Nomenclature for Chromatography IUPAC

8/13/2019 Nomenclature for Chromatography IUPAC

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Pure &A pp l , Chem., Vol. 65, No. 4, pp. 8 1 H 7 2 , 1993.Printed in Great Britain.@ 1993 IUPAC

INTERNATIONAL UNION OF PUREAND APPLIED CHEMISTRYANALYTICAL CHEMISTRY DIVISIONCOMMISSION ON CHROMATOGRAPHY AND OTHER

ANALYTICAL SEPARATIONS*COMMISSION ON ANALYTICAL NOMENCLATUREt

NOMENCLATURE FOR CHROMATOGRAPHY(IUPAC Recommendations 1993)

Prepared forpublication byL. S. ETI RE

Department of Chemical Engineering, Yale University, New Haven, CT06520, USA*M emb ership of the Com mission during the period (1989-1993) when this report w as prepared w as as follows:Chairman: P. C. Uden (USA, 1989-93); Secretary: C. A . M. G . Cramers (Netherlands, 1989-91); R. M . Smith(U K , 1991-93); Titular Members: H . M. K ingston (US A, 1989-93); A . Marton (Hu ngary, 1991-93); AssociateMembers: V. A. Davankov (USSR, 1991-93); F. M. Everaerts (Netherlands, 1989-93); K. Jinno (Japan, 1991-93); J. A. Jonsson (Sweden, 1991-93); A. Marton (Hungary, 1989-91); R. M. Smith (UK, 1989-91); G. Vigh(1989-91); W . Yu (C hina, 1989-93); National Representatives: R. M . Habib (E gypt, 1990-93); F. Radler de A quinoNet0 (1991-93); J. Ga raj (Czec hoslov akia, 1989-91); P. BoEek (C zechos lovakia, 1991-93); D. B aylocq (France,1989-93); W. Engelwald (Germany, 1989-93); D. P. A . Siskos (Greece, 1989-93); S.N. T andon (Ind ia, 1989-93);D . W . Lee (Korea, 1991-93); J. A. Garcia Dominguez (Spain, 1991-93); S . &de n (Turk ey, 1991-93); U . L.Haldna (USSR, 1989-93).+M emb ership of t he C omm ission during the pe riod (1977-1989) when this repo rt was being prepared is givenhereunder. (Note: The Comm ission ceased to exist after 35th IUPAC General A ssembly, Lund, 1989).Chairman: H. Zettler (Germany, 1977-79); G. G. Guilbault (USA, 1979-83); G. Svehla (UK, 1983-85);R . E . V an Grieken (Belgium, 1985-89); Secretary: G . G . Guilbault (US A, 1977-79); G . Svehla (U K, 1979-83);S . P. Perone (U SA , 1983-85); C. L. Graham (UK , 1985-89); Titular and Associate M em ber s: D . Betteridge (UK,1977-79); C. A . M. G . Cramers (Netherlands, 1979-89); L. A . Currie (U SA , 1983-89); J. R . Devoe (US A, 1985-87); D. Dyrssen (Sweden, 1977-81); L. S. Ettre (USA, 1981-89); D. M. Everaerts (Netherlands, 1985-89);A . E. Fein (USA , 1981-85); R . W. Frei (Netherlands, 1977-85); H. Freiser (USA, 1977-85); P. S.Goel (India,1987-89); Y. G ohshi (Japan, 1987-89); R . E . Van G rieken (Belgium, 1979-85); G. G. Guilbault (USA , 1981-87);W. Horwitz (USA, 1981-89); H. M. N . H . Irving (RS A, 1977-83); H. M. Kingston (1987-89); G . F. Kirkbright(UK, 1977-81); B. R. Kowalski (USA, 1981-85); D. Klockow (Germany, 1977-89); M. A. Leonard (UK, 1983-87); D. Leyden (USA, 1983-85); R. F. Martin (USA, 1981-85); 0 . Menis (USA, 1977-81); M. Parkany(Switzerland, 1985-89); G. J . Patriarche (Belgium, 1987-89); S . P. Perone (USA, 1977-83); D. L. Rabenstein(US A, 1985-89); N . M. Rice (U K, 1977-83); L. B. R ogers (US A, 1977-79); B . Schreibe r (Sw itzerland, 1981-87);W. Simon (Switzerland, 1977-85); J. W. Stahl (US A, 1985-89); G . Svehla (U K, 1977-79); A . Town shend (UK,1977-79); H. Zettler (Germany, 1979-81); National Representatives: C. J. De Ranter (Belgium, 1985-87);A. C. S. Costa (Brazil, 1979-83); I. Giolito (Brazil, 1983-85); W . E. Harris (Canada, 1979-85); J. Stary(Czechoslovakia, 1981-89); A. M. Shams El-Din (Egypt, 1977-79); W . Rosset (France, 1981-85); K. Doerffel(Germ any, 1983-87); E. Grushka (Israel, 1981-85); M. Ariel (Israel, 1985-89); R. D . Reeves (New Z ealand, 1987-89); H. M . N . H. Irving (R SA , 1983-85); D . Jagner (Swed en, 1981-85); G . Svehla (UK , 1987-89); U . L. H aldna(USSR, 1985-89).Names of countries given after Mem bers' n ames are in accordance with the IU PA C Handb ook 1991-1993; changeswill be effected in the 1993-1995 edition.Republication of this report is permitted without the need fo r formal IU PA C permission on condition that anacknowledgement, with full reference together with IUP AC copyright sym bol 0 1993 IUPAC), is printed.Publication of a translation into another language is subject to the additional condition of prior approval from therelevant IUPAC National Adhering Organization.


