simultaneous spectrophotometric determination of rifampicin, isoniazid and pyrazinamide in a single step

three antituberculosis medications are investigated in this work consist of rifampicin, isoniazid and pyrazinamide. the ultra violet (uv) spectra of these compounds are overlapped, thus use of suitable chemometric methods are helpful for simultaneous spectrophotometric determination of them. a generalized version of net analyte signal standard addition method (gnassam) was used for determination of three antituberculosis medications as a model system. in generalized net analyte signal standard addition method only one standard solution was prepared for all analytes. this standard solution contains a mixture of all analytes of interest, and the addition of such solution to sample, causes increases in net analyte signal of each analyte which are proportional to the concentrations of analytes in added standards solution. for determination of concentration of each analyte in some synthetic mixtures, the uv spectra of pure analytes and each sample were recorded in the range of 210 nm-550 nm. the standard addition procedure was performed for each sample and the uv spectrum was recorded after each addition and finally the results were analyzed by net analyte signal method. obtained concentrations show acceptable performance of gnassam in these cases.