Determination of the Related Substance of Codeine Phosphate by HPLC

OBJECTIVE To establish an HPLC method for determination of the related substances in codeine phosphate. METHODS The test was based on an octadecylsilyl silica gel column; the mobile phase A consisted of 0.2% potassium dihydrogen phosphate and 1% sodium heptanesulfonate (pH was adjusted to 3.2±0.2 with phosphoric acid)-methanol(7:3), the mobile phase B consisted of mobile phase A and acetonitrile(6:4), with gradient elution at the flow rate of 1.0 mL·min^-1; the detection wavelength was 245 nm; the column temperature was 40℃. RESULTS The separation between the main component of the method and each impurity(A-K) were >1.5. The calibration curves of codeine and known impurities were linear in the self-concentration range; and the average recovery rates(n=9) were in the range of 96.7%-103.8% while RSDs were in th range of 1.4%-6.0%. CONCLUSION The method is improved with good specificity and linearity. The self-control method for proposed main component with correction factors is suitable for the quality control of this drug.