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Nom enclature for ch rom atography(IUPAC Recom m endat ion s 1993)

AbstractThis report presents def ini t ions of terms and sy mbo ls used in a l l chromatograp hicseparations. The reports covers gas, liquid, size-exclusion, ion-exchange and supercritical-fluidchromatography and both column and planar modes of separation. Definitions are included for

the description of the separation process, the chrom atograph ic system and equ ipmen t and theproperties of detectors.

INTRODUCTIONThe Com mission on Ana lytical Nom enclature of IUPAC has been act ive for a long t ime inestablishing nomenclatures for chromatography. After p roposing suitable nom enclatures for gaschromatography [1-21 and ion exch ange [3-41 the Com mission developed a unified n omenclature forchrom atography [5-61. Parallel to these activities other standardization bodies and scien tists have also dealtwith nom enclatures on ga s chromatography [7- 151, supercritical-fluid chrom atography [ 161, liquidchromatography [17-20], exclusion chrom atography [21-231 and planar chromatography [24].The original activities of the IUPAC Comm ission on Analy tical Nom enclature aim ed to create aunified nomenclature applicable to all forms of chromatography, took place o ver 20 years ago. S ince thattime chromatographic techniques have advanced significantly. Based on these developmen ts it was decided

to prepare a new, up- to-date universal chromatograph y nomenclature , which also co nsiders therecommendations incorporated in the various other nom enclatures developed since the original work ofIUPAC.The present nomenclature was prepared by Dr L. S. Ettre originally for the Comm ission on AnalyticalNom enclature. Following the reorganisation of the C omm issions of the Analytical Division at the G eneralAssembly in Lund in 1989,this project became the responsibility of the Comm ission on Chromatographyand O ther Analytical Separations (LLTC). The N omenclature considers all the previous nomenclaturesreferenced above as well as the four publications dealing with these nomenclatures [25-271.The presen t nomenclature deals with all chromatographic terms and definitions used in the major

chromatographic techniques such as gas, liquid and supercritical-fluid chromatography, column and planarchromatography, partition, adsorption, ion-exchange and exclusion chromatography. However, it does notinclude terms related to the results calculated from chromatography data such as e.g., the various molecularweight terms com puted from the primary data obtained by exclusion chromatography, Also it doe s not dealwith detailed information related to detection and detectors or the relationships between chem ical structureand chromatograph ic retention.820


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Nomenclature for chromatography 82 1

