Gas chromatography coupled to time‐of‐flight mass spectrometry using parallel electron and chemical ionization with permeation tube facilitated reagent ion control for material emission analysis

Abstract

Rationale: Volatile organic compounds (VOCs) emitted by an artificial leather part for car interiors are determined using GC-MS (gas chromatograph coupled to a mass spectrometer) using simultaneous electron and chemical ionization (EI&CI). A device for swift reagent ion switching in CI mode between consecutive runs is presented. Methods: VOCs emitted from the investigated material were sampled onto Tenax ® absorption tubes using micro emission chambers and subsequently injected into the GC through thermal desorption. The detector was a time-of-flight mass spectrometer (TOFMS) simultaneously operating in EI and CI modes during a single chromatographic run. A custom permeation tube setup allowed for swift selection between various reagent ions in CI mode, e.g., [N 2 H] + , [H 3 O] + , [(H 2 O) 2 H] + , and [NH 4 ] + . Results: Different reagent ions are swiftly selectable between single GC runs without hardware changes. Differences in precursor ion survival yields and the selectivity of the various reactants were carefully assessed. Several examples for the improved identification of unknown compounds with the available complementary and comprehensive EI&CI data set are demonstrated for a relevant material emission application. Conclusion:The presented technique provides additional value to the standard GC-EI/MS procedure commonly used for material emission characterization. It allows for a non-targeted analysis approach with moderate analysis time. | INTRODUCTIONVolatile organic compounds (VOCs) are released from many different materials and can negatively impact human health, indoor air quality, production quality, or just produce unwanted odors. Prone to intense VOC emission are materials such as plastics, leather, paint, adhesives, and flooring. [1][2][3][4][5][6][7] Characterization of the VOC profile and single compound identification are necessary to evaluate the potential

Evaluation of GC-EI&CI-TOFMS for Nontarget Analysis of Industrial Wastewater Using Hydrophilic–Lipophilic-Balanced SPME

“…Especially at high retention time, many alkylbenzenes eluted (see SI Table S2), which are not ionizable by [NH 4 ] + . However, [NH 4 ] + may improve the precursor ion yield for very fragile compounds, as previously presented by Brakling et al, 20 and enhances the identification if the Applying the identification confidence levels by Schymanski et al, 29 6% of the compound identities were confirmed with a reference standard (level 1), for 41% a structure was proposed (level 2a and b), for 24% a tentative structure was proposed (level 3), for 29% a molecular formula was stated (level 4) and for 4% only the accurate mass could be gained (level 5) (see Figure 5G). However, for level 2, an identification confirmation by RI was necessary, which originally was not included by Schymanski et al, as the workflow was developed for LC-based methods.…”

“…Especially at high retention time, many alkylbenzenes eluted (see SI Table S2), which are not ionizable by [NH 4 ] + . However, [NH 4 ] + may improve the precursor ion yield for very fragile compounds, as previously presented by Bräkling et al, and enhances the identification if the precursor ion shows a low abundance with protonation reaction CI reagents or if the resulting ions of other reagents can not be unequivocally assigned to a molecular structure. The overall coverage of accurate mass precursor ion information is ∼86%, which highlights the advantage of using three different CI reagents.…”

“…For CI, H 2 , produced by a hydrogen generator (Precision Hydrogen Trace, Peak Scientific Instruments, London, U.K.), N 2 (99.9999 mol %, Carbagas, Gümligen, Switzerland), water, and 30% ammonia in water mixture using a permeation tube setup were used for the generation of reagent ions [N 2 H] + /[N 4 H] + , [H 3 O] + and [NH 4 ] + (more details in the SI and ref ). By using a reagent gas supply unit, the CI reagents could be switched between two GC runs without hardware changes. Each sample was measured three times while changing the CI reagents for each measurement, resulting in a data set of EI triplicates, with each having a different CI reagent.…”

“…18 In contrast, soft ionization methods compatible with GC, e.g., chemical ionization (CI), show less to no fragmentation and can therefore provide complementary information to EI. An instrument combining both EI and CI using a single time-offlight (TOF) mass analyzer, also referred to as the ecTOF (TOFWERK, Thun, Switzerland), was introduced recently 19,20 offering improved compound identification of known and unknown compounds. GC, compared to HPLC, often requires more sophisticated sample preparation methods.…”

Combining Metabolomics and Machine Learning to Identify Diagnostic and Prognostic Biomarkers in Patients with Non-Small Cell Lung Cancer Pre- and Post-Radiation Therapy

“…Semi-targeted metabolomics assessed the plasma levels of 74 metabolites involved in carbohydrates, amino acids, lipids, cofactors, vitamins, nucleotide pathways, energy metabolism, and xenobiotic biodegradation [20,21]. Plasma samples (50 μL) were mixed with an 8:2 (v/v) methanol: water solution containing internal standards, vortexed, and centrifuged.…”