Impact of comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry experimental design on data trilinearity and parallel factor analysis deconvolution.

Comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC × GC-TOFMS) is a powerful instrument for the analysis of complex samples. Deconvolution of overlapped analytes using a suitable chemometric data analysis method such as Parallel Factor Analysis (PARAFAC) is often required. However, PARAFAC is designed to require a strict data trilinearity requirement. In this study we examine how strict this requirement is in the context of GC × GC experimental conditions, and demonstrate that under suitable conditions the data is sufficiently trilinear to achieve accurate deconvolution. The term trilinear deviation ratio (TDR) was previously introduced as a quantitative metric to predict the accuracy of PARAFAC deconvolution. Trilinear deviation ratio is defined as the run-to-run retention time shift, Δt, for a given analyte on the second dimension (D) separation, divided by the D analyte peak width-at-base, W. We demonstrate that experimental conditions impact the TDR range produced and PARAFAC performance. Column selection and modulation period, P, are shown to significantly influence the TDR range. Two column sets were evaluated, giving rise to different k' ranges for the D separations. Each column set was used with an optimum P as well as a longer P to demonstrate the effect of P selection on the TDR range and PARAFAC quantification. A P of 6 s produced a Δt range from -19.5 ms to -98 ms and TDRs from 0.157 to 0.439, translating into a PARAFAC bias from +1.6% to -13.5%. However, a P of 1.5 s produced a Δt range of -1.1 ms to -8.8 ms, and significantly lower TDRs from 0.013 to 0.057, translating into PARAFAC errors from +2.1% to -3.9%, with an average of -1.1% ± 1.4. These results validate the idea that a suitable GC × GC experimental design will provide accurate quantification with PARAFAC.