Liquid chromatography–tandem mass spectrometry for quantification of cefaclor in rat plasma and its application to pharmacokinetic studies

A simple and sensitive liquid chromatography–tandem mass spectrometry (LC–MS/MS) in the positive electrospray ionization mode was developed and validated in order to analyze cefaclor, a second generation cephalosporin antibiotic, in rat plasma. The plasma was pre-treated by a single step of protein precipitation with methanol, and then injected directly into the LC/MS/MS system for quantification. Drugs were separated on a Synergi 4μ Polar-RP 80 A column (150 × 2.0 mm) with a mixture of 0.1 % formic acid and methanol (65 : 35, v/v) as the mobile phase at 0.2 mL/min. Detection was performed with multiple reaction-monitoring modes at m/z 368.1 → 174.2 (for cefaclor) and m/z 396.0 → 227.1 (for cefdinir, the internal standard). The limit of quantification (LOQ) was determined to be 10 ng/mL with acceptable linearity ranging from 10 to 10,000 ng/mL. Validation parameters for cefaclor, including accuracy, precision, absolute matrix effect, and stability in rat plasma, were acceptable according to the assay validation guidelines of the FDA (U.S. Department of Health & Human Services, Food and Drug Administration, Guidance for Industry, Bioanalytical Method Validation, 2001). The developed analytical method was successfully applied to the pharmacokinetic studies of cefaclor in rats. These observations suggest, therefore, that the validated assay can be used in routine pharmacokinetic studies of cefaclor in rats.