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A new method has been developed for the determination of chemical oxygen demand (COD) in pulping effluent using chemometrics-assisted spectrophotometry. Two calibration models were established by inducing UV-visible spectroscopy (model 1) and derivative spectroscopy (model 2), combined with the chemometrics software Smica-P. Correlation coefficients of the two models are 0.9954 (model 1) and 0.9963 (model 2) when COD of samples is in the range of 0 to 405 mg/L. Sensitivities of the two models are 0.0061 (model 1) and 0.0056 (model 2) and method detection limits are 2.02-2.45 mg/L (model 1) and 2.13-2.51 mg/L (model 2). Validation experiment showed that the average standard deviation of model 2 was 1.11 and that of model 1 was 1.54. Similarly, average relative error of model 2 (4.25%) was lower than model 1 (5.00%), which indicated that the predictability of model 2 was better than that of model 1. Chemometrics-assisted spectrophotometry method did not need chemical reagents and digestion which were required in the conventional methods, and the testing time of the new method was significantly shorter than the conventional ones. The proposed method can be used to measure COD in pulping effluent as an environmentally friendly approach with satisfactory results.

The traditional Douglas colorimetric method (phloroglucinol - glacial acetic acid colorimetry) could only be used to measure all forms of five-carbon sugars, including mono-, oligo- and poly- saccharides. Relative improvement is done on this method to achieve simultaneous determination of pentosan, hexosan and their monosaccharides, by the dual-wavelength method. Results indicate that 425 nm is the equal molar absorption wavelength of pentose and hexose, while 553 nm is the maximum absorption wavelength of pentoses. So the calculating formula has been greatly simplified based on the absorbance at 425 and 553 nm. The research results of interfering substances in the extraction liquor show that the lignin and glucuronic acid has no significant influence on the determination of pentoses or hexoses. It is concluded that this improved method has high precision and accuracy, and its recovery range is from 97.4% to 101.9%. Therefore, as a simple and rapid method, it is quite appropriate for measuring mixed sugars of pentoses and hexoses in the extraction liquor from hardwood or gra minaceous plant.

This is a new technique to assay virtually any endoglycanase activity where enough polysaccharide material is available to allow for production of the amorphous, dyed beads used as substrates. It allows for a direct comparison of endoglycanase activities between laboratories since dyed beads from at least the most common polysaccharides such as cellulose, xylan, mannan, and chitin are now under development and will soon be commercially available; cellulose beads already are. It is a very sensitive technique and enzyme activities can be measured using a nonsophisticated spectrophotometer., (Copyright 2000 Academic Press.)