Sulfur-specific detection of impurities in cimetidine drug substance using liquid chromatography coupled to high resolution inductively coupled plasma mass spectrometry and electrospray mass spectrometry.

The use of liquid chromatography coupled to sector field inductively coupled plasma mass spectrometry (SF-ICP-MS) for the specific detection of sulfur-containing compounds is described. In the sulfur-containing drug substance cimetidine, structurally related impurities well below the 0.1% mass fraction level relative to the main drug substance could easily be detected. The structure of most of the impurities was confirmed by electrospray mass spectrometry (ESI-MS), and thus, the complementarity of the two techniques for drug analysis is shown. The limit of detection by SF-ICP-MS for cimetidine in solution was approximately 4-20 ng x g(-1), but it was blank-limited.