Monitoring of vancomycin in human plasma via portable microchip electrophoresis with contactless conductivity detector and multi-stacking strategy

Abstract

A new online multi-stacking preconcentration technique based on the hybrid integration of field-enhanced sample injection (FESI) and micelle-to-solvent stacking (MSS) was developed and implemented in a battery-operated aqueous-based microchip capillary electrophoresis (MCE) device with a commercially available double T-junction glass chip. Cationic analytes from two sample reservoirs were injected under FESI conditions and subsequently focused by MSS within the sample loading channel. The proposed multi-stacking strategy was verified under a fluorescence microscope using Rhodamine 6G as the model analyte, and a sensitivity enhancement factor (SEF) of up to 217-fold was achieved. The developed approach was subsequently implemented in the MCE, coupled with contactless conductivity detection (C4D) in order to monitor the targeted antibiotic, namely vancomycin which was present in the human plasma samples. Moreover, the operation and parameters affecting the MSS, such as the BGE concentration, micelle concentration, focusing time, and methanol percentage in the sample solution were optimized and investigated. The multi-stacking and analysis time for vancomycin were 50 s and 250 s respectively, with the SEF of 83-fold as compared to the typical gated injection method. The detection limit of the method for the vancomycin spiked human plasma was 2.5 µg/mL, with intraday and interday repeatability (RSD) of 2.6% and 4.3%, respectively. The recoveries in the vancomycin spiked human plasma samples were 99.0 % –99.2 %.