USE OF SUPERCRITICAL-FLUID EXTRACTION FOR PIRIMICARB DETERMINATION IN SOIL

The suitability of a variety of neat supercritical fluids (carbon dioxide, nitrous oxide, and chlorodifluoromethane) and modifiers (toluene, methanol, pyridine, triethylamine, and pyrrolidine) with different physical-chemical properties at two temperatures (50 and 100 degrees C) was evaluated for the extraction of incurred pirimicarb from topsoil. From the extraction efficiency obtained with the different modifiers and their chemical properties, the prevailing interactions between pesticide residue and the soil organic matter are proposed. The most effective extraction fluid was carbon dioxide modified with basic compounds (pyridine or triethylamine), which reflects the significance of acid-base interaction in the binding of pirimicarb to the matrix. Further, the developed SFE procedure using carbon dioxide (100 degrees C, 30 MPa, 20 mL) modified with triethylamine (5% cell volume) was compared with Soxhlet extraction (18 h) using methanol. Results indicate that the supercritical fluid extraction offers better precision, shorter analysis time, and a reduction in the solvent usage by a factor of 10.