1、Designation: E1151 93 (Reapproved 2011)Standard Practice forIon Chromatography Terms and Relationships1This standard is issued under the fixed designation E1151; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revi
2、sion. 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 deals primarily with identifying the termsand relationships of those techniques that use ion exchangechromatograp
3、hy to separate mixtures and a conductivity detec-tor to detect the separated components. However, most of theterms should also apply to ion chromatographic techniques thatemploy other separation and detection mechanisms.1.2 Because ion chromatography is a liquid chromato-graphic technique, this prac
4、tice uses, whenever possible theterms and relationships identified in Practice E682.1.3 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 problems, if any, associated
5、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:2E682 Practice for Liquid Chromatography Terms and Rela-tionships
6、3. Descriptions of Techniques3.1 Ion Chromatography, (IC)a general term for severalliquid column chromatographic techniques for the analysis ofionic or ionizable compounds. Of the many useful separationand detection schemes, those most widely used have been thetwo techniques described in 3.2 and 3.3
7、 in which ion exchangeseparation is combined with conductimetric detection. Bydescribing only these two techniques, this practice does notmean to imply that IC is tied only to ion exchange chroma-tography or conductimetric detection.3.2 Chemically Suppressed Ion Chromatography, (DualColumn Ion Chrom
8、atography)In this technique, samplecomponents are separated on a low capacity ion exchanger anddetected conductimetrically. Detection of the analyte ions isenhanced by selectively suppressing the conductivity of themobile phase through post separation ion exchange reactions.3.3 Single Column Ion Chr
9、omatography, (ElectronicallySuppressed Ion Chromatography)In this technique samplecomponents are separated on a low capacity ion exchanger anddetected conductimetrically. Generally, lower capacity ionexchangers are used with electronic suppression than withchemical suppression. Mobile phases with io
10、nic equivalentconductance significantly different from that of the sample ionsand a low electrolytic conductivity are used, permitting analyteion detection with only electronic suppression of the baselineconductivity signal.4. Apparatus4.1 PumpsAny of various machines that deliver the mo-bile phase
11、at a controlled flow rate through the chromato-graphic system.4.1.1 Syringe Pumps, having a piston that advances at acontrolled rate within a cylinder to displace the mobile phase.4.1.2 Reciprocating Pumps, having one or more chambersfrom which mobile phase is displaced by reciprocating pis-ton(s) o
12、r diaphragm(s). The chamber volume is normally smallcompared to the volume of the column.4.1.3 Pneumatic Pumps, employing a gas to displace themobile phase either directly from a pressurized container orindirectly through a piston or collapsible container. The vol-ume within these pumps is normally
13、large as compared to thevolume of the column.4.2 Sample Inlet Systems, devices for introducing samplesinto the column.4.2.1 Septum InjectorsThe sample contained in a syringeis introduced directly into the pressurized flowing mobile phaseby piercing an elastomeric barrier with a needle attached to as
14、yringe. The syringe is exposed to pressure and defines thesample volume.4.2.2 Valve InjectorsThe sample contained in a syringe(or contained in a sample vial) is injected into (or drawn into)an ambient-pressure chamber through which the pressurizedflowing mobile phase is subsequently diverted, after
15、sealing1This practice 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 1993. Last previo
16、us edition approved in 2006 as E1151 93 (2006).DOI: 10.1520/E1151-93R11.2For 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 AS
17、TM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.against ambient pressure. The displacement is by means ofrotary or sliding motion. The chamber is a section (loop) oftubing or an internal chamber. The chamber can be complet
18、elyfilled, in which case the chamber volume defines the samplevolume, or it can be partially filled, in which case the syringecalibration marks define the sample volume.4.3 Columns, tubes, containing a stationary phase andthrough which the mobile phase can flow.4.3.1 Precolumns, positioned before th
19、e sample inlet systemand used to condition the mobile phase.4.3.2 Concentrator Columns, installed in place of thesample chamber of a valve injector and used to concentrateselected sample components.4.3.3 Guard Columns, positioned between the sample inletsystem and the separating columns and used to
