ASTM_E_1172_-_16.pdf

Designation:E117216Standard Practice forDescribing and Specifying a Wavelength Dispersive X-RaySpectrometer1This standard is issued under the fixed designation E1172;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 practice covers the components of a wavelengthdispersive X-ray spectrometer that are basic to its operationand to the quality of its performance.It is not the intent of thispractice to specify component tolerances or performancecriteria,as these are unique for each instrument.However,thepractice does attempt to identify which tolerances are criticaland thus which should be specified.1.2 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 health practices and to determine theapplicability of regulatory limitations prior to use.Specificsafety hazard statements are given in 5.3.1.2 and 5.3.2.4,and inSection 7.2.Referenced Documents2.1 ASTM Standards:2E135 Terminology Relating to Analytical Chemistry forMetals,Ores,and Related MaterialsE2857 Guide for Validating Analytical Methods3.Terminology3.1 For terminology relating to X-ray spectrometry,refer toTerminology E135.4.Significance and Use4.1 This practice describes the essential components of awavelength dispersive X-ray spectrometer.This description ispresented so that the user or potential user may gain a cursoryunderstanding of the structure of an X-ray spectrometer sys-tem.It also provides a means for comparing and evaluatingdifferent systems as well as understanding the capabilities andlimitations of each instrument.4.2 It is understood that a laboratory may implement thispractice or an X-ray fluorescence method in partnership with amanufacturer of the analytical instrumentation.If a laboratorychooses to consult with an instrument manufacturer,then thefollowing should be considered.The laboratory should have anidea of the alloy matrices to be analyzed,elements and massfraction ranges to be determined,and the expected perfor-mance requirements for each of these elements.The laboratoryshould inform the instrument manufacturer of these require-ments so they may develop an analytical method which meetsthe laboratorys expectations.Typically,instrument manufac-turers customize the instrument configuration to satisfy theend-users requirements for elemental coverage,elementalprecision,and detection limits.Instrument manufacturer devel-oped analytical methods may include specific parameters forsample excitation,wavelengths,inter-element interferencecorrections,calibrationandregression,equipmentconfiguration/installation,and sample preparation require-ments.Laboratories should have a basic understanding of theparameters derived by the manufacturer.5.Description of Equipment5.1 Types of SpectrometersX-ray spectrometers can beclassified as sequential,simultaneous,or hybrid(see 5.1.3).5.1.1 Sequential SpectrometersThe sequential spectrom-eter disperses and detects secondary X-rays by means of anadjustable monochromator called a goniometer.SecondaryX-rays emitted from the specimen pass through a mask thatdefines the viewed region of the specimen.Next,they enter acollimator,typically a Soller slit,and nonparallel X-rays areeliminated by being absorbed by the blades of the collimator.The parallel beam of X-rays strikes an analyzing crystal thatdisperses the X-rays according to their wavelengths.Thedispersed X-rays are measured by suitable detectors,whichmay have an attached collimator in front of the entrancewindow.Adjustment of the goniometer changes the anglebetween the specimen,crystal,and detector,permitting themeasurement of different wavelengths,and therefore,of dif-ferent elements.1This practice 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 June 1,2016.Published June 2016.Originallyapproved in 1987.Last previous edition approved in 2011 as E1172 87(2011).DOI:10.1520/E1172-16.2For 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 5.1.2 Simultaneous SpectrometersSimultaneous spec-trometers use an individual monochromator to measure aselected wavelength of X-rays for each element.A typicalmonochromator consists of an entrance slit,a curved(focus-ing)analyzing crystal,an exit slit,and a suitable detector.Secondary X-ray