Two-Dimensional Retention Indices Improve Component Identification in Comprehensive Two-Dimensional Gas Chromatography of Saffron

Comprehensive two-dimensional gas chromatography hyphenated with accurate mass time-of-flight mass spectrometry (GC X GC-accTOFMS) Was applied for improved analytical accuracy of saffron analysis, by using retention indices in the two-dimensional separation. This constitutes 3 dimensions of identification. In addition to accTOFMS specificity, and first dimension retention indices (I-1), a simple method involving direct multiple injections with stepwise isothermal temperature programming is described for construction of isovolatility curves for reference alkane series in GC X GC. This gives access to calculated second dimension retention indices (I-2). Reliability of the calculated I-2 was evaluated by using a Grob test mixture, and saturated alkanes, revealing good correlation between previously reported I values from the literature, with R-2 correlation being,0.9997. This essentially recognizes the retention property of peaks in the GC x GC 2D space as being reducible to a retention index in each. dimension, which should be a valuable tool supporting identification. The benefit of I-2 data, in supplementing I-1 and MS library matching, was clearly demonstrated by the progressive reduction of the number of possible compound matches for peaks observed in saffron: 114 analytes were assessed according to I-1 and I-2 values within +/- 20 index unit of reference values, and by MS. spectrum matching above a match,statistic of 750 (including mass accuracy of the molecular ion <20 ppm) and their possible identities derived. The described method provides a new avenue to utilize the full capability of the two-dimensional separation (GC X GC), in combination with MS library matching in complex sample analysis, to provide improved component identification.