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United States Department of Agriculture

Agricultural Research Service

Research Project: Influence of Structure and Moisture on Cotton Fiber Properties

Location: Cotton Structure and Quality Research

Title: Reference test methods for total water in lint cotton by Karl Fischer Titration and low temperature distillation

Authors
item Montalvo, Joseph
item von Hoven, Terri
item Cheuk, Sherwin
item Byler, Richard

Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: February 8, 2011
Publication Date: March 22, 2011
Citation: Montalvo Jr, J.G., Von Hoven, T.M., Cheuk, S.Y., Byler, R.K. 2011. Reference test methods for total water in lint cotton by Karl Fischer Titration and low temperature distillation. National Cotton Council Beltwide Cotton Conference. p. 1319-1329.

Interpretive Summary: Two new reference methods for total water content in lint cotton have been developed by ARS scientists in New Orleans. The methods were dubbed Karl Fischer Titration (KFT) and Low Temperature Distillation (LTD). In both methods, water vapor is extracted from the fibers by heating in an oven and transporting the vapor out of the sample container by dry nitrogen gas. To measure water content by KFT, the water vapor is titrated with the chemical iodine. In LTD, the temperature of the oven is set below the boiling point of water, which slows down the distillation process and makes weight loss of the sample specific for water. The aim of the present study was to compare KFT and LTD results on conditioned cottons with a limited number of replications and delaying LTD runs two months after KFT analysis. The cottons had been grown in Stoneville, MS, in 2009, represented three cultivars, early and late defoliation, and high and low gin dryer heat. Average values by each method for the raw cottons were in agreement, about 7.6%, and confirms the accuracy of the new reference methods. Unexpectedly, the range of values by each method was only 0.2 %, compared to a larger range by standard oven drying. Also, variability in textile testing conditions in the conditioning room over a two week period produced changes in water content of a control cotton of the same order of magnitude as the differences between KFT and the delayed LTD results on the six cottons.

Technical Abstract: In a study of comparability of total water contents (%) of conditioned cottons by Karl Fischer Titration (KFT) and Low Temperature Distillation (LTD) reference methods, we demonstrated a match of averaged results based on a large number of replications and weighing the test specimens at the same time. For on-going studies and analysis of large sample sets, a more practical approach is to analyze fewer replicates weighed over extended time periods. The objective of the present study was to compare KFT and LTD results based on limiting the process of repeated determinations and delaying LTD runs two months after KFT analysis. Averaged values on six cottons were based on only three replicates and ranged from: raw fibers, KFT 7.45 % to 7.65 % and LTD 7.46 % to 7.67 %; cleaned fibers, KFT 7.37 % to 7.62 % and LTD 7.39 % to 7.60 %. Between KFT and LTD method differences within cottons ranged from: raw fibers, 0.04 % to 0.18 % and cleaned fibers, 0.02 % to 0.10 %. The cottons had been grown in Stoneville, MS, in 2009, represented three cultivars, early and late defoliation, and high and low gin dryer heat. Additionally, standard oven drying results based on five replicates and run concurrently with KFT determinations demonstrated both significant and minor differences in moisture contents compared to the total water contents by the other two methods. Variability in textile testing conditions in the conditioning room over a two week period produced changes in water content of a control cotton of the same order of magnitude as the differences between KFT and LTD results on the six cottons.

Last Modified: 10/24/2014
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