Solid-phase extraction followed by gas chromatography-mass spectrometry for the quantitative analysis of small molecule N-nitrosamine impurities in antitussive syrups

A quantitative testing method was developed for the analysis of low molecular weight (small molecules) nitrosamine impurities in cough syrups using solid phase extraction (SPE) on strong cation-exchange functionalized polymeric sorbent cartridges followed by gas chromatography-mass spectrometry. The matrix spike recoveries of the nitrosamine impurities from the cough syrup samples was observed to be within the range of 90 %-120 %. Limit of detection (LOD) achieved for NNitrosodimethylamine (NDMA) and NNitroso morpholine (NMOR) was about 0.1 ng/mL while the LOD for NNitrosodiethylamine (NDEA), NNitrosodiisopropylamine (NDIPA) and NNitrosoisopropylethylamine (NIPEA) impurities was about 0.02 ng/mL. The method was evaluated and found to meet the acceptable criteria as per the ICH Q2 guidelines for a working concentration range of 0.02 ng/mL to 1.2 ng/mL for the analyzed impurities. The selectivity of the nitrosamine impurities against the presence of drug product was established using multiple reaction monitoring (MRM) transitions during analysis.