1. Rationale
Sections 8.2 and 8.4 (in the Calibration section of the method), as well as sections 9.10 and 9.14 (in the Procedure section of the method) currently require the prescriptive use of a pipet to dispense a fixed volume quantity of the sulfuric acid solution and molybdate-hydrazine reagent used in this test method. As such, this currently precludes other equivalent volume dispensing or transferring devices (such as a bottle-top dispenser) from being used in the test in order to be in compliance. Secondly, in the current method, there are no specifications given for the pipets in the apparatus section. A proposed revision is identified to add a new section 5.11 in the Apparatus section to define the functional requirements for Pipets, or equivalent volume dispensing devices to provide users with additional flexibility in meeting the method requirements without adversely impacting results. Addition of the same volume to each flask is more critical than the actual volume added, as for example, a significant stoichiometric excess of the molybdate-hydrazine reagent is added. Achievement of the addition of reproducible volumes is significantly improved by the use of bottle-top dispensers rather than by hand-pipeting. There is also less chance for exposure on the part of the laboratory technician to the sulfuric acid solution.
Keywords
gasoline; phosphorous; spectrophotometer; Spectrophotometry--atomic absorption (petroleum); Gasoline; Phosphorus content--petroleum products;
Citing ASTM Standards
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