FADING OF COLORANTS BY ATMOSPHERIC POLLUTANTS - MASS-SPECTROMETRY STUDIES

Chemical ionization mass spectra have been recorded for a number of ar tists' colorants that fade rapidly when exposed to atmospheric levels of ozone and other photochemical air pollutants. These colorants inclu de the natural colorant curcumin, several indigos and a number of aliz arin derivatives. Also included are isatins, which are produced in the fading of indigo colorants by atmospheric pollutants. The protonated molecular ion MH (M = compound mol. wt.) was the most abundant peak in the methane chemical ionization spectra of most of the artists' color ants studied. Other peaks that are of important diagnostic value are d iscussed for each category of colorant. Examples of applications are i ncluded and illustrate the usefulness of chemical ionization mass spec trometry in assessing air pollutant-induced damage to paintings and ot her colorant-containing objects of artistic and historical value.