ASTM D2887 Boiling Range Distribution of Petroleum Fractions by Gas Chromatography
9. Preparation of Apparatus
9.1 Chromatograph - Place in service in accordance with the manufacturer's instructions. Typical operating conditions are shown in Table 1.
9.1.1 When a FID is used, regularly remove the deposits formed in the detector from combustion of the silicone liquid phase decomposition products. These deposits will change the response characteristics of the detector.

9.1.2 If the sample inlet system is heated above 300°C (572°F), a blank analysis must be made after a new septum is installed to ensure that no extraneous detector response is produced by septum bleed. At the sensitivity levels commonly employed in this test method, conditioning of the septum at the operating temperature of the sample inlet system for several hours will minimize this problem. A recommended practice is to change the septum at the end of a series of analyses rather than at the beginning of the series.

9.2 Column Preparation:
9.2.1 Packed Columns - Any satisfactory method that will produce a column meeting the requirements of 9.3.1 and 9.3.3 can be used. In general, use liquid phase loadings of 3 to 10 %. Condition the column at the maximum operating temperature to reduce baseline shifts due to bleeding of the column substrate. The column can be conditioned very rapidly and effectively using the following procedure:
9.2.1.1 Connect the column to the inlet but leave the detector end free.

9.2.1.2 Purge the column thoroughly at ambient temperature with carrier gas.

9.2.1.3 Turn off the carrier gas and allow the column to depressurize completely.

9.2.1.4 Seal off the open end (detector) of the column with an appropriate fitting.

9.2.1.5 Raise the column temperature to the maximum operating temperature.

9.2.1.6 Hold the column at this temperature for at least 1 h with no flow through the column.

9.2.1.7 Cool the column to ambient temperature.

9.2.1.8 Remove the cap from the detector end of the column and turn the carrier gas back on.

9.2.1.9 Program the column temperature up to the maximum several times with normal carrier gas flow. Connect the free end of the column to the detector.

9.2.1.10 An alternative method of column conditioning that has been found effective for columns with an initial loading of 10 % liquid phase consists of purging the column with carrier gas at the normal flow rate while holding the column at the maximum operating temperature for 12 to 16 h, while detached from the detector.

9.2.2 Open Tubular Columns - Open tubular columns with cross-linked and bonded stationary phases are available from many manufacturers and are usually pre-conditioned. These columns have much lower column bleed than packed columns. Column conditioning is less critical with these columns but some conditioning may be necessary. The column can be conditioned very rapidly and effectively using the following procedure.
9.2.2.1 Once the open tubular column has been properly installed into the gas chromatograph and tested to be leak free, set the column and detector gas flows. Before heating the column, allow the system to purge with carrier gas at ambient temperature for at least 30 min.

9.2.2.2 Increase the oven temperature about 5 to 10°C per minute to the final operating temperature and hold for about 30 min.

9.2.2.3 Cycle the gas chromatograph several times through its temperature program until a stable baseline is obtained.

9.3 System Performance Specification:
9.3.1 Column Resolution - The column resolution, influenced by both the column physical parameters and operating conditions, affects the overall determination of boiling range distribution. Resolution is therefore specified to maintain equivalence between different systems (laboratories) employing this test method. Resolution is determined using Eq 1 and the C16 and C18 paraffins from a column resolution test mixture analysis (see 7.7 and Section 10), and is illustrated in Fig. 1. Resolution (R) should be at least three, using the identical conditions employed for sample analyses:
R = 2(t2 - t1) / [1.699(w2 + w1)]
where:
R = resolution,
t1 = time(s) for the n-C16 peak maximum,
t2 = time(s) for the n-C18 peak maximum,
w1 = peak width(s), at half height, of the n-C16 peak, and
w2 = peak width(s), at half height, of the n-C18 peak.

9.3.2 Detector Response Calibration - This test method assumes that the detector response to petroleum hydrocarbons is proportional to the mass of individual components. This must be verified when the system is put in service, and whenever any changes are made to the system or operational parameters. Analyze the calibration mixture using the identical procedure to be used for the analysis of samples (see Section 10). Calculate the relative response factor for each n-paraffin (relative to n-decane) in accordance with Practice D4626 and Eq 2:
Fn = (Mn / An) / (M10 / A10)
where:
Fn = relative response factor,
Mn = mass of the n-paraffin in the mixture,
An = peak area of the n-paraffin in the mixture,
M10 = mass of the n-decane in the mixture, and
A10 = peak area of the n-decane in the mixture.

The relative response factor (Fn) of each n-paraffin must not deviate from unity (1) by more than ±10 %.

9.3.3 Column Elution Characteristics - The column material, stationary phase, or other parameters can affect the elution order of non-paraffinic sample components, resulting in deviations from a TBP versus retention time relationship. If stationary phases other than those referenced in 7.3 are used, the retention times of a few alkylbenzenes (for example, o-xylene, n-butyl-benzene, 1,3,5-triisopropylbenzene, n-decyl-benzene, and tetradecylbenzene) across the boiling range should be analyzed to make certain that the column is separating in accordance with the boiling point order (see Appendix X1).