LINKED GAS CHROMATOGRAPHY FOURIER TRANSFORM INFRARED MASS SPECTROMETER MIXTURE ANALYSIS SYSTEM

A linked gas chromatography Fourier transform infrared mass spectrometer (GC/FTIR/MS) system was developed for the purpose of identifying the components of mixtures by the use of the complementary information available from infrared and mass spectra. Individually, a mass spectrum or an infrared spectrum of a compound can provide much information about the compound\u27s identity, yet there exist many cases where an infrared or mass spectrum does not provide enough information to unambiguously identify the compound. Alkanes have very similar infrared spectra and are therefore difficult to distinguish. But the mass spectra of alkanes make their identification much simpler. Mass spectra of isomers pose a similar problem; they are quite often identical. By combining the information available in a mass spectrum and an infrared spectrum through the use of a linked GC/FTIR/MS system, identification of mixture components often can be made unambiguously. The linked GC/FTIR/MS system was tested with several mixtures of known composition to evaluate the value of the complementary information from the infrared and mass spectra. Identifications were easily made of compounds that, if only an infrared or mass spectrum were available, would have net been possible. The linked GC/FTIR/MS was also tested with more complex mixtures typical of laboratory reaction products and natural products. These were peppermint oil, which contained 18 components that could be studied and lacquer thinner, which had 30 components. This demonstrated that the GC/FTIR/MS system could be used to analyze unknown mixtures. It was noted in the analysis of peppermint oil that the sensitivity of the GC/FTIR was not sufficient for effective identification of the lower concentration components. A study of the GC/FTIR interface, the lightpipe, was initiated to determine the effect on sensitivity of the dimensions of the lightpipe. Also, as an aid in correlating the reconstructed chromatograms from the mass spectrometer and the infrared spectrometer, the two most common infrared chromatogram reconstruction methods were compared and evaluated as to their effectiveness in representing the GC effluent