ASTM_E_1257_-_16.pdf

Designation:E125716Standard Guide forEvaluating Grinding Materials Used for Surface Preparationin Spectrochemical Analysis1This standard is issued under the fixed designation E1257;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 parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This guide covers recommendations for the evaluationof various grinding materials used to prepare the surfaces ofspecimens to be analyzed by spark atomic emission or X-rayfluorescence spectrometry.1.2 This standard does not purport to address all of thesafety problems,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-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2E135 Terminology Relating to Analytical Chemistry forMetals,Ores,and Related Materials3.Terminology3.1 For definitions of terms used in this guide,refer toTerminology E135.4.Significance and Use4.1 The grinding materials used for the preparation of thesurfaces of specimens prior to analysis by spark atomicemission or X-ray fluorescence spectrometry can contaminatethe surface and thus produce erroneous results.This guideprovides examples of the effects of these contaminations andrecommendations for evaluating grinding materials to elimi-nate or reduce these effects in spectrochemical analysis.4.2 The examples given in this guide are not the onlycontaminationsthatcanoccur.EspeciallyinX-rayspectrometry,all phases of the surface preparation should beexamined for potential contamination effects.4.3 Analytical significance of the contaminations observeddepends on the needs of the analyst for the particular applica-tion at a given composition.5.Evaluation of Grinding Materials by Direct Analysis5.1 Table 1 shows an example of semiquantitative spectro-metric analysis of various grinding belts from different pro-ducers.An examination of these analyses identifies the ele-ments most likely to contaminate the surface of the specimen.The more critical the element and the lower its mass fraction inthe specimen,the more important are low-level contaminantsin the belts.5.1.1 For example,using the 80-grit zircon belt in thedetermination of 0.5%chromium,the trace level of chromiumin the belt should cause no problem,but in the determination of0.02%aluminum,that belt probably will cause a problem.Inthe determination of calcium at g/g levels in steel,even lowlevels of calcium in the belts cause problems.5.2 Figs.1-6 show energy dispersive X-ray analyses ofvarious belts and the same logic applied in 5.1 can be used withthese analyses.Major components in the belts will causegreater problems in the determination of these elements.5.2.1 Direct analysis of the grinding material is particularlyuseful in such analyses as the determination of calcium in steel,where the analyte is generally too inhomogeneous to use themethods described in Section 6.This analysis requires avirtually calcium-free belt as in Fig.2.6.Evaluation of Grinding Materials by SpecimenExamination6.1 The effect of grinding materials depends on the analyti-cal method.In spark atomic emission analysis,the preburnwill,in general,volatilize the grinding material left on ordriven into the surface(see 6.3).For X-ray fluorescenceanalysis,the material left on the surface will be analyzed asbeing specimen material.6.2 Table 2 shows X-ray fluorescence analyses of a steelspecimen after surfacing with various grinding materials.Bytabulating the results in this manner,it becomes obvious whatproblems are occurring from the various grinding materials.Where there is no change from material to material,beyond theprecision of the method of analysis and the homogeneity of the1This 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 Feb.1,2016.Published March 2016.Originallyapproved in 1988.Last previous edition approved in 2008 as E1257 93(2008).DOI:10.1520/E1257-16.2For 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 ASTM website.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 material,no contamination has occurred.But where the com-position of a given element appears higher,there has beencontamination.Such is the case with the determination ofsilicon using the silicon carbide belt and the bonded diamondwheels;with the determination of zirconium using zircon belts;with the determination of aluminum using th