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Stable Isotope Geochemistry

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from ursa.cus.cam.ac.uk ([log in to unmask] [131.111.8.6]) by elk.uvm.edu (8.7.3/8.7.3) with SMTP id OAA16304 for <[log in to unmask]>; Mon, 6 May 1996 14:43:52 -0400 by ursa.cus.cam.ac.uk (Smail-3.1.29.0 #77) id m0uGVFy-000121C; Mon, 6 May 96 19:43 BST
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On Mon, 6 May 1996 [log in to unmask] wrote:

> 	Does anybody know something about a good way to homogenise either the 
> wood itself or the cellulose samples?

	We found that transfer losses were too high when small (less than
50 mg) wood samples were ground. Therefore, rather than grind small wood
samples, we remove shavings from cores or disks using a craft knife with
the help of a microscope. These samples are approximately 60 micrometers
thick and alpha-cellulose may be extracted by the standard techniques of
Green. The product should be placed in an ultra-sonic bath for ten minutes
during the treatment with sodium hydroxide to break down the fibrous
structure of the wood. 
	The resulting alpha-cellulose should be homogeneous as the results
for the repeat analysis of alpha-cellulose extracted from oak samples
demonstrate: 
	
Sample year  n   d13C     s.d.(n-1)

1920         4   -24.28   0.06
1921         4   -22.97   0.08
1922         4   -24.62   0.04
1923         4   -23.47   0.08
1924         4   -24.66   0.14
1925         4   -24.91   0.03

Therefore I would recommend that you avoid grinding small samples. Best 
wishes.

Iain


*************************************************************************
Iain Robertson                                + 
Godwin Institute for Quaternary Research,     +
University of Cambridge, Free School Lane,    + Tel. ++ 44 (0)1223 334881 
Cambridge, UNITED KINGDOM CB2 3RS             + Fax. ++ 44 (0)1223 334871 
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Godwin Institute homepage              http://www.esc.cam.ac.uk/GIQR.html
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