Leading Non-Targeted Analysis to the Next Level Using GC-MS with Cold EI

Alex Yakovchuk, School of Chemistry, Tel Aviv University, Tel Aviv, Israel (yakovchuk@mail.tau.ac.il)
Aviv Amirav, School Of Chemistry, Tel Aviv University, Tel Aviv, Israel

Non-targeted analysis (NTA) and screening (NTS) are notorious challenges in analytical science. Most analytical methods are "targeted" and unfit for such challenges by design, being suitable only for a limited range of known compounds. Even in instances where non-targeted analysis is attempted it is often prohibitively expensive and incomplete due to reliance on multiple analyses, additional instruments, and expert analysts to provide supplementary data for a reliable determination. Thus, many potential breakthroughs, health hazards, and discoveries remain inaccessible or ignored.

Today, gas chromatography-mass spectrometry (GC-MS) with standard electron ionization (EI) technology has very limited NTA and NTS capabilities, considering:

(1) weak or absent molecular ions hinder identification reliability, increase dependence on supplementary information

(2) elution times of low-volatility compounds go beyond the scope of typical analysis time, making those compounds effectively undetectable

(3) degradation of thermally-labile compounds prevents their detection

(4) weak signal of polar compounds at low amounts due to ion source-induced peak tailing and degradation

GC-MS with Cold EI is based on interfacing a gas chromatograph (GC) and a mass spectrometer (MS) with a supersonic molecular beam (SMB), and electron ionization of vibrationally cold compounds in the SMB by a fly-through ion source. It excels in NTA and NTS by eliminating all forementioned limitations: providing enhanced molecular ions, reducing elution times by up to an order of magnitude, lowering elution temperatures by up to 100°C, and increasing the signal of polar compounds by orders of magnitude by eliminating ion source related peak tailing.

We demonstrate significant improvements in NTA and NST capabilities by comparing standard and cold EI using several compound types with varying sizes (m/z = 226-774) and polarities: linear and branched hydrocarbons, drugs, large PAHs, and phthalates. Improvement was sufficient to eliminate the need for supplementary data and instrumentation. Compounds and their residues were detected and identified using data from a single analysis.

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Short Biography of Presenting Author

Ph.D. candidate, Tel-Aviv University, Prof. Amirav's group.

working on GC-MS instrumentation and application development.