23.1 Prepare the gas chromatograph as outlined by the manufacturer.
23.2 Prepare the sample for injection by first dissolving any gas bubble present into the volume of oil by compressing the plunger into the barrel of the syringe and agitating the gas by tipping the syringe up and down. Any bubble present in the syringe must be dissolved to obtain a representative aliquot of the sample for injection. Small volumes of oil are needed for flushing and sample, typically a total of several millitres. Flushing is required to displace the previous sample from the column.
23.3 Once the sample is connected to the gas chromatograph, flush enough oil through the injection system to ensure that no gas bubbles remain in the line.
23.4 If high concentrations of the more soluble gases are found, in particular C2H2, the injection column can be back flushed. Use a blank run of degassed insulating oil to check that no residual gases remain.
24. Calculation
24.1 Determine the integrated area of each peak of the chromatogram.
24.2 Identify the gases represented by each peak by comparison of elution times with those obtained for the reference standard gas mixture in the calibration procedure.
24.3 Determine the amount of each identified gas component by comparing respective peak areas with those obtained for the reference standard gas mixture in the calibration procedure.
24.4 Correct the values obtained based on the efficiency values obtained in the efficiency determination procedure, and express as parts per million of (specific gas) in oil, by volume as shown in the following calculation:
25. Report
25.1 Report the following information:
25.1.1 Identification of oil sample,
25.1.2 Temperature of oil at time of sampling,
25.1.3 Volume concentration in the oil, for each component gas, expressed in parts per million, and
25.1.4 The test method used (for example, D 3612, Part B).