General RulesIn developing the unified nomenclature the rules and recomm endations set up by IUPAC 's Division ofPhysical Chemistry [28] were followed. According to these, the following sym bols should be used for

major physical and physico-chemical quantities and units:area ........................................ Adiameter ................................. ddiffusion coefficient ...............Dequilibrium constant .............. K

....................................ensity P

mass (weight).......................... Wpressure .................................. p or Ptemperature (kelvin) ..............Tradius ..................................... rrate constant ........................... ktime ........................................ tvelocity .................................. uviscosity ................................. qvolume ................................... V

The only deviatio n from the rules set by the Division of Physical Chemistry of IUPAC is the use of L(instead of r for length. The reason for this is the easy interchangeability in a p rinted, and particularlytyped, text of the letter 1 with the numeral one . Additional basic symbo ls accepted were F for thevolumetric flow rates and w for the peak widths. Also, differentiation has been made between p (forpressures) and P for relative pressure).In addition to these basic rules the following additional rules are followed in the present proposal:

Excep t for a few superscripts further differentiation is always made by using subscripts and nevercomposite symbols.Superscripts are used for various retention times and volumes and to specifically indicate dataobtained in programmed-temperature conditions.Subsc ripts referring to the physical conditions or the phase are capitalized, e.g., M and S for themobile and stationary phases respectively, or, in g as chromatography, G for the gas and L for theliquid phase. Thus, e.g., the diffusion coefficient in the mobile phase is D, and not D,,,.In addition to those mentioned abov e, a few capitalized sub scripts are used such as R forretention (as in rR and V,), N for net (as in f and VN) nd F in R,, the retardation factor used inplanar chromatography.Compound subs cripts are avoided. If a given compound is indicated and there is already asubscript, and if the compound is characterized by mo re than a simple num ber or letter, then thenew subscript should be in parentheses . Thus, while it is rRi it should be tR(stj r tR(z+,yIn addition to reference to the outlet of a column, subscript 0 s also used in a num ber of terms todescribe some fundamental values. Similarly subscript i has various meanings, depend ing on theterm in which it is used.Physical parts of the system are generally characterized by lower-case subscripts such as, c forcolumn, p for particles or pores, and f for film.

Three tables follow the nomenclature, listing alphabetically the terms, symbols and acronymsincluded in the text.


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6.

COMMISSIONS ON CHROMATOGRAPHY AND ANALYTICAL NOMENCLATURETABLE OF CONTENTS

GENERAL TERMI NOLOGY1.1 Basic Definitions1.2 Principal Methods1.31.41.51.6 Special TechniquesTERM S RELATED TO TH E CHROMATOGRAPI-I IC SYSTEM2.1 Apparatus in Column Chromatography2.2 Apparatus in Planar ChromatographyT E R M S R E LA T ED T O T H E C H R O M A T O G R A PH I C PR O C E S SAND TH E THEORY O F CHROMATOGRAPHY3.1 Th e Chromatographic Medium3.2 The Column3.3 The Chromatogram3.4 Diffusion3.5 Temperatures3.6 The M obile Phase3.73.83.9 Distribution Constants3.10TERMS RELATED TO DETECTI ON4.1 Classification of Detectors4.2 Detector Response4.3 Noise and Drift4.4 Minimum Detectability4.5 Linear and Dynamic Ranges

Classification According to the Shape of the Chrom atographic BedClassification According to the Physical State of the Mobile PhaseClassification According to the Mechanism of Separation

Retention Parameters in Column ChromatographyRetention Parameters in Planar ChromatographyTerms Expressing the Efficiency of Separation

SPECIAL TERMINOLOGY USED IN ION-EXCHANGE CHROMA TOGRA PHY5.1 Basic Definitions5.2 Th e Mobile Phase5.3 The Chromatographic Medium5.4 Capacity Values5.5 Diffusion, Selectivity and Separation5.6 Distributioii ConstantsSPECIAL TERMINOLOGY USED IN EXCLUSION CHRO MATO GRAPH Y6.1 The Column6.2 Retention Parameters6.3 Efficiency TermsTABLES1 Index of Terms2 List of Symbols3FIGURES1 Typical Chromatograms2 Typical Plane Chromatogram34567

