Sequential injection analysis with spectrophotometric detection of cefadroxil and amoxicillin in pharmaceuticals

A fast, economical, and automated spectrophotometric method with sequential injection for determination of phenolic drugs cefadroxil and amoxicillin has been proposed. The analysis was based on the determination of the red product of the reaction of drugs with 4-amino-antipyrine in the presence of potassium hexacyanoferrate(Ill) in alkaline solution. Absorbance of the investigated system was measured at 505 run. Various chemical and physical parameters affecting the reaction have been examined. The linear ranges were 4.0-52 mu g mL(-1) for cefadroxil and 2.6-87 mu g mL(-1) for amoxicillin, and the respective limits of detection were 0.6 mu g mL(-1) and 0.7 mu g mL(-1). Sampling frequency was 26 h(-1), and total reagent consumption was only 240 mu L per run. The proposed method has been applied for determination of cefadroxil and amoxicillin in pharmaceuticals with RSD lower than 2.5%. The obtained results were in good agreement with these obtained by HPLC method.