Acidic pesticdes using QuEChERS method

1 Acidic pesticdesusing QuEChERS methodAcidic pesticidespH-issue:Ionization of pesticides at low or high pH-values Acids:HX H++ X- Bases: B + H+ BH+ Ionic form prefers to stay in the water phasepH-range of agricultural samples: ~ 7 Acidic pesticides influence of pH on recoverypH 6pH 5pH 4pH 3 MCPB 2,4-DBBromacil FluazifopBromoxynilBentazonIoxynil Propyzamid2,4-DP2,4,5-TPTriclopyrMecopro p2,4,5-TFluoxypyr Naphthylacetic acidImazaquin2,4-D MCPA Dicamba Imazethapyr4-CPAB enazolinPicloramClopyralidImazapyr 020406080100120 Recovery % max. pH pKa general trend higher pKaAcidic pesticides cleanup issueExample: Extract of red currant Losses of Acidic components after cleanup Acidic compounds interact with PSAC itrate-BufferedSample pH 2,41,00,5pH= Extract PSA 25mg/mLPSA 50mg/mLmg/mL0123456789pHmg co-extractives/mL ExtractpHQuEChERS has to be modified, to include Acidic pesticides Avoid special cleanup with PSA Avoid special cleanup with PSA Special conditions during chromatographySpecial conditions during chromatographyCompoundpKa-valueChemical Classacidic structure2,4,5-T2,852,4,5-TP2,842,4-D2,7 32,4-DB4,82,4-DP3,674-CPA3,56 Fenoxaprop-P3,2 Fluazifop3,2 Fluazifop-P-Butyl3,1 Haloxyfop2,9 MCPA3,07 MCPB4,84 MCPP3,78 Fluroxypyr2,94 Triclopyr3,97 Naphthoxyacetic acid.

2 2-naphthoxyacetic herbicideBromoxynil3,86 Ioxynil3,96 Clopyralid2pyridine herbicideDicamba1,97benzoic acidImazapyr1,9 Imazaquin3,8 Imazethapyr2,1 Quinmerac4,32quinolinecarboxylic acidPicloram2,3pyridine herbicideBentazone3,3unclassifiedFomesaf en2,83amide herbicideImazosulfuron4pyrimidinylsulfon ylurea herbicidesThifensulfuron-Methyl4 Metsulfuron-Methyl3,3 Metosulam4,8sulfonanilide herbicideCycloxydim4,17cyclohexene oxime herbicidespecial caseFludioxonilno acidtriazinylsulfonylurea herbicidesphenoxyalcanoic acidpyridine herbicidephenolic herbicideimidazolinone herbicideAcidic pesticides pesticide listAcidic pesticides pesticide listCycloxydim Three mesomeric structuresThree mesomeric structures Difficult chromatogramic behaviourDifficult chromatogramic behaviourAcidic pesticides - findingsPesticideCITRUS & POME FRUITLEAFY & TUBERALL I 91/414 Fludioxonil452976517103283 PendingFluazifop112547985421 Out2,4-D9817711314 InHaloxyfop144526146 OutBentazone72194 InMCPA6181 InClopyralid30149 InDicamba8431 Pending2,4-DP14225 InMCPP2224 Pending4-CPA1818 PendingNaphthoxyacetic acid.

3 2-11618pendingBromoxynil1016 InTriclopyr29 Imazaquin7 Pending2,4,5-T16 InQuinmerac13 Fluroxypyr12 InIoxynil22In2,4-DB1 InCycloxydim1 PendingMetosulam11 Pending2,4,5-TPInFenoxaprop-PPendingForm esafenImazapyrOutImazethapyrOutImazosulf uronInMCPBOutMetsulfuron-MethylPicloramO utThifensulfuron-MethylIn2004 - 2007N of samples with positive findingsRelatively often found: Fluazifop 2,4-DInterlaboratory method Validation StudyModified QuEChERS (without PSA-cleanup)August 2006: 1919 Labs expressed interest from 99 Countries(Germany, Latvia, Spain, Czech Republic, Switzerland, Finland, Austria, The Netherlands and Great Britain) 4 Commodities(Raisins, Cucumber, Lemon, Wheat Flour) 32 pesticides (LC-MS/MS, ESI pos and neg) with 2 Levels ( and mg/kg)

4 0204060801001201402,4,5-T2,4,5-TP2,4-D2, 4-DB2,4-DP4-CPAB entazoneBromoxynilClopyralidCycloxydimDi cambaFenoxaprop-PFluazifopFluazifop-P-Bu tylFludioxonilFluroxypyrFomesafenHaloxyf opImazapyrImazaquinImazethapyrImazosulfu ronIoxynilMCPAMCPBMCPPM etosulamMetsulfuron-MethylNaphthoxyaceti c acid, 2-PicloramQuinmeracThifensulfuron-Methyl Triclopyrmean recovery in %Spiking Level mg/kgSpiking Level mg/kgILMV 2006 Acids Results (Example Cucumber) QuEChERS alkaline hydrolysisAcids are often covalently bound to matrix components and Acids are often covalently bound to matrix components and thus their concentration underestimated!thus their concentration underestimated!Example 2,4-D Selective systemic herbicideSelective systemic herbicide Control of broad leaved weedControl of broad leaved weed Plant growth regulator used to prevent premature fruit dropPlant growth regulator used to prevent premature fruit drop Formulations include free acid, salts, estersFormulations include free acid, salts, esters May form conjugatesMay form conjugates method designed to convert all possible residues to free acidMethod designed to convert all possible residues to free acidCitrate-Buffered QuEChERSW eigh 10 g of Frozen SampleShakeShake and CentrifugeAdd ISTD-SolutionAnalysis of Acidic pesticides by LC-MS/MSAdd 10 mL AcetonitrileAdd 4 g MgSO4/ 1 g NaCl / Citrate Buffer(pH )

5 Optionally: Freeze-out of extracted fat over nightQuEChERS schematic description with AHoptionally: Add NaOH to adjust pHalkaline hydrolysis: Add NaOH and store for 30 min at RT,then neutralizeShake Alkaline Hydrolysis for the release of phenoxy-acid pesticideswheat sample6066197153362751351000200400600800 100012001400 pH 12/30 min pH 10/30 min pH 12/30min pH 10/60 min pH 10/30 min pH 9/30 minQuEChERS w/o concentrationAt 70 CAt Room TemperaturepH 1230 minpH 1060 minpH 1030 minpH 930 min! " # " " Alkaline Hydrolysis Level of MCPAin berries$%$&$$&%$'$$'%$($$(%$ # ) ) * +,-. / #/ Alkaline Hydrolysis Level of 2,4-Din different citrus samples # 0 &12 3 %12