ASTM_E_169_-_04_2014.pdf

Designation:E16904(Reapproved 2014)Standard Practices forGeneral Techniques of Ultraviolet-Visible QuantitativeAnalysis1This standard is issued under the fixed designation E169;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 These practices are intended to provide general infor-mation on the techniques most often used in ultraviolet andvisible quantitative analysis.The purpose is to render unnec-essary the repetition of these descriptions of techniques inindividual methods for quantitative analysis.1.2 The values stated 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 health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2E131 Terminology Relating to Molecular SpectroscopyE168 Practices for General Techniques of Infrared Quanti-tative Analysis(Withdrawn 2015)3E275 Practice for Describing and Measuring Performance ofUltraviolet and Visible SpectrophotometersE925 Practice for Monitoring the Calibration of Ultraviolet-Visible Spectrophotometers whose Spectral Bandwidthdoes not Exceed 2 nmE958 Practice for Estimation of the Spectral Bandwidth ofUltraviolet-Visible Spectrophotometers3.Summary of Practice3.1 Quantitative ultraviolet and visible analyses are basedupon the absorption law,known as Beers law.The units of thislaw are defined in Terminology E131.Beers law(Note 1)holds at a single wavelength and when applied to a singlecomponent sample it may be expressed in the following form(see Section 10):A 5 abc(1)When applied to a mixture of n non-interacting components,it may be expressed as follows:A 5 a1bc11a2bc21.1anbcn(2)NOTE1Detailed discussion of the origin and validity of Beers lawmay be found in the books and articles listed in the bibliography at the endof these practices.3.2 This practice describes the application of Beers law intypical spectrophotometric analytical applications.It also de-scribes operating parameters that must be considered whenusing these techniques.4.Significance and Use4.1 These practices are a source of general information onthe techniques of ultraviolet and visible quantitative analyses.They provide the user with background information that shouldhelp ensure the reliability of spectrophotometric measure-ments.4.2 These practices are not intended as a substitute for athorough understanding of any particular analytical method.Itis the responsibility of the users to familiarize themselves withthe critical details of a method and the proper operation of theavailable instrumentation.5.Sample Preparation5.1 Accurately weigh the specified amount of the sample(solid or liquid).Dissolve in the appropriate solvent and diluteto the specified volume in volumetric glassware of the requiredaccuracy,ensuring that all appropriate temperature rangetolerances are maintained.If needed,a dilution should be madewith a calibrated pipet and volumetric flask,using adequatevolumes for accuracy.With the availability of moderin widerange electronic balances,(capable of reading kg quantities tofour or five decimal places),gravimetric dilution should beconsidered as a more accurate alternative to volumetric,ifavailable.Fill the absorption cell with the solution,and fill the1These practices are under the jurisdiction of ASTM Committee E13 onMolecular Spectroscopy and Separation Science and are the direct responsibility ofSubcommittee E13.01 on Ultra-Violet,Visible,and Luminescence Spectroscopy.Current edition approved Aug.1,2014.Published August 2014.Originallyapproved in 1960.Last previous edition approved in 2009 as E169 04(2009).DOI:10.1520/E0169-04R14.2For 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.3The last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 comparison or blank cell with the pure solvent,at least 2 to 3(if sufficient sample or solvent is available),before measuring.6.Cell and Base-Line Checks6.1 Clean and match the cells.Suggested cleaning proce-dures are presented in Practice E275.6.2 Establish the base line of a recording double-beamspectrophotometer by scanning over the appropriate wave-length region with pure solvent in both cells.Determineapparent absorbance of the sample cell at each wavelength ofinterest