Acidic pesticdes using QuEChERS method

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-naphthoxyacetic herbicideBromoxynil3,86 Ioxynil3,96 Clopyralid2pyridine herbicideDicamba1,97benzoic acidImazapyr1,9 I

Acidic pesticides – influence of pH on recovery 6 5 4 2,4 MCPB 3 2,4 Propyzamid Ioxynil Bentazon Bromoxynil Fluazifop Bromacil DB-DP 2,4,5-2,4,5 Mecoprop Triclopyr TP

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  Using, Pesticides, Quechers, Using quechers

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