I want to analyze Whole Oil by GC for geochemical fingerprinting. Can anyone suggest me the best procedure for preparation of crude oil sample before injection?
I read in some references which suggest a dilution of crude oil by N-pentane or N-hexane. Whether these solvents are the best for Whole Oil GC or other procedures should I follow?
Hello, for analysis oils by GC you shuld receive fatty acids methyl esters for better analysis. Several methods are available for formation of fatty acids methyl esters.
If you have GC with FID detector and FAME column or equivalent go by steps below.
1.Take pure methanol 100ml add 4g of metallic Na by small parts to methanol to receive Na-methylate in methanol (Sol A).
2. Take 50ug of oil sample dilute in 500ul of N hexane and add 250ml of prepared solution A. Mix well.
3.use upper layer for direct injection to GC.
If interested in fatty acid composition you can use slpit 1:50 for better view of cromatogram.
Hope this info will help you.
Good luck!
Hi.
It depends on what you mean by "geochemical fingerprinting". Which group/family of compounds are you targeting and what information you want to extract from them.....
Generally speaking, the biggest issue is not dissolving the crude oil in heptane or hexane, or any other solvent. It is the chromatographic separation and compound identification. 2D chromatography and fraction cuts are often required depending on the purpose and target compounds. Read the following document, it is good for a start, to acquire insight. Then, I think you should start by defining the application more clearly and maybe ask from there.
https://gsm.org.my/products/702001-101393-PDF.pdf
Good luck
Hi Karen,
Morteza doesn't want to analyze vegetable oil but crude oil. I think there is a misunderstanding.
@Morteza: Maybe this will be helpful to you:
https://www.researchgate.net/post/Crude_Oil_Characterization
Regards
Markus
Morteza,
you can analyze the sample in the form of solution in CS2.
Such approach is used for simulated distillation (check my papers).
Same solution you can use for GCxGC to get a great fingerprint type chromatogram.
best regards,
GB
First off, I would never consider using GC-FID for fingerprinting. This to me requires a mass spectrometer, so that you can pull out and take advantage of spectral information (such as sulfur-containing compounds, aromatic/aliphatic ratios, etc). Mass spec changes your solvent selection, so you need to determine if you are using GC-FID or GC-MS. If you only have GC then Gregorz's approach is the best since CS2 is essentially invisible to your detector. If you are using MS then I would stay away from CS2, in which case your best bet is pentane or hexane or even dichloromethane.
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