A capillary column gas chromatography, resonance enhanced multiphoton ionization, time-of-flight mass spectrometry, laser-induced fluorescence, flame ionization detection system for the determination of polynuclear aromatic compounds in complex mixtures
Of the thousands of chemical compounds that have been deemed mutagenic or carcinogenic, it is generally agreed that the polynuclear aromatic hydrocarbons (PAC) are among the most potent. Typically, a multitude of different PAC are present, at trace levels, in a variety of environmental samples. Because of the wide range of potency of PAC, even among geometric isomers and substitutional derivatives, it is important to fully characterize these samples. This task is a formidable one, usually requiring elaborate sample clean-up and fractionation prior to analysis. Even with extensive sample preparation, however, many isomers cannot be distinguished by conventional GC/MS techniques. A multidimensional, laser-based analytical instrument has been developed that, when utilized to the full extent of its capabilities could be the solution to this complex analytical problem. The over- all technique is termed Capillary Column Gas Chromatography, Resonance Enhanced Multiphoton Ionization, Time-Of-Flight Mass Spectrometry, Laser-induced Fluorescence, with parallel Flame Ionization Detection (CC/GC-REMPI-TOF/MS-LIF-FID). This system combines the selectivity and sensitivity of two complementary laser-based methods, REMPI and LIF, with an extremely powerful and proven analytical tool, GC/MS. The GC effluent passes through the ion source of a TOF/MS, where it is interrogated by a tunable ultraviolet laser beam. Thus, PAC and other absorbing species may be selectively excited and/or ionized in the presence of nonabsorbing components. All laser-analyte interaction products (cations, electrons, and photons) are simultaneously monitored utilizing the TOF/MS, a total electron current detector (TECD), and a LIF detector. The beauty of this technique is that all analytically useful data for each absorbing chromatographic eluent may be collected "on-the-fly." The simultaneous availability of this information simplifies the characterization task. The present absolute detection limits for several PAC have been determined to be low picogram range. Also, a linear dynamic range of approximately four orders of magnitude has been established for the TECD, indicating that this technique is both sensitive and quantitative. Further, the use of deuterated analogs, of selected PAC, as internal reference standards greatly assists in quantitation. ('(UPSILON))DOE Report IS-T-1262. This work was performed under Contract W-7405-Eng-82 with the U.S. Department of Energy.