I've done analyses of that by solid-state 13C NMR combining both SP-MAS for quantitation and CP-MAS for more rapid qualitative analysis. The cellulose itself yields rather narrow peaks while the hemicellulose is at similar shifts but yields broader resonances with slight offsets. A lot of work has been done with lineshape analysis - see this thesis and a number of papers that are referenced within it. www.diva-portal.org/smash/get/diva2:565072/FULLTEXT01.pdf
You can play around with variable contact time arrays and find that the cellulose and the hemicelulose behave differently. On top of that you will see aliphatic, aromatic and methoxy carbons that are from the complex lignin chemistry.
It is possible with various extractions to separate the various components and do NMR on them that can later be used to fit the 13C spectra obtained on the whole.
I would perform the lineshape deconvolution in order to obtain a way of quantifying the relative areas from the three components and then use that to allow sample to sample variation do be determined and then correlate that variability to whatever processing differences you might see between various samples.
Thanks for your kind attention and answer Mr. John, i have estimated holocellulose *(cellulose + hemicellulose) and lignin with +- 5% accuracy in physical blends but in presence of hemicellulose results are not so good. Already i have played with variable contact time arrays in High resolution NMR. We have developed a method by NIR for their quantification, i will appriciate if you guide me for same work on time domain NMR, which you are a expert. thanks for your reply
I'm not sure you can do much with TD-NMR. My main exposure to these types of sample are through solid-state 13C NMR. I haven't thought to look at these thinks purely through relaxometry. There may be a difference in T1/T2 and some of the T1/T2 multidimensional Laplace calculations might show the three components but how quantitative that would be is difficult to say - my experience of the 2D Laplace inversions is that they are very unstable and difficult to perform and difficult to interpret, especially in materials that are solid in the first place. Not having looked at how these materials would behave in the TD-NMR experiments I'm not sure I can add anything to the conversation. If you swell the cellulose with a controlled amount of moisture does that offer a way of differentiating between hemicellulose and cellulose ? There are a number of things to think about in the thought process of some pre-treatment of the samples that might increase a property that allows you to properly quantify.
Thanks for nice reply, we are trying to solid state NMR spectra ASCII files for NIR PLS software for developing a model for cellulose, hemicellulose and lignin quantification just like based model. In NIR spectrum there is not clear diffrences in these three components but in NMR spectra may be more accurate than NIR.
Hi,
maybe of interest. I read somewhere that it is possible to dissolve lignaceous material in some ionic liquids. If so then this would make them addessable by NMR but such solutions may be like syrup and need heating to get the liquidity high enough to get decent proton signals. There seems to be some literature details in the internet on ionic liquids dissolving lignin. Not sure yet whether it has been used for NMR studies or what other limitations there might be in the methodology. Could be of help to you. Best regards, Michael
http://www.academia.edu/3504083/Ionic_Liquids_for_Lignin_Processing_Dissolution_Isolation_and_Conversion
I always worry in the situation where you are observing a polymeric material such as cellulose and hemicellulose and even lignin that are not happy in the same solvent system as to what you are not seeing when you look at it in the liquid-state. We've done a lot of alginate and chitosan analysis and unless you reduce the degree of polymerization you run into issues of not observing the high Mw material and skewing your results. If you can look at in the solid-state you can be confident you are seeing the whole thing. I wish more people would look at polymeric polysaccharides with solid-state nMR because the sample preparation for liquid-state NMR can be a bit of a long-winded nightmare.
@Ravindra - how do the samples look to an FTIR-ATR - they may be more uniquely observable.
Thaks for your nice answers. i am agree with Mr John, solid state NMR or NIR is more suiatbale rather than liquid state NMR for lignocellulosic materials.
Dear R Kumar,
Are you applying PLS regression to establish a NIR-based model for estimating lignin and/or holocellulose content? The major challenge can be the determination of the lignin, cellulose and hemicellulose content by wet chemistry. It's hard to degrade only lignin, without attacking the holocellulose. I'm curious about your findings with RMN. Good luck!
Dear Kumar,
see this paper
http://www.sciencedirect.com/science/article/pii/S0066410308600149
I am using the traditional techniques to determine these fraction of wood. If you find such a method then please share that with me. thanks
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