ASTM E1621-2005 Standard Guide for X-Ray Emission Spectrometric Analysis《X射线发散光谱分析标准指南》.pdf

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1、Designation: E 1621 05Standard Guide forX-Ray Emission Spectrometric Analysis1This standard is issued under the fixed designation E 1621; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parent

2、heses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide covers guidelines for developing and de-scribing analytical procedures using a wavelength-dispersiveX-ray spectrometer.1.2 The values state

3、d 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 and

4、health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E 135 Terminology Relating to Analytical Chemistry forMetals, Ores, and Related MaterialsE 305 Practice for Establishing and Controlling Spectro-chemical Analytical Cur

5、ves3E 1257 Guide for Evaluating Grinding Materials Used forSurface Preparation in Spectrochemical AnalysisE 1329 Practice for Verification and the Use of ControlCharts in Spectrochemical AnalysisE 1361 Guide for Correction of Interelement Effects inX-ray Spectrometric AnalysisE 1601 Practice for Con

6、ducting an Interlaboratory Study toEvaluate the Performance of an Analytical Method3. Terminology3.1 DefinitionsFor definitions of terms used in this guide,refer to Terminologies E 135 and the terminology section ofE 1361.4. Summary of Guide4.1 The test specimen is prepared with a clean, uniform, fl

7、atsurface. It may be prepared by grinding, polishing, or lathing ametal surface or by fusing or briquetting a powder.This surfaceis irradiated with a primary source of X rays. The secondary Xrays produced in the specimen are dispersed according to theirwavelength by means of crystals or synthetic mu

8、ltilayers.Theirintensities are measured by suitable detectors at selectedwavelengths and converted to counts by the detector. Concen-trations of the elements are determined from the measuredintensities of analyte X-ray lines using analytical curvesprepared with suitable reference materials. Either a

9、 fixedmulti-channel simultaneous system or a sequential monochro-mator system may be used to provide determinations of theelements.5. Significance and Use5.1 X-ray fluorescence spectrometry can provide an accu-rate and precise determination of metallic and many non-metallic elements. This guide cove

10、rs the information thatshould be included in an X-ray spectrometric analytical methodand provides direction to the analyst for determining theoptimum conditions needed to achieve acceptable accuracy.5.2 The accuracy of an analysis is a function of thecalibration scheme, the sample preparation, and t

11、he samplehomogeneity. Close attention to all aspects of these areas isnecessary to achieve the best results.6. Interferences6.1 Line overlaps, either total or partial, may occur for someelements. Fundamental parameter equations require that the netintensities be free from line overlap effects. Some

12、empiricalschemes incorporate line overlap corrections in their equations.See Appendix X1 for correction of line overlap effects.6.2 Interelement effects or matrix effects may exist for someelements. An empirical way to compensate for these effects isto prepare a series of calibration curves that cov

13、er the desig-nated concentration ranges to be analyzed. A large suite ofcarefully designed reference materials is necessary for thisprocedure. A series of samples in which all elements arerelatively constant, except for the analyte, is necessary for eachanalyte that can be affected by other elements

14、 in the matrix. In1This guide is under the jurisdiction of ASTM Committee E01 on AnalyticalChemistry for Metals, Ores, and Related Materials and is the direct responsibility ofSubcommittee E01.20 on Fundamental Practices.Current edition approved July 15, 2005. Published August 2005. Originallyapprov

15、ed in 1994. Last previous edition approved in 1999 as E 1621 94 (1999).2For referenced ASTM 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 AST

16、M website.3Withdrawn.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.addition, several series for the same analyte may be necessary,if the analyte is subject to large effects from some otherelement in the matrix. The composition of t

17、he specimen beinganalyzed must match closely the composition of the referencematerials used to prepare the particular calibration curves.6.2.1 Alternatively, mathematical methods may be used tocompensate for interelement or matrix effects. Various math-ematical correction procedures are commonly uti

18、lized. SeeGuide E 1361. Any of these that will achieve the necessaryanalytical accuracy is acceptable.NOTE 1Interelement effects are not interferences in the spectrometricsense, but will contribute to errors in the analysis if not properlyaddressed. Caution must be used with empirical mathematical m

19、odels tobe sure that sufficient data is provided to adequately compensate for theseeffects. Reference materials that were not used in the calibration should beanalyzed as unknowns to verify the calibration.6.3 Additionally, interferences may occur from Comptonlines or characteristic lines generated