List of A cronyms Used in Chromatography

Widths of a Gaussian Peak at Various Heights as a Function of theStandard Deviation of the PeakMeasurement of the No ise and Drift of a C hromatog raphic DetectorLinearity Plot of a C hromatog raphic DetectorDeterm ination of the L inear and Dynamic Ranges of aChromatographic D etectorRetention Characteristics in Exclusion Chromatog raphy


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Nom enclature for chromatography 823

1 GENERAL TERMINOLOGY

1.1 BASIC DEFINITIONS1.1.01

1.1.02

1.1.03

1.1.04

1.1.05

1.1.05.1

1.1.05.2

ChromatographyChromatography is a physical method of separation in which the componen ts to be separated aredistributed between two phases , one of which is stationary (stationary phase) while the other (themobile phase) moves in a de finite direction.ChromatogramA graphica l or other presentation of detector response, concentration of analyte in the effluent orother quantity used a s a measu re of effluent concentration versus effluent volum e or time. Inplanar chromatography chromatogram may refer to the paper or layer with the separatedzones.Chromatograph (verb)To separate by chromatography .Chromatograph (noun)The assembly of apparatus for carrying out chromatographic separation.Stationary PhaseThe stationary phase is one of the two phases forming a chrom atographic system. It may be asolid, a gel or a liquid. If a liquid, it may be distributed on a solid. This solid may or may n otcontribute to the separation process. The liquid may also be chemica lly bonded to the solid(Bonded Phase) or imm obilized onto it (ImmobilizedPhase).The expression Chromatographic Bed or Sorbent may be used as a general term to den ote any ofthe different forms in which the s tationary phase is used.Note: Particularly in gas chrom atography where the stationary phase is most o ften a liquid,the term Liquid Phase is used for it as compared to the Gas Phase, i.e., the mobilephase. H owever, particularly in the early deve lopment of liquid chrom atograph y, theterm liquid phase had also been used to characterize the mobile phase as comparedto the solid phase i.e., the stationary phase. Due to this ambiguity, the use of theterm liquid phase is discourag ed. If the physical state of the stationary phase is tobe expressed, the use of the adjective forms such as Liquid Stationary Phase and SolidStationary Phase, Bonded Phase or Immobilized Phase is proposed.Bonded PhaseA stationary phase which is covalently bonded to the suppo rt partic les or to the inside wall of thecolumn tubing.Immobilized PhaseA stationary phase which is imm obilized on the support particles, or on the inner wall of thecolumn tubing , e.g., by in situ polymerization (cross-linking) after coating.


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COMMISSIONS O N CHROMATOGRAPHY AND ANALYTICAL NOMENCLATURE241.1.06

1.1.07

1.1.08

1.1.09

1.1.10

1.1.11

1.1.12

1.1.13

1.2.0 1

1.2.02

1.2.03

Mobile PhaseA fluid which perco lates through or along the stationary bed, in a de finite direction. It may be aliquid (Liquid Chromatography) or a gas (Gus Chromatography) or a supercritical fluid(Supercritical-Fluid Chromatography). In gas chromatog raphy the expression Carrier Gas maybe used for the mobile phase. In elution chromatography the expression Eluent is also used for themob ile phase.Elute (verb)To chromatograph by elution chrom atography. The process of elution may be stopped while allthe samp le components are still on the chromatographic bed or continued until the componen tshave left the chromatographic bedNote: The term elute is preferred to the term Develop used in form er nom enclatures ofplanar chromatography.EfluentThe m obile phase leaving the column.SampleTh e mixture consisting of a number of components the separation of w hich is attempted on thechromatographicbed as they are carried or eluted by the mobile phase.Sample ComponentsThe chemically pure constituents of the sample. They may be unretained (Le. ,not delayed ) bythe stationary phase, partially retained (Le.,eluted at different times) or retained permanently.The terms Eluite or Analyre are also acceptable for a sample component.SoluteA term referring to the sample components in partition chromatography.SolventA term sometimes referring to the liquid stationary phase in partition chromatog raphy.Note: In liquid chromatography the teim solvent has been often used for the mobile phase.This usage is not recommended.ZoneA region in the chrom atographic bed where one or more com ponents of the sample are located.The term Band may also be used for it.1.2 PRINCIPAL METHODSFrontal ChromatographyA procedure in which the sample (liquid or gas) is fed continuously into the chromatographicbed. In frontal chromatography no additional mobile phase is u sed.Displacement ChromatographyA procedure in which the mobile phase contains a compound (the Displacer)more stronglyretained than the compo nents of the sample under exam ination. The sam ple is fed into thesystem as a finite slug.Elution ChromatographyA proced ure in which the mobi le phase i s cont inuous ly passed through or a long thechromatographic bed and the sam ple is fed into the system as a finite slug.


