ANALYSIS OF METHYLPHOSPHONIC ACID, ETHYL METHYLPHOSPHONIC ACID AND ISOPROPYL METHYLPHOSPHONIC ACID AT LOW MICROGRAM PER LITER LEVELS IN GROUNDWATER

A method is described for determining methylphosphonic acid, ethyl met hylphosphonic acid and isopropyl methylphosphonic acid, which are hydr olysis products of the nerve agents VX (S-2-diisopropylaminoethyl O-et hyl methyl phosphonothiolate) and GB (sarin, isopropylmethyl phosphono fluoridate). The analytes are extracted from 50 mi groundwater using a solid-phase extraction column packed with 500 mg of silica with a bon ded quaternary amine phase, and are eluted and derivatized with methan olic trimethylphenylammonium hydroxide. Separation and quantitation ar e achieved using a capillary column gas chromatograph equipped with a flame photometric detector operated in its phosphorus-selective mode. Two independent statistically-unbiased procedures were employed to det ermine the detection limits, which ranged between 3 and 9 mu g/l, for the three analytes. Published by Elsevier Science B.V.