ASTM_E_1449_-_92_2011.pdf

Designation:E144992(Reapproved 2011)Standard Guide forSupercritical Fluid Chromatography Terms andRelationships1This standard is issued under the fixed designation E1449;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 deals primarily with the terms and relation-ships used in supercritical fluid chromatography.1.2 Since many of the basic terms and definitions also applyto gas chromatography and liquid chromatography,this guideis using,whenever possible,symbols identical to PracticesE355 and E682.1.3 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.2.Referenced Documents2.1 ASTM Standards:2E355 Practice for Gas Chromatography Terms and Relation-shipsE682 Practice for Liquid Chromatography Terms and Rela-tionships3.Names of Techniques3.1 Supercritical Fluid Chromatography,abbreviated asSFC,comprises all chromatographic methods in which boththe mobile phase is supercritical under the conditions ofanalysis and where the solvating properties of the fluid have ameasurable affect on the separation.Early work in the field wasperformed under a broader headingdense gas chromatogra-phy.Related work in the field uses subcritical or near-criticalconditions to affect separation.3.2 Separation is achieved by differences in the distributionof the components of a sample between the mobile andstationary phases,causing them to move through the column atdifferent rates(differential migration).3.3 In supercritical fluid chromatography,the pressure maybe constant or changing during a chromatographic separation.3.3.1 Isobaric is a term used when the mobile phase is keptat constant pressure.This may be for a specified time intervalor for the entire chromatographic separation.3.3.2 Programmed Pressure Supercritical Fluid Chroma-tography is the version of the technique in which the columnpressure is changed with time during the passage of the samplecomponents through the separation column.Isobaric intervalsmay be included in the pressure program.3.4 In supercritical fluid chromatography,the temperaturemay be constant,or changing during a chromatographicseparation.3.4.1 Isothermal Supercritical Fluid Chromatography is theversion of the technique in which the column temperature isheld constant during the passage of the sample componentsthrough the separation column.3.4.2 Programmed Temperature Supercritical Fluid Chro-matography is the version of the technique in which thecolumn temperature is changed with time during the passage ofthe sample components through the separation column.Iso-thermal intervals may be included in the temperature program.3.5 In supercritical fluid chromatography,the density maybe constant or changing during the chromatographic separa-tion.3.5.1 Isoconfertic is a term used when the density of themobile phase is kept constant for a specified time or for theentire chromatographic separation.3.5.2 Programmed Density Supercritical Fluid Chromatog-raphy is the version of the technique in which the columndensity is changed with time during the passage of the samplecomponents through the separation column.Isoconfertic inter-vals may be included in the density program.3.5.3 Flow Programming is a technique where the mobilephase linear velocity is changed during the chromatographicprocedure.However,with fixed orifice restrictors,flow pro-gramming is more complex requiring an increase in pressure toeffect an increase in linear velocity.3.6 In supercritical fluid chromatography,the compositionof the mobile phase may be constant or changing during achromatographic separation.1This guide is under the jurisdiction of ASTM Committee E13 on MolecularSpectroscopy and Separation Science and is the direct responsibility of Subcom-mittee E13.19 on Separation Science.Current edition approved Nov.1,2011.Published December 2011.Originallyapproved in 1992.Last previous edition approved in 2006 as E1449 92(2006).DOI:10.1520/E1449-92R11.2For 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 3.6.1 The term Isocratic is used when the composition ofthe mobile phase is kept constant during a chromatographicseparation.3.6.2 The term Gradient Elution is used to specify thetechnique when a deliberate change in the mobile phasecomposition is made during the chromatographic procedure.Isocratic intervals may be included in the gradient program.4.Apparatus4.1 PumpsThe function of the pumps is to deliver themobile phase at a controlled