20. Reagent and Materials
20.1 Suitable Chromatography Columns - Several combinations have been found to be suitable including molecular sieve, Porapak Q, Porapak N, diisodecyl phthalateA, Silica Gel J, Chromosorb 102, Carbosieve B, and Sperocarb. Molecular sieve is used to separate H2, O2, N2, CH4, and CO. Porapak N, Q, or combinations of both are used to separate CO2, C2H4, C2H6, C2H2, C3H6, C3H6, and C4H10. Sperocarb is used to separate the carbon oxide and hydrocarbon gases.
20.2 Argon, or Nitrogen Carrier Gas, having a minimum purity of 99.95 mol % with total hydrocarbons of less than 0.5ppm and CO2 of less than 1 ppm. (See Note 7.)
20.2.1 With the use of an argon carrier gas, a catalytic converter containing powdered nickel, located after the separating columns, is used to convert carbon monoxide and carbon dioxide to methane for detection with a flame ionization detector for acceptable sensitivity. (The condition of the nickel catalyst can be evaluated by checking the linearity of the response to carbon dioxide.)
20.3 Flame Ionization Detector Gases - Hydrogen having a purity of 99.99 mol % with total hydrocarbons of less than 0.5ppm and air having a purity of less than 1 ppm total hydrocarbons.
20.4 Reference Standard Gas Mixtures - Low-concentration standard containing known percentages of the gases in 1.2 at concentrations approximately the magnitude of the values normally encountered. The high-concentration gas standard should contain levels approximately one order of magnitude higher than contained in the low-concentration gas standard. The gas standards should be a primary grade (each component added gravimetrically). The high gas standard is used for preparing gas in oil standards as outlined in Annex A1.
