Pressure-assisted electrokinetic supercharging for the enhancement of non-steroidal anti-inflammatory drugs

Electrokinetic supercharging (EKS) combines field-amplified sample injection with transient isotachophoresis (tITP) to create a powerful on-line preconcentration technique for capillary electrophoresis. In this work, EKS is enhanced with a positive pressure (pressure-assisted EKS, or PA-EKS) during injection to improve stacking of non-steroidal anti-inflammatory drugs (NSAIDs). Several parameters, including buffer composition and concentration, terminating electrolyte, organic modifier, and injection voltage and injection time of both terminating electrolyte and sample were optimized. Detection limits for seven NSAIDs were determined and an enhancement in sensitivity of almost 50,000-fold was obtained. The PA-EKS method has the potential to be a simple MS compatible preconcentration method to improve the sensitivity of CE.