Enhanced chemical analysis using parallel column gas chromatography with single-detector time-of-flight mass spectrometry and chemometric analysis

A parallel gas chromatographic instrument with time-of-night mass spectrome tric detection (GC/TOF-MS) is reported. An injected sample is first split b etween two GC columns that provide complementary separations. The effluent from the two columns is recombined prior to detection with a single TOF-MS, Switching from single to parallel columns increases the chemical selectivi ty of a GC/TOF-MS data set without increasing analysis time, by doubling th e number of peaks, or features, in the chromatographic dimension. The resul ting analyzer can be used to reduce analysis times for partially resolved p eaks. Simulations compare the quantitative precision of parallel-and single -column instruments using the generalized rank annihilation method (GRAM), Results indicate that a parallel column GC/TOF-MS should substantially impr ove the chemical selectivity and quantitative precision of the analysis rel ative to a single-column instrument, For a column at half its peak capacity , for example, a single-column instrument met the target precision less tha n 75% of the time, while a parallel-column instrument achieved 95% success. Parallel-column analyses of methyl tert-butyl ether (MTBE) and benzene in gasoline samples were also performed to support the simulation studies. An objective chromatographic standardization technique corrected for retention time shifts before GRAM was applied. Although MTBE and benzene were poorly resolved in the 40-s runs, chemometric techniques successfully quantitated them.