Identification of Organic Pigments in Automotive Coatings Using Laser Desorption Mass Spectrometry

The study found that when paint pigments, either in a simple or complex mixture, were irradiated with pulsed ultraviolet radiation, the pigments selectively absorbed the energy and were desorbed and ionized. With no sample preparation, positive- and negative-ion mass spectra of the ions formed can be collected. At the pigment levels used in car paint, signals can be produced with high signal-to-noise ratios. Inorganic pigments in the presence of organic pigments can be detected. Collected data (pigment color, molecular weight, isotopic information, and tendency to form fragment ions) were used with information on available and commonly used organic pigments to make molecular identifications. The automotive paints used in this study were obtained from in-house automotive paint collections at the New Jersey State Police as well as sample panels from the Reference Collection of Automotive Paints. The description of materials and methods addresses instrumentation, the pigments tested, sampling procedures, and instrument calibration. 1 table, 6 figures, and 32 references