HPLC Determination of Aminopyridines Remained as Genetoxic Impurities in 3-Aminopiperidine Dihydrochloride

Aminopyridines remained in 3-aminopiperidine dihydrochloride, which was an important compound used in the synthesis of the diabetic drug-alogliptin benzoate, might lead to un-safety of using of the drug due to their genetoxicity. Hence, a method for simultaneous determination of 3 aminopyridines (i.e., 4-aminopyridine, 3-aminopyridine and 2-aminopyridine) by HPLC was tested and proposed. 0.3 g of the sample was taken and dissolved with a mixture of phosphate buffer solution (pH 7.0) and methanol (90+10) and the volume of the solution was made up to 10.0 mL with the same buffer-CH₃OH mixture. Shim-pack Scepter C₁₈ chromatographic column was chosen as separation column. Mixture of phosphate buffer solution and CH₃OH (90+10) was used for isometric elution at a flow-rate of 0.5 mL·min^-1 and keeping the column temperature at 35 ℃. Detections were made at the wavelength of 280 nm. Volume taken for sample injection was 10 μL. Under the optimum chromatographic condition, the 3 aminopyridines were separated very well, giving values of resolutions between 4-aminopyridine, 3-aminopyridine and 2-aminopyridine 30.0, and 8.4 respectively. Detection limits (3S/N) found for the 3 compounds were 0.028 9, 0.071 1, 0.070 2 mg·L^-1 respectively. Test for recovery was made by addition of standards at 3 concentration levels, giving values of average recoveries 101%, 98.4% and 97.2% respectively. Values of RSDs (n=6) for repeatability found were 1.5%, 0.90% and 0.70%, and for reproducibility found were 6.2%, 3.0% and 2.2% for 4-aminopyridine, 3-aminopyridine and 2-aminopyridine respectively. The sample solution with addition of standard solutions and the reference solutions were found stable within 24 h under room temperature.