Comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC × GC-TOFMS) was used to identify methylhopanes in oils. 2α-Methyl-17α(H),21β(H)-hopane and 2α-methyl-17β(H),21α(H)-hopane (2α-methylhopane) series were found in oils from Ceará Basin, Brazil. In the 3β-methylhopane series, only C31 3β-methyl-17α(H),21β(H)-hopane was detected. In addition, a novel terpane series (C30−C34), which eluted after the regular hopanes (comparing compounds of both families with the same carbon number) either in 1D (first dimension) or 2D (second dimension), was identified. A compound likely to be bisnorgammacerane was separated from C29 25-norhopane in the 2D, and consequently identified. An unusual compound pair eluting after the C35R moretane was tentatively identified as C36 17α(H),21β(H)-homohopanes (22S, 22R). The presence of 2α-methylhopanes in oils from Ceará Basin may indicate oxygen-producing cyanobacteria were important biological inputs in the deposition environment. This is the first study that shows the separation between hopane and 2α-methylhopane series and their tentative spectral identification using GC × GC-TOFMS, as they are usually not well separated in one-dimensional gas chromatography.

No abstract