Testing for cannabinoids in MCT/Olive oils has been difficult because the oils elute later than the cannas and in the case of Olive oil, much later. To address this problem, SRI has released a modification of the 310MM GC which includes a short 5 meter pre-column and a way of stopping the flow though the pre-column and then backflushing the high boiling oils out through a carbon trap. The benefit is that no extra sample prep ( to get rid of the oils ) is required.
Because the pre-column is just a short 5 meter length, its cheap to replace if it does get contaminated with sugars etc.
There is also a benefit from something called " the focussing effect". When you have two columns in series and the first column is a thinner film than the main column the peaks travel faster through the thinner film than through the main column. When the peaks arrive at the main column the molecules bunch up, noticeably sharpening the peaks.
See this doc for a fuller explanation.
http://www.srigc.com/cn/downloads/428/EdiblesGCSept2021.pdf
Hugh
SRI