Analytical Pyrolysis Principles and Applications to Environmental Science

Over the past half century, analytical pyrolysis has proven itself to be an effective means for the semiquantitative characterization of complex macromolecular organic substances. It has been demonstrated that instruments such as Py-FID, Py-MS, and in particular, Py-GC/MS can provide valuable geochemical insights when applied to a wide variety of problems in environmental science. The more widespread use of analytical pyrolysis methods in the evaluation of environmental pollution is recommended, because of their relatively low cost and information-rich results. Pyrolysis is the heating of organic substances in an inert, oxygen-free atmosphere, thereby avoiding combustion. When performed on a large scale, pyrolysis is involved in industrial processes as diverse as the manufacture of coke from coal and the conversion of biomass into biofuels. In contrast, analytical pyrolysis is a laboratory procedure in which small amounts of organic materials undergo thermal treatment, the products of which are subsequently quantified and/or characterized, for example, by gas chromatography. The pyrolysis may be performed “off-line” or “on-line.” In the off-line case, pyrolysis occurs in stand-alone reactor. The pyrolysis products are then extracted or trapped manually prior to further evaluation by chromatographic or other means. In on-line methods, the pyrolysis reactor is coupled directly to the analytical system, be it the injector of a gas chromatograph or a detector such as a flame ionization device or a mass spectrometer, with the pyrolyzate swept along its course by inert carrier gas. In some cases, a trapping mechanism such as cryofocusing is employed, which can permit the use of multiple detection or analytical systems. On-line methods typically only require milligram or even submilligram quantities of sample. Samples may be analyzed with little pretreatment, thereby minimizing the use of hazardous solvents in the spirit of environmentally conscious “green chemistry.