Sensitivity comparison of gas chromatography–mass spectrometry with Cold EI and standard EI

Abstract

Gas chromatography–mass spectrometry (GC–MS) with Cold EI is based on interfacing GC and MS with supersonic molecular beams (SMBs) along with electron ionization of vibrationally cold sample compounds in SMB in a fly‐through ion source (hence the name Cold EI). Cold EI improves all the central performance aspects of GC–MS, and in this paper, we focus on its improvement of signal‐to‐noise ratio (S/N) and limits of detection (LODs). We found that the harder the compound for analysis with standard EI, the greater the Cold EI gain in S/N and LOD. The lower LOD and higher S/N of Cold EI emerge from a few reasons: (a) similar ionization yield as standard EI, (b) enhanced abundance of molecular ions, (c) elimination of vacuum background noise, (d) elimination of ion source‐related peak tailing and degradation, (e) ability to lower the elution temperatures via the use of high column flow rates, and (f) greater range of thermally labile and low‐volatility compounds that can be analyzed. We demonstrate the superior S/N and lower LOD of Cold EI versus standard EI in a range of compounds, from the simple‐to‐analyze octafluoronaphthalene all the way to reserpine and an organo‐metallic compound that cannot be analyzed by standard EI. These compounds include methyl stearate, cholesterol, n‐C32H66, large polycyclic aromatic hydrocarbons, dioctyl phthalates, diundecyl phthalate, pentachlorophenol, benzidine, lambda‐cyhalothrin, and methidathion. The significantly lower Cold EI LODs that can be over 1000 times better than in standard EI further result in far superior response linearity and greater measurement dynamic range.

Fast saliva analysis by GC–MS with Cold EI and Open Probe Fast GC–MS with Cold EI for the detection of cannabis usage

“…The GC–MS with Cold EI system that was used is based on the combination of an Agilent 7890A GC + 5977 MSD (Agilent Technologies, Santa Clara, CA, USA) with the Aviv Analytical Cold EI (Aviv Analytical LTD, Hod Hasharon, Israel). GC–MS with Cold EI is reviewed in previous studies 14–16 and further described in previous studies 18,28–31 . In Cold EI, the GC column flow output is mixed with helium make‐up gas (~50–60 mL/min total column and make‐up flow rate), in front of a supersonic nozzle at the end of a temperature‐controlled transfer line.…”

“…GC–MS with Cold EI is based on coupling of the gas chromatograph (GC) and mass spectrometer (MS) with a supersonic molecular beam (SMB) and on EI of vibrationally cold sample molecules during their flight through a contact‐free ion source (thereby named Cold EI). Cold EI was developed in 1990 by Amirav and Danon, 12,13 and it is reviewed in Amirav et al 14,15 A book was recently published on GC–MS with Cold EI 16 . Cold EI improves all the major GC–MS performance aspects including (a) it provides enhanced molecular ions yet retains NIST library identification and improves sample identification; (b) it significantly extends the range of compounds amenable for analysis; (c) it provides uniform response to all analytes for improved internal quantification; (d) it enables faster analysis; (e) it provides greater selectivity; and (f) it provides lower limits of detection 14–17 .…”

“…Cold EI was developed in 1990 by Amirav and Danon, 12,13 and it is reviewed in Amirav et al 14,15 A book was recently published on GC–MS with Cold EI 16 . Cold EI improves all the major GC–MS performance aspects including (a) it provides enhanced molecular ions yet retains NIST library identification and improves sample identification; (b) it significantly extends the range of compounds amenable for analysis; (c) it provides uniform response to all analytes for improved internal quantification; (d) it enables faster analysis; (e) it provides greater selectivity; and (f) it provides lower limits of detection 14–17 . The aim of this study is to describe the application of GC–MS with Cold EI for the analysis of cannabinoids in saliva without any sample preparation and in fast, real‐time analysis time.…”

Sample Injection for Real-Time Analysis (SIRTA) Using GC-MS with Cold EI

“…The GC-MS with Cold EI system that was used is based on the combination of an Agilent 7890A GC + 5977 MSD (Agilent Technologies, Santa Clara, CA) with the Aviv Analytical Cold EI (Aviv Analytical LTD, Hod Hasharon, Israel). Cold EI has been reviewed − and further described. , In Cold EI, the GC column flow output is mixed with helium makeup gas (∼50–60 mL/min total column and makeup flow rate at stabilized nozzle backing pressure), in front of a supersonic nozzle at the end of a temperature-controlled transfer line. The helium makeup gas can be mixed with perfluorotributylamine (PFTBA) for system tuning and mass calibration.…”

“…Cold EI was developed in 1990 by Amirav and his group , and has been reviewed. , Also, a book was recently published on GC-MS with Cold EI . Cold EI improves all the major GC-MS performance aspects including the following: (a) enhanced molecular ions while retaining NIST library identification; (b) significant extension of the range of compounds that are amenable for GC-MS analysis; (c) uniform response to all analytes for improved internal quantification; (d) faster analysis; (e) greater selectivity; (f) lower limits of detection . The aim of this paper is to describe the application of SIRTA with Cold EI after minimal or no sample preparation.…”