1、Designation: E1621 05E1621 13Standard Guide forX-Ray Emission Spectrometric AnalysisElemental Analysisby Wavelength Dispersive X-Ray FluorescenceSpectrometry1This standard is issued under the fixed designation E1621; the number immediately following the designation indicates the year oforiginal adop
2、tion or, 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 guide coversprovides guidelines for developing and describing analy
3、tical procedures using a wavelength-dispersiveX-ray spectrometer. wavelength dispersive X-ray spectrometer for elemental analysis of solid metals, ores, and related materials.Material forms discussed herein include solids, powders, and solid forms prepared by chemical and physical processes such asb
4、orate fusion and pressing of briquettes.1.2 Liquids are not discussed in this guide because they are much less frequently encountered in metals and mining laboratories.However, aqueous liquids can be processed by borate fusion to create solids specimens, and X-ray spectrometers can be equippedto han
5、dle liquids directly.1.3 Some provisions of this guide may be applicable to the use of an energy dispersive X-ray spectrometer.1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.5 This standard does not purport to address a
6、ll of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E135 Terminology Rela
7、ting to Analytical Chemistry for Metals, Ores, and Related MaterialsE305 Practice for Establishing and Controlling Atomic Emission Spectrochemical Analytical CurvesE1257 Guide for Evaluating Grinding Materials Used for Surface Preparation in Spectrochemical AnalysisE1329 Practice for Verification an
8、d Use of Control Charts in Spectrochemical AnalysisE1361 Guide for Correction of Interelement Effects in X-Ray Spectrometric AnalysisE1601 Practice for Conducting an Interlaboratory Study to Evaluate the Performance of an Analytical MethodE2857 Guide for Validating Analytical Methods3. Terminology3.
9、1 DefinitionsFor definitions of terms used in this guide, refer to Terminologies E135 and the terminology section of E1361.4. Summary of Guide4.1 Important aspects of test equipment for wavelength dispersive X-ray fluorescence spectrometry are discussed includingequipment components and accessories,
10、 reagents, and materials. Key aspects of the application of X-ray spectrometry to materialsanalysis are discussed including interferences and correction options, specimen preparation by a variety of procedures, andmaterials and accessories for presentation of specimens for measurement in spectromete
11、rs. Key elements of measurementprocedures, calibrations procedures, and result reporting are explained.1 This guide is under the jurisdiction of ASTM Committee E01 on Analytical Chemistry for Metals, Ores, and Related Materials and is the direct responsibility ofSubcommittee E01.20 on Fundamental Pr
12、actices.Current edition approved July 15, 2005Oct. 1, 2013. Published August 2005November 2013. Originally approved in 1994. Last previous edition approved in 19992005as E1621 94 (1999).E1621 05. DOI: 10.1520/E1621-05.10.1520/E1621-13.2 For referencedASTM standards, visit theASTM website, www.astm.o
13、rg, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what chang
14、es have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the offici
15、al document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14.2 The test In an X-ray spectrometric test method, the test specimen is prepared with a clean, uniform, flat surface. It may beprepared by grinding, polishing, or lathing a
16、metal surface or by fusing or briquetting a powder. This surface is irradiated with aprimary source of X rays. X-rays. The secondary X rays X-rays produced in the specimen are dispersed according to theirwavelength by means of crystals or synthetic multilayers. Their intensities count rates at selec
17、ted wavelengths, hereinafter calledintensities, are measured by suitable detectors at selected wavelengths and converted to counts by the detector. Concentrationsdetector systems. Amounts of the elements are determined from the measured intensities of analyte X-ray lines using analyticalcurves prepa
18、red with suitable reference materials. Either a fixed multi-channel simultaneous system or a sequential monochromatorsystem may be used to provide determinations of the elements.calibrants.4.3 Important aspects of background estimation are covered in an appendix to the guide.5. Significance and Use5
19、.1 X-ray fluorescence spectrometry can provide an accurate and precise determination of metallic and many non-metallicelements. elements in a wide variety of solid and liquid materials. This guide covers the information that should be included inan X-ray spectrometric analytical method and provides
