Comprehensive two-dimensional gas chromatography with flow modulator coupled via tube plasma ionization to an atmospheric pressure high-resolution mass spectrometer for the analysis of vermouth volatile profile

Abstract

The analysis of complex samples is a big analytical challenge due to the vast number of compounds present in these samples as well as the influence matrix components could cause in the methodology. In this way, comprehensive two-dimensional gas chromatography coupled to mass spectrometry (GC × GC–MS) is a very powerful tool to achieve the characterization of complex samples. Nevertheless, due to possible coelutions occurring in these matrices, mixed spectra are generally obtained with electron ionization (EI) which could extremely complicate the identification of the analytes. Thereby, new methodology setups are required to improve the confidence on the identification in non-targeted determinations. Here, we present a high-throughput methodology consisting of GC × GC with flow modulation coupled to high-resolution atmospheric pressure mass spectrometry (HRMS) via a novel tube plasma ion source (TPI). The flow modulator allows to easily automate the GC × GC method compared to traditional cryo-modulators, while the soft ionization provided by TPI helps to preserve the [M]+• or [M+H]+ ions, thus increasing the confidence in the identification. Additionally, the combination of a flow modulation with an atmospheric pressure mass spectrometer significantly improves the sensitivity over flow modulated GC × GC-EI-MS methods because no split is required. This methodology was applied to the analysis of a complex sample such as vermouth where the volatile profile is usually considered by consumers as a product quality indicator since it raises the first sensations produced during its consumption. Using this approach, different classes of compounds were tentatively identified in the sample, including monoterpenes, terpenoids, sesquiterpenoids and carboxylic acid, and carboxylate esters among others, showing the great potential of a GC × GC-TPI-qTOF-MS platform for improving the confidence of the identifications in non-targeted applications.

Diverse thermal desorption combined with self-aspirating corona discharge ionization for direct mass spectrometry analysis of complex samples

“…1–3 Since the detection of specific substances can be affected by spectral interference and suppression among complex components, the samples often require appropriate pretreatment before instrumental analysis. 4 Common pretreatment processes include dissolution, extraction, filtration, etc , and chromatography is also widely used for the separation of various components. 5–7 These treatments facilitate the identification of multiple ingredients in raw samples, but they also have some disadvantages, such as being time-consuming and high solvent consumption.…”

Performance Evaluation of an EI&CI Dual Ionization TOFMS Hyphenated with a Flow Modulated GC×GC System

“…Here the sample is split after chromatography and just a fraction of the effluent is introduced into the MS, therefore affecting sensitivity. 20 Nevertheless, flow modulation is of increasing interest in the community due to cheaper, less maintenance, and less fault prone hardware compared to thermal modulation setups. 19 In this work the coupling of an EI&CI-TOFMS to flow modulation GC×GC is presented with a special focus on the characterization of the chromatographic alignment and the EI/ CI switching behavior of the instrument as well as the advantages of using flow modulation in combination with a medium-pressure CI source.…”

“…To prevent this disturbance, a parallel use of additional detectors such as flame ionization detectors (FID) is required. Here the sample is split after chromatography and just a fraction of the effluent is introduced into the MS, therefore affecting sensitivity . Nevertheless, flow modulation is of increasing interest in the community due to cheaper, less maintenance, and less fault prone hardware compared to thermal modulation setups …”