Extraction of Phenoxyacid Herbicides from House Dust Using Methanol/CO2 Mixtures

Current extraction techniques including conventional liquid−solid methods, supercritical fluid extraction, and accelerated solvent extraction all suffer some potential drawbacks for the recovery of phenoxyacid herbicides from solid environmental matrices due to the polarity, acidity, and low volatility of the analytes. The use of methanol/CO 2 mixtures consisting of 10−40 mol % methanol at both liquid and supercritical conditions is investigated herein as an alternative. Four herbicides (dicamba, 2,4-D, 2,4,5-TP, and 2,4,5-T) were extracted from a house dust matrix. Highest yields (83−95%) were obtained using 20/80 mol % methanol/CO 2 at 442 atm and 100 or 150 °C. The addition of hexane directly to the sample followed by extraction with CO 2 offered a simple method to preextract extraneous matrix material. Subsequent CO 2 extractions with methanol or 0.1 M trimethylphenylammonium hydroxide in methanol added directly to the sample yielded considerably lower results than those obtained with the methanol/CO 2 binary mixtures. Soxhlet extractions, performed for comparison, were slow and inefficient.