ASTM D5307 Determination of Boiling Range Distribution of Crude Petroleum by Gas Chromatography
9. Preparation of Apparatus
9.1 Column Preparation - Any satisfactory method used in the practice of the art, that will produce a column meeting the requirements of Section 10, may be used.
9.2 Column Conditioning - The column must be conditioned at the maximum operating temperature to reduce baseline shifts due to bleeding of the column substrate. The column can be conditioned rapidly and effectively using the following procedure:
9.2.1 Connect the column to the inlet system but leave the detector end free.
9.2.2 Purge the column at ambient temperature with carrier gas.
9.2.3 Turn off the carrier gas and allow the column to depressurize completely.
9.2.4 Seal off the open end of the column with an appropriate fitting.
9.2.5 Raise the column to the maximum operating temperature and hold at this temperature 4 to 6 h, with no flow through the column.
9.2.6 Cool the column to ambient temperature.
9.2.7 Remove the cap from the column and connect the column to the detector. Re-establish carrier flow.
9.2.8 Program the column temperature to the maximum several times with normal carrier gas flow rate.
9.3 An alternate method of column conditioning, that has been found effective with columns with an initial loading of 5 % liquid phase, consists of purging the column (disconnected from the detector) with normal carrier gas flow rate for 12 to 16 h, while holding the column at the maximum operating temperature.
9.4 Chromatograph - Place the chromatograph in service in accordance with the manufacturer's instructions. Typical operating conditions are shown in Table 1.
9.4.1 Excessively low initial column temperature must be avoided to ensure that the column phase functions as gas-liquid chromatographic column. Consult the stationary phase manufacturer's literature for minimum operating temperature. The initial temperature of the column should be only low enough to obtain a calibration curve meeting the specifications under 6.1.3.
9.4.2 Silica from combustion of column material deposits on the FID parts. This deposit must be removed regularly, by brushing, because it changes response characteristics of the detector.
9.4.3 Silica deposits also can plug the end of the flame jet. This problem can be alleviated greatly by utilizing a flame jet with an inside diameter of at least 0.76 mm (0.030 in.)
