ASTM D6732-04(R2020) pdf free download

ASTM D6732-04(R2020) pdf free download.Standard Test Method for Determination of Copper in Jet Fuels by Graphite Furnace Atomic Absorption Spectrometry
1. Scope
1.1 This test method covers the determination of copper in jet fuels in the range of 5 µg ⁄kg to 100 µg ⁄kg using graphite furnace atomic absorption spectrometry. Copper contents above 100 µg ⁄kg may be determined by sample dilution with kerosine to bring the copper level into the aforementioned method range. When sample dilution is used, the precision statements do not apply. 1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appro- priate safety, health, and environmental practices and deter- mine the applicability ofregulatory limitations prior to use. 1.4 This international standard was developed in accor- dance with internationally recognized principles on standard- ization established in the Decision on Principles for the Development of International Standards, Guides and Recom- mendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
4. Summary of Test Method
4.1 The graphite furnace is aligned in the light path of the atomic absorption spectrometer equipped with background correction. An aliquot (typically 10 µL) of the sample is pipetted onto a platform in the furnace. The furnace is heated to low temperature to dry the sample completely without spattering. The furnace is then heated to a moderate tempera- ture to eliminate excess sample matrix. The furnace is further heated very rapidly to a temperature high enough to volatilize the analyte of interest. It is during this step that the amount of light absorbed by the copper atoms is measured by the spectrometer. 4.2 The light absorbed is measured over a specified period. The integrated absorbance A i produced by the copper in the samples is compared to a calibration curve constructed from measured A i values for organo-metallic standards.
5. Significance and Use
5.1 At high temperatures aviation turbine fuels can oxidize and produce insoluble deposits that are detrimental to aircraft propulsion systems. Very low copper concentrations (in excess of50 µg ⁄kg) can significantly accelerate this thermal instability of aviation turbine fuel. Naval shipboard aviation fuel delivery systems contain copper-nickel piping, which can increase copper levels in the fuel. This test method may be used for quality checks of copper levels in aviation fuel samples taken on shipboard, in refineries, and at fuel storage depots.
10. Calibration and Standardization
10.1 Preparation ofStandards: 10.1.1 Nominal 1 mg ⁄kg Intermediate Stock Standard— Accurately weigh a nominal 0.50 g of the 100 mg ⁄kg stock organo-metallic standard into a suitable container (capable of being sealed for mixing). (All masses are measured to the nearest 0.0001 g.) Suitable sample containers are described in Practice D4306. Add enough odorless kerosine to bring the total mass to a nominal 50.00 g. Seal the container and mix well. See 12.1.1 for calculation of actual concentration. 10.1.2 Working Standards of Nominally (20, 40, 60, 80, 100) µg ⁄kg—Accurately weigh a nominal (0.20, 0.40, 0.60, 0.80, 1.00) g of the nominal 1 mg ⁄kg intermediate stock standard into five suitable containers. (All masses are measured to the nearest 0.0001 g.) Add enough odorless kerosine to each container to bring the total mass to a nominal 10.00 g. Seal containers and mix well. This produces working standards of nominal (20, 40, 60, 80, 100) µg ⁄kg, respectively. See 12.1.2 for calculations of actual concentrations. 10.2 Calibration: 10.2.1 Prepare a standard calibration curve by using the odorless kerosine as a blank and each of the five working standards. The instrument measures the integrated absorbance A i of 10 µL of each working standard and blank. The interme- diate stock standard and working standards shall be prepared daily. 10.2.2 The calibration curve is constructed by plotting the corrected integrated absorbances (on y-axis) versus the con- centrations of copper in the working standards in µg/kg (on x-axis). See 12.2.1 for calculating corrected integrated absor- bance. Fig. 1 shows a typical calibration curve for atomic absorption spectroscopy. Many atomic absorption spectrom- eters have the capability of constructing the calibration curve internally or by way of computer software. Construct the best possible fit of the data with available means.