Gas Chromatographic Determination of Phosphorus-Containing Pesticide Metabolites via Benzylation

Mono- and di-protic alkyl and aryl phosphates, phosphonates, and thio analogues were determined in spiked samples of bacterial growth medium and human urine using a new procedure with a detection limit of less than 2 pmol each. The acids were fully protonated by passing the aqueous samples through BioRad AG 50W-X8 (H+) resin and dried thoroughly before refluxing with 3-benzyl-1-p-tolyltriazene in acetone. The benzyl esters that formed partitioned quantitatively into cyclohexane and were determined by gas-liquid chromatography with a flame-photometric detector (phosphorus mode) and a glass column (5% OV-210 on 80/100 mesh Gas Chrom 0). Linear recovery curves were obtained. Inorganic orthophosphate did not interfere with urine analysis, although it could be easily removed by Ca(OH)2 precipitation