Applicability of mass spectrometry to detect coeluting impurities in high-performance liquid chromatography

An array of pharmaceutical compounds and impurities were used to investigate the applicability of atmospheric pressure ionization mass spectrometry (MS) to routinely detect coeluting impurities in HPLC (i.e. peak purity). Four drugs were individually tested against their related impurity set using a straightforward HPLC–MS peak purity strategy. For the investigated set, which represents 24 unique drug-impurity permutations, 75% of the coeluting impurities were detected at levels <1.0%, including one-third at 0.1% (%, w/w). Factors that affect the applicability of this peak purity approach are also discussed.