Detection of Trace Skin Sensitizers Using Novel Nucleophiles with Quaternary Ammonium by Liquid Chromatography–Mass Spectrometry

Various methods for assessing the risk of skin sensitization have been developed to reduce the number of animal tests. Although sensitization can be induced by trace amounts of impurities in the raw materials, current test methods have limitations in detecting sensitization from impurities and in not identifying the cause. In this study, novel nucleophiles, N-(4-trimethylammoniobenzoyl)-2-sulfanylethylamine (TMAS) and N-(4-trimethylammoniobenzoyl)-6-aminohexylamine (TMAA), were synthesized for the highly sensitive detection of trace skin sensitizers using mass spectrometry. The reactivities of TMAS and TMAA were verified using several sensitizers. TMAS and TMAA were selectively reactive with sensitizers, and adducts were detected with a sensitivity of 10 μg/L in solution. Because a specific product ion (m/z 148.08) was detected in all adducts, selective detection by various tandem mass spectrometric analyses, such as selective reaction monitoring, is feasible. This method is effective for the detection and structural analysis of skin sensitizers present in raw materials.