DETERMINATION OF DEGREE OF SUBSTITUTION OF CARBOXYTHEYL CELLULOSE BY FTIR EXTERNAL REFERENCE METHOD

摘要

In the present determination of its degree of substitution (DS), carboxymethyl cellulose (CMC) suffers from many disadvantages as it is used as a fast detection method in industry, such as complex operation, long-time consumption, and DS range limit. A method to determine the DS of CMC by the FTIR spectra of CMC and CMC-H, was proposed, which is low-cost, fast and easy to carry out. Firstly, some effects on absorbance change of the 1735cm-1 band, which is attributed to the stretching of vibration absorption caused by carbonyl group (-C=O) of CMC-H were discussed, and then 1735cm-1 was chosen as the marker band. Secondly, by using the absorption at 2060cm-1 absorption of KSCN as the basic peak, a curve of A1735/A2060 and DS/C(KSCN) was obtained. Finally, according to Lambert-Beer law, we drew linear regression, y=0.362+0.396x (y: A1735/A2060, x: DS/C(KSCN) ) to the curves, which concluded the DS of CMC . Furthermore, we applied the method to determine the DS of CMC samples. Compared with that from GB method, the result showed that when the DS ranges from 0.76 to 1.32, the relative deviations of the results are below 8.0%. So the method has high accuracy in the determination of the DS of industrial CMC(DS= 0.70~1.20).