20、by the target material ofthe X-ray tube. These may be reduced or eliminated by the useof primary beam filters, but this will cause some loss of analyteline intensity.6.4 Errors From Metallurgical StructureBecause the ana-lyte intensity is affected by the mass absorption of the sampleand mathematical

21、 models assume a homogeneous sample, anerror may result if the analyte exists in a separate phase, suchas an inclusion. For example, in a steel that contains carbon andcarbide formers such as titanium and niobium, the titaniummay exist in a titanium-niobium carbide that has a lower massabsorption co

22、efficient than iron for the titanium K-a line. Theintensity for titanium is higher in this sample than it would beif the titanium were in solid solution.7. Apparatus7.1 Specimen Preparation Equipment for Metals:7.1.1 Surface Grinder or Sander With Abrasive Belts orDisks, or Lathe, capable of providi

23、ng a flat, uniform surface onboth the reference materials and test specimens.7.1.1.1 Abrasive disks are preferred over belts because theplaten on a belt sander tends to wear and produce a convexsurface on the specimen. If belt sanders are used, care must beexercised to be sure the platen is maintain

24、ed flat.7.1.1.2 The grinding material should be selected so that nosignificant contamination occurs for the elements of interestduring the sample preparation. (Refer to Guide E 1257.)7.1.1.3 Grinding belts or disks shall be changed at regular,specified intervals in order that changes in abrasive gri

25、t due torepeated use do not affect the repeatability of the roughness ofthe sample finish. This is particularly important in alloys whichexhibit smearing of a softer component over the sample matrix.7.2 Specimen Preparation Equipment for Powders:7.2.1 Jaw Crusher or Steel Mortar and Pestle, for init

26、ialcrushing of lumps.7.2.2 Plate Grinder or Pulverizer, with one static and onerotating disk for further grinding.7.2.3 Rotary Disk Mill or Shatterbox, with hardened grind-ing containers and timer control for final grinding.7.2.4 Briquetting Press, providing pressures of up to 550MPa (80 000 psi). T

27、he press shall be equipped with a moldassembly that provides a briquette that is compatible with theX-ray specimen holder.7.2.5 Fusion Equipment, with a timer, capable of heating thesample and flux to at least 1000C and homogenizing the melt.7.2.6 Fusion Crucibles, compatible with the flux and sampl

28、etype:7.2.6.1 Vitreous Carbon, 20 to 30-mL capacity, with flatbottom 30 to 35 mm in diameter.7.2.6.2 95 % Platinum/5 % Gold Alloy, with 30 to 35-mLcapacity.7.2.7 Platinum/Gold Casting Mold (95 %/5 %),30to35-mL capacity, with flat bottom 30 to 40 mm in diameter.7.2.8 Polishing Wheel, suitable for pol

29、ishing the fusedbutton to obtain a flat uniform surface for irradiation.7.3 Excitation Source:7.3.1 X-Ray Tube Power Supply, providing a stable voltageof sufficient energy to produce secondary radiation from thespecimen for the elements specified.7.3.1.1 The instrument may be equipped with an extern

30、alline voltage regulator or a transient voltage suppressor.7.3.2 X-Ray Tubes, with targets of various high-purityelements, that are capable of continuous operation at potentialsand currents that will excite the elements to be determined.7.4 Spectrometer, designed for X-ray emission analysis, andequi

31、pped with specimen holders and a specimen chamber. Thechamber may contain a specimen spinner, and must beequipped for vacuum or helium-flushed operation for thedetermination of elements of atomic number 20 (calcium) orlower.7.4.1 Analyzing Crystals, flat or curved crystals with opti-mized capability

32、 for the diffraction of the wavelengths ofinterest. This may also include synthetic multi-layers for lowatomic number elements.7.4.2 Collimator, for limiting the characteristic X rays to aparallel bundle when flat crystals are used in the instrument.For curved crystal optics, a collimator is not nec

33、essary, but isreplaced by entrance and exit slits.7.4.3 Masks, for restricting the incident beam pattern on thespecimen.7.4.4 Detectorssealed or gas-flow proportional countersand scintillation counters are most commonly used.7.4.5 Vacuum System, for the determination of elementswhose radiation is ab

34、sorbed by air. The system shall consist ofa vacuum pump, gage, and electrical controls to provideautomatic pumpdown of the optical path, and maintain acontrolled pressure, usually 13 Pa (100 m Hg) or less,controlled to 6 3Pa(6 20 m Hg).7.5 Measuring System, consisting of electronic circuits ca-pable

