Determination of sulfonated azo dyes by liquid chromatography/atmospheric pressure ionization mass spectrometry

Sulfonated azo dyes are separated by high-performance liquid chromatography and introduced into the atmospheric pressure ion source of a triple quadrupole mass spectrometer using pneumatic nebulizers. A heated nebulizer together with a corona discharge produces ions by gas phase chemical ionization. Two related nebulizers operating at room temperature and floating at a high voltage make use of ions present in the liquid phase. Collision induced dissociation of (M - H)/sup -/ ions shows SO/sub 3//sup -/ as a fragment characteristic of sulfonated azo dyes and parent ion scans on SO/sub 3//sup -/ are used for identification of azo dyes in environmental samples. Selected ion monitoring and selected reaction monitoring are used for the determination of specific dyes.