ASTM D5134 Standard Test Method for Detailed Analysis of Petroleum Naphthas
ASTM D5134 Standard Test Method for Detailed Analysis of Petroleum Naphthas through n-Nonane by Capillary Gas Chromatography
9. Preparation of Apparatus
9.1 Install and condition column as per manufacturer's or supplier's instructions. After conditioning, attach column outlet to flame ionization detector inlet and check for leaks throughout the system. If leaks are found, tighten or replace fittings before proceeding.
9.2 Calibrate the gas chromatograph column oven temperature sensors using an independent, electronic temperature measuring device such as a thermocouple or platinum resistance temperature detector.
9.2.1 Place the independent temperature measuring probe in the oven in the region occupied by the column. Do not allow sensor to touch the walls of the oven.
9.2.2 Set the oven temperature to 35°C and allow oven to equilibrate for at least 15 min, then observe the temperature reading.
9.2.3 If the reading of the independent temperature sensor is more than 0.5°C different from 35°C, follow manufacturer's instructions to adjust calibration of GC oven temperature.
NOTE 1 - Caution: Differences of as little as 1°C can change the resolution of two closely eluting peaks (of dissimilar hydrocarbon types) enough to affect integration and quantitation while 2 to 3°C may cause those same peaks to be unresolved or even reverse their elution order.
9.3 Adjust the operating conditions of the gas chromatograph to conform to the list in Table 2. Turn on the detector, ignite flame, and allow the system to equilibrate.
9.4 Set carrier gas flow rate such that the retention time of toluene at 35°C is 29.6 more or less 0.2 min.
9.4.1 As a matter of practicality, it may be easier to first set an approximately correct flow rate, using methane gas injections. To do this, adjust the carrier gas flow (or column head pressure) until the retention time of methane on the 50-m column is 3.6 min.
9.4.2 Make final adjustments to flow rate so that toluene is retained for the specified 29.6 more or less 0.2 min. As this specification is critical to achieving reproducibility of retention times among different laboratories, care must be taken that the toluene does not overload the column and cause skewed peaks with resultant shifts in peak apex position. Injection of a 1 % toluene solution should preclude this possibility.
