STUDIES ON THE DETERMINATION OF PENTOSANS BY ULTRA-VIOLET ABSORPTION SPECTRUM

Abstract

A new method for determination of pentosans in pulps by means of UV Absorption spectrum is described.This method is based on the experimental results, that UV Absorption spectrum of the distillate of pulp with 12% HCl is an additive of two spectra. One is the spectrum of furfural converted from pentosans and the other the products from glucose by the 12% HCl distillation (this is refered to as glucose component).Furfural and glucose components from pulp can be determined quantitively by analysing algerbraically the absorption of spectrum the distillates of pulp, using the UV absorption spectra of fulfural and glucose components which are obtained preliminary. Here absorptions are measured at two or more wave lengths, which may be called a “multi-points” method.The ratio of glucose component of the pulp determined by this method to that of pure glucose is called as “glucose number”.The glucose number is a value of the parts, reacted as glucose of pulp during 12% HCl distillation and also shows the accessibility of pulp.The spectroscopic method suggested by Smith and Rogers is based on the colorimetric method using aniline acetate, which is specific for furfural only, and is generally considered suitable for the determination of pentosan in highly purified pulp. The new method is based on the results of the absorption spectrum only.The glucose component contains, besides 5-hydroxy methyl-furfural (HMF), some amount of furfural converted from glucose. Therefore the values obtained by colorimetric method shows the total of furfural from pentosan and glucose (cellulose). On the other hand this method gives the value of furfural from pentosan only, regardless of the accessibility of pulp according to the above principles.Applying these methods for many kinds of pulps, the results obtained are as follows:1. Pentosan values obtained by this new method agrees not only with those obtained by colorimetric method but also, with those of Smith-Rogers.2. The glucose number has almost the same value in case of pulps only, and also agrees with the experimental results of Smith's, who described that the amount of 5-hydroxy-methyl furfural from pulps is almost constant.3. Since the glucose number of pulp is as small as 0.3 furfural converted from cellulose (in pulp) can be practically neglected.Therefore it is found that the colorimetric method even though it is disadvantageous as shown above, can give satisfactory results for pentosan content in pulp.