Counterflow isotachophoresis capillary zone electrophoresis on directly coupled columns of different diameters

Counterflow isotachophoresis-capillary zone electrophoresis (ITP-CZE) on directly coupled columns of different diameters was explored to increase the injection volume and lower the detection limits in CZE. A solution of neostigmine bromide and propantheline bromide was used to evaluate the system; the relative standard deviations for four injections of 3.3 mu L of 0.1 mu M neostigmine bromide and propantheline bromide were 1.4 and 4.0%, respectively. The correlation coefficients for volumetric calibration curves over the range of 1.7-8.3 mu L of the neostigmine bromide and propantheline bromide solution were 0.9979 and 0.9975, respectively, and a 2.5 nM solution could be detected easily from 8.3 mu L of sample. Approximately 40 min was required for focusing.