Spectrophotometric determination of rifampicin S in the presence of rifampicin O

The limits of the use of the methods of direct photometric and differential spectrophotometric determination of rifamycin S containing rifamycin O as an admixture were discussed. The method of direct photometry did not provide determination of rifamycin S in the presence of rifamycin O since instability of the latter under the analysis conditions. A possibility of using the differential-spectrophotometric method for determination of rifamycin S in the presence of not more than 5 per cent of rifamycin O was shown.