Separation and determination of sulfonamides in pharmaceutical preparations by a microfluidic capillary electrophoresis system with a continuous sample introduction interface

A simple, rapid microfluidic capillary electrophoresis system with a continuous sample introduction interface is described in the present paper. The interface with an H-channel structure was produced using a non-lithographic approach. The H-channel structure fixed on a planar plastic base utilized a horizontal 6.5-centimeter-long separation capillary with two vertical sidearm tubes on each end that served as inlet and outlet flow-through electrode reservoirs. The inlet reservoir also functioned as interface for coupling to the FI system. The performance of the system was demonstrated in the separation and determination of trimethoprim (TMP), sulfadiazine (SDZ), and sulfamethoxazole (SMZ) with UV detection at 214 nm, achieving baseline separation within 2.5 min. The sample throughput rate can reach up to 30 samples h(-1). The repeatability (defined as relative standard deviation, RSD) was 2.23%, 1.19%, 2.64% with peak height evaluation and 2.43%, 1.46%, 3.58% for peak area evaluation, respectively. The limits of detection (S/N = 3) were 0.17 mug/mL, 1.05 mug/mL, and 1.28 mug/mL for TMP, SDZ, and SMZ, respectively. This technique has been applied to the analysis of two commercial pharmaceutical preparations containing TMP, SDZ, and SMZ for the first time and has achieved satisfactory results.