ABSTRACT
A permanganometric method for the quantitative determination of the intact doxycycline hydrochloride is described. The method depends upon the preliminary TLC separation of 1-14 mg of doxycycline hydrochloride on silica gel-H glass plates, using n-butanol, NH4OH, water [5: 1: 5] as a developing solvent. The spot corresponding to the intact molecule parallel to that of a reference sample is identified under U.V. lamp, scratched extracted with water, treated with 25% H2SO4 heated to 60-70C and titrated with 0.05 N KMnO4. The concentration of doxycycline hydrochloride is computed from a standard calibration curve, or from the equivalence factor calculated to be 0.542 mg doxycycline hydrochloride for each milliliter of 0.05 N KMnO4. The efficiency of the method is assessed by mixing a reference sample of doxycycline hydrochloride with controlled, alkaline degraded samples, and the results obtained are found to concord nicely. The method is applied to doxycycline hydrochloride bulk power and to its capsule pharmaceutical formulation