Critical evaluation of gas standards based on hydrogen |
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Authors: | N P Neves Jr C H Collins |
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Institution: | (1) Lab. Hidrogênio, Instituto de Física Gleb Wataghin, UNICAMP, PO Box 6039, 13083-970 Campinas, SP, Brazil;(2) Lab. Cromatografia, Instituto de Quimica, UNICAMP, PO Box 6154, 13083-970 Campinas, SP, Brazil |
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Abstract: | Summary Six commercial hydrogen standards containing helium, oxygen, nitrogen, methane and carbon dioxide at trace levels were analyzed
by gas chromatography, for periods up to 105 days. The concentrations, in the range of 0–120 μmol mol−1, were stable (with the exception of oxygen) but often significantly different from the certified values provided by the suppliers,
especially for helium, oxygen and nitrogen. Concurrently, some experiments were carried out to verify the stability of gas
mixtures based on hydrogen stored in cylinders submitted to different chemical and physical treatments. The causes that led
to the deviations observed, as well as the decreases in oxygen, are discussed.
Presented at the 21st ISC held in Stuttgart, Germany, 15th–20th September, 1996. |
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Keywords: | Gas chromatography Hydrogen-based gas standards Permanent gas mixtures Storage stability of gas mixtures |
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