Determination of eight illegal drugs in human urine by combination of magnetic solid‐phase extraction with capillary zone electrophoresis

Using magnetite/silica/poly(methacrylic acid-co-ethylene glycol dimethacrylate) (Fe(3)O(4)/SiO(2)/poly(MAA-co-EDMA)) magnetic microspheres, a rapid and high-throughput magnetic solid-phase extraction coupled with capillary zone electrophoresis (MSPE-CZE) method was developed for the determination of illegal drugs (ketamine, amphetamines, opiates, and metabolites). The MSPE of target analytes could be completed within 2 min, and the eight target analytes could be baseline separated within 15 min by CZE with 30 mM phosphate buffer solution (PBS, pH 2.0) containing 15% v/v ACN as background electrolyte. Furthermore, hydrodynamic injection with field-amplified sample stacking (FASS) was employed to enhance the sensitivity of this MSPE-CZE method. Under such optimal conditions, the limits of detection for the eight target analytes ranged from 0.015 to 0.105 μg/mL. The application feasibility of MSPE-CZE in illegal drugs monitoring was demonstrated by analyzing urine samples, and the recoveries of target drugs for the spiked sample ranging from 85.4 to 110.1%. The method reproducibility was tested by evaluating the intra- and interday precisions, and relative standard deviations of <10.3 and 12.4%, respectively, were obtained. To increase throughput of the analysis, a home-made MSPE array that has potential application to the treatment of 96 samples simultaneously was used.