Kinetic determination of ansamicins in pharmaceutical formulations and human urine. Manual and semiautomatic (stopped-flow) procedures

Manual and semiautomatic kinetic methods to determine ansamicins (rifamycin SV and rifampicin), based in the catalytic effect of Cu(II) ion on the aer ial oxidation of rifamycin, is described. The effect of pH, temperature and presence of foreign species are studied. A selective and fast kinetic-phot ometric determination of ansamicins, between 0.50 and 10 mu g ml(-1), is pr oposed by the application of a semiautomatic procedure in which the samplin g-time is 20 a per sample. The method has been applied to determine rifamyc in SV and rifampicin in pharmaceutical formulations and urine. Interference s like isoniazide and pyrazinamide are avoided. Statistical comparison with a chromatographic method is reported. (C) 1998 Elsevier Science B.V. All r ights reserved.