## 2 Materials and Methods
### Chemicals  
High-purity pesticide standards (250) were used for testing (98-99%, Dr. Ehrenstorfer GmbH, Augsburg, Niemcy; ChemService, West Chester, PA, USA): 2,4,5-T, 2,4-D, 2,4-DB, 3,5-dichloraniline, 3-hydroxycarbofuran, abamectin, acephate, acetaminophen, carinathrin, alachlor, aldicarb, aldicarb sulfoxide, aldicarb sulphone, ametryn, amitraz, atrazine, azinophosphethyl, azinophos-methyl, azoxystrobin, benfuracarb, bentazon, benzoylprop ethyl, bifenazate, bromacil, bromoxynil, bromovanzole, buprofzeine, butoxycarboxin, cAp (captan), carbaryl, carbendazim, carbetamide, carbofuran, carbosulfan, carboxin, chlorantraniliprole, chloridazon, chlorotoluron, chloropyrifos, chlorosulfuron, clofentzeine, clomazone, clothianidin, coumaphos, cyanazine, cyanofenphos, cycloate, cymoxanil, cyphenothrin, cyprofuram, dEf (decafentin), demeton-S-methyl, demeton-S-methylsulphphon, desethyl atrazin, desisopropyl atrazin, desmetipham, desmetryn, diafenthuiron, dialifos, diazinon, dicamba, dichlofluamid, dichloprop (2.4-dP), dichlorvos, dicotophos, difulbenzuron, dimethachlor, dimethenamide, dimethoate, dimethomorph, diniconazole, diphenamidie, diphenylamine, disulfoton, ditalimfos, diuron, dMf (2,4-dimethyl-phenyl-formamidine), dodine, epoxiconazole, etaconazole, ethiofencarb, ethiromol, ethofenprox, etoxazole, etrimphos, fenamidon, fenamiphos, fenazaquin, fenbuconazole, fenhexamid, fencoxap-p-ethyl, fenoxycarb, fenpropimorph, fenpyroximate, fenthion, fenthion sulfon, fenuron, fipronil, fiazasulfuron, floorsulam, fluazifop, fluazifop-p-butyl, fluazinam, fluidoxoxnil, flufenacet, flufenoxuron, fluometuron, fluoxypyf, flurtamon, fithiacet methyl, flutriafol, fonofos, fosthiazate, fuberidazol, furathiocarb, halfenprox, haloxyfop, haloxyfop methyl, haloxyfop-2-ethoxyethyl, heptenophos, hexafluoruron, hexazinone, hexythiazx, imazazolim, imazamy, imidacloprid, indoxcarb, ioxynil, iprodione, iprovalicarb, isazofos, isocarbamide, isomethiozin, isoproturon, isoxaflutole, lenacil, liunuron, lufenuron, malaoxon, malathion, mCpA (2-methyl-4-chlorophenoxyoxyacetic acid), mCpB (4-(2-methyl-4-chlorophenoxyoxy) butyric acid), mCpP (mecoprop), mecarbam, mepanipyrim, metalaxyl, metalaxyl-M, metanitron, metanachlor, metenokem, methenozrhitazuron, methorcifos, methanolglobos, methidathion, methicordynte, metchoyfernozide, metobromuron, metolachlor, metolachlor, gtecuslam, metouxon, metrafenon, monocrotoposh, monolinuuron, monuron, myclobutanil, nicosulfuron, nitenpyram, norfluxazon, novaluron, onethehoate, oxamyl, oxycarbonix, oxydemethon methyl, paraoxon ethyl, paraoxon methyl, parathion ethyl, pebulat, penconazole, pencyuron, phenkapton, phenedipham, phenothrin, phenothoate, phonate, phosalone, phosmet, phosphamidon, phoxin, picoxystrobin, pirimicarb, pirimiphos methyl, prochloraz, profenofos, prometryn, propomocarb, propanil, propaquizafop, prophos, prosulfuron, pyraclostrobin, pyraflufen ethyl, pyridaphenthion, pyridine, pyrimiphos ethyl, pyriproxyfen, quinmerac, quizalofop-p-ethyl, resembrrine, rim-sulfuron, sebuthylazin, sethoxydim, siltiopham, simazine, simetryn, spinosad A, spinosad D, spirotetramat, spiroxamin, sulfotep, sulprofos, tebuconazole, tebufenzo, tebufenpyrad, tebutam, tefulbenzuron, tepraloxydim, terbucarb, terbumeton, terbutualize desethyl, terbutylazine, tetamethrin, thiabendazole, thiacloprid, thiamethoxam, thiodicarb, thiophanate methyl, tolclofos methyl, toylfluamid, triadiimefon, tri-allate, triamiphos, triazophos, trichlorofon, tridolopyr, trifoxystrobin, triflumuron, trifurine. Standard solutions of pesticide in acetonitrile, with a concentration of approximately 1000 mg/L, were prepared. Next, standard solutions of a mixture of pesticides in acetonitrile, with concentration of about 35 mg/L, were prepared for each of the compounds. Working standard solutions were prepared by diluting the standard mixtures of pesticide solutions with acetonitrile.