LASER DESORPTION LASER PHOTOIONIZATION TIME-OF-FLIGHT MASS-SPECTROMETRY OF DYES

The mass spectra of a number of dye species have been investigated using two-step laser desorption laser photoionization time-of-flight mass spectrometry (L2TOFMS). A pulsed CO2 laser, wavelength 10.6 mum, was used to vaporize the samples as intact neutral molecules which were photoionized using either 193- or 266-nm laser radiation. Four classes of dyestuffs have been examined: azo, anthraquinone, phthalocyanine, and coumarin. Significant differences were found in the fragmentation patterns and ionization efficiencies at these two laser wavelengths particularly for the azo dyes. The applicability of this mass spectrometric technique to the identification, characterization, and detection of aromatic dyestuffs is discussed.