ASTM_E_2227_-_13.pdf

Designation:E222713Standard Guide forForensic Examination of Non-Reactive Dyes in TextileFibers by Thin-Layer Chromatography1This standard is issued under the fixed designation E2227;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 Metameric coloration of fibers can be detected usingUV/visible spectrophotometry.If spectrophotometry is re-stricted to the visible spectral range only,differences in dyecomponents may remain undetected.One method of detectingadditional components is to use thin-layer chromatography(TLC).TLC is an inexpensive,simple,well-documented tech-nique that,under certain conditions,can be used to comple-ment the use of visible spectroscopy in comparisons of fibercolorants.The principle of the method is that the dye compo-nents are separated by their differential migration caused by amobile phase flowing through a porous,adsorptive medium.1.2 This standard does not replace knowledge,skill,ability,experience,education,or training and should be used inconjunction with professional judgment.1.3 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.4 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:2E1459 Guide for Physical Evidence Labeling and RelatedDocumentationE1492 Practice for Receiving,Documenting,Storing,andRetrieving Evidence in a Forensic Science LaboratoryE2224 Guide for Forensic Analysis of Fibers by InfraredSpectroscopyE2228 Guide for Microscopical Examination of Textile Fi-bers3.Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 activationthe heating of the adsorbent layer on aplate to dry out the moisture and maximize its adsorptivepower.3.1.2 adsorbentthe stationary phase for adsorption TLC.3.1.3 adsorptionthe attraction between the surface atomsof a solid and an external molecule by intermolecular forces.3.1.4 chambera glass chamber in which TLC develop-ment is carried out.3.1.5 chromatographya method of analysis in which sub-stances are separated by their differential migration in a mobilephase flowing through or past a stationary phase.3.1.6 developmentthe movement of the mobile phasethrough the adsorbent layer to form a chromatogram.3.1.7 dye extractionthe removal of the dye from a fiber byincubating it in an appropriate solvent.3.1.8 eluentthe solvent mixture that acts as the mobilephase in TLC.3.1.9 metameric pairtwo colors that appear the sameunder one illumination,but different under other illumination.3.1.10 mobile phasethe moving liquid phase used fordevelopment.3.1.11 normal-phase chromatogramadsorption in whichthe stationary phase is polar in relation to the mobile phase.3.1.12 originthe location of the applied sample or thestarting point for the chromatographic development of theapplied sample.3.1.13 resolutionthe ability to visually separate two spots.3.1.14 retardation factor(Rf)the ratio of the distancetraveled by the solute spots center divided by the distancetraveled by the solvent front,both measured from the origin.3.1.15 saturation chamberequilibration with mobilephase solvent vapor prior to chromatography.3.1.16 solutein TLC,a mixture of components to beseparated.1This guide is under the jurisdiction of ASTM Committee E30 on ForensicSciences and is the direct responsibility of Subcommittee E30.01 on Criminalistics.Current edition approved Sept.1,2013.Published September 2013.Originallyapproved in 2002.Last previous edition approved in 2008 as E2227 02(2008).DOI:10.1520/E2227-13.2For 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 3.1.17 solvent frontthe final point reached by the mobilephase as it flows up or across the TLC plate during develop-ment of the chromatogram.3.1.18 spota round zone of sample application at theorigin;or in a chromatogram,a round zone caused by migra-tion of a separated component of the solute where the sharp-ness of the spot relates to the efficiency of the chromatographicband.3.1.19 spottingapplying a solute sample at the origin ofthe TLC plate.3.1.20 stationary phasethe solid adsorbent coating layerof a TLC plate.3.1.21 tailinga spot distorted during development into anelongated streak.3.1.22 thin-layer chromatogramthe series of spots visibleon