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ARS Home » Southeast Area » New Orleans, Louisiana » Southern Regional Research Center » Cotton Structure and Quality Research » Research » Publications at this Location » Publication #299148
Title: Probing bias reduction to improve comparability of lint cotton water and moisture contents at moisture equilibrium

Author
item Montalvo Jr, Joseph
item von Hoven, Terri
item Byler, Richard
item Boykin, Deborah

Submitted to: Journal of Cotton Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/23/2014
Publication Date: 4/15/2015
Citation: Montalvo Jr, J.G., Von Hoven, T.M., Byler, R.K., Boykin, D.L. 2015. Probing bias reduction to improve comparability of lint cotton water and moisture contents at moisture equilibrium. Journal of Cotton Science. pp 194-211.

Interpretive Summary: Water content of cotton fibers, as determined by Karl Fischer Titration (KFT), produces different results than moisture content by oven drying (OD) measurements. Because KFT specifically measures water in lint cotton (ASTM D 7785) biases are limited. In OD (ASTM 2495), the water content is calculated by the weight loss and all weight loss is attributed to water. At moisture equilibrium, these two methods produce different results. To study these differences, different OD procedures, with dissimilar sample conditioning systems, drying ovens, size and number of weighing bottles in the oven, are being used to make measurements. This research evaluates the influence of cultivar, defoliation time and gin-drying temperature on equilibrium water and moisture content of raw cottons. To explain some of the observed difference in water and moisture values, a list of six potential OD biases was developed. The bias values were applied to the moisture content data from four different OD methods. Method grand mean results were 7.73% water compared to moisture contents before and after bias correction, respectively: OD1, 7.19 and 7.80; OD2, 7.50 and 7.80; OD3, 7.42 and 7.69; and OD4, 7.79 and 7.92. By changing OD features it was possible to suppress one bias over the other and to get OD and KFT values to more closely agree. When dealing with a small range of equilibrium data, more stringent conditioning specifications can be used to produce the most precise data.

Technical Abstract: The Karl Fischer Titration (KFT) reference method is specific for water in lint cotton and was designed for samples conditioned to moisture equilibrium, thus limiting its biases. There is a standard method for moisture content – weight loss – by oven drying (OD), just not for equilibrium moisture content. The results from OD we call ‘moisture content” and from KFT we have termed “water content”. Different OD procedures, with dissimilar sample conditioning systems, drying ovens, size and number of weighing bottles in the oven, are being used to make measurements. Yet, no comprehensive study of the multiple causes of the difference between equilibrium water and moisture content has been reported. The present effort evaluates the influence of cultivar, defoliation time and gin-drying temperature on equilibrium water and moisture content of raw cottons. To assist with explaining the observed difference in water and moisture values, a list of six potential OD biases was developed. The bias values were applied to the moisture content data from four different OD methods dubbed OD1 to OD4. Method grand mean results were 7.73% water compared to moisture contents before and after bias correction, respectively: OD1, 7.19 and 7.80; OD2, 7.50 and 7.80; OD3, 7.42 and 7.69; and OD4, 7.79 and 7.92. By changing OD features it was possible to suppress one bias over the other; details are in the paper. Given the small range of equilibrium data, more stringent conditioning specifications produced the most precise data.