Optimization by factorial design of a capillary zone electrophoresis method for the simultaneous separation of antihistamines

A 32 full factorial design was used to optimize the experimental conditions of a capillary zone electrophoresis method aimed at achieving simultaneous separation and quantification of the antihistamines brompheniramine, chlorpheniramine, cyproheptadine, diphenhydramine, doxylamine, hydroxyzine, and loratadine according to their therapeutic group. A statistical program, SPSS, was used to calculate the mathematical model with which to obtain the response surface. Critical parameters such as pH and applied voltage were studied to evaluate their effect on resolution and on efficiency. Optimum separation conditions were phosphate buffer pH 2.0, 5 kV, and 2 psi s−1 at 214 nm. The analysis time was below 9 min and the theoretical plates were between 6000 and 63,000 N. Calibration curves were prepared for the antihistamines. The limits of detection were 4–14 ng mL−1, which allow their quantification in pharmaceuticals. The RSD% of each antihistamine was fairly good. Up to seven antihistamines belonging to the antihistaminic H1-receptor group were separated in the same electropherogram. The proposed method was then applied to the determination of antihistamines in pharmaceutical, urine, and serum samples with recoveries in agreement with the stated contents.