NEW AND IMPROVED ASSESSMENTS OF COTTON QUALITY
Location: Cotton Structure and Quality Research
Title: Simple X-ray diffraction algorithm for direct determination of cotton crystallinity
Submitted to: Proceedings of SPIE
Publication Type: Proceedings
Publication Acceptance Date: April 10, 2012
Publication Date: July 9, 2012
Citation: Liu, Y., Thibodeaux, D.P., Gamble, G.R., Bauer, P.J., Vanderveer, D. 2012. Simple X-ray diffraction algorithm for direct determination of cotton crystallinity. Proceedings of SPIE. 8374: 87370A-1 - 83740A-7.
Interpretive Summary: Crystallinity index (CI) of cotton fibers has been assessed predominantly by X-ray diffraction (XRD) spectroscopy. It requires computing software to separate amorphous and crystalline contributions through a time-consuming and subjective curve-fitting process. In general, XRD provides a qualitative or semi-quantitative evaluation of CI. To generate a reliable quantitative cellulose CI, it should have appropriate cellulose standards to calibrate or validate the XRD measurement. Apparently, these absolute standards are not easy to be prepared or determined. In the latest Fourier transform infrared (FT-IR) investigation on immature and mature cotton fibers, we proposed a ratio algorithm R2 by linking it with the relative amount of Iß to Ia crystal forms, which yielded an overall 96% of correct classification accuracy. This study first developed the simple algorithms from XRD spectra, and then demonstrated the effectiveness of both FT-IR and XRD techniques in describing the structural changes of developing cottons at single boll level. In addition, it reported the strategy of applying easy- and fast- determinable CI from FT-IR acquisition to calibrate the XRD measurement for cellulose CI. This proposal provides agricultural engineers, cotton fiber and cellulose researchers a new sight in applying FT-IR spectroscopy for rapid, routine, and direct measurement of cotton fiber crystallinity.
Traditionally, XRD had been used to study the crystalline structure of cotton celluloses. Despite considerable efforts in developing the curve-fitting protocol to evaluate the crystallinity index (CI), in its present state, XRD measurement can only provide a qualitative or semi-quantitative assessment of the amounts of crystalline and amorphous cellulosic components in a sample. The greatest barrier to establish quantitative XRD is the lack of appropriate cellulose standards needed to calibrate the measurements. In practical, samples with known CIs are very difficult to be prepared or determined. As an approach, we might assign the samples with reported CIs from FT-IR procedure, in which the three-band ratios were first calculated and then were converted into CIs within a large and diversified pool of cotton fibers. This study reports the development of simple XRD algorithm, over time-consuming and subjective curve-fitting process, for direct determination of cotton cellulose CI by correlating XRD with the FT-IR CI references.