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Nomenclature for chromatography 8251.3 CLA SSIFICATION ACCORDING TO THE SHA PEOF THE CHROMATOGRA PHIC BED

1.3.01 Column ChromatographyA separation technique in which the stationary bed is within a tube. The particles of the solidstationary phase or the support coated with a liquid stationary phase may fill the who le insidevolume of the tube (Packed Column) or be concentrated on or along the inside tube wall leavingan open, unrestricted path for the mobile phase in the middle part of the tube (Open-TubularColumn.

1.3.02 Planar ChromatographyA separation technique in which the stationary phase is present as or on a plane. The plane canbe a paper, servin g as such or impregnated by a substan ce as the sta tionary bed (PaperChromatography, PC) or a layer of solid particles spread on a su pport, e.g., a g lass plate (ThinLayer Chromatography, TLC). Som etimes planar chromatography is also termed Open-BedChromatography.

1.4 CLA SSIFICATION ACCORDING TO THE PHYSICAL STATEOF THE MOB ILE PHASE1.4.01 Chromatographic techniques are often classified by specifying the physical state of both phasesused. Accordingly, the following terms are in use:

Gas-liquid chromatography (GLC)Gas-solid chromatography (GSC)Liquid-liquid chromatography (LLC)Liquid-solid chromatography (LSC)The term Gas-Liquid Partition Chromatography (GLPC) can also be foun d in the literature.How ever, often distinction between these modes is not easy. For example, in GC , a liquid maybe used to m odify an adsorbent-type solid stationary phase.

1.4.02 GasChromatography (GC)A separation technique in which the mobile phase is a gas. Ga s chromatography is alwayscarried out in a column.

1.4.03 Liquid Chromatography (LC)A separation technique in which the mobile phase is a liquid. L iquid chromatography can becarried out either in a colum n or on a plane.Note: Present-day liquid chromatography generally utilizing very small particles and arelatively high in let pressure is often Characterized by the term High-Pe?$ormance (orHigh-pressure)Liquid Chromatography, and the acronym HPLC.

1.4.04 Supercritical-Fluid Chromatography (SFC)A separation technique in which the m obile phase is a fluid abo ve and relatively close to itscritical temperature and pressure.Note: In general the terms and definitions used in gas or liqu id chromatography are equallyapplicable to supercritical-fluid chromatography.


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826 COMMISSIONS ON CHROMATOGRAPHY A ND ANA LYTICAL NOMENCLATURE

1.5.01

1.5.02

1.5.03

1.5.04

1.5.05

1.6.01

1.6.02

1.6.03

1.6.04

1.5 CLA SSIFICATION ACCORDING TO THE MECHA NISM OF SEPARA TIONAdrorption ChromatographySeparation is based mainly on differences between the adsorption affinit ies of the samplecomponents for the surface of an active solid.Partition ChromatographySeparation is based mainly on differences between the solubilities of the sample components inthe stationary phase (gas chromatogra phy), or on differences between the solu bilities of thecomponents in the mobile and stationsuy phases (liquid chromatography).Ion-Exchange ChromatographySepa rat ion is based mainly on di fferences in the ion exchange a f f in i t ie s of the samplecomponents.Note: Present day ion-exchange chromatography on sm all particle high efficiency columns

and usually utilising conductom etric or spe ctroscopic detectors is often referred to asIon Chromatography (IC).Exclusion chromatographySeparation is based m ainly on exclusion effects, such as differences in m olecular size and/orshape or in charge. Th e term Size-Exclusion Chromatography may also be used whensepara t ion i s based on molecula r s i ze . The t e rms G el F i l t r a t i o n a n d G el - P er m ea t io nChromatography (GPC) ere used earlier to describe this process when the stationary phase is aswollen gel. The term Ion-Exclusion Chromutography is specifically used fo r the separation ofions in an aqueous phase.Afi nity ChromatographyThis expression characterizes the particular variant of chrom atograph y in which the uniquebiological specificity of the analyte and ligand interaction is utilized for the separation.

