21.1 Prepare the gas chromatograph for use as directed by the manufacturer, and establish a set of operating conditions capable of separating the indicated component gases.
21.2 Inject a pre-established volume of the reference standard (low concentration) gas mixture into the chromatograph and establish a pattern of elution times for the gas components known to be in the mixture, at an established set of operating conditions and sample sizes. Repeat the analysis until consistent operating conditions provide consistent chromatograms. Repeat calibration daily when analyses are being conducted.
22. Efficiency Determination
22.1 Inject the oil standard prepared from one of the procedures in the Annexes into the system. Determine the dissolved gas content of this oil chromatographically based upon the low-concentration gas standard. The difference between the calculated concentration and the observed concentration is the degassing efficiency of a given component and may be calculated as follows:
22.2 The degassing efficiency factor is used to correct the determined concentration values for incomplete extraction. Repeat the procedure until consistent results are obtained. Conduct this efficiency determination weekly for at least one concentration of standard gas. Whenever there are changes in the chromatographic system, redetermine the extraction efficiency.
22.3 Determine the linearity of the detector response monthly by testing a range of gas concentrations expected to be encountered in actual samples. Extraction efficiencies should also be determined over a corresponding range to ensure they are linear and constant over time. Samples can be prepared by simple dilution of pure gases with either nitrogen or carrier gas (for gas standards) or degassed oil (for gas-in-oil standards). If commercially supplied standard mixtures are used, they may be checked using this method. Check efficiencies and linearity whenever chromatographic conditions are changed.