Abstract
Gas chromatography-mass spectrometry (GC-MS) with Cold electron ionization (EI) is based on interfacing the GC and MS with a supersonic molecular beam (SMB) along with electron ionization of vibrationally cold sample compounds in the SMB in a contact-free fly-through ion source (hence the name Cold EI). Cold EI improves all the central performance aspects of GC-MS, including: a significantly extended range of compounds that are amenable for analysis, enhanced molecular ions, highly improved sample identification, faster analysis (much faster), uniform response to all analytes, greater selectivity and higher signal to noise ratios and lower limits of detection, particularly for compounds that are difficult to analyze. GC-MS with Cold EI executes the analysis of the full range of standard EI applications and most with major improvements of various metrics. Furthermore, it significantly extends the range of compounds and applications amenable for GC-MS analysis. Accordingly, it is a highly superior replacement ion source. In this review article, we describe Cold EI and its main features, discuss its benefits, and demonstrate several of its unique applications including cannabinoids analysis, synthetic organic compounds analysis, whole blood analysis for medical diagnostics, isomer distribution analysis for improved fuels and oils, and explosives analysis.