Search

Abstract: Hydrocarbon analysis with standard GC–MS is confronted by the limited range of volatile compounds amenable for analysis and by the similarity of electron ionization mass spectra for many compounds which show weak or no molecular ions for heavy hydrocarbons. The use of GC–MS with supersonic molecular beams (Supersonic GC–MS) significantly extends the range of heavy hydrocarbons that can be analyzed, and provides trustworthy enhanced molecular ion to all hydrocarbons. In addition, unique isomer mass spectral features are obtained in the ionization of vibrationally cold hydrocarbons. The availability of molecular ions for all hydrocarbons results in the ability to obtain unique chromatographic isomer distribution patterns that can serve as a new method for fuel characterization and identification. Examples of the applicability and use of this novel isomer abundance analysis (IAA) method to diesel fuel, kerosene and oil analyses are shown. It is suggested that in similarity to the “three ions method” for identification purposes, three isomer abundance patterns can serve for fuel characterization. The applications of the Supersonic GC–MS for engine motor oil analysis and transformer oil analysis are also demonstrated and discussed, including the capability to achieve fast 1–2s sampling without separation for oil and fuel fingerprinting. The relatively fast analysis of biodiesel is described, demonstrating the provision of molecular ions to heavy triglycerides. Isomer abundance analysis with the Supersonic GC–MS could find broad range of applications including petrochemicals and fuel analysis, arson analysis, environmental oil/fuel spill analysis, fuel adulteration analysis and motor oil analysis. [Copyright &y& Elsevier]

Abstract: A new approach of flow modulation comprehensive two-dimensional gas chromatography–mass spectrometry (GC×GC–MS) with supersonic molecular beam (SMB) and a quadrupole mass analyzer is presented. Flow modulation uniquely enables GC×GC–MS to be achieved even with the limited scan speed of quadrupole MS, and its 20ml/min column flow rate is handled, splitless, by the SMB interface. Flow modulation GC×GC–SMB–MS shares all the major benefits of GC×GC and combines them with GC–MS including: (a) increased GC separation capability; (b) improved sensitivity via narrower GC peaks; (c) improved sensitivity through reduced matrix interference and chemical noise; (d) polarity and functional group sample information via the order of elution from the second polar column. In addition, GC×GC–SMB–MS is uniquely characterized by the features of GC–MS with SMB of enhanced and trustworthy molecular ion plus isotope abundance analysis (IAA) for improved sample identification and fast fly-through ion source response time. The combination of flow modulation GC×GC with GC–MS with SMB (supersonic GC–MS) was explored with complex matrices such as diesel fuel analysis and pesticide analysis in agricultural products. [Copyright &y& Elsevier]