Determination of basic pharmaceuticals in human serum by hydrophilic interaction capillary electrochromatography

Hydrophilic interaction capillary electrochromatography (HI-CEC) for the determination of basic pharmaceuticals spiked in human serum is described. The organic modifier content, ionic strength, and pH value of the mobile phase as well as the applied voltage are optimized for separation and elution of these drug analytes. Excellent separation was achieved for drugs using a mobile phase composition of 80% v/v acetonitrile in 100 mm triethylamine phosphate (TEAP) buffer at pH 2.8 with column efficiencies for analytes more than 200 000 plates/m. The samples of human serum spiked with basic drugs were directly injected after a simple acetonitrile treatment. The linear range and reproducibility of these basic drugs using an external and internal standard method were compared. As a result, the reproducibility could be greatly improved by using the internal standard method. Good calibration curves with regression coefficients more than 0.998 in the range of 5-160 mug/mL were observed with the internal standard method. The limits of quantitation, based on standards with acceptable relative standard deviations (RSDs), were below 5 mug/mL. The intra- and inter-day precisions, determined as RSDs, were less than 4.57%.