GC/FT-IR/MS: Identification of Chemical Unknowns Via Computer Searches of Reference Spectral Libraries

摘要

Rapid and positive identification of compounds and complex mixtures has long been a goal of analytical laboratories. Pursuit of this goal has lead to sophisticated instrumentation that is often associated with dedicated computers. Since these computers are required for data collection and manipulation, they may often be utilized for retrieval of reference spectra. At the Morgantown Energy Technology Center, the Digilab Fourier transform infrared (FT-IR) spectrometer has been interfaced to a Perkin Elmer gas chromatograph (GC) through a Digilab GC/IR interface and related software. This paper reports the initial results of the GC/FT-IR/MS system, which is comprised of the Digilab FT-IR model FTS-15B, reconfigured with a Digilab FTS-GCS interface, a Perkin Elmer Sigma 1 GC, and a DuPont 21-491B mass spectrometer (MS) with a 21-094B data system and a 21-093 mass marker. This report describes the operational GC/FT-IR/MS system. A schematic diagram of this system is presented. Using this system, the infrared spectrum of each gas chromatographic effluent and its mass spectrum can be obtained. The infrared spectrum is a measure of the vibrational energy levels of a substance that is uniquely characteristic of that substance. Since this analysis is nondestructive, the mass spectrum can also be obtained: mass spectrum is a measure of the mass of a molecule after ionization and the fragments formed by breaking chemical bonds. This simultaneously provides two complementary methods of identifying complex mixtures. With the use of dedicated computers, standard reference libraries may be rapidly searched for comparable spectra of the GC-separated unknowns. Two independent sets of libraries greatly enhance the reliability of positive identification. 1 ref., 13 figs., 3 tabs. (ERA citation 10:049126)