20、protect theseparator column from harmful sample components.4.3.4 Separating Columns, positioned after the sample inletsystem and the guard column and used to separate the samplecomponents.4.3.5 Suppressor Columns, positioned after the separatingcolumn and a type of post column reactor where the cond
21、uc-tivity of the mobile phase is selectively reduced to enhancesample detection.4.4 Postcolumn Reactors, reaction systems in which theeffluent from the separating columns is chemically or physi-cally treated to enhance the detectability of the sample com-ponents.4.4.1 Conductivity Suppressors, post
22、column reactors inwhich the conductivity of the mobile phase is reduced throughreactions with ion exchangers. Conductivity suppressors aredifferentiated by their type (cationic or anionic), by their form(H+,Na+, etc.), and by their method of regeneration (batch orcontinuous).4.4.2 Suppressor Columns
23、Tubular reactors packed withion exchangers. Suppressor columns require batch regenerationwhen the breakthrough capacity of the column is exceeded.4.4.3 Membrane SuppressorsReactors made from tubularshaped ion exchange membranes. On the inside of the tubeflows the mobile phase; a regenerative solutio
24、n surrounds thetube. These membrane suppressors can be in the form of anopened tube, hollow fiber suppressors, or a flattened tube forhigher capacity. Tubular membranes can be packed with inertmaterials to reduce band broadening.4.4.4 Micromembrane SuppressorReactors made fromtwo sizes of ion-exchan
25、ge screen. A fine screen is used for themobile phase chamber and a coarse screen is used for theregenerant chambers. The mobile phase screen is sandwichedbetween ion-exchange membranes, and on either side of eachmembrane is a regenerant screen. The stack is laminated bypressure, causing intimate con
26、tact between screens and mem-branes. Mobile phase passes through a hole in the upperregenerant screen and membrane. It enters the screen-filledmobile phase chamber and passes through it. It then exitsthrough a second set of holes in the upper membrane andregenerant screen. The regenerant flows count
27、ercurrent to themobile phase through the screen-filled regenerant chamber.4.5 DetectorsDevices that respond to the presence ofeluted sample components. Detectors may be divided eitheraccording to the type of measurement or the principle ofdetection.4.5.1 Bulk Property Detectors, measuring the change
28、 in aphysical property of the liquid phase exiting the column. Thusa change in the refractive index, conductivity, or dielectricconstant of a mobile phase can indicate the presence of elutingsample components. Conductimetric parameters, symbols,units and definitions are given in Appendix X1.4.5.2 So
29、lute Property Detectors, measuring the physical orchemical characteristics of eluting sample components. Thus,light absorption (ultraviolet, visible, infrared), fluorescence,and polarography are examples of detectors capable of re-sponding in such a manner.5. Reagents5.1 Mobile PhaseLiquid used to s
30、weep or elute thesample components through the chromatographic system. Itmay consist of a single component or a mixture of components.5.2 Stationary PhaseActive immobile material within thecolumn that delays the passage of sample components by oneof a number of processes or their combination. Inert
31、materialsthat merely provide physical support for the stationary phaseare not part of the stationary phase. The following are threetypes of stationary phase:5.2.1 Liquid PhaseA stationary phase that has beensorbed (but not covalently bonded) to a solid support. Differ-ences in the solubilities of th
32、e sample components in the liquidand mobile phase constitute the basis for their separation.5.2.2 Interactive SolidAstationary phase that comprises arelatively homogeneous surface on which the sample compo-nents sorb and desorb effecting a separation. Examples aresilica, alumina, graphite, and ion e
33、xchangers. In ion chroma-tography the interactive material is usually an ion exchangerthat has ionic groups that are either ionized or capable ofdissociation into fixed ions and mobile counter-ions. Mobileionic species in an ion exchanger with a charge of the samesign as the fixed ions are termed “c
34、o-ions.” An ion exchangerwith cations as counter-ions is termed a “cation exchanger,”and an ion exchanger with anions as counter-ions is termed an“anion exchanger.” The ionic form of an ion exchanger isdetermined by the counter-ion, for example, if the counter-ionsare hydrogen ions then the cation e