1.6 SPECIAL TECHNIQUESReversed-Phase ChromatographyAn elution procedure used in liquid chromatography in which the mobile phase is significantlymore polar then the stationary phase, e.g., a microporous silica-based material with chemicallybonded alkyl chains.Note: The term reverse phase is an incorrect expression to be avoided.Normal-Phase ChromatographyAn elution procedure in which the stationary phase is more polar than the mobile phase. Thist e r m i s u s e d i n l i q u i d c h r o m a t o g r a p h y t o e m p h a s i z e t h e c o n t r a s t t o r e v e r s ed - p h a s echromatography.Isocratic AnalysisThe procedure in which the com position of the mobile phase remains constant during the elutionprocess.Gradient ElutionThe proced ure in which the composi t ion of the mobi le phase is changed cont inuously orstepwise during the elution process.


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Nomenclature for chromatography 827

1.6.05 Stepwise ElutionThe elution process in which the comp osition of the mo bile phase is changed in steps during asingle chrom atographic run.

1.6.06 Two-Dimensional ChromatographyA procedure in which parts or all of the separated sample componen ts are su bjected to additionalseparation steps. This can be done e.g., by conducting a particular fraction eluting from thecolumn in to another column (system) having different separation characteristics. Whencom bined with ad ditional separation steps , his may be described as Multi-DimensionalChromatography.In planar chromatography two-dimensional chromatography refers to the chromatographicprocess in which the comp onents are caused to m igrate first in one direction and subsequently ina direction at right ang les to the first one; the two elutions are carried out with different eluents.

1.6.07 Isothermal ChromatographyA procedure in which the tem perature of the column is kept con stant during the separation.

1.6.08 Programmed-Temperature Chromatography (Temperature Programming)A procedure in which the temperature of the column is changed systematically during a part orthe whole of the separation.1.6.09 Programmed-Flow Chromatography (Flow Programming)A procedure in which the rate of flow of the mobile phase is changed systematically during a

part or the whole of the separation .1.6.10 Programmed-Pressure Chromatography (Pressure Programming)

A procedure in which the inlet pressure of the mobile phase is changed system atically during apart or whole of the separation.1.6.11 Reaction Chromatography

A technique in which the identities of the samp le comp onents are intentionally changed betweensample introduction and detection. The reaction can take place upstream of the column when thechemical identity of the individual compon ents passing through the co lumn differs from that ofthe or iginal samp le, or between the column and the detector when the or iginal samplecompo nents are separated in the column but their identity is changed prior to entering thedetection device.1.6.1 1.1 Pyroly sis-Gas ChromatographyA version of reaction chromatography in which a sample is thermally decomposed to simpler

fragments before entering the column.1.6.1 1.2 Post-Column DerivatizationA version of reaction chromatography in which the separated sam ple components eluting fromthe column are derivatized prior to entering the detector. The derivatization process is generallycarried out on-the-fly , i.e., during transfer of the sample components from the column to thedetector. Derivatization may also be carried out before the sam ple enters the column or theplanar medium; this is pre-column (preliminary) derivatization.


