The Analysis of Forensic Samples Using Laser micro-Pyrolysis Gas Chromatography Mass Spectroscopy

Abstract

Laser micropyrolysis gaschromatograpby-mass spectrometry is used for the analysis of paint, photocopier toner, and synthetic fiber materials to test the forensiopotential of this emerging technology. It uses a laser microprobe to selectively target very small parts of the materials for GC-MS· analysis. Whereas the paint and the toner samples were amenable to direct laser pyrolysis, the synthetic fibers proved transparent to the 1064 urn laser radiation. The difficulty with the fibers demonstrates that a specific laser wavelength may not be appropriate for all types of materials. Nevertheless, the fibers were able to be indirectly pyrolyzed by impregnation in a strongly absorbing graphite matrix. A vast array of hydrocarbon pyrolysates was detected from the different materials studied. Unique product distributions were detected from each sample and in sufficient detail to facilitate individual molecular characterization (i.e., molecular fingerprinting). The integrity of the laser data were confirmed by comparison to data obtained from the same samples by the more conventional pyroprobe pyrolysis GC-MS method. The high spatial resolution and selectivity of the laser method may be advantageous for specific forensic applications, however, further work may be required to improve the reproducibility of the data.