Analytical method for the metabolites of diphenyl ether herbicides in soil

3 Analytical method for the metabolites of diphenyl ether herbicides in soil 

Under flooded soil conditions, the diphenyl ether herbicides are substantially transformed into the amino derivatives, which are incorporated tightly into the soil particles. An analytical method for these amino derivatives in soil has been developed. 

Niki and Kuwatsuka reported a method involving trifluoroacetylation of the amino derivatives of chlornitrofen, nitrofen and chlomethoxyfen. A 1-mL volume of 10 M NaOH solution was added to 50 g of soil and the mixture was extracted with 100 mL of benzene. After separation and drying over anhydrous Na2S04, the benzene solution was trifluoroacetylated by adding successively 1 mL of 0.1% trifluoroacetic anhydride in benzene and 1 mL of 0.1% triethylamine in benzene. The mixture was shaken for 30 s and diluted to 10 mL with benzene. To remove the excess of trifluoroacetic anhydride, about 2 mL of water were added to the mixture and shaken for 30 s. The benzene layer was dried over anhydrous Na2S04 and injected for gas chromatography/flame ionization detection (GC/FID). 

The GC/FID conditions were as follows column, 1.5% OV-17 (2 m x 3-mm i.d.) glass column N2 carrier gas flow rate, 45mLmin temperature of injection port, column and detector, 240,235 and 235 °C, respectively. The recoveries of these amino derivatives with fortification level ranging from 0.5 to lO.Omgkg were 62-101% for chlornitrofen, 62-101% for nitrofen and 58-101% for chlomethoxyfen, and satisfactory recoveries from soil were obtained at high concentrations, but the recoveries at lower concentration averaged about 66% for the least recovered compound. Interference from other substances in the soil extracts derived from the acetylation reaction was negligible. 

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