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828 COMMISSIONS ON CHROMATOGRAPHY AND ANALYTICAL NOMENCLATURE

2 TERMS RELATED TO THE CHROMATOGRAPHIC SYSTEM2.1 APPARATUS IN COLUMN CHROMATOGRAPHY

2.1 o1 PumpA device designed to deliver the mobile phase at a controlled flow-rate to the separation system.Pumps are generally used in liquid chromatography.2.1O 1.1 Syringe PumpsPumps with a piston, which advances at a controlled rate within a sm ooth cylinder to displacethe m obile phase.2.1.01.2 Reciprocating Pumps

Pumps with a sing le or multiple chamber, from which the mo bile phase is displaced byreciprocating piston(s) or diaphragm(s).2.1.01.3 Pneumatic PumpsPumps which em ploy a gas to displace the liquid mobile phase either directly or via a piston.2.1.02 Sample InjectorA device by w hich a liquid, solid or gaseous sample is introduced into the mobile phase or thechromatographicbed.2.1.02.1 Direc t Injector

A device which directly introduces the sample into the mobile-phase stream.2.1.02.2 Bypass Injector

A device in w hich the sample is first introduced into a cham ber (loop), temporarily isolated fromthe mobile phase system by valves, which can be switched to make an instantaneous diversion ofthe mobile phase stream through the chamber to carry the sample to the column. A bypassinjector may also be known as a Valve Injector or Sampling Valve (see 2.1.02.7).2.1.02.3 On-Column InjectorA device in which the sample is directly introduced into the column. In gas chromatography the

on-column injector permits the introduction of the liquid sample into the column without priorevaporation.2.1.02.4 Flash Vaporizer

A heated device used in gas chromatography. Here the liquid sample is introduced into thecarrier gas stream with simu ltaneous evaporation and m ixing with the carrier gas prior toentering the column.2.1.02.5 Split InjectionA sample introduction technique used in g as chromatography. Th e sample is flash vaporizedand afte r thorough mixing of the samp le with the carrie r gas, the stream is spli t into twoportions, one being conducted to the column and the other being discarded .2.1.02.6 Programmed Temperature Vaporizer (PTV)

A samp le introduction device used in g as chromatography. The liquid sample is introduced,usually with a syringe, into a device similar to a flash vaporizer, the temperature of which is kept


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low, below the boiling point of the sample components. After withdrawal of the syringe, thedevice is heated up very rapidly in a controlled fashion to evaporate the sample into thecontinuously flowing carrier gas stream. The PTV may also be used in the split mode: in thiscase, the carrier gas stream containing the evaporated sample components is split into twoportions, one of which is conducted into the column while the other is discarded.2.1J2.7 Gas Sampling ValveA bypass injector permitting the introduction of a gaseous sample of a given volume into a gas

chromatograph.2.1.03 Column OvenA thermostatically controlled oven containing the column, the temperature of which (SeparationTemperature or Column Temperature) can be varied within in a wide range.2.1.04 Fraction CollectorA device for recovering fractional volumes of the column effluent.2.1.05 DetectorA device that measures the change in the composition of the eluent by measuring physical orchemical properties.

2.2 APPARATUS IN PLANAR CHROMATOGRAPHY2.2.01 Spotting DeviceThe syringe or micropipet used to deliver a fixed volume of sample as a spot or streak to thepaper or thin-layer media at the origin.2.2.02 Elution Chamber (Developing Chamber)A closed container, the purpose of which is to enclose the media used as well as the mobilephase to maintain a constant environment in the vapor phase.2.2.02.1 Sandwich ChamberA chamber in which the walls are close enough to the paper or plate to provide a relatively fastequilibration.2.2.02.2 Ascending Elution (Ascending Development)

A mode of operation in which the paper or plate is in a vertical or slanted position and themobile phase is supplied to its lower edge; the upward movement depends on capillary action.2.2.02.3 Horizontal Elution (Horizontal Development)A mode of operation in which the paper or plate is in a horizontal position and the mobile-phasemovement along the plane depends on capillary action.2.2.02.4 Descending Elution (Descending Development)

A mode of operation in which the mobile phase is supplied to the upper edge of the paper orplate and the downward movement is governed mainly by gravity.2.2.02.5 Radial Elution (Radial Development) or Circular Elution (Circular Developm ent)A mode of operation in which the sample is spotted at a point source at or near the middle of theplane and is carried outward in a circle by the mobile phase, also applied at that place.


