Determination of amoxicillin and cephalexin in mixtures by second-derivative spectrophotometry

Abstract
A method for the simultaneous determination of amoxicillin and cephalexin in mixtures by second-derivative spectrophotometry is described, using zero-crossing measurements. The procedure does not require any separation step. The calibration graphs are linear up to 60.0 µg ml–1 of cephalexin at 267.5 nm and up to 390 µg ml–1 of amoxicillin at 276 nm in the presence of each other.