An expert system has been developed for the interpretation of the gas chromatography/mass spectrometry (GC/MS) spectra of fossil fuel distillates. The approach extends the scope of commercially available data systems by using interpretation rules generally carried out by a skilled professional expert. The rules and procedures incorporated in the program deconvolute unresolved peaks, set acceptability limits for the identifications provided by commercial data systems, and identify components that the commercial data systems fail to identify, or identify incorrectly, at least as to compound class and carbon number.
Need for such an approach stems from the inability of commercial data systems to deal adequately with complex hydrocarbon mixtures. The spectral matching algorithms used by these systems do not consider spectra/structure correlations and fail when GC/MS peaks are unresolved or pure compound spectra are not available for comparison or both. These conditions occur in the majority of cases with boiling range above 149°C (300°F). The expert program discussed in the paper obviates these difficulties. It results in 90 to 95% correct identifications, 99% plus on a concentration basis, and it saves 20 to 30 h of skilled time per sample.