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T-SEP® is a proprietary, small scale, thermal separation technique that has been developed by KAT in partnership with the University of Plymouth, primarily as a novel “Topping” method for crude oil and condensate samples although it is also applicable to a number of other processes.

Compound specific (δ13C VPDB) isotope ratio (CSIR) measurement of individual n-alkanes from C27 - 33 is widely used for paleoclimate reconstruction throughout geological time. However, efficient isolation of n-alkanes from the total organic extract obtained from sediments can be difficult and time-consuming. Established techniques such as urea adduction do not always adequately remove co-eluting (by GC) branched hydrocarbons.

Isotope measurements of n-alkanes isolated in this manner may be influenced by the background mixture of branched hydrocarbons such that the δ13C value may not be truly representative of individual n-alkanes. T-SEP® can be used to readily separate n-alkanes from branched and polar compounds to allow more precise CSIR measurements. δ13C analysis of a mixture of nC27 - 33 before and after separation using T-SEP® demonstrated that Δ δ13C were within instrumental variability (< 0.5 ‰ VPDB).

Gas chromatograms of non-alkane (upper) and n-alkane (lower) fractions isolated using T-SEP® Enhanced Sample Preparation of sediment total organic extract

The total organic extract was recovered from Palaeocene-Eocene marine sediment (0.3 Wt% total organic carbon). The peaks that appear to co-elute in the non-alkane fraction are branched hydrocarbons as determined by mass spectrometry. Please note the low background of branched compounds in the n-alkane fraction. Figure courtesy of H. Manners

δ13C compound specific isotope ratio measurements for nC27 - 33 before and after T-SEP® Enhanced Sample Preparation

C# δ13C (‰ VPDB) Δ δ13C
Pre T-SEP® Post T-SEP®
27 -25.74 -25.27 0.47
27 -26.89 -26.41 0.48
29 -30.12 -29.86 0.26
30 -32.81 -32.31 0.49
31 -32.08 -31.73 0.36
32 -28.90 -28.41 0.49
33 -30.62 -30.48 0.14

Δ δ13C within instrumental variability < 0.5 ‰ VPDB