Gas Chromatography in Coatings Analysis
Published Online: 15 SEP 2006
Copyright © 2000 John Wiley & Sons, Ltd. All rights reserved.
Encyclopedia of Analytical Chemistry
How to Cite
Haken, J. 2006. Gas Chromatography in Coatings Analysis. Encyclopedia of Analytical Chemistry. .
- Published Online: 15 SEP 2006
This work describes the analysis of coating materials using gas chromatography (GC). An element of volatility is necessary for samples to be amenable to the technique and early applications concerned the analysis of solvents and their mixtures. The examination of low molecular weight and volatile components of coatings followed; these included trace or residual products in resins. The resinous or binder components are essentially nonvolatile, and to be amenable to GC a considerable reduction in molecular weight is necessary. This has been achieved by chemical cleavage of condensation systems, with examination of the reconstituted reactants or their derivatives, or by thermal means in the absence of oxygen where pyrolysis provides fragments which may be related to the initial composition. Chemical cleavage was applied to alkyd resins, acrylics, polysiloxanes, polyurethanes and polyethers during the 1960s and while the results were most satisfactory, the time required was considered excessive. Several decades later, some of the problems have been eliminated but the procedures have found little application. Pyrolysis was also introduced at the same time and while the early reports were of low reproducibility, refinements in technique allow reproducible results to be achieved rapidly. The major area of the application of GC to coating materials is pyrolysis, where, in combination with mass spectroscopy (MS), valuable information is achieved in minutes.
Other coating applications of GC include inverse chromatography which has found negligible use and headspace chromatography which is widely used in determining the source of odors or taints in coated food packaging. Special applications of GC include use in forensic science where accelerants used by arsonists are readily detected and also examination and identification of paint flakes by pyrolysis GC/MS. Similarly pyrolysis techniques are used in conservation studies, with the analysis of old paints on art works.