Sample preparation using trichloroacetic acid

Chromatography Forum: GC Archives: Sample preparation using trichloroacetic acid
Top of pagePrevious messageNext messageBottom of pageLink to this message  By Uberto on Sunday, July 28, 2002 - 08:49 pm:

Dear all,

I am sorry of cross-posting such queries, as I think chromatographers do lots of chromatographic analysis after a series of sample preparation and they should have lots of experience in this area. I am wondering if anyone has the experience working on tissue extraction by aqueous medium in the presence of trichloroacetic acid. I understand that TCA is used for deproteination but I don't know how it works c.f. other inorganic acids such as metaphosphoric acid or hydrochloric acid. Does TCA have certain pros c.f. others? What conc. should TCA be normally used to achieve a complete deproteination?
Thanks in advance.


Top of pagePrevious messageNext messageBottom of pageLink to this message  By H W Mueller on Sunday, July 28, 2002 - 11:51 pm:

Be shure to check recovery if you use TCA to extract substances with low solubility in water! They have a strong tendency to precipitate with the proteins. Itīs better to use MeOH, MeCN, etc., with such compounds as they help keeping these solvated, see for instance J Chrom B, 678, 137 (1996) on the low extraction of cortisol with TCA. If you have limited access to the lit I can take the time to dig out some numbers for you, the internet should have lots of material on this as well.


Top of pagePrevious messageNext messageBottom of pageLink to this message  By Uberto on Monday, July 29, 2002 - 12:13 am:

Mueller:
Thanks for your prompt reply. Meanwhile I have been dealing with the extraction of antibiotics in tissue samples. The antibiotics are all water soluble to a great extent. I have read thru quite a lot of the literature in extracting antibiotics in tissues. Some uses acetonitrile, others use aqueous medium with acids such as metaphosphoric acid, TCA, TFA, HCl etc. Co-precipitation of the analyte with protein may be a problem of low recovery. Does TCA have the ability of lowering the co-precipitation problem due to some kind of ion-pairing ?? Do you know the mechanism of deproteination using TCA?


Top of pagePrevious messageNext messageBottom of pageLink to this message  By H W Mueller on Monday, July 29, 2002 - 11:35 pm:

Sorry, I donīt know the exact mechanism of TCA protein interaction, who does? One can imagine that analytes which can ionize to anions might be displaced by TCA. Usually, highly water soluble materials can be separated from proteins very nicely via ultrafiltration/dialysis. Remember that most substances interact reversibly (if they interact at all) with proteins, so if you keep adding liquids that do not denature, you can usually separate your analyte through the filter.
Modern ultrafilters remove more proteins than any precipitation methods.
I think itīs good advise to say: Stay away from TCA if you can (to a lesser extend this holds for other acids,ACN, MeOH . . .).


Top of pagePrevious messageNext messageBottom of pageLink to this message  By Anonymous on Tuesday, August 13, 2002 - 08:11 am:

Depending on what compound you are extracting, you could use a variety of organic solvents, polar or non polar. TCA is quite a strong "solvent" and its primary use is for deproteinizing.


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