Investigating Adsorption/Desorption of Carbon Dioxide in Aluminum Compressed Gas Cylinders
Walter R. Miller Jr., George C. Rhoderick, Franklin R. Guenther
Between June 2010 and June 2011, the National Institute of Standards and Technology gravimetrically prepared a suite of 20 carbon dioxide [CO2] in air primary standard mixtures [PSMs]. Ambient mole fraction levels were obtained through six levels of dilution from pure CO2. The sixth level covered the ambient range from 355 to 403 µmol/mol. This level will be used to certify cylinder mixtures of compressed dry whole air from both the northern and southern hemisphere as National Institute of Standards and Technology standard reference materials [SRMs]. The first five levels of PSMs were verified against existing PSMs in a balance of air or nitrogen with excellent agreement. After preparation of the new suite of PSMs at ambient level they were compared to an existing suite of PSMs. It was observed that the analyzed concentration of the new PSMs was less than the calculated gravimetric concentration by as much as 0.3 % relative. In order to determine the magnitude of these losses, a series of "daughter / mother" tests were conducted where the gas mixture containing CO2 from a "mother" cylinder was transferred into an evacuated "daughter" cylinder. These cylinder pairs were then compared using Cavity Ring down Spectroscopy [CRDS] under high reproducibility conditions. A ratio of the daughter instrument response to the mother response was calculated with the resultant deviation from unity being a measure of the CO2 loss or gain. Cylinders from three specialty gas vendors were tested to find the appropriate cylinder in which to prepare the new PSMs. All cylinders tested showed a loss of CO2, presumably to the walls of the cylinder. The most appropriate cylinders were then used to gravimetrically
, Rhoderick, G.
and Guenther, F.
Investigating Adsorption/Desorption of Carbon Dioxide in Aluminum Compressed Gas Cylinders, Analytical Chemistry, [online], https://doi.org/10.1021/ac504351b
(Accessed June 2, 2023)