ASTM D6352 test method for boiling range distribution of petroleum distillates
ASTM D6352 standard test method for boiling range distribution of petroleum distillates in boiling range from 174 to 700°C by 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. Typical operating conditions are shown in Table 3.
8.1.2 Attach one of the column specified in Table 4 to the detector inlet by ensuring that the end of the column terminates as close as possible to the FID jet tip. 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 If the sample inlet system is heated, a blank analysis shall be made after a new septum is installed to ensure that no extraneous peaks are produced by septum bleed. At the sensitivity levels commonly employed in this test method, conditioning of the septum at the upper operating temperature of the sample inlet system for several hours will minimize this problem. The inlet liner and initial portion of the column shall 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 to produce or generate a stable and repeatable 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 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 (or a polywax retention time boiling point mixture). Resolution (R) should be at least two (2) and not more than four (4), using the identical conditions employed for sample analyses.
R = 2 (t2 - t1)/(1.699 (w2 + w1))
where:
t1 = time (s) for the n-C50 peak max,
t2 = time (s) for the n-C52 peak max,
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 shall 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 7.6) 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) in accordance with Practice D4626 and Eq 2:
Fn = (Cn/An)/(Cn - C40/An - C40)
where:
Cn = concentration of the n-paraffin in the mixture,
An = peak area of the n-paraffin in the mixture,
Cn-C40 = concentration of the n-tetracontane in the mixture, and
An-C40 = peak area of the n-tetracontane in the mixture.
The relative response factor (Fn) of each n-paraffin shall not deviate from unity by more than +/- 5 %. Results of response factor determinations by one lab are presented in Table 5.
8.2.3 Column Temperature - The column temperature program profile is selected such that there is baseline separation between the solvent and the first n-paraffin peak (C10) in the calibration mixture and the maximum boiling point (700°C). n-Paraffin (C90) is eluted from the column before reaching the end of the temperature program. The actual program rate used will be influenced by other operating conditions, such as column dimensions, carrier gas and flow rate, and sample size. Thin liquid phase film thickness and narrower bore columns may require lower carrier gas flow rates and faster column temperature program rates to compensate for sample component overloading (see 9.3.1).
8.2.4 Column Elution Characteristics - The column phase is non-polar and having McReynolds numbers of x = 15-17, y = 53-57, z = 43-46, u = 65-67, and s = 42-45.
