Use of Solid-Phase Microextraction for the Quantitative Determination of Herbicides in Soil and Water Samples

An in-depth study of SPME optimization and application has been made, considering not only aqueous (surface water and groundwater samples) but also the more complex soil samples. Seven herbicides widely used in the area of study have been selected including five triazine herbicides (atrazine, simazine, terbumeton, terbuthylazine, terbutryn), molinate, and bromacil. Linearity range was between 0.1 and 10 ng/mL and the repeatability below 10% when applying the optimized SPME procedure to water samples. Reproducibility was found to be lower than 20% at the 1 ng/mL level, and the limits of determination in environmental water samples using GC/MS (SIM mode) were well below 0.1 ng/mL (values ranging from 10 to 60 ng/L). Extraction of selected herbicides from soil was carried out by microwave-assisted solvent extraction using methanol in screw-capped vials, leading to recoveries over 80% in spiked soil samples at the 5−200 ng/g level. SPME application over methanolic soil extracts required a 10-fold dilution with distilled water. The recommended procedure was found to be fully applicable for quantitative determination of selected herbicides in soils containing low organic matter content with coefficients of variation below or around 10% and limits of determination ranging from 1 to 10 ng/g. Both procedures were applied to real-world surface water and soil samples where several pesticides were detected including atrazine, simazine, terbuthylazine, and molinate.