ASTM D7345 Standard Test Method for Distillation of Petroleum Products and Liquid Fuels at Atmospheric Pressure (Micro Distillation Method)
8. Sampling, Storage, and Sample Conditioning
8.1 Sampling:
8.1.1 The extreme sensitivity of volatility measurements to losses through evaporation and the resulting changes in composition is such as to require the utmost precaution in the drawing and handling of volatile product samples.
8.1.2 Obtain a sample and test specimen in accordance with Practice D4057, D4177, or D5854 when appropriate. At least 50 mL of sample is recommended.
8.1.3 Sample shall be free from any suspended solids or other insoluble contaminations. Obtain another sample or remove solid particle by filtration. During filtration operation take care to minimize any loss of light ends.
8.2 Sample Storage:
8.2.1 All samples shall be stored in a tightly closed and leak-free container away from direct sunlight or sources of direct heat.
8.2.2 Protect samples containing light materials having expected initial boiling point lower than 100 °C from excessive temperatures prior to testing. This can be accomplished by storage of the sample container in an appropriate ice bath or refrigerator at a temperature below 10 °C. Other samples can be stored at ambient or lower temperature.
8.2.3 If the sample has partially or completely solidified during storage, it is to be carefully heated to a temperature when it is completely fluid. It shall be vigorously shaken after melting, prior to opening the sample container, to ensure homogeneity.
8.3 Wet Samples:
8.3.1 Samples of materials that visibly contain water are not suitable for testing by this test method. If the sample is not dry, obtain another sample that is free from suspended water.
8.3.2 If such a sample cannot be obtained, remove any free water by placing approximately 30 mL of the sample to be tested in a glass conical flask containing approximately 10 g of the drying agent. Stopper and shake gently. Allow the mixture to settle for approximately 15 min. Once the sample shows no visible signs of water, use a decanted portion of the sample for the analysis. It is recommended to filter the test portion from the residual or suspended drying agent. During this drying and filtration operations take care to minimize any loss of light ends. Report that the sample has been dried by the addition of a drying agent.
9. Preparation of Apparatus
9.1 Install the analyzer for operation in accordance with the manufacturer's instructions.
9.2 This instrument shall be located away from direct sunlight, sources of direct heat or air draft.
9.3 Turn on the main power switch of the analyzer.
10. Verification Quality Control Checks
10.1 To verify the temperature measurement system, distill high purity toluene in accordance with this test method and comparing the temperature reading at 50 % distilled. If the temperature reading differs more than 0.5 °C from the expected temperature of 109.3 °C (see Note 1), then check the instrument calibration (see Section 11).
10.2 To verify the temperature measurement system at elevated temperatures, use n-hexadecane and record the temperature at 50 % distilled. If the temperature reading differs more than 1.0 °C from the expected temperature of 278.6 °C (see Note 1, then check the instrument calibration (see Section 11).
NOTE 1 - These temperatures are those that would be obtained if the toluene and hexadecane were distilled using Test Method D86 and are not the figures that are given as the boiling points of these materials in literature.
10.3 Verification of apparatus performance under dynamic conditions and wide temperature range can be done by distillation of a Certified Reference Material (CRM) or Secondary Working Standard (SWS).
10.3.1 Certified Reference Material (CRM) - CRM is a stable mixture of hydrocarbon or other stable petroleum product with a method-specific distillation characteristic established by a method-specific interlaboratory study following Practice D6300 or ISO Guide 34 and Guide 35. Suppliers of CRMs will provide certificates stating the method-specific distillation characteristic for each material of the current production batch.
10.3.2 Secondary Working Standard (SWS) - SWS is a stable mixture of pure hydrocarbons, or other petroleum product whose composition is known to remain appreciably stable. Establish the mean value of control points and the statistical control limits for the SWS using standard statistical techniques. See Practice D6299.
11. Calibration
11.1 Follow the manufacturer's instructions for verifying the correct operation of the apparatus.
11.2 Temperature Measurement System - At intervals of not more than six months or after the system has been replaced or repaired, or both, following the apparatus instruction manual, check the calibration of the liquid and vapor temperature measuring sensors by distilling of pure compounds, like toluene and n-hexadecane.
NOTE 2 - The melting point of n-hexadecane is 18 °C. If the sample is solid, heat it to about 25 °C and wait until all the material is liquid before starting the test.
11.3 External Pressure Measuring Device - At intervals of not more than six months, or after the system has been replaced or repaired, or both, the external pressure measuring device reading of the apparatus shall be verified against a barometer, as described in 6.3.
11.4 Differential Pressure Measuring Device - At intervals of not more than six months, or after the system has been replaced or repaired, or both, the differential pressure measuring device reading of the apparatus shall be verified in accordance with the manufacturer's instructions.
