What is the most appropriate technique to find out what chemical components are present in wood extractives from native species in Brazil? And what is the best technique to quantify each type of extractive?
Dear Paulo,
It depends of your goal.
The first thing you need to do is the separation of lipophilic and hydrophilic extractives. This separation will make easy the identification and the analysis by different techniques. Ethanol (high purity) and chloroform are good solvents to extract hydrophilic and lipophilic extractives, respectively.
The most common technique is GC-MS. It's a good alternative to identify/quantify the compounds.
Confocal Raman spectroscopy can be useful to show important chemical characteristics of the extractives. If you are interested in the carbohydrates presented in the extractives, you can use the HPLC.
Best wishes,
Pedro
Hello Paulo,
To get maximum extractives Ethanol/Toluene mix is the best solvent. Also Asetone/H2O can be used. GC-FID (long and short column) and GC-MS are the best for complete characterization of extractives. Internal standards to be used for quantitation are as: sorbitol (for carbohydrates: mono-, di- and possibly tetrasaccharides or glycosides), heneicosanoic acid (for fatty acids), cholesterol (for sterols), cholesteryl heptadecanate (for steryl esters/pentasacharides/glycosides), and 1,3-dipalmitoyl-2-oleyl-glycerol (for triglycerides/ pentasaccharides/glycosides).
Hope it helps.
BR
Saleem
Dear Paulo,
Yo can find the Laboratory Analytical Procedure (LAP) for Determination of Extractives in Biomass in the link:
http://www.nrel.gov/docs/gen/fy08/42619.pdf
Best regards.
Dear Paulo,
In my area you can find an article with a complete description of how to determine extractives by GC-MS "Extractive composition and summative chemical analysis
of thermally treated eucalypt wood". If you need more help just contact me.
Dear Paulo,
I'd recommend extracting the wood (Wiley milled, 40 mesh) using solvents of decreasing polarity. For example, if you use a Soxhlet method, I'd start with water, then methanol, then acetone, and finally chloroform. In this way, you end with a fairly dry extractive-free material. The collected extractives can then be analyzed separately by polarity and this narrows down the types of chemical structures present in each isolated extractive group. To analyze the quality and quantity, a robust approach is to use two-dimensional (2D) 1H-13C correlation NMR experiments, such as HSQC and HMBC. One-dimensional NMR would give too many overlapping peaks. These 2D NMR experiments would allow you to see the exact types of structures present and allow for semi-quantitative analysis. I'd be happy to answer any questions to assist you on this.
Cheers,
Daniel
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