US EPA

2992984 

Technical Report 

Analysis of alkyl phosphates by extractive alkylation 

Bradway, DE; Noseman, R; May, R 

1981 

PESTAB/81/2367 

Environ 

4 

PESTAB. The extraction of the alkyl phosphate from urine as an ion-pair with a lipophilic quaternary ammonium cation may be a promising technique for analysis of alkyl phosphate metabolites of organophosphorus pesticides. The ion pair in this study was extracted into dichloromethane, which contains the alkylating agent pentafluorobenzyl bromide. As the non-polar solvent possesses poor solvating ability, it renders the alkyl phosphate highly reactive toward nucleophilic displacement. The resulting pentafluorobenzyl ester derivative is thermally stable and highly responsive under conditions of gas chromatographic analysis using a flame photometric detector or nitrogen-phosphorus detector. Each of the 6 following alkyl phosphates was analyzed by this method: O,O'-dimethyl phosphate (DMP), O,O'-diethyl phosphate (DEP), O,O'-dimethyl phosphorothioate (DMTP), O,O'-diethyl phosphorothioate (DETP), O,O'-dimethyl phosphorodithioate (DMDTP), and O,O'-diethyl phosphorodithioate (DEDTP). DMTP, DETP, DMDTP, and DEDTP were adequately extracted from water as the ion pair with tetrabutylammonium hydrogen sulfate. The extraction of DEP and DMP was incomplete. Using tetrahexylammonium hydrogen sulfate as the counter ion, DEP was also extracted and derivatized, although recovery of DMP was still very low.