ATOMIC-EMISSION DETECTION FOR THE QUANTITATION OF TRIMETHYLSILYL DERIVATIVES OF CHEMICAL-WARFARE-AGENT RELATED-COMPOUNDS IN ENVIRONMENTAL-SAMPLES

Quantitation of nerve agent degradation products is needed to develop methods for analysis of environmental samples for verification of the Chemical Weapons Convention. A procedure has been characterized which involves formation of the trimethyisilyl esters of alkylmethylphosphonic acids using 1% trimethylchlorosilane in bis-(trimethylsilyl)trifluoroacetamide as a derivatizing agent. Eight phosphorus-containing acids were extracted from spiked water, wipes, and two soil samples at low ppm levels, prepared using solid-phase extraction with a strong anion-exchange column, and derivatized. A gas chromatograph (GC) interfaced to an atomic emission detector (AED) was used to quantitate the derivatives in order to determine the extraction and derivatization efficiencies for environmental sample preparation. Because elemental response factors for the AED are independent of the type of compound, quantitation can be accomplished using an external standard, for which dimethylmethylphosphonate (DMMP) is used. The derivatization efficiencies ranged from 80% to 110% (six trials, with R.S.D. in the range 2-7%). The extraction efficiencies ranged from 13% to 99% in water, and they were lower from the soil and wipes. Gas chromatography-mass spectrometry of the derivatives was used to provide positive identifications.