Optimization using central composite design for antihistamines separation by nonaqueous capillary electrophoresis with electrochemical and electrochemiluminescence detections.

The first detailed examination of non-aqueous capillary electrophoresis with electrochemical and electrochemiluminescence detections (NACE-EC/ECL), separation parameters and their interactions via central composite design was presented. This concept was demonstrated by examining the optimization separation conditions of seven antihistamines (chlorpheniramine, cyproheptadine, diphenhydramine, doxylamine, methapyrilene, terfenadine, and triprolidine) by NACE-EC/ECL. To evaluate the NACE separation quality, the chromatography resolution statistic function (CRS(-1) function) with regard to the resolution and migration time was established as the response variable. The influences of three experimental variables (buffer apparent pH value (pH*), buffer (TBAP) concentration, and separation voltage) on the response were investigated. A set of optimal conditions was obtained from central composite design: 9.2 mM TBAP in ACN (pH* 4.0) and voltage (12.7 kV), and under these optimum conditions, the seven antihistamines could be well separated in less than 10 min. The obtained electropherograms indicated that the dual EC/ECL detection system was indispensable since the six antihistamines (except for triprolidine) displayed both EC and ECL response, whereas triprolidine only displayed the EC response. This work is instructive for investigators in simplifying the NACE-EC/ECL development procedures for multi-component analysis.