Determination of the Signal-To-Noise Ratio Enhancement in Comprehensive Three-Dimensional Gas Chromatography

We investigate the extent to which comprehensive three-dimensional gas chromatography (GC(3)) provides a signal enhancement (SE) and a signal-to-noise ratio enhancement (S/N-Rel) relative to one-dimensional (1D)-GC. Specifically, the SE is defined as the ratio of the tallest D-3 peak height from the GC(3) separation to the 1D peak height from the unmodulated 1D-GC separation. A model is proposed which allows the analyst to predict the theoretically attainable SE (SET) based upon the peak width and sampling density inputs. The model is validated via comparison of the SET to the experimentally measured SE (SEM) obtained using total-transfer GC(3) (100% duty cycle for both modulators) with time-of-flight mass spectrometry detection. Two experimental conditions were studied using the same GC(3) column set, differing principally in the modulation period from the D-1 to D-2 columns: 4 s versus 8 s. Under the first set of conditions, the average SEM was 97 (+/- 22), in excellent agreement with the SET of 97 (+/- 18). The second set of conditions improved the average SEM to 181 (+/- 27), also in agreement with the average SET of 176 (+/- 26). The average S/N-Rel following correction for the mass spectrum acquisition frequency was 38.8 (+/- 11.2) and 59.0 (+/- 27.2) for the two sets of conditions. The enhancement in S/N is largely attributed to moving the signal to a higher frequency domain where the impact of low frequency noise is less detrimental. The findings here provide strong evidence that GC(3) separations can provide enhanced detectability relative to 1D-GC and comprehensive two-dimensional gas chromatography (GCxGC) separations.

Automated summary

The study investigates the signal enhancement and signal-to-noise ratio enhancement provided by comprehensive three-dimensional gas chromatography compared to one-dimensional gas chromatography. A model is proposed and validated through experimental comparison, demonstrating that GC(3) can offer enhanced detectability.