Location: Cotton Structure and Quality Research
Title: Moisture in Cotton by the Karl Fischer Titration Reference Method Authors
Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: January 15, 2009
Publication Date: May 15, 2009
Citation: Montalvo Jr, J.G., Von Hoven, T.M., North, T.F. 2009. MOISTURE IN COTTON BY THE KARL FISCHER TITRATION REFERENCE METHOD. National Cotton Council Beltwide Cotton Conference. p. 1163-1168. Interpretive Summary: Moisture in cotton is important because the fiber properties (mechanical, dimensional and electrical) are dependent on the moisture content. The standard test methods for moisture in lint cotton are based on oven drying; all of the loss in weight is attributable to moisture. The U.S. cotton industry questions the reliability of the oven-drying test and has requested that this laboratory develop improved standard test methods. One of the methods under development is the Karl Fischer Titration technique, which is based on the chemical reaction between water and iodine. The amount of moisture in a sample is titrated with a mechanical burette containing the iodine. Moisture is isolated from the cotton matrix by heating; an inert gas carries the released moisture to the titration cell, and the moisture is detected and measured. Analysis time is only a few minutes per specimen compared to several hours for the standard oven-drying test. The mean measured moisture levels in over a dozen cottons, compared to two traditional oven-drying methods, were about 0.5 % lower with a standard deviation about half that of the oven procedures. This work confirms the need by the industry for improved standard test methods for moisture in cotton.
Technical Abstract: Moisture is a critical parameter that influences many aspects of cotton fiber from harvesting and ginning to various fiber properties. Because of their importance, reference moisture methods that are more accurate than the existing oven-drying techniques and relatively easy to generate results are necessary. One such method is the Karl Fischer Titration technique, which is based on the chemical reaction between water, iodine and sulfur dioxide in a non-aqueous medium. The moisture in a sample is titrated with iodine. Used in 126 ASTM reference methods, the Karl Fischer approach is popular because of its precision, its small sample size and simple sample preparation, as well as its ability to measure water with a high degree of specificity. In this paper, cotton fiber moisture is measured in 13 cottons by fully automated KFT instrumentation that uses a novel oven design to extract moisture in solid samples, a dry sweep gas to transport the released moisture to the titration cell, and software to detect the end point. Analysis time is about 5 min per specimen. The mean measured moisture levels, compared to two traditional oven-drying methods, were 0.43 % lower with a standard deviation about half that of the oven procedures.