ASTM D6748 for Determination of Potential Instability of Middle Distillate Fuels
ASTM D6748 Standard Test Method for Determination of Potential Instability of Middle Distillate Fuels Caused by the Presence of Phenalenes and Phenalenones (Rapid Method by Portable Spectrophotometer)
8. Sampling
8.1 Field Sampling - Take field samples in accordance with Practices D4057, D4177, or other comparable sampling practices. Record the sampling date. Sample bulk fuel above its cloud point and thoroughly mix prior to aliquot sampling. For shipping field samples, use only epoxy-lined steel cans that have been cleaned according to Practice D4306.
8.2 Store samples at normal room temperature (20 to 25°C) or colder.
8.3 Filter samples which contain free water or a water haze through a qualitative filter paper or a loose plug of cotton to remove such water.
8.4 Laboratory Subsampling - Sample fuel above its cloud point and thoroughly mix prior to aliquot sampling. At least 5 mL of sample is required for each test. Follow Practices D4057 and D5854. Use clean amber or clean borosilicate glass containers for laboratory handling. Shield fuel in clear bottles from sunlight to prevent photochemical reactions. Other laboratory containers may be used provided they are shown not to affect the results of the test.
8.5 Allow the test sample to reach the local ambient temperature (10 to 30°C) before commencing the test.
9. Preparation and Calibration of Apparatus
9.1 For portable use ensure that the battery has been charged.
9.2 Zeroing the Spectrophotometer - Turn on the portable spectrophotometer for at least 2 min. Fill a test cuvette with Reagent 1, to within 5 mm of its top. Place the filled test cuvette into the spectrophotometer drawer. Zero both wavelengths individually by separately pressing each select button and turning the corresponding zero button until 0.00 AU is displayed.
9.2.1 Dispose of the cuvette and the aliquot of Reagent 1. Do not reuse the cuvette.
NOTE 3 - The spectrophotometer is correctly calibrated if the two wavelength readings are 0.00 +/- 0.01 AU.
9.3 Verification - A verification fluid is under development.
