Determination of some herbicides in soil samples by supramolecular solvent based microextraction method

Supramolecular solvents (SUPRAS) are the nano-structured liquids generated from amphiphiles through a self-assembly process, and constitute an alternative to molecular organic solvents with becoming more environmentally friendly in sample preparation step. Alkylcarboxylic acids and alkanols can form reverse micelles in an organic solvent such as tetrahydrofuran due to their amphiphilic nature. Addition of water to such a solution causes an increase in micelle-micelle interactions. In this case the phase separation occurs with the formation of bigger aggregates and SUPRAS which is a new micelle-rich phase is obtained. In this study, a SUPRAS-based analytical method has been proposed for the microextraction of propachlor and prometryn herbicides in soil samples. The SUPRAS, used in the microextraction step, was made up of reverse micelles of decanol that formed in a tetrahydrofuran:water solution through self-assembly processes. The proposed method involved the vortex mixing of the 300 mg of soil sample with 300 µL of SUPRAS for 8 min, subsequent centrifugation for the phase separation, and direct analysis of the SUPRAS phase by liquid chromatography with ultraviolet detection. Some important parameters affecting the extraction efficiency such as type of alkanol, composition supramolecular solvent, volume of supramolecular solvent, and extraction time have been optimized. Under optimal extraction conditions, the extraction recoveries for the herbicides ranged from 81 to 87 %. The method detection limits for propachlor and prometryn were 0,07 and 0,01 μg/g, respectively. Relative standard deviations obtained for the herbicides were less than 8,8% and 12,1% for intra-day and inter-day precisions, respectively. The microextraction of related herbicides from soil samples collected from the Zonguldak region was carried out efficiently. The recoveries obtained from spiked soil samples were in the range of 80–108%.