20、direction to the analyst for determining the optimum conditions needed toachieve acceptable accuracy.5.2 The accuracy of an analysisa determination is a function of the calibration scheme, the sample preparation, and the samplehomogeneity. Close attention to all aspects of these areas is necessary t
21、o achieve the best acceptable results.5.3 All concepts discussed in this guide are explored in detail in a number of published texts and in the scientific literature.6. Interferences6.1 Line overlaps, either total or partial, may occur for some elements. Fundamental parameter equations require that
22、the netintensities be free from line overlap effects. Some empirical schemes incorporate line overlap corrections in their equations. Ifsufficient sensitivity exists, it may be possible to reduce or eliminate the overlap by choosing a higher level of collimation in thesecondary X-ray path from speci
23、men to dispersive element or detector. See Appendix X1 for optional approaches to the correctionof line overlap effects.6.1.1 Fundamental parameter (FP) equations require that the net intensities with line overlaps and background subtractionperformed before the FP calculations are carried out. Some
24、empirical schemes incorporate line overlap corrections in theirequations, and some software allows combinations of empirical and FP calculations chosen by element or other analyte.6.1.2 Additionally, line overlap interferences may occur from characteristic lines generated from the target material of
25、 the X-raytube and scattered from the specimen either inelastically (known as Compton scatter) or elastically (known as Rayleigh scatter).These may be reduced or eliminated by the use of primary beam filters, with a consequent loss of sensitivity.6.2 Interelement effects or matrix effects (sometimes
26、 called matrix effects, see Note 1) may exist be significant for someelements. An empirical way to compensate for these effects is to prepare a series of calibration curves that cover the designatedconcentration ranges to be analyzed. A large suite of carefully designed reference materials is necess
27、ary for this procedure.ap-proach. A series of samples in which all elements are relatively constant, except for the analyte, is necessary for each analyte thatcan be affected by other elements in the matrix. In addition, several series for the same analyte may be necessary, if the analyteis subject
28、to large effects from some other element in the matrix. The composition of the specimen being analyzed must matchclosely the composition of the reference materials Typically, more accurate results are obtained when the compositions of thecalibrants used to prepare the particular calibration curves.c
29、urves are similar to the compositions of materials being analyzed.6.2.1 Alternatively, mathematical methods may be used to compensate for interelement or matrix effects. Various mathematicalcorrection procedures are commonly utilized. See Guide E1361. Any of these that will achieve the necessary ana
30、lytical accuracyis acceptable.NOTE 1Interelement effects are not interferences in the spectrometric sense, but will contribute to errors in the analysis if not properly addressed.Interelement effects result from the absorption of X-rays to differing extents by the atoms in the specimen according to
31、the mass absorption coefficient.Caution must be used with empirical mathematical models to be sure that sufficient data isare provided to adequately compensate for these effects.Reference materials that were not used in the calibration should be analyzed as unknowns to verify the calibration.6.3 Add
32、itionally, interferences may occur from Compton lines or characteristic lines generated by the target material of theX-ray tube. These may be reduced or eliminated by the use of primary beam filters, but this will cause some loss of analyte lineintensity.6.3 Errors From Metallurgical StructureBecaus
33、e the analyte intensity is affected by the mass absorption of the sample andmathematical models assume a homogeneous sample, an error may result if the analyte exists in a separate phase, such as aninclusion. For example, in a steel that contains carbon and carbide formers such as titanium and niobi
34、um, the titanium may existin a titanium-niobium carbide that has a lower mass absorption coefficient than iron for the titanium K- line. The intensity fortitanium is higher in this sample than it would be if the titanium were titanium, niobium, carbon, and iron were always in solidsolution.E1621 132
