Determination of sulfonylurea herbicides in soil samples via supercritical fluid extraction followed by nanostructured supramolecular solvent microextraction

The present work describes a sensitive procedure for extraction and determination of three sulfonylurea herbicides (metsulfuron-methyl, bensulfuron-methyl and chlorsulfuron) in water samples using supramolecular solvent microextraction. A supramolecular solvent with a nano structure made up of decanoic acid assemblies dispersed in tetrahydrofuran and water was proposed. Also, a supercritical fluid extraction coupled with supramolecular solvent microextraction was applied for extraction and determination of ultra-trace amounts of sulfonylurea herbicides in soil samples. A Taguchi orthogonal array experimental design with an OA₁₆ (4⁵) matrix was employed to optimize the supercritical fluid extraction conditions. In supercritical fluid extraction–supramolecular solvent microextraction procedure, a mixture of decanoic acid and the SFE collecting solvent (tetrahydrofuran) was added to water for supramolecular solvent formation. The effective parameters on the supramolecular solvent microextraction efficiency were studied and optimized using two different optimization methods: one variable at a time and face centered design. Under the optimum conditions, linear dynamic ranges varied within 0.1–5 mg kg^?1 (0.9978 ≤ R² ≤ 0.9987) and 0.5–100 μg L^?1 (0.9973 ≤ R² ≤ 0.9995) for all of the sulfonylurea herbicides in the supercritical fluid extraction–supramolecular solvent microextraction and supramolecular solvent microextraction, respectively. The intraday (n = 5) and interday standard deviations were calculated by extracting the SUHs from water and soil samples through supramolecular solvent microextraction and supercritical fluid extraction–supramolecular solvent microextraction. Interday RSDs% lower than 7.1% and intraday RSDs% lower than 3.8% were obtained. Limits of detection, based on a S/N ratio of 3, were 0.5 μg L^?1 and 0.7 mg kg^?1 for supramolecular solvent microextraction and supercritical fluid extraction–supramolecular solvent microextraction, respectively.