1、Designation: D 6732 04An American National StandardStandard Test Method forDetermination of Copper in Jet Fuels by Graphite FurnaceAtomic Absorption Spectrometry1This standard is issued under the fixed designation D 6732; the number immediately following the designation indicates the year oforiginal
2、 adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method covers the determination of copper injet fuels i
3、n the range of 5 to 100 g/kg using graphite furnaceatomic absorption spectrometry. Copper contents above 100g/kg may be determined by sample dilution with kerosine tobring the copper level into the aforementioned method range.When sample dilution is used, the precision statements do notapply.1.2 The
4、 values stated in SI units are to be regarded asstandard.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bili
5、ty of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 4057 Practice for Manual Sampling of Petroleum andPetroleum ProductsD 4306 Practice for Aviation Fuel Sample Containers forTests Affected by Trace ContaminationD 6299 Practice for Applying Statistical Quality Assu
6、ranceTechniques to Evaluate Analytical Measurement SystemPerformance3. Terminology3.1 Definitions:3.1.1 radiant power, P, nthe rate at which energy istransported in a beam of radiant energy.3.1.2 transmittance, T, nthe ratio of the radiant powertransmitted by a material to the radiant power incident
7、 upon it.3.2 Definitions of Terms Specific to This Standard:3.2.1 absorbance, A, nthe logarithm to the base 10 of theratio of the reciprocal of the transmittance, T:A 5 log101/T! 5 log10T (1)3.2.2 integrated absorbance, Ai, nthe integrated areaunder the absorbance peak generated by the atomic absorp
8、tionspectrometer.4. Summary of Test Method4.1 The graphite furnace is aligned in the light path of theatomic absorption spectrometer equipped with backgroundcorrection. An aliquot (typically 10 L) of the sample ispipetted onto a platform in the furnace. The furnace is heatedto low temperature to dry
9、 the sample completely withoutspattering. The furnace is then heated to a moderate tempera-ture to eliminate excess sample matrix. The furnace is furtherheated very rapidly to a temperature high enough to volatilizethe analyte of interest. It is during this step that the amount oflight absorbed by t
10、he copper atoms is measured by thespectrometer.4.2 The light absorbed is measured over a specified period.The integrated absorbance Aiproduced by the copper in thesamples is compared to a calibration curve constructed frommeasured Aivalues for organo-metallic standards.5. Significance and Use5.1 At
11、high temperatures aviation turbine fuels can oxidizeand produce insoluble deposits that are detrimental to aircraftpropulsion systems. Very low copper concentrations (in excessof 50 g/kg) can significantly accelerate this thermal instabilityof aviation turbine fuel. Naval shipboard aviation fuel del
12、iverysystems contain copper-nickel piping, which can increasecopper levels in the fuel. This test method may be used forquality checks of copper levels in aviation fuel samples takenon shipboard, in refineries, and at fuel storage depots.6. Interferences6.1 Interferences most commonly occur due to l
13、ight that isabsorbed by species other than the atomic species of interest.Generally, this is due to undissociated molecular particles fromthe sample matrix. The char step in the furnace program is usedto eliminate as much of the matrix as possible before the1This test method is under the jurisdictio
14、n of ASTM Committee D02 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.03 on Elemental Analysis.Current edition approved Nov. 1, 2004. Published November 2004. Originallyapproved in 2001. Last previous edition approved in 2002 as D 673202.2For referenced ASTM
15、 standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM
16、 International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.atomization step. Spectrometers are equipped with backgroundcorrection capabilities to control further possibilities of erro-neous results due to molecular absorption.7. Apparatus7.1 Atomic Absorption
17、 SpectrometerAn atomic absorp-tion spectrometer with the capability of setting the wavelengthat 324.8 nm, setting the slit width at typically 0.7 nm, and usingpeak area integration for the atomic and background readingsshall be used. The spectrometer shall be equipped with thefollowing:7.1.1 Copper
18、Hollow Cathode Lampas the elemental lightsource.7.1.2 Background Correction Capabilityto cover the324.8 nm wavelength range.7.1.3 Graphite Furnace Atomizerwhich uses pyrolyticallycoated graphite tubes with Lvov platforms.7.2 Autosampler or Manual Pipettorcapable of reproduc-ibly delivering 10 6 0.5
