ASTM_E_2055_-_99.pdf

Designation:E 2055 99Standard Practice forReferencing Test Methods for Chemical Analysis of Metalsand Related Materials1This standard is issued under the fixed designation E 2055;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(e)indicates an editorial change since the last revision or reapproval.1.Scope1.1 This practice outlines procedures for relating resultsfrom test methods to a practical basis,that is,analyticaltraceability.It explores strategies to ensure the accuracy of atest method and to document reliability of results obtained inindividual laboratories.2.Referenced Documents2.1 ASTM Standards:E 882 Guide for Accountability and Quality Control in theChemical Analysis Laboratory2E 1601 Practice for Conducting an Interlaboratory Study toEvaluate the Performance of an Analytical Method2E 2054 Practice for Performance-Based Description of In-struments in Chemical Analysis Methods23.Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 analytical traceability,na process relating a mea-surement or result to a defined chemical basis.3.1.2 pure substance,nof known purity such that theuncertainty of the sum of impurities has no observable effect onthe accuracy of calibration.4.Significance and Use4.1 Practice E 1601 covers error to be expected in resultsobtained from two or more laboratories.Practice E 2054 coversvariability expected in results obtained within an individuallaboratory.This practice deals with the accuracy of a testmethod as used within an individual laboratory.4.2 The information in this practice is to be used to identifysuitable reference materials.A standard test method requiresreference materials for calibrating instruments or for standard-izing reagents.In writing an analytical test method,referencematerials are described to emphasize required characteristics,and identify at least one source for uncommon materials.Analysts shall use reference materials specified in test methodsin accordance with this practice.4.3 Procedures from this practice are to be used to verifythat the test method produces acceptable results.5.Types of Reference Materials5.1 Analytical TechniquesChoice of optimum materialsfor calibration or standardization depends primarily on thecharacteristics of the analytical system.5.1.1 Reference materials of three classes are generallyrecognized.In nominal order of decreasing quality they are:5.1.1.1 Certified reference materials,CRMs,having thecontent of one or more analytes certified by a recognizedstandardization agency or group,5.1.1.2 Reference materials,RMs,having the content of oneor more analytes accepted for use in calibrating instruments,and5.1.1.3 Analyzed materials,AMs,having the content of oneor more analytes determined by a test method referenced to apure substance.5.1.2 This hierarchy often reflects the resources employedin preparing the materials and in establishing their reportedvalues.5.1.3 For test methods in which samples are presented formeasurement as solutions,refer to 5.2.For solid-samplemethods,refer to 5.3.5.2 Solution-Based Test MethodsPrepare solutions forcalibration of test methods from the analyte,if available as astable material having a purity of at least 99.9%.For example,metallic zinc of nominal 99.99%purity is a preferred referencematerial for a zinc test method.Metals unaffected by atmo-spheric oxygen normally require no special preparation,butmust be protected from corrosive vapors.For other analytes,use stable compounds of known stoichiometry.For example,reagent grade NaCl is an acceptable reference material fordetermining sodium or chloride.Reference compounds nor-mally require preparation before use;dry them in air at 100 Cfor 1 h,cool in a desiccator,and maintain in a water-vapor-freeenvironment until weighed.Results of test methods of chemi-cal analysis shall be traceable to pure substances that arepurchased or prepared in the laboratory.Except for isotopicallyenriched analytes,calibration materials are expected to be,orbe composed of,elements having commonly occurring isotopicratios.5.3 Solids-Based Test MethodsIf possible,prepare solidreference materials for calibration in the same manner andunder the same conditions as specified for test specimens.Note1This practice is under the jurisdiction of Committee E-1 on AnalyticalChemistry for Metals,Ores and Related Materials and is the direct responsibility ofSubcommittee E01.22 on Statistics and Quality Control.Current edition approved Dec.10,1999.Published February 2000.2Annual Book of ASTM Standards,Vol 03.06.1Copyright ASTM,100 Barr Harbor Drive,West Conshohocken,PA 19428-2959,United States.the uncertainty in reported results and determine that CRMsand RMs match the compositions of samples specified in thetest method.Select those that best provide required analytelevels.In most cases,available mate