Determination of degradation products and impurities of amoxicillin capsules using ternary gradient elution high-performance liquid chromatography.

A specific high-performance liquid chromatography method has been developed for the determination of amoxicillin penicilloic acids (PA), p-hydroxyphenylglycine (p-HPG), 6-aminopenicillanic acid (6-APA) and unidentified materials in amoxicillin capsules. The accuracy of the measurements was demonstrated by the standard addition technique on actual capsule samples. Within-day and between-day precision studies gave coefficients of variation of 3.15 and 1.70% for PA, 4.75 and 3.81% for p-HPG, and 5.59 and 32.23% for 6-APA, respectively. Typical calibration and expanded linearity of response curves for these components show no curvature over the range of interest. The detection limits for PA, p-HPG and 6-APA are 0.7, 0.2 and 0.6 micrograms/ml of sample extract and are considered adequate for the intended use of the method. These levels correspond to 0.35, 0.10, 0.30 mg per 500-mg Amoxil capsule, respectively.