35、xchanger is in the acid formor hydrogen form, or if the counter-ions are hydroxide ionsthen the anion exchanger is in the base form or hydroxide form.Ionic groups can be covalently bonded to organic polymers (forexample, styrene/divinylbenzene) or an inorganic material (forexample, silica gel). Ion
36、exchange parameters, symbols, unitsand definitions are given in Appendix X2. Separation mecha-nisms on ion exchangers are described in Appendix X3.5.2.3 Bonded PhaseA stationary phase that comprises achemical (or chemicals) that has been covalently attached to asolid support. The sample components s
37、orb onto and off thebonded phase differentially to effect separation. Octadecylsilylgroups bonded to silica represent a typical example for abonded phase.E1151 93 (2011)25.3 Solid SupportInert material to which the stationaryphase is sorbed (liquid phases) or covalently attached (bondedphases). It h
38、olds the stationary phase in contact with the mobilephase.5.4 Column PackingThe column packing consists of allthe material used to fill packed columns. The two types are asfollows:5.4.1 Totally Porous PackingOne where the stationaryphase is found throughout each porous particle.5.4.2 Pellicular Pack
39、ingOne where the stationary phaseis found only on the porous outer shell of the otherwiseimpermeable particle. Surface agglomerated packings are con-sidered to be a type of pellicular packing.6. Readout6.1 ChromatogramGraphic representation of the detectorresponse versus retention time or retention
40、volume as thesample components elute from the column(s) and through thedetector. An idealized chromatogram of an unretained and aretained component is shown in Fig. X1.1.6.2 BaselinePortion of a chromatogram recording thedetector response when only the mobile phase emerges fromthe column.6.3 PeakPor
41、tion of a chromatogram recording detectorresponse when a single component, or two or more unresolvedcomponents, elute from the column.6.4 Peak Base (CD in Fig. X1.1)Interpolation of thebaseline between the extremities of a peak.6.5 Peak Area (CHFEGJD in Fig. X1.1)Area enclosedbetween the peak and th
42、e peak base.6.6 Peak Height (EB in Fig. X1.1)Distance measured inthe direction of detector response, from the peak base to peakmaximum.6.7 Peak WidthsRepresent retention dimensions parallelto the baseline. Peak width at base or base width, (KL in Fig.X1.1) is the retention dimension of the peak base
43、 interceptedby the tangents drawn to the inflection points on both sides ofthe peak. Peak width at half height, (HJ in Fig. X1.1) is theretention dimension drawn at 50 % of peak height parallel tothe peak base. The peak width at inflection points, (FG in Fig.X1.1), is the retention dimension drawn a
44、t the inflection points(= 60.7 % of peak height) parallel to the peak base.7. Retention Parameters, Symbols, and Units7.1 Retention parameters, symbols, units, and their defini-tions or relationship to other parameters are listed in TableX3.1.NOTE 1The adjusted retention time, capacity ratio, number
45、 of theo-retical plates, and relative retention times are exactly true only in anisocratic, constant-flow system yielding perfectly Gaussian peak shapes.7.2 Fig. X1.1 can be used to illustrate some of the followingmost common parameters measured from chromatograms:Retention time of unretained compon
46、ent, tM= OARetention time, tR= OBAdjusted retention time, tR= ABCapacity factor, k8 = (OB OA)/OAPeak width at base, wb= KLPeak width at half height, wh= HJPeak width at inflection points, = FG = 0.607(EB)Number of theoretical plates, N = 16(OB)/(KL)2= 5.54(OB)/(HJ)2Relative retention, r (Note 2)=(AB
47、)i/(AB)sPeak resolution, Rs(Note 2 and Note 3) = 2(OB)j(OB)i/(KL)i+(KL)j. (OB)j(OB)i/(KL)jNOTE 2Subscripts i, j, and s refer to some peak, a following peak, anda reference peak (standard), respectively.NOTE 3The second fraction may be used if peak resolution of twoclosely spaced peaks is expressed;
48、in such as case (KL)i=(KL)j.APPENDIXES(Nonmandatory Information)X1. SEPARATION MECHANISMSX1.1 Ion Exchange ChromatographySample and mobilecounter-ions compete to form neutral ion pairs with the fixedions of an ion exchanger. When paired, the sample ions do notmove through the ion exchange column. Se
49、paration is achievedbecause the fixed ions have different thermodynamic compl-exation constants resulting in chromatographic selectivity be-tween ions.X1.2 Ion Exclusion Chromatography (or Donnan exclusionchromatography)Sample co-ions are excluded from enteringthe ion exchanger pore structure (or Donnan membrane) byelectrostatic repulsion from the fixed ions while neutral andpartially ionized sample components can enter and be retainedby a partition or adsorption mechanism. Separation of partiallyionized sample components, such as weak acids,
