Comprehensive two-dimensional gas chromatography hyphenated
with accurate mass time-of-flight mass spectrometry (GC × 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 (1
I), 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 × GC. This gives access to calculated second dimension retention indices
(2
I). Reliability of the calculated 2
I was evaluated by using a Grob test mixture, and
saturated alkanes, revealing good correlation between previously reported I values from the literature, with R2 correlation being
0.9997. This essentially recognizes the retention property of peaks in the GC × GC 2D space as being reducible to a retention
index in each dimension, which should be a valuable tool supporting identification. The benefit of 2
I data, in supplementing 1
I
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 1
I and 2
I 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