Determination of Commonly Used Excipients in Pharmaceutical Preparations by Microchip Electrophoresis with Conductivity Detection

In this study, a microchip electrophoresis method for simultaneous determination of three frequently used pharmaceutical excipients (methylparaben, propylparaben and erythrosine) was described. Anionic zone electrophoresis (ZE) separations were performed on the microchip with contact conductivity detection using a high pH buffer (9.8). Sufficient resolution of the analytes (≥ 2.6) was achieved by 1 mmol L−1 β-cyclodextrin added to the buffer. Adsorption of the analytes on the walls of a poly(methylmethacrylate) microchip was suppressed by adding 1 mmol L− 1 sulfate to the sample. The LOD values for the excipients ranged from 0.5 to 11.1 μmol L− 1. High repeatability of the migration times of the analytes in model (< 2.9% RSD) and real pharmaceutical (< 4.1% RSD) samples was reached on the microchip. Peak areas of the analytes in all analyzed samples were characterized by RSD values ranging from 0.4 to 5.7%. The ZE method was successfully applied to the analysis of pharmaceutical syrups after a simple pretreatment (centrifugation and dilution), and gave recoveries of the a nalytes in the range 86.1–96.6%. The results showed a good agreement with those obtained by CZE with UV detection (254 nm) at 95% confidence level.