in the extraction process of some secondary metabolites from bacteria, we are sometimes using an organic solvent such as, ethyl acetate or resins such as XAD. why?
Your question is not clear. Ethyl acetate is organic solvent (liquid) to extract organic compound from the sample. XAD is solid polymer (not liquid), so you are comparing two different things. Need to see the detail of protocol before I can answer this question. Since it is your protocol (in your lab), you should ask the author of that protocol.
Dear Sir. Concerning your issue about the extraction process of some secondary metabolites from bacteria.The extraction is done by ethyl acetate and then the crude extract was run in the column chromatography. For more detail, I think the following below links may help you in your analysis:
http://www.bashanfoundation.org/reddy/reddymetabolites.pdf
http://jjbs.hu.edu.jo/files/v8n2/Paper%20Number%208m.pdf
Thanks
I may did so let me explain it for you in different way:
What is the mechanism by which XAD is working in the extraction process?
And what is the mechanism by which Ethel acetate is working in the same process?
(In this particular case,It does not matter liquid or solid because both of them are using in this type of
Extraction process).
if you focus on the Xad only (mechanism),I will appreciate that
Thanks
Amberlite XAD-4, a nonpolar adsorbent which can be employed in reversed-phase chromatography, was evaluated as the stationary phase for preparative liquid chromatography. The column parameters studied include XAD-4 particle size, packing of particles, column diameter, flow rate, mass and volume overload, and eluting conditions. Columns that were 8.0 mm i.d. (3/8 in. o.d.) × 25 cm packed with 37-44 μm XAD-4 particles provided efficiencies of 500-1500 plates/m. Similar efficiencies were also obtained on a 20.5 mm i.d. (1 in. o.d.) × 32 cm column packed with 75-105 μm XAD-4 particles. Flow rates over the range studied did not have a significant effect on capacity factor or efficiency for the two columns. For a capacity factor of about 2 the mass overload limit, defined as a 10% decrease in efficiency, was about 0.23% wt/wt load on the 8 mm i.d. column and 0.25% wt/wt load on the 20.5 mm i.d. column. Mass overloading is possible, and for k' less than 10 for the sample, the two columns can handle quantities of a few hundred milligrams and several grams, respectively. In general, these trends are similar to those observed for silica and alkyl-modified silica stationary phases. Eluting conditions studied include pH control under conditions in which silica type columns cannot be used and/or in the presence of mixed solvents. Mixtures of benzene-sulfonic acids, chlorophenoxyacetic acids, phenols, amino acids, and dipeptides were separated.
The article above explains the mechanism of XAD as a reversed-phase column. Please Google it yourself. You will load the extract in water and elute the analyte with organic solvent. It is similar to liquid-liquid extraction between aqueous phase and ethyl acetate shake. XAD is liquid-solid extraction, while ethyl acetate is liquid-liquid extraction process.
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