A determination method of pentosan content in pulps using UV absorption spectrum was reported by E. D. Smith and L. N. Rogers in 1953. This method is a simple one and depends upon the experimental results that furfural and hydroxymethyl furfural (HMF) have the same UV absorption spectrum, the colorimetric method using anilin acetate gives the correct furfural content and by using the constant distillation conditions the yield of HMF is constant and not affected by the type of pulps.
Further to make sure of the validity and practicality of this new method, we have compared its results with those obtained by the usual colorimetric method (modified O'Brien and Davis method).
From these studies it is shown that (1) the UV method is very much rapider and simpler to use than the colorimetric method and has the same precision, (2) the distillation rate and distillate volume should be 2ml/min., and 200ml., respectively, therefore in these conditions we can obtain the comparable data with those obtained from the usual method (e. g. TAPPI distillation conditions 3ml/min, 300ml.), (3) the amount of the sample has little effect on the results and 0.5g. of dry pulp seems to be of advantage, (4) this method is more affected by distillation condition than colorimetric method, therefore the distillation condition should be kept strickly constant.