Determination of cefadroxil by three simple spectrophotometric methods using oxidative coupling reactions

Three simple and sensitive visible spectrophotometric methods for the assay of cefadroxil have been developed. Method A (lambda(max), 410 nm) is based on the reaction of cefadroxil with 3-methyl-2-benzothiazolinone hydrazone hydrochloride In the presence of eerie ammonium sulphate. Method B (lambda(max), 510 nm) involves the reaction with 4-aminophenazone in the presence of potassium hexacyanoferrate (III). Method C (lambda(max), 620 nm) involves reaction with 2, 6-dichloroquinone-4-chlorimide (Gibb's reagent). All variables have been optimised and the reaction mechanisms presented. Regression analysis of the Beer's plots showed good correlation in the concentration ranges 1.0-6.0, 2.0-24.0 and 1.0-6.0 mu g/ml for methods A, B and C, respectively. No interferences were observed from excipients and the validity of the methods was tested by analysing pharmaceutical dosage forms. Recoveries were 98.0-100.3%. The concentration measurements were reproducible within a relative standard deviation of 1.0%.