DISPERSIVE LIQUID-LIQUID MICROEXTRACTION BASED ON SOLIDIFICATION OF FLOATING ORGANIC DROP COMBINED WITH COUNTER-ELECTROOSMOTIC FLOW NORMAL STACKING MODE IN CAPILLARY ELECTROPHORESIS FOR THE DETERMINATION OF BISPHENOL A IN WATER AND URINE SAMPLES

Abstract

Dispersive liquid–liquid microextraction method based on solidification of floating organic drop (DLLME-SFO) was combined for the first time with counter-electroosmotic flow normal stacking mode (counter-EOF NSM) in capillary electrophoresis (CE) for preconcentration and determination of bisphenol A (BPA) in water and urine samples. Several parameters affecting extraction efficiency, including type and volume of the extraction and disperser solvents, pH, volume of sample and back-extraction solutions, and ionic strength, were systematically studied. In-vial back-extraction of the target analyte from the resulting organic drop into an aqueous phase facilitated the direct application of DLLME-SFO with CE. Under optimum conditions, improvement factors of 1250 (water) and 430 (urine) as compared to conventional capillary zone electrophoresis (CZE) were obtained. Calibration graphs were linear up to 100 µg L−1 with coefficients of determination (R2) ≥ 0.9989 and relative standard deviation (RSD %) ≤ 1.9. Limits of detection (LOD) of 0.8 µg L−1 (water) and 2.5 µg L−1 (urine) were achieved. Because this method required simple and inexpensive devices and very small volumes of nontoxic organic solvents, it is an affordable, efficient, and convenient method for extraction and determination of trace amounts of BPA in water and human urine samples.