Analysis of Multiple Classes of Cigarette Smoke Constituents by GCxGC-TOFMS

Tobacco pyrolysis produces harmful vapors that contain toxic and carcinogenic components. Characterization of these components is challenging because tobacco smoke is a complex mixture containing compounds from several chemical classes. This complexity has traditionally required multiple analysis methods along with considerable sample clean-up to target compound classes individually. GC×GC provides improved peak capacity and low level detection to measure multiple compound classes simultaneously, thus minimizing sample clean-up and the need for multiple analyses.

Experimental

Smoke was generated from Kentucky 3R4F reference cigarettes with an automated smoking machine per ISO smoking conditions (Arista Laboratories, Richmond, Virginia). Smoke constituents were collected on Cambridge filter pads, extracted into methanol, and analyzed with LECO's Pegasus® 4D as follows:

Injection: 1.5 µL splitless with inlet at 250 °C

Carrier Gas: He at 1.0 ml/min, corrected constant flow

Columns: 30 m Rtx-5Sil MS (0.25 mm × 0.25 µm) with 1.5 m Rtx-200 (0.18 mm × 0.20 µm) (Restek, Bellefonte, Pennsylvania)

Temperature Program: 3 min at 45 °C, ramped 8 °C/min to 300 °C, held 10 min; secondary oven +10 °C

Modulation: 3 s (temperature +25 °C from main oven)

Transfer Line Temperature: 280 °C

MS Acquisition: 33–400 m/z at 200 spectra/s with source at 250 °C

Data processing: ChromaTOF® software

Results

A TIC contour plot of tobacco smoke extract is shown in Figure 1A. Deconvolution via ChromaTOF isolated individual analytes from the matrix for identification and quantification by mass spectral matching and peak area/height, respectively. Several target compounds were identified and analytes were grouped by compound classes through ChromaTOF's Classification tools. Peak marker color, in Figure 1B, indicates approximate class assignment. Representative reference standards were also analyzed to generate calibration information for quantification. Linear calibrations ranged from 1 ppb to 50 ppm, analyte dependent. The calibrations were applied to quantify compounds extracted from the filter in the smoke extract data. Typical masses were in the µg range.

Figure 1: Representative chromatogram (A) with analytes grouped based on their compound class (B), using ChromaTOF’s Classification Feature.

Discussion

GC×GC-TOFMS provided a comprehensive analysis of tobacco smoke across several compound classes. Characterization was accomplished with a single separation lasting under 45 min. Individual constituents of smoke were efficiently isolated from the complex matrix with sufficient resolution to identify and quantify representative analytes from many of the target compound classes. Full mass range TOFMS acquisition allowed for positive identification of both target and non-targeted compounds through mass spectral matching to data base standards. TOFMS detection also offered quantitative calibration of representative analytes from the target compound classes, using ChromaTOF's Calibration Feature. This methodology reduces the need for time consuming sample clean-up and/or repeat injections that individually target each compound class.

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