Determination of triazines in soil by microwave-assisted extraction followed by solid-phase microextraction and gas chromatography - mass spectrometry

A method for determining triazine herbicides in soil samples that combines microwave-assisted extraction with solid-phase microextraction is described. Water containing 1% methanol was employed as extractant. The parameters of solid-phase microextraction and microwave-assisted extraction were investigated. In solid-phase rmcroextraction, particular attention was paid to the negative effect of salt on fiber stability. Our experiments showed that this effect could be effectively reduced by simply washing the fiber with deionized water. The selected triazines could be efficiently extracted by the aqueous extractant at 105 degreesC for 3 min, with 80% output of maximum power (1200 W). The extraction procedure provided good precision (<7%) and recoveries (76.1-87.2%). The limits of detection were in the range 2-4 mug/kg. Compared with conventional liquid extraction, microwave-assisted extraction-solid-phase microextraction was more efficient, accurate and faster, and used a very small amount of organic solvent (only 250 muL methanol). The extraction of aged spiked soil samples indicated that, although the recoveries were lower than those of freshly spiked samples, they were nevertheless satisfactory for the quantitative analysis of real-world samples. (C) 2002 Elsevier Science B.V. All rights reserved.