Liquid-Solid Sample Preparation Followed by Headspace Solid-Phase Microextraction Determination of Multiclass Pesticides in Soil

This paper describes development and validation of a multiresidue method for the determination of five pesticides (terbufos, prochloraz, chloridazon, pendimethalin, and fluorochloridone) belonging to different pesticide groups in soil samples by GC/MS, followed by its application in the analysis of some agricultural soil samples. The method is based on a headspace solid-phase microextraction method. Microextraction conditions, namely temperature, extraction time, and NaCl content, were tested and optimized using a 100 pm polydimethylsiloxane fiber. Three extraction solvents [methanol, methanol acetone (1 + 1, v/v), and methanol acetone hexane (2 + 2 + 1, v/v/v)] and the optimum number of extraction steps within the sample preparation stage were optimized for the extraction procedure. LOD values for all the studied compounds were less than 12 mu g/kg. Recovery values for multiple analyses of soil samples fortified at 30 mu g/kg of each pesticide were higher than 64%. The method was proven to be repeatable, with RSD lower than 15%.