulfone diazinon dichlorfenthion dicloran dicrotophos dieldrin dimethoate dioxathion diphenylamine disulfoton disulfoton sulfone endosulfan sulfate endrin endrin ketone EPN esfenvalerate ethalfluralin ethion ethoprophos famphur fenarimol fenchlorphos fenitrothion fenpropathrin
tR (min)
LCL (ng/g)
1 ng/g
5 ng/g
4.553 4.825 4.13 4.529 6.259 6.124 4.23 5.73 4.86 5.032 5.8 5.192 5.216 3.903 3.653 4.149 5.496 5.11 4.928 4.363 3.95 4.526 4.527 5.092 5.425 6.381 6.493 4.259 6.706 6.864 4.903 4.288 7.999 3.883 4.648 4.246 4.482 4.182 3.752 5.278 4.156 4.24 3.673 3.883 5.08 5.582 5.358 5.86 5.799 7.52 3.898 5.348 3.903 5.481 6.31 4.611 4.666 5.789
0.5 0.5 0.5 0.5 1 1 0.5 1 0.5 0.5 0.5 5 1 0.5 1 0.5 1 1 0.5 0.5 0.5 0.5 0.5 0.5 0.5 1 1 0.5 1 5 0.5 0.5 1 0.5 1 0.5 0.5 0.5 0.5 1 1 1 1 1 0.5 0.5 1 0.5 1 1 0.5 1 0.5 1 1 0.5 0.5 1
112 ± 14 70 ± 10 94 ± 20 109 ± 10
