A sensitive assay of amoxicillin in mouse serum and broncho-alveolar lavage fluid by liquid-liquid extraction and reversed-phase HPLC

A sensitive and simple high-performance liquid chromatography (HPLC) method was developed and validated for the analysis of amoxicillin in mouse serum and broncho-alveolar lavage (BAL) fluid. One hundred microlitres of sample were needed for the assay. Sample processing was carried out with liquid-liquid extraction. Cefadroxil was used as an internal standard. The chromatographic separation was achieved on a C18 reversed-phase column with a mobile phase consisting of phosphate buffer, 1-octanesulphonic acid sodium salt and acetonitrile. The detection was conducted at 210 nm. The ranges of the standard curves were 0.2-20 and 0.05-5 μg/ml for serum and BAL samples, respectively. The recoveries of amoxicillin from serum and normal saline were 87 and 88%, respectively. The coefficients of variation were 1.78-6.13% for intra-day and 0.82-6.42% for inter-day analyses. The accuracy was within 100 ± 6%. This method was successfully applied to analyze amoxicillin in mouse serum and BAL samples from a pharmacokinetic study.