Continuous on-line concentration based on dynamic pH junction for trimethoprim and sulfamethoxazole by microfluidic capillary electrophoresis combined with flow injection analysis system.

A novel, rapid and continuous on-line concentration approach based on dynamic pH junction for the analysis of trimethoprim (TMP) and sulfamethoxazole (SMZ) by microfluidic capillary electrophoresis (CE) combined with flow injection analysis is developed in this paper. Stacking is due to decreases in the velocity of analytes when migrating from the low-pH sample zone (sample was dissolved in 50 mM HCl) to a relatively high-pH buffer (30 mM phosphate buffer, pH 8.5) filled in the capillary. This results in 2.9-4.7-fold improvement in concentration sensitivity relative to conventional capillary electrophoresis methods. The separation could be achieved within 2 min and sample throughput rate can reach up to 38 h(-1).