35、 of amplifying and shaping pulses received from thedetectors. The system shall be equipped with an appropriatedata output device.7.5.1 Pulse Height Selectors, used to reduce pulses fromhigher order X-ray lines and background.8. Reagents and Materials8.1 Purity of ReagentsAll reagents used in this te

36、stmethod shall conform to the “Reagent Grade” specifications ofE1621052theAmerican Chemical Society4. Other chemicals may be usedprovided it is first ascertained that they are of sufficient purityto permit their use without adversely affecting the expectedperformance of the analysis.8.2 BindersSodiu

37、m tetraborate (Na2B4O7), polyethyleneglycol, fibrous cellulose, or spectrographic grade graphite(200 mesh, briquetting type).8.3 Detector Gas (P-10), consisting of a mixture of 90 %argon and 10 % methane, for use with gas-flow proportionalcounters.8.4 FluxesSodium tetraborate (Na2B4O7), fused anddri

38、ed; lithium tetraborate (Li2B4O7), lithium metaborate(LiBO2) or lithium tetraborate and boric anhydrite (B2O3)mixture (4 g + 6 g).9. Reference Materials9.1 Certified Reference Materials are available from theNational Institute of Standards and Technology5and othercertification agencies.9.2 Reference

39、 Materials with compositions similar to thatof the test specimen and containing varying amounts of theelements to be determined may be used provided they havebeen previously analyzed in accordance with ASTM testmethods. These reference materials shall be homogeneous, andfree of voids or porosity.9.3

40、 The reference materials should cover the concentrationranges of the elements being determined. An appropriatenumber of reference materials shall be used for each element,depending on the mathematical models being used.10. Hazards10.1 Occupational Health and Safety Standards for ionizingradiation6sh

41、all be observed at all X-ray emission spectrometerinstallations. Operating and maintenance personnel shall fol-low the guidelines of safe operating procedures given incurrent handbooks and publications from the National Instituteof Standards and Technology,7,8the U.S. Government PrintingOffice,9or s

42、imilar handbooks on radiation safety, as well asspecific state regulations.10.2 Monitoring Devices, either film badges or dosimeters10may be worn by all operating and maintenance personnel.Safety practices shall conform to applicable local, state, andfederal regulations. To meet local, state, and fe

43、deral radiationstandards, periodic radiation surveys of the equipment for leaksand excessive scattered radiation shall be made by a qualifiedperson using an ionization-chamber detector.11The personalfilm badge survey record, the radiation survey record, and anequipment maintenance record shall be av

44、ailable upon request.10.3 Special precautions for operators and maintenancepersonnel shall be posted at the equipment site.10.4 Radiation Caution Signs shall be posted near theX-ray equipment and at all entrances to the radiation area.10.5 Fail-Safe “X-Ray On” Warning Lights shall be usedon the equi

45、pment.10.6 Routine checks of safety interlocks shall be docu-mented.11. Preparation of Reference Materials and TestSpecimens11.1 Throughout the procedure, treat reference materialsand test specimens exactly the same way. Consistency inpreparation of reference materials and specimens is essential toe

46、nsure reproducible results. After the preparation procedure isestablished, it must be followed exactly. Variations in tech-nique, such as grinding time, abrasive grit size or material,particle size, binder material, sample-binder ratio, briquettingpressure, or holding times, can cause unreliable res

47、ults.11.2 Metal SamplesPrepare the reference materials andtest specimens to provide a clean, flat uniform surface to beexposed to the X-ray beam. For abrasive sanding, select a gritsize and use it exclusively for all reference materials and testspecimens. See 7.1.1.2 and 7.1.1.3. Refinish the surfac

48、e of thereference materials and test specimens as needed to eliminateoxidation before measurement.11.3 Nonmetallic SamplesDry the material. Then reduceit both in particle size and quantity, by crushing and pulveriz-ing integrated with splitting or riffling, ending with approxi-mately 100 g of materi

49、al that has a particle size of less than 200mesh (74 m).11.3.1 BriquettesMix the sample with a suitable binder.(See 8.2.) Ratios of 10 g + 1 g to 20 g + 1 g of sample + binderare common. Grind and blend the sample and binder for a fixedtime (generally 2 to 4 min in a disk mill). Press the sample-binder mixture into a briquette using a fixed pressure of 140 to550 MPa (20 000 to 80 000 psi) and maintaining the pressurefor a minimum of 10 s before releasing the briquette. Holdingthe pressure at 140 MPa (20 000 psi) for about 10 s beforeincreasing it to maximum allows air t