19、L aliquots of samples, standards, andblank to the graphite furnace.7.3 Analytical Balancecapable of weighing 100 g 60.0001 g.8. Reagents and Materials8.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents conform to the sp
20、ecifications of the Committee onAnalytical Reagents of the American Chemical Society wheresuch specifications are available.3Other grades may be used,provided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use without lessening the accuracy ofthe determination.8
21、.2 Odorless or Low Odor Kerosine, filtered through silicagel.8.3 100 mg/kg Organo-metallic Standard for Copper,oramultielement standard containing copper at 100 mg/kg.8.4 Silica Gel, 100 to 200 mesh.8.5 Argon Gas, 99.999%,(WarningArgon is a com-pressed gas under high pressure) for graphite furnace g
22、as flowsystem.8.6 Quality Control (QC) Samples, preferably are portionsof one or more kerosine materials that are stable and represen-tative of the samples of interest. These QC samples can be usedto check the validity of the testing process as described inSection 14. Use a stable QC concentrate, an
23、d dilute it on theday of the QC check to the trace level required.9. Sampling9.1 Samples shall be taken in accordance with proceduresdescribed in Practice D 4057.9.2 Samples shall be thoroughly mixed in their containersimmediately prior to testing.10. Calibration and Standardization10.1 Preparation
24、of Standards:10.1.1 Nominal 1 mg/kg Intermediate Stock StandardAccurately weigh a nominal 0.50 g of the 100 mg/kg stockorgano-metallic standard into a suitable container (capable ofbeing sealed for mixing). (All masses are measured to thenearest 0.0001 g.) Suitable sample containers are described in
25、Practice D 4306. Add enough odorless kerosine to bring thetotal mass to a nominal 50.00 g. Seal the container and mixwell. See 12.1.1 for calculation of actual concentration.10.1.2 Working Standards of Nominally 20, 40, 60, 80, and100 g/kgAccurately weigh a nominal 0.20, 0.40, 0.60, 0.80,and 1.00 g
26、of the nominal 1 mg/kg intermediate stock standardinto five suitable containers. (All masses are measured to thenearest 0.0001 g.) Add enough odorless kerosine to eachcontainer to bring the total mass to a nominal 10.00 g. Sealcontainers and mix well. This produces working standards ofnominal 20, 40
27、, 60, 80, and 100 g/kg, respectively. See 12.1.2for calculations of actual concentrations.10.2 Calibration:10.2.1 Prepare a standard calibration curve by using theodorless kerosine as a blank and each of the five workingstandards. The instrument measures the integrated absorbanceAiof 10 L of each wo
28、rking standard and blank. Theintermediate stock standard and working standards shall beprepared daily.10.2.2 The calibration curve is constructed by plotting thecorrected integrated absorbances (on y-axis) versus the con-centrations of copper in the working standards in g/kg (onx-axis). See 12.2.1 f
29、or calculating corrected integrated absor-bance. Fig. 1 shows a typical calibration curve for atomicabsorption spectroscopy. Many atomic absorption spectrom-eters have the capability of constructing the calibration curveinternally or by way of computer software. Construct the bestpossible fit of the
30、 data with available means.11. Procedure11.1 Set the spectrometer at a wavelength of 324.8 nm anda slit width of typically 0.7 nm. Align the hollow cathode lampand furnace assembly to obtain maximum transmittance.11.2 Condition new (or reinstalled) graphite tube and Lvovplatform with the temperature
31、 program provided by the spec-trometer manufacturer until the baseline shows no peaks.11.3 Calibrate the graphite furnace temperature controller at2300C according to the spectrometer manufacturers instruc-tions.11.4 When an autosampler is used with the graphite furnace,use odorless kerosine as the r
32、inse solution. Use only autosam-pler cups made of polyethylene, polypropylene, or TFE-fluorocarbon. Do not use polystyrene cups as these degrade andleak when used with organic solvents.11.5 Calibrate the instrument by pipetting a 10 L aliquot ofodorless kerosine as a blank and then 10 L of each of t
33、hestandards onto the platform in the graphite tube. Then pipette10 L of each sample into the furnace and carry each throughthe furnace program. Run each blank, standard, and samplethrough the furnace program listed in Table 1. Compare the3Reagent Chemicals, American Chemical Society Specifications,
34、AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc.
