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A Capacitance Sensor for Water: Trace Moisture Measurement in Gases and Organic Solvents

The determination of water in various matrices is one of the most important analytical measurements. We report on a high-resolution capacitance-based moisture sensor utilizing a thin film of a perfluorosulfonate ionomer (PFSI)–H3PO4 composite in a flow-through configuration, for both gas and liquid samples. Incorporation of H3PO4 into a PFSI sensing film improved the limit of detection (LOD) (signal-to-noise ratio, S/N = 3) by a factor of 16 in the gas phase to 0.075% relative humidity (RH) (dew point = −56 °C). The response time was dependent on the sensing film thickness and composition and was as low as ∼60 ms. The temperature dependence of the sensor response, and its relative selectivity over alcohol and various other solvents, are reported. Measurement of water in organic solvents was carried out in two different ways. In one procedure, the sample was vaporized and swept into the detector (e.g., in a gas chromatograph (GC) without a column); it permitted a throughput of 80 samples/h. This is well-su...

Authors:   Shin-Ichi Ohira; Kayoko Goto; Kei Toda; Purnendu K. Dasgupta
Journal:   Analytical Chemistry
Year:   2012
DOI:   10.1021/ac3024069
Publication date:   27-Sep-2012
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