Application of the least-squares method in the matrix form: simultaneous spectrophotometric determination of rifampicin and isoniazid in binary pharmaceutical formulations.

A least-squares method in the matrix form is described for the simultaneous determination of rifampicin and isoniazid in a mixture. The method allows the rapid analysis of binary pharmaceutical formulations with minimum error. The concentration of each component in the mixture has been determined spectrophotometrically by measuring the absorbance of the mixture at 5-nm intervals from 230 to 290 nm. To calculate the matrix of the proportionality constant a standard mixture was used for each component. All data analyses were performed on a personal computer.