Determination of Trace Genotoxic Impurity in Lidocaine by HPLC-MS/MS

OBJECTIVE To develop a high-performance liquid chromatography-triple quadrupole mass spectrometry (HPLC-MS/MS) method for the determination of the genotoxic impurity N-(2,6-dimethylphenyl)-2-ethyl(nitroso)amino acetamide(NDLC) in lidocaine.

METHODS Chromatographic separation was achieved on a Shiseido C₁₈ column(150 mm×4.6 mm, 5 μm) using a mobile phase consisting of 0.020 mol·L⁻¹ ammonium acetate solution-acetonitrile (90∶10) as mobile phase A and acetonitrile as mobile phase B with gradient elution. The autosampler temperature was maintained at 5 ℃ with a flow rate of 1.0 mL·min⁻¹. The column temperature was set at 30 ℃, and the injection volume was 10 μL. Mass spectrometric detection was carried out using a positive-ion electrospray ionization source in multiple reaction monitoring mode. The monitored ion transitions were m/z 236.2→105.1(quantitative ion pair) and m/z 236.2→58.1(qualitative ion pair). Quantification was carried out using the standard curve method.

RESULTS The method demonstrated a linear range of 1.058–21.160 ng·mL⁻¹ for NDLC with a correlation coefficient(r) of 0.999 7. The limit of detection and limit of quantification were 0.349 ng·mL⁻¹ and 1.058 ng·mL⁻¹, respectively. The average recovery was 99.1% with RSD of 1.5%. The method was successfully applied to the determination of NDLC in 3 batches of lidocaine bulk drug, with detected levels ranging from 1.9–2.9 ng·g⁻¹, which did not exceed the acceptable limit.

CONCLUSION The developed method is sensitive, accurate, and all validation results meet the requirements for trace analysis. It has been successfully applied to the determination of NDLC in lidocaine, and can provide effective support for process monitoring and quality control.