A Novel Modification of Klason Lignin Quantitaitve Method

In this paper, a convenient method has been reformed which enables a quick, lightly labored and accurate analysis of acid-insoluble lignin (or Klason lignin ; abreviated to KL) in both woods and non-wood. The method in essentially based on the conventional standard quantitative determination of lignin (JIS (Japanese Industrial Standards) P8008-1976 and TAPPI standards T 222 os-74). The latters (JIS and TAPPI method) are now current ; however, is time consuming, and analytical procedures are comparatively cumbersome, and needs a lot of labor for the secondary hydrolysis step to apply especially when many samples must be analyzed. This paper deals with some analytical conditions (involving the primary and secondary hydrolysis conditions) with special reference to a poplar (Poplus Sieboldii Miq.) to establish the modification method.The novel modification is suggested as follows : For the primary hydrolysis, about one gram of 4260 mesh wood or non-wood meal is admitted into a 18 × 105 mm test tube or a 50 to 100 ml beaker, and 10 ml of 72% sulfuric acid is pipetted followed by standing for 2 to 24 hr at 10 to 25°C with occasional stirring with a glass rod. For the secondary hydrolysis, the content is washed with 375 ml of distilled water into a 500 ml Erlenmeyer flask to make a final concentration of sulfuric acid of 3%. The flask is autoclaved for 30 min at 121°C (103 kPa) in a autoclave (sterilizer). Preheating of the autoclave is not necessary. Each flask is capped with alminum foil or alminum cap. The total (primary and secondary) hydrolysis can be completed within at least 4 hr, but the requisite hydrolysis time depends on the number of flasks. The procedures after the secondary hydrolysis are the same as the standard method prescribed JIS or TAPPI.With a capacity volume of a 45l (300 mm in inner diameter and 630 mm in height) laboratory scale autoclave used in this experiment, about 15 flasks are able to be treated at once for about 1 hr, so that the modification is so adoptable especially when many samples need to be analyzed, swiftly, easily, and acculately. The analyses by the modification method of lignins from four wood species and one non-wood species involving three hard woods (poplar, Poplus sieboldii Miq. ; beech, Fagur crenata Blume ; and white birch, Betula platyphylla Sukachev), a soft wood (japanese red pine, Pinus densiflora Sieb. et Zucc.), and a bamboo (Phyllostachys pubescens Mazel) are presented comparing with those by the standard method (JIS). For all tested samples, the values obtained by the modification are in full accord with those by the standard method. The measurement also seems to exhibit a good repeatability, though a few replicate values were obtained for each sample (Table 2 and Table 3).But for the filtrates after secondary hydrolysis of some samples, the shapes of absorption curves in the ultraviolet region (190 to 300 nm) and acid-soluble lignin values are found to be more or less different between the modification method and JIS method. Furthermore, for the hydrolysis percents (ratios of monosaccharides winch have reducing power to polysaccharides in the samples), it is found that they are lower by both methods (JIS method, 74%; the modification method, 86%) in comparison with those by TAPPI method using GLC analysis.