ASTM D6417 Estimation of Engine Oil Volatility by Capillary Gas Chromatography
8. Preparation of Apparatus
8.1 Gas Chromatograph Setup:
8.1.1 Place the gas chromatograph and ancillary equipment into operation in accordance with the manufacturer's instructions. Recommended operating conditions are shown in Table 2.
8.1.2 When attaching the column to the detector inlet, ensure that the end of the column terminates as close as possible to the FID jet. Follow the instructions in Practice E 1510.
8.1.3 The FID should be periodically inspected and, if necessary, remove any foreign deposits formed in the detector from combustion of silicone liquid phase or other materials. Such deposits will change the response characteristics of the detector.
8.1.4 The inlet liner and initial portion of the column must be periodically inspected and replaced, if necessary, to remove extraneous deposits or sample residue.
8.1.5 Column Conditioning - A new column will require conditioning at the upper test method operating temperature to reduce or eliminate significant liquid phase bleed, resulting in a stable chromatographic baseline. Follow the guidelines outlined in Practice E 1510.
8.2 System Performance Specification:
8.2.1 Column Resolution - The column resolution, influenced by both the column's 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 C50 and C52 paraffins from a calibration mixture analysis (see 7.6). A resolution (R) of at least one and not more than twelve, using the identical conditions employed for sample analyses, has been found to be acceptable.
R = 2 (t2 - t1) / (1.699 (w2 + w1))
where:
R = resolution,
t1 = time (s) for the n-C50 peak maximum,
t2 = time (s) for the n-C52 peak maximum,
w1 = peak width (s), at half height, of the n-C50 peak, and
w2 = peak width (s), at half height, of the n-C52 peak.
8.2.2 Detector Response Calibration - This test method assumes that the FID 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 response linearity mixture (see 7.7), using the identical procedure to be used for the analysis of samples (see Section 9). Calculate the relative response factor for each n-paraffin (relative to n-tetracontane) as per Practice D4626 and Eq 2:
Fn = (Mn/An) / (M40/A40)
where:
Fn = relative response factor,
Mn = mass of the n-paraffin in the mixture,
An = peak area of the n-paraffin in the mixture,
M40 = concentration of the n-tetracontane in the mixture, and
A40 = peak area of the n-tetracontane in the mixture.
The Fn of each n-paraffin should not deviate from unity by more than +/- 5 %.
8.2.3 Column Temperature - The column temperature program profile is selected such that there is separation between the solvent and the first n-paraffin peak (n-C8) in the calibration mixture and the maximum boiling point (615°C) n-paraffin (n-C60) is eluted from the column before reaching the end of the temperature program. The actual program rate used will be influenced by other operating variables, such as column dimensions, carrier gas and flow rate, and sample size.
8.2.4 Column Elution Characteristics - The recommended column liquid phase is a nonpolar phase, such as 100 % methyl silicone.
