Supercritical fluid extraction of chemical warfare agent simulants from soil

Chemical warfare agent simulants are efficiently recovered from 2-ppm spikes in 1 g of Rocky Mountain Arsenal Standard Soil using methanol-carbon dioxide (5:95) at 300 atm for 2 min at 60 degrees C. Recoveries (n = 3) were 79 +/- 23% for dimethylmethylphosphonate, 93 +/- 14% for 2-chloroethylethyl sulfide, 92 +/- 13% for diisopropylfluorophosphate and 95 +/- 17% for diisopropylmethylphosphonate. Recoveries are higher than, but less precise than those achieved from a 5-min ultrasonic micro-scale extraction using methanol. Much less laboratory waste is generated than the current standard organic solvent extraction method (33 g of soil shaken with 100 ml of chloroform).