Highly sensitive transient isotachophoresis sample stacking coupling with capillary electrophoresis-amperometric detection for analysis of doping substances

A simple and effective method of capillary electrophoresis-amperometric detection (CE–AD) coupled with transient isotachophoresis (tITP) was developed for the trace determination of doping substances. Compared with the conventional capillary electrophoresis method, the maximum enhancement factor in terms of peak heights was up to 5500-fold when the tITP technique was adopted. Under the optimum conditions, the detection limit (S/N = 3) for methylephedrine (MDP), celiprolol (CEL), sotalol (SOT) and indapamide (IDP) were 4.2 × 10−14, 6.3 × 10−13, 5.8 × 10−14 and 9.5 × 10−13 mol L−1, respectively. The RSDs of four analytes were 1.0–2.3% for migration time and 2.6–3.8% for peak current, respectively. The proposed method was successfully applied to determine the contents of SOT and IDP in real urine sample, and the excretion curve of IDP within 48 h was also investigated. The recoveries of the four doping in urine ranged from 90.0 to 102%.