Rapid determination of amoxicillin in premixes by HPLC

A rapid analytical procedure for routine identification and quantification of amoxicillin in premixes by high performance liquid chromatography was developed and tested. The ground premix samples were extracted for 10 min using 100 ml extraction mixture water-methanol (800:200, v/v). The extract was analyzed by reversed-phase on Agilent Zorbax SB-C18 column (4.6 mm × 150 mm, i.d., 5 μm particle size) with water-methanol-phosphoric acid-triethylamine (842:150:4:4) containing 10 mM hexane-1-sulfonic acid sodium salt (pH 3.5) as mobile phase. UV detection was carried out at 230 nm. The method was validated for specificity, linearity, solution stability, accuracy, precision, limit of detection, and limit of determination. The detector response for amoxicillin was linear over the selected concentration range from 2.0 to 40.0 mg ml−1 with a correlation coefficient 0.9999. The mean accuracy was 100.1% with a standard deviation of 0.6%. The limit of detection and the limit of determination are 0.1 and 0.3 mg ml−1, respectively, which corresponds to 10 and 30 mg kg−1, respectively, in real premix sample. The sample and standard solutions were stable for 4 h. The method is selective and can be used in routine analysis.