Quantitative LC-MS/MS analysis of azide and azidoalanine in in vitro samples following derivatisation with dansyl chloride

An LC-MS/MS method for the simultaneous quantification of azide and azidoalanine in bacterial and mammalian cellular systems was developed to support mutagenicity evaluation of azido containing nucleoside drugs. With the aim to enhance ionization efficiency and chromatographic retention, derivatisation with dansyl chloride was optimized; study samples (diluted 1/10) were derivatised for 2 h at room temperature and subsequently analysed with reversed phase liquid chromatography in combination with electrospray mass spectrometry in the positive ion mode. Good linearity and accuracy were obtained with a lower limit of quantification of 10.0 ng mL−1 for both analytes. The method was applied in mutagenicity experiments and showed time-dependent release of azide, but no formation of azidoalanine could be detected.