35、7. Apparatus7.1 Specimen Preparation Equipment for Solid Metals:7.1.1 Surface Grinder or Sander With Abrasive Belts or Disks, or Lathe, capable of providing a flat, uniform surface on boththe reference materials and test specimens.7.1.1.1 Abrasive disks are preferred over belts because the platen on
36、 a belt sander tends to wear and produce a convex surfaceon the specimen. If belt sanders are used, care must be exercised to be sure the platen is maintained flat.7.1.1.2 The grinding material should be selected so that no significant contamination occurs for the elements of interest duringthe samp
37、le preparation. (Refer to Guide E1257.)7.1.1.3 Grinding belts or disks shall be changed at regular, specified intervals in order that changes in abrasive grit due torepeated use do not affect the repeatability of the roughness of the sample finish. because abrasives lose their ability to removemater
38、ial efficiently and without inducing contamination. This is particularly important in alloys whichthat exhibit smearing of asofter component overacross the sample matrix.surface.7.1.1.4 Provision of flowing water across the surface of a grinding wheel cools the specimen and removes debris. Chemicalc
39、oolants, such as those used in machine shops, should not be used, except for special purposes.7.1.1.5 The use of a lathe, or similar type of machine, is recommended for soft metals or metals that have components that cansmear when surfaced with an abrasive disk. The feed on the cutting tools should
40、be constant, automatically controlled, to give aconsistent finish.7.2 Specimen Preparation Equipment for Powders:7.2.1 Jaw Crusher or Steel Mortar and Pestle, for initial crushing of lumps.larger chunks of material.7.2.2 Plate Grinder or Pulverizer, with one static and one rotating disk for further
41、grinding.grinding or crushing.7.2.3 Rotary Disk Mill or Shatterbox, Swing Mill, with hardened grinding containers and timer control for final grinding.7.2.4 Briquetting Press, providing pressures of up to 550 MPa (80 000 psi). The press shall be equipped with a mold assemblythat provides a briquette
42、 that is compatible with the X-ray specimen holder.7.2.5 Fusion Equipment, with a timer, capable of heating the sample and flux to at least 1000C 975 C and homogenizing themelt.7.2.6 Fusion Crucibles, compatible with the flux and sample type:7.2.6.1 Vitreous Carbon, 2020-mL to 30-mL capacity, with f
43、lat bottom 30 mm to 35 mm in diameter.7.2.6.2 95 % Platinum/5 % Gold Alloy, with 3030-mL to 35-mL capacity.7.2.7 Platinum/Gold Casting Mold (95 %/5 %), 30 to 35- mL capacity, with flat bottom 30 to 40 mm in diameter.having a flat,optical-polished bottom and sufficient capacity to hold the quantity o
44、f glass needed to make a cast bead of roughly uniformthickness across the entire diameter, typically 30 mm to 40 mm.7.2.8 Polishing Wheel, suitable for polishing the fused button to obtain a flat uniform surface for irradiation. For machines thatcast a bead in a polished dish, this step may not be n
45、ecessary.7.3 Excitation Source:7.3.1 X-Ray Tubes, with targets of various high-purity elements that are capable of continuous operation at potentials andcurrents that will excite the elements to be determined.7.3.2 X-Ray Tube Power Supply, providing a stable voltage of sufficient energy to produce s
46、econdary radiation from thespecimen for the elements specified.7.3.1.1 The instrument may be equipped with an external line voltage regulator or a transient voltage suppressor.7.3.3 X-Ray Tubes, with targets of various high-purity elements, that are capable of continuous operation at potentials andc
47、urrents that will excite the elements to be determined. The instrument may be equipped with an external line voltage regulatoror a transient voltage suppressor.7.4 Spectrometer, designed for X-ray emission analysis, and equipped with specimen holders and a specimen chamber. Thechamber may contain a
48、specimen spinner, and must be equipped for vacuum or helium-flushed operation for the determination ofelements of atomic number 20 (calcium) or lower.7.4.1 Analyzing Crystals, flat or curved crystals with optimized capability for the diffraction of the wavelengths of interest. Thismay also include s
49、ynthetic multi-layers for low atomic number elements.7.4.2 Collimator, for limiting the characteristic X rays X-rays to a parallel bundle when flat crystals are used in the instrument.For curved crystal optics, a collimator is not necessary, but is replaced by entrance and exit slits.7.4.3 Masks, for restricting the incident beam pattern on the specimen.7.4.4 Detectorssealed or gas-flow proportional counters and scintillation counters are most commonly used.7.4.5 Vacuum System, for the determination of elements whose radiation is absorbed by air. The system shall consist
