Comprehensive analysis of tobacco smoke using TD–GC×GC–TOF MS with Tandem Ionisation

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Courtesy of SepSolve Analytical

The hazardous constituents of cigarette smoke have attracted considerable attention lately, especially with increasing regulation around the world limiting or banning smoking in public places – and even in private cars if children are present.

From an analytical perspective, however, there is much that remains to be learnt about the composition of cigarette smoke, because of its high degree of complexity – tobacco smoke is thought to contain thousands of components across multiple chemical classes and wide concentration ranges.

Thermal desorption (TD) is widely used for the analysis of volatile and semivolatile organic compounds (VOCs and SVOCs) by GC–MS, in a variety of sample types and over a wide concentration range. It greatly improves sample throughput, by allowing the full automation of sample preparation, desorption/ extraction, pre‑concentration and GC injection.

Comprehensive two-dimensional gas chromatography (GC×GC), when coupled with time-of-flight mass spectrometry (TOF MS), is also a powerful approach to the analysis of complex samples, improving chemical fingerprinting in areas of study as diverse as petrochemical analysis[1] and fragrance profiling.[2] In this study, we use thermal desorption (TD) for collection and analysis of whole cigarette emissions, and couple it with flow-modulated GC×GC–TOF MS, to enable smoke constituents to be routinely and confidently sampled, separated and identified.

The use of Tandem Ionisation [3] is also harnessed to increase the analytical resolution of the system, by providing both reference-quality 70 eV spectra and soft electron ionisation (EI) spectra simultaneously in a single analysis.

Experimental
Sample preparation: Smoke from three commercial cigarette brands (A, B and C) was analysed. Cigarette smoke was drawn (on the fourth ‘puff’) directly onto an inert-coated Tenax TA sorbent tube using an ACTI-VOC low-flow pump (Markes International). A flow of 300 mL/min was applied for 10 s, sampling ~50 mL of cigarette aerosols. Aluminium foil was wrapped around the interface between the tube and cigarette filter (Figure 1) and made airtight by applying a piece of Scotch tape. After the sampling period the tube was capped and placed in the automated thermal desorber ready for analysis.

TD: Instrument: TD100-xr (Markes International); Flow path: 190°C; Pre-purge: 1 min, 20 mL/min; Tube desorb: 10 min, 300°C, 50 mL/min, no split; Trap: Generalpurpose; Desorb split flow: 200:1; Pre-trapfire purge: 1 min, 50 mL/min; Trap low: 20°C; Heating rate: Max; Trap high: 300°C, 5 min.

2D column set: 1st dimension: BPX5, 20 m × 0.18 mm × 0.18 μm; 2nd dimension: DB17MS, 5 m × 0.25 mm × 0.25 μm; Temp. program: Main oven: 40°C (5 min), 5°C/min to 240°C (5 min); Modulator: Insight flow modulator (SepSolve Analytical); Loop dimensions: 227 mm, 1/32″ o.d., 0.53 mm i.d.; Loop volume: 50 μL; Loop fill time: 7.75 s; Loop flush time: 0.25 s; Modulation period (PM): 8.0 s.

TOF MS: Instrument: BenchTOF-Select (Markes International); Filament voltage: 1.7 V; Ion source: 250°C; Transfer line: 250°C; Mass range: m/z 35–400; Data rate: 100 Hz; Tandem Ionisation: Simultaneous acquisition of 70 eV and 14 eV data.

Software: Instrument control and acquisition: TOF-DS (Markes International); GC×GC data visualisation and processing: ChromSpace plug-in (Markes International).

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