ARS | Publication request: Validation studies of Karl Fisher reference method for moisture in cotton

Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: February 8, 2010
Publication Date: April 28, 2010
Citation: Montalvo Jr, J.G., Von Hoven, T.M., North, T.F., Cheuk, S.Y. 2010. Validation studies of Karl Fisher reference method for moisture in cotton. Proceeding of the 2010 National Cotton Council Beltwide Cotton Conference, January 5-7, 2010, New Orleans, Louisiana. pp. 1378-1383. CDROM.

Interpretive Summary: Many different fields of research utilize the technology of volumetric Karl Fischer Titration (KFT) to measure moisture content. In fact, it is actively used in ASTM methods, NIST SRMs, and testing labs run constantly. The technique is lauded for its selectivity for water, easy sample preparation, small sample size, rapid measurement and of course, excellent accuracy and precision. Since moisture in cotton fibers is such an important parameter, the KFT method is desirable for the cotton industry. In this study, validation of the method’s ability to quantify the water in cotton fibers is explored and cotton is distilled to confirm the presence, if any, of non-aqueous volatiles that confound the standard oven drying results. Results demonstrate high selectivity by the KFT technique for measuring water over the interferences in cotton. Also, the release of non-aqueous volatiles in cotton was confirmed by distillation.

Technical Abstract: With current international standard oven drying (SOD) techniques lacking precision and accuracy statements, a new standard reference method is needed. Volumetric Karl Fischer Titration (KFT) is a widely used measure of moisture content. The method is used in many ASTM methods, 14 NIST SRMs, and testing labs that run 24 hours a day, seven days a week. In this study, validation of the method’s ability to quantify the water in cotton fibers is explored and cotton is distilled to confirm the presence, if any, of non-aqueous volatiles. Results on three cottons investigated demonstrate high selectivity by the KFT technique for measuring water over the interferences in cotton. Also, the release of non-aqueous volatiles in cotton by SOD was confirmed by distillation. This can explain most of the variance between standard oven drying and KFT results.