To develop an HPLC method for the determination of related substances and assay of levamisole hydrochloride tablets.

The chromatographic separation of related substances was performed on a Thermo Hypsil C₁₈ column(100 mm×4.6 mm, 3 μm). A gradient elution was applied with a mobile phase composed of 0.75% monobasic ammonium phosphate solution(adjusted at pH 6.5 with diiopropylamine) and acetonitrile. The assay analytical column was packed with IntertSustain C₁₈ column(150 mm×4.6 mm, 5 μm). The mobile phase was 70 volumes of 0.75% monobasic ammonium phosphate solution(adjusted at pH 7.0 with diiopropylamine) with 30 volumes of acetonitrile. The wavelength detection was set at 215 nm, the injection volumn was 10 μL, and the flow rate was 1.0 mL·min^-1.

Levamisole and its impurities were separated well by related substances HPLC method above. Impurities A, B, C, D, E showed the good linearities in the concentration ranges of 10.87-25.37 μg·mL^-1, 11.62-27.10 μg·mL^-1, 12.38-28.90 μg·mL^-1, 30.89-72.07 μg·mL^-1, 12.41-28.95 μg·mL^-1 (r>0.999). The average correction factors of impurities A, B, C, D, E determined by three columns and liquid chromatographies were 1.6, 1.4, 2.6, 1.2, 2.4, respectively, the recovery rates(n=9) were 98.1%, 99.0%, 98.6%, 100.1%, 99.9% and the RSDs were 0.63%, 0.79%, 0.92%, 0.96%, 0.33%. The separation of levamisole and impurity C was good by assay HPLC method. Levamisole showed the good linearity in the concentration range of 0.10 14-0.304 3 mg·mL^-1 (r=0.999 9). The average recovery rate(n=9) of levamisole was 100.2%, RSD=0.52%. Ten batches levamisole hydrochloride tablets from five domestic pharmaceutical enterprises were determined by the above related substances and assay HPLC method, the total impurities mass were 0.05%-0.62%, and the assays were 99.5%-104.3%.

The established method is high selection and accurate. It is suitable applied for determination of related substances and assay of levamiole hydrochloride tablets.