Ultra-high-purity gases

Ultra high purity gases are used with oxygen traps to remove trace impurities of oxygen. 

Note Ultra-high purity gases may require specialized cylinder treatment and filling procedures. 

Gas supply for R D applications involving ultra-high purities, e g. in microelectronics, for production plants using ultra-high purity gases and gas mixtures as well as corrosive and toxic process gases, e.g. for VLSI circuits, sensors and solar cells... 

Dynamic headspace GC utilizes a constant purge of the sample with an ultra-high purity gas (i.e., helium). The purged volatiles are then adsorbed onto a trap, followed by heat desorption onto the GC for analysis. Either a flame ionization detector or mass selective detector can be used. The protocol presented here is designed to analyze a meat sample. 

A more recent development in ethylene polymerization is the simplified low pressure LDPE process. The pressure range is 0.7—2.1 MPa with temperatures less than 100°C. The reaction takes place in the gas phase instead of Hquid phase as in the conventional LDPE technology. These new technologies demand ultra high purity ethylene. 

Argon (Ultra High Purity, 99.999%), hydrogen (Research Purity, 99.9995%) and ethylene (Research Purity, 99.99%) were purchased from Matheson. The argon was further purified using a Matheson Gas Purifier Model 6406in conjunction with an Alltech indicating oxy-trap. 

Hydrogen can be produced by steam methane reformation (the most widely used process) or by off-gas purification. Hydrogen can be produced at normal purity (95-98%) or at ultra-high purity (99.99%). The first step to obtain pure hydrogen in the steam reformer process when using a natural gas feedstock is to perform a pretreatment. There are small amounts of sulfur in natural gas that must be... 

Adsorption equilibria and uptakes were gravimetrically measured with two balances, i.e., Cahn 1100 microbalance and Magnetic Suspension Balance (Rubotherm Co.). Adsorbents were loaded and regenerated in the balance under the flow of ultra high purity Helium gas at ISO 3S0 C, then adjusted to the measuring temperature and evacuated to 10 mmHg by using a turbo molecular pump. Adsorbates used were as follows propane (min.99.5), isobutane (min.99.5%), n-butane (min.99.S%), 1-butene (min.99.5%), isobutene (min.99.5%) and t-2-butene (min.99.8%). 

A gas chromatograph with a HECD is not practical for transporting to a field laboratory. The fittings on the reactor and conductivity cell of the HECD are very fragile. In addition, the ultra-high purity operating conditions and sensitive settings of flow rates confine a HECD system exclusively to laboratory use. 

Hydrogen can be purchased in various grades of purity. Research grade is 99.9995%, ultra high purity is 99.999%, high purity is 99.99%, and industrial grade is 99.95%. Of course, the purer the gas, the more expensive it is. 

Thermal spreading was studied by treating the catalysts in an oven at a consUint temperature for 1 h. Both loose powder catalysts and samples pressed into self-supporting wafers were investigated in the current studies. After the thermal treatments, Raman spectra of the catalysts were recorded in an ambient environment or in a controlled oxygen atmosphere. In the latter case, the samples were heated in oxygen (Linde Gas, ultra-high purity) in a dehydration cell for 45 minutes at 300°C and then cooled to about 50°C to obtain the Raman spectra. Additional details about the Raman spectrometer can be found elsewhere [5]. 

McDowell and Metcalfe proposed the use of supercritical fluid extraction (SEE) with ultra high purity CO2 as supercritical fluid for the extraction of phthalate esters from sediment samples. Extracts were collected by bubbling the vented gas through 12 ml hexane, and solvent... 

The input feed stream is composed of an effluent gas (argon) and one of the hydrogen isotopes, H or D, at a time. The output species from reactor were monitored by the mass spectrometer, with a constant inner pressure of 6 x 10 torr. The gases used in all experiments are of ultra high purity (min 99.99 % voL). 

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