HPLC Gradient Elution Determination of Related Substances of Clindamycin Phosphate and Its Injection

OBJECTIVE To establish a suitable high-performance liquid chromatography for the determination of the related substances of clindamycin phosphate and its injection. METHODS The HPLC method was carried out using a Supelco Discovery C₁₈ column (4.6 mm×250 mm, 5 mm); where the column temperature was 40 ℃ and the detection wavelength was 210 nm; mobile phase A was phosphate buffer-90% acetonitrile-methanol solution (92∶8), mobile phase B was phosphate buffer -90% acetonitrile-methanol solution (52∶48); the flow rate was 1.2 mL·min-1. RESULTS Clindamycin phosphate and related substances could be well isolated, the standard curves for lincomycin, clindamycin-B-phosphate clindamycin and other unspecified impurities were all linear in the range of 0.006%-1.137%, 0.016%-0.157%, 0.005%-0.195% and 0.0163%- 2.933%. The limit of detection (LOD) of lincomycin, clindamycin-B-phosphate, clindamycin and clindamycin phosphate were 0.170 5 mg·mL^-1, 0.160 0 mg·mL^-1, 0.146 2 mg·mL^-1 and 0.488 8 mg·mL^-1. The average recovery of lincomycin, clindamycin-B-phosphate and clindamycin were 104.0%(RSD=1.8%, n=9), 106.8%(RSD=1.8%, n=9) and 104.9%(RSD=1.8%, n=9). CONCLUSION The method shows much higher chromatographic performance and specificity than existing national standard method and USP monographs method. It is more suitable for determination of the related substances of clindamycin phosphate and its injection.