Determination of Trace Water in Gas Samples by an Improved Karl Fischer Coulometer

Abstract

The determination of trace water in gas samples, such as isobutene, chloromethane (polymeric staple gases) and SF6 by a conventional Karl Fischer coulometer is very difficult, because of the adsorption of trace water on the surface of sample pipe, the gasification of the liquefied samples, and the migration of moisture into the measuring cell from the surroundings. To solve these problems, we improved a device for coulometric determination of water by Karl Fischer method. The improved coulometer was used to determine the trace water in isobutene, chloromethane and SF6; RSD was less than 5%, and recoveries ranged from 94.1 to 109.1%, which is adequate for the analysis of industry.

Measurements of Hydrate Dissociation Temperature of Methane, Ethane, and CO2 in the Absence of Any Aqueous Phase and Prediction with the Cubic Plus Association Equation of State

“…The Karl Fischer method is mostly used to measure the water content in the liquid phase. Only a few works report the measurement of water content in a gas: Muroi and Ono measured the moisture in hydrogen chloride gas and Dong et al determined the water trace in gas samples (isobutene, chloromethane, and SF 6 ).…”

Determination of Water Content of Nitrogen Containing Hydrogen Sulfide by Karl Fischer Coulometric Titration

“…16 The application of KFCT was partly restricted by an inaccurate determination of the gas volume and a rather high drift before titration. 17 A measurement using the commercial Karl Fischer coulometric titrator (875, Metrohm) equipped with a mass flowmeter employed a procedure that involved two rounds of purging with dried nitrogen, one before and one after titration, to drive off the residual moisture in the pipeline. Therefore, repeatable results can be acquired conveniently.…”

“…8 KFT methods, including coulometry and volumetry, are widely used for determining the water content of liquid and solid samples, as well as gas samples. 4,5,[12][13][14][15][16][17] In the Karl Fischer reaction, water reacts with iodine (I2) according to the stoichiometry of 1:1, and thus the amount of water in the analyte is equal to that of I2, which is calculated through the electric quantity according to Faraday's law. 13 Because the Karl Fischer coulometric titration (KFCT) is a direct method, it is regarded as not only the reference method, 11 but also an internationalstandard method (ISO 10101) for the determination of water content in natural gas.…”

Water vapour monitoring in natural gas in the presence of methanol

“…Correct subtraction of response from background moisture, diffusing into the titration cell through various connections, is one of the major challenges when using Karl Fischer for determination of trace amounts of moisture in gas (Dong et al, 2005). Accurate measurement of the titrated gas volume is another challenge.…”