I tried hexane, but most of VFAs were not detected. The used column is: [Stabilwax-DA Columns (fused silica) polar phase; Crossbond acid-deactivated Carbowax polyethylene glycol]; 30m, 0.25mm ID, 0.25µm
The determination of short-and long-chain free fatty acids in milk
AMA Salih, M Anderson, B Tuckley
Journal of Dairy Research 44 (3), 601-605, 1977
Generally try with DCM. But maybe, Think about proper sample preparation - SPME or DLLME.
What is your pH during extraction?
Regards
GB
Generally, VFAs are small molecules like Acetic, Proprionic, or Butyric Acids (commonly found in cheese) and will evaporate because they are volatile. pH is a BIG factor, since acids are more likely to be volatile when compared to esters. Thus, many GC techniques derivatize the sample before (like using Hydrazine or DNPH) GC analysis.
As an alternative to GC you can use also ion exclusion chromatography.
Regards
GB
Samples have been acidified using H2SO4, just after sampling. Do you think extraction via DCM will be more suitable than hexane? Thank you very much! Grzegorz Boczkaj
Thanks a lot. Yes, I want to measure such acids. Samples have been acidified before extraction. Do you think that using Hydrazine or DNPH will be more suitable that hexane, considering the type of used column (mentioned above)? Bruce Neagle
Ahmed,
The answer depends on your expected concentration and/or sample matrix. I like HPLC, however VOAs will evaporate no matter what technique (GC or HPLC) is used. Thus, I have used a cold water bath to store the extracted sample. Timing of the injection is key!
Derivatization agents can be consumed by other components or excipients (so I don't like derivatization). This may mean you have to use an exotic detector like an ELSD or CAD.
Hi Ahmed. Check out my paper on granulation at high salinity. We also measured with GC FID at salinity as high as 50 g NaCl/L
This is the one: Article Fast anaerobic sludge granulation at elevated salinity
Under analytical methods.
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