ASTM D7169 Test Method for Boiling Point Distribution of Samples with Residues
ASTM D7169 Standard Test Method for Boiling Point Distribution of Samples with Residues Such as Crude Oils and Atmospheric and Vacuum Residues by High Temperature Gas Chromatography
9. Preparation of the Gas Chromatograph
9.1 A summary of the conditions used for developing the precision statement is given in Table 1.
9.2 Column Installation - The column is installed using graphite ferrules and an electronic leak detector is used to ascertain the absence of leaks. Follow the instructions given in Test Method D2887 and Practice E1510 for the installation of silica or aluminum clad silica columns. Metal columns require slightly different techniques in cutting and installation. Follow the recommendations of the column supplier.
9.3 Detector Temperature - Select a detector temperature that is at least 5 to 10°C higher than the highest oven temperature.
9.4 Initial Oven Temperature - The initial temperature of the oven is chosen according to the sample type to be analyzed as follows:
9.4.1 Crude Oil Samples - Crude oil samples may contain hydrocarbons starting from methane, C2, C3, and C4 which probably co-eleute with C5. Therefore, even at an initial temperature of -20°C, C5 and C6 are partially resolved from the CS2. Further decreases in oven temperature do not increase the separation of C5 from C1-C4 hydrocarbons which co-elute with n-C5.
9.4.2 Residues and Samples Having Higher IBP - For samples that have an initial boiling point of 100°C or greater, such as vacuum residues or atmospheric residues, the initial oven temperature is set to 35 to 40°C. Ensure that the sample is resolved from the solvent peak at the initial oven temperature selected. If the light ends cannot be separated from the solvent, then proceed as in 9.4.1. If the user does not know the type of sample to be analyzed, all samples can be analyzed with an initial temperature of -20°C.
10. Sample Preparation
10.1 Ensure that the sample is a representative sample. Follow the guidelines established in Practice D4057. Samples should be handled according to their content of volatile components. Store crude oil samples at 4°C or below until ready for analysis. If the sample is submitted for other analyses, remove a small aliquot (~10 mL) early in the testing sequence in order to avoid loss of volatile components. Allow sample to warm to room temperature prior to weighing.
10.2 Samples that are solid or semi-solid at room temperature may require heating up to as high as 60°C in order to pour them into a weighed container.
10.3 Weigh 0.2 to 0.25 g of the sample to the nearest 0.1 mg. Add 10 mL of CS2. Record this weight also to the nearest 0.1 mg. Enter these values in the data acquisition system if appropriate.
10.4 Store all prepared solutions at a temperature of 4°C. Care should be taken that the solution is prepared a short time prior to running the analysis. Samples can be stored in the auto sampler vials.
10.5 Prepare as many vials of a sample as are necessary to carry out multiple analyses of that sample. Do not use the same vial to run duplicates; use separate vials containing the same solution.
11. Preparation of the Response Factor Standard
11.1 Weigh 0.2 to 0.25 g of Reference Oil 5010 to the nearest 0.1 mg. Add 10 mL of CS2 and record the weight of the solvent to the nearest 0.1 mg. Store this solution at 4°C, if not used immediately.
12. Preparation of the Apparatus and Data System
12.1 After the column is installed and checked for leaks, prepare the gas chromatograph to analyze the sample according to the conditions given in Table 1.
12.2 Set the acquisition system to digitize the data at 10 Hz. This will result in a slice width of 0.1 s. This data acquisition rate is kept constant for all samples, standards, and the solvent blank in order to acquire the same number of slices. The baseline chromatogram may contain the same or larger number of slices than the sample chromatograms, depending on when the data acquisition stops. Thus, various chromatograms taken in a sequence may differ by 5 to 10 slices. This fact is of no consequence with regard to the calculations.
12.3 Arrange to save the acquired data files. Build the sequence of samples to be injected by the gas chromatograph.
