An effective configuration for automated magnetic micro solid-phase extraction of phenylurea herbicides from water samples followed by high-performance liquid chromatography.

In this study, a new automated magnetic micro solid-phase extraction was introduced. A Tygon tube was folded and fixed around the pole of a cylindrical magnet. Nanosized magnetic sorbents modified with diphenyldichlorosilane were uniformly immobilized on one side of the inner wall of the tube. Sample solution and desorption solvent were passed through the tube using a peristaltic pump. Four phenylurea herbicides (tebuthiuron, monolinuron, isoproturon, and monuron) were used as the model compounds to evaluate the method performance. HPLC-UV was used to separate and quantify the analytes. The effective parameters influencing the performance of the extraction process (i.e., extraction and desorption flow rates, eluent and sample volumes, type of eluent and sample ionic strength) were investigated. The limit of detection was 0.04 μg L-1 for all studied compounds. Calibration curves were linear in the range of 0.1-500 μg L-1 with a determination coefficient between 0.9988 and 0.9999. Intra-day, inter-day and batch-to-batch precisions expressed as relative standard deviation were less than 7%. Several environmental water samples were investigated to assess the applicability of the method for real sample analysis.