1、Designation: D6732 04 (Reapproved 2015)Standard Test Method forDetermination of Copper in Jet Fuels by Graphite FurnaceAtomic Absorption Spectrometry1This standard is issued under the fixed designation D6732; the number immediately following the designation indicates the year oforiginal adoption or,
2、 in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of copper injet fuels in the range of
3、5 g kg to 100 g kg using graphitefurnace atomic absorption spectrometry. Copper contentsabove 100 g kg may be determined by sample dilution withkerosine to bring the copper level into the aforementionedmethod range. When sample dilution is used, the precisionstatements do not apply.1.2 The values st
4、ated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.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 a
5、nd health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D4057 Practice for Manual Sampling of Petroleum andPetroleum ProductsD4306 Practice for Aviation Fuel Sample Containers forTests Affected by Trace ContaminationD6299
6、 Practice for Applying Statistical Quality Assuranceand Control Charting Techniques to Evaluate AnalyticalMeasurement System Performance3. 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
7、radiant powertransmitted by a material to the radiant power incident 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! 52log10T (1)3.2.2 integrated absorbance, Ai,nthe inte
8、grated area un-der the absorbance peak generated by the atomic absorptionspectrometer.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 pl
9、atform in the furnace. The furnace is heatedto low temperature to dry 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 i
10、nterest. It is during this step that the amount oflight absorbed by the 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
11、Aivalues for organo-metallic standards.5. Significance and Use5.1 At 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 i
12、nstabil-ity of aviation turbine fuel. Naval shipboard aviation fueldelivery systems contain copper-nickel piping, which canincrease copper levels in the fuel. This test method may be usedfor quality checks of copper levels in aviation fuel samplestaken on shipboard, in refineries, and at fuel storag
13、e depots.6. Interferences6.1 Interferences most commonly occur due to light that isabsorbed by species other than the atomic species of interest.1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products, Liquid Fuels, and Lubricantsand is the direct responsibility ofSubc
14、ommittee D02.03 on Elemental Analysis.Current edition approved April 1, 2015. Published May 2015. Originallyapproved in 2001. Last previous edition approved in 2010 as D6732 04 (2010).DOI: 10.1520/D6732-04R15.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Custom
15、er Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1Generally, this is due to undissociate
16、d molecular particles fromthe sample matrix. The char step in the furnace program is usedto eliminate as much of the matrix as possible before theatomization step. Spectrometers are equipped with backgroundcorrection capabilities to control further possibilities of erro-neous results due to molecula
17、r absorption.7. Apparatus7.1 Atomic Absorption SpectrometerAn atomic absorptionspectrometer with the capability of setting the wavelength at324.8 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
18、 be equipped with thefollowing:7.1.1 Copper 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 Lvovplatforms.7.2 Autosampler or Manual Pipettorca
19、pable of reproduc-ibly delivering 10 L 6 0.5 L aliquots of samples, standards,and blank 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 i
20、s intended thatall reagents conform to the specifications 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
21、 lessening the accuracy ofthe determination.8.2 Odorless or Low Odor Kerosine, filtered through silicagel.8.3 100 mg/kg Organo-metallic Standard for Copper, or amultielement standard containing copper at 100 mg kg.8.4 Silica Gel, 100 mesh to 200 mesh.8.5 Argon Gas, 99.999 %, (WarningArgon is a com-p
22、ressed gas under high pressure) for graphite furnace gas 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 d
23、escribed inSection 14. Use a stable QC concentrate, and 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 D4057.9.2 Samples shall be thoroughly mixed in their containersimmediately prior to testing
24、.10. Calibration and Standardization10.1 Preparation 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
25、.0001 g.) Suitable sample containers are described inPractice D4306. 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, 80,100) g kgAccurately
26、weigh a nominal (0.20, 0.40, 0.60,0.80, 1.00) g of the nominal 1 mg kg intermediate stockstandard into five suitable containers. (All masses are measuredto the nearest 0.0001 g.) Add enough odorless kerosine to eachcontainer to bring the total mass to a nominal 10.00 g. Sealcontainers and mix well.
27、This produces working standards ofnominal (20, 40, 60, 80, 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
28、 the integrated absorbanceAiof 10 L of each working standard and blank. The interme-diate stock standard and working standards shall be prepareddaily.10.2.2 The calibration curve is constructed by plotting thecorrected integrated absorbances (on y-axis) versus the con-centrations of copper in the wo
29、rking standards in g/kg (onx-axis). See 12.2.1 for 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
30、 software. Construct the bestpossible fit of the 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) gra
31、phite tube and Lvovplatform with the temperature 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
32、 graphite furnace,use odorless kerosine as the rinse 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.3Reagent Chemicals, American Chemical Society Specifications, Ameri
33、canChemical 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. (USPC
34、), Rockville,MD.D6732 04 (2015)211.5 Calibrate the instrument by pipetting a 10 L aliquot ofodorless kerosine as a blank and then 10 L of each of thestandards onto the platform in the graphite tube. Then pipette10 L of each sample into the furnace and carry each throughthe furnace program. Run each
35、blank, standard, and samplethrough the furnace program listed in Table 1. Compare theintegrated 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 1
36、0 L may be pipetted into the furnace.Volumes from 5 L to 40 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. Calculation
37、s12.1 Standard Concentrations:12.1.1 Calculate the copper concentration of the nominal1 mg kg intermediate stock standard as follows:ci5 csms/mt(2)where:ci= copper concentration of the intermediate stockstandard, mg/kg,cs= copper concentration of the certified (nominal100 mg kg) organo-metallic stan
38、dard, mg/kg,ms= measured mass of certified organo-metallic standard, g,andmt= measured mass of solution of organo-metallic standardand kerosine diluent, g.12.1.2 Calculate the copper concentrations of the workingstandards (nominal (20, 40, 60, 80, 100) g/kg) as follows:cw5 1000 cimi/mf(3)where:cw= c
39、opper concentration of a working standard, g/kg,ci= 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 stock stan-dard and kerosine diluent, g.12.2 Standard Calibra
40、tion Curve Correction and Fuel Cop-per Determination:12.2.1 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
41、 absorbance 5 Aw2 Ao(4)12.2.2 Plot the corrected integrated 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
42、 curve.13. Report13.1 Report the average value of the two runs, rounded tothe nearest 1 g kg.14. Quality Control (QC)14.1 Confirm the performance of the instrument or the testprocedure by analyzing a QC sample (see 8.6). Fig. 2 illustratesthe problem of trace level copper migration to sample contain
43、erwalls at ambient temperature which depletes trace organo-copper QC samples with time. Storage in a refrigeratedenvironment (5 C) minimizes the migration of trace levelcopper.14.1.1 When QC/Quality Assurance (QA) protocols arealready established in the testing facility, these may be usedwhen they c
44、onfirm 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.FIG. 1 Typical Calibration Curve of Copper Concentration versus Integrated Absorbance (Ai)D6732 04 (2015)315. Precision and Bias415.1 Precis
45、ionThe 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 condi
46、tions 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 X11!0.5(5)where:X = the average of two results in g/kg.15.1.2 ReproducibilityThe difference between two singleand independ
47、ent 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 X11!0.5(6)where:X = the average of two results in g/kg.15.2 BiasSince there is no accepted refer
48、ence material fordetermining bias for this test method, no statement on bias isbeing made.4Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D02-1512.TABLE 1 Typical Graphite Furnace Operational ParametersStep Dry 1ADry 2ACharBAtom
49、izeCClean CoolTemp, C 100 150 800 2300 2600 20Ramp, s 10 10 15 0 1 1Hold, s 15 20 35 5 5 10Gas 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 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 e
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