35、(USPC), Rockville,MD.D6732042integrated absorbance of each sample to the corrected calibra-tion curve generated from the blank and standards to determinethe copper concentration of each. Run each sample in dupli-cate.NOTE 1Aliquots other than 10 L may be pipetted into the furnace.Volumes from 5 to 4
36、0 L may be used, as long as the volume used isconsistent between blanks, standards, and samples. If this is done, drytemperatures, char temperature, ramp times, or hold times, or a combina-tion thereof, may need to be adjusted.12. Calculations12.1 Standard Concentrations:12.1.1 Calculate the copper
37、concentration of the nominal 1mg/kg intermediate stock standard as follows:ci5 csms/mt(2)where:ci= copper concentration of the intermediate stock stan-dard, mg/kg,cs= copper concentration of the certified (nominal 100mg/kg) organo-metallic standard, mg/kg,ms= measured mass of certified organo-metall
38、ic standard,g, andmt= measured mass of solution of organo-metallic stan-dard and kerosine diluent, g.12.1.2 Calculate the copper concentrations of the workingstandards (nominal 20, 40, 60, 80, and 100 g/kg) as follows:cw5 1000 cimi/mf(3)where:cw= copper concentration of a working standard, g/kg,ci=
39、copper concentration of the (nominal 1 mg/kg) inter-mediate stock standard, mg/kg,mi= measured mass of the intermediate stock standard, g,andmf= measured mass of solution of intermediate stockstandard and kerosine diluent, g.12.2 Standard Calibration Curve Correction and Fuel Cop-per Determination:1
40、2.2.1 Correct the standard calibration curve for any copperpresent in the kerosine blank and diluent by subtracting thekerosine blank integrated absorbance Aofrom each of theintegrated absorbances of the working standards, Aw:corrected integrated absorbance 5 Aw Ao(4)12.2.2 Plot the corrected integr
41、ated absorbance values forthe working standards versus their concentrations to providethe corrected standard calibration curve. The fuel sampleconcentration is determined from its integrated absorbancevalue and the corrected standard calibration curve.13. Report13.1 Report the average value of the t
42、wo runs, rounded tothe nearest 1 g/kg.FIG. 1 Typical Calibration Curve of Copper Concentration versus Integrated Absorbance (Ai)TABLE 1 Typical Graphite Furnace Operational ParametersStep Dry 1ADry 2ACharBAtomizeCClean CoolTemp, C 100 150 800 2300 2600 20Ramp, s 10 10 15 0 1 1Hold, s 15 20 35 5 5 10
43、Gas Flow, mL/min 300 300 300 0 300 300Read ONAThe dry temperatures, ramp times, and hold times shall be optimized so that the sample dries completely, without boiling and spattering.BThe ramp time for the char step may be lengthened if it appears that an excess amount of smoke from the sample matrix
44、 is generated very quickly as the furnace heatsfrom Dry 2 to char. Also, all of the smoke shall be evolved at least 5 s before the end of the char cycle. If smoke still evolves at the end of the char step, the hold timeshall be lengthened.CFor the spectrometer trace of absorbance versus atomization
45、hold time, the absorbance at the end of the atomization hold time should return to the initial baselineabsorbance. If this is not observed, increase the atomization hold time until this is attained.D673204314. Quality Control (QC)14.1 Confirm the performance of the instrument or the testprocedure by
46、 analyzing a QC sample (see 8.6). Fig. 2 illustratesthe problem of trace level copper migration to sample containerwalls at ambient temperature which depletes trace organo-copper QC samples with time. Storage in a refrigeratedenvironment (5C) minimizes the migration of trace levelcopper.14.1.1 When
47、QC/Quality Assurance (QA) protocols arealready established in the testing facility, these may be usedwhen they confirm the reliability of the test result.14.1.2 When there is no QC/QA protocol established in thetesting facility, Appendix X1 can be used as the QC/QAsystem.15. Precision and Bias415.1
48、PrecisionThe precision of this test method (illus-trated in Fig. 3) as determined by the statistical examination ofthe interlaboratory test results is as follows:15.1.1 RepeatabilityThe difference between successiveresults obtained by the same operator with the same apparatusunder constant operating
49、 conditions on identical test materialwould, in the long run, in the normal and correct operation ofthe test method, exceed the following values only one case intwenty:Repeatability 5 X 1 1!0.5(5)where:X = the average of two results in g/kg.15.1.2 ReproducibilityThe difference between two singleand independent results obtained by different operators work-ing in different laboratories on identical test material would inthe long run, exceed the following values only in one case intwenty:Reproducibility 5 4.5 X 1 1!0.5(6)where:X = the averag
