Comparison of free fatty acid values with individually determined organic and inorganic acid concentrations in the extracts of Malaysian natural rubber
1990
Crafts, R.C. | Davey, J.E. | McSweeney, G.P. | Stephens, I.S. (Malaysian Rubber Producer's Research Association, Brickendonbury, Hertford (UK))
Free fatty acid (FFA) values are frequently taken to be a measure of the long-chain fatty acid content of rubber samples. However, from an analytical view-point, it is apparent that the acidity measured during this test could not be due, entirely, to acids containing more than ten carbon atoms. Ion chromatography and gas chromatography have been used to identify and quantify the acidic components of the acetone extract of natural rubber. The combined acid concentrations measured by these techniques account for more than 85 percent of the FFA value and, of this figure, low molecular weight organic and inorganic acids account for up to one half. It may be concluded that expressing the result of an FFA titration as 'stearic acid' can seriously over-estimate the quantity of long-chain fatty acids present in natural rubber and may mask important differences in the composition of both these and the low molecular weight materials.
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