11. Apparatus
11.1 Gas Chromatograph, consisting essentially of a carrier gas source, a pressure regulator, a sample injection port and chromatography column(s), flow meter(s), detector(s), and recorder(s) or recording integrator(s).
11.2 Provide means for measuring and controlling temperatures of the adsorption column, the inlet port, and the detector to within more or less 0.5°C.
NOTE 6 - Use Practice E 260 as a reference for good chromatographic techniques.
11.3 The apparatus shall be capable of sufficiently separating the component gases, at the sensitivity levels shown as follows, to ensure quantitative measurement of the respective peak areas:
11.4 The apparatus shall provide sufficient repeatability so that successive runs of a reference standard agree within more or less 1% with respect to area under the peaks for hydrocarbon and carbon oxide components.
11.5 A wide range of chromatographic conditions have been successfully employed. Both argon and helium have been used as carrier gases (see Note 7). In some cases, a separate GC or other device is used for the detection and quantification of hydrogen when helium is used as a carrier gas.
NOTE 7 - If helium is used as a carrier gas with a thermal conductivity detector, medium to high concentrations of hydrogen may give a nonlinear response, due to the closed heat capacity values of helium and hydrogen. The limit of detection will be higher than with an argon carrier gas under similar conditions. If nitrogen is used as a carrier gas, nitrogen cannot be detected in the sample.
11.5.1 With the use of an argon carrier gas, a catalytic converter containing powdered nickel located after the chromatographic 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.) With helium as a carrier gas, a catalytic converter is not necessary but may be used to enhance sensitivity.
11.5.2 A flame ionization detector, instead of a thermal conductivity detector, is often used to detect hydrocarbon gases due to its greater sensitivity for these components. A wide range of injector, column, and detector temperatures can be used. Both isothermal and temperature programs can be used to provide adequate separation and sensitivity. A typical chromatogram is shown in Fig.4.
11.6 Fixed Needle Gas-Tight Syringes, of suitable sizes are needed for transfer of the gases.