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830 COMMISSIONS O N CHROMATOGRAPHY AND ANALYTICAL NOMENCLATURE

2.2.02.6 Anticircular Elution (Anticircular Development)The opposite of 2.2.02.5.Here the sample as well as the m obile phase is applied at the peripheryof a circle and both move towards the center.2.2.02.1 Chamber Saturation (Satura ted Development)This exp ression refers to the uniform distribution of the m obile phase vapor through the elution

chamber prior to chromatography.2.2.02.8 Unsaturated Elution (Unsaturated Development)This expressio n refers to chromatography in an elution cham ber without attaining chambersaturation.2.2.02.9 EquilibrationThe expression refers to the level of sa turation of the chromatographic bed by the mobile-phasevapor prior to chromatography.

2.2.03 Visualization ChamberA device in wh ich the planar media may be viewed under controlled -wavelen gth light, perhapsafter spraying with chemical reagents to render the separated com ponen ts as visible spots underspecified conditions.2.2.04 DensitometerA device which allows portions of the developed paper or thin-layer media to be scanned with abeam of light of a specified wavelength for measurements of UV or visible light absorption orf luores cence , providing values which can be used for the quanti ta t ion of the separatedcompounds.

3. TERMS RELATED TO THE CHROMATOGRAPHIC PROCESSAND THE THEORY OF CHROMATOGRAPHY3.1 THE CHROMATOGRAPHIC MEDIUM

3.1.01 Active SolidA solid with sorptive properties.3.1.02 Modified Active Solid

An active solid the sorptive properties of which have been changed by some treatment.3.1.03 Solid SupportA solid that holds the stationary phase but, ideally, does not contribute to the separation process.3.1.04 BindersAdd itives used to hold the solid stationary phase to the inactive plate or sheet in thin-layerchromatography.3.1.05 Gradient Layer

The chromatographic bed used in thin-layer chromatography in which there is a gradualtransition in some property.3.1.06 ImpregnationThe modification of the separation properties of the chromatographic bed used in planarchromatography by appropriate additives.


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3.1.07 PackingThe active solid , stationary liquid plus solid support, or swollen gel contained in a tube.3.1.07.1 Totally Porous PackingHere the stationary phase perm eates each porous particle.3.1.07.2 Pellicular PackingIn this case the stationary phase forms a porous outer shell on an impermeable particle.3.1.08 Particle Diameter (dJThe average diameter of the solid particles.3.1.09 Pore Radius


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832 COMMISSIONS ON CHROMATOGRAPHY AND A NAL YTICAL NOMENCLATURE

3.2.05 Column Volume (V ,)The geometric volum e of the part of the tube that contains the packing:V c = A c Lwhere Ac is the in ternal cross-sectional area of the tube and L is the length of the packed part ofthe column.In the case of wall-coated open-tubular columns the column volume corresp ond s to thegeom etric volum e of the whole tube having a liquid or a solid stationary phase on its wall.

3.2.06 Bed VolumeSynonym ous with Column Volume for a packed column.3.2.07 Column Diameter (d c )The inner diameter of the tubing.3.2.08 Column Radius ( r c )The inside radius of the tubing.3.2.09 Column Length (L )The length of that part of the tube which contains the stationary phase.3.2.10 Cross-Sectional Area of the Column ( A c )The cross-sectional area of the empty tube:

3.2.11 Interparticle Volume of he Column (V ,)Th e volume occup ied by the mobile phase between the particles in the packed section of acolumn. It is also called the Interstitial Volume or the Void Volume of the column.3.2.11.1 In liquid chromatography, the interparticle volume is equal to the m obile-phase holdup volume(V,) in the ideal case, neglecting any extra-column volume.3.2.1 1 .2 In gas chrom atography , the symbol VGmay be used for the interparticle volum e of the column.In the ideal case, neglecting any extra-column volum e, VG s equal to the corrected gas hold-up

volume (VJ (see 3.6.03 and 3.7.04):v G = v ; V , . J

3.2.12 Interparticle Porosity ( )The interparticle volum e of a packed column per unit column volume:

It is also called the Interstitial Fraction of the colum n.3.2.13 Extra-column VolumeThe volume between the effective injection point and the effective detection point, excluding thepart of the column con taining the stationary phase. It is composed of the volum es of the injector,connecting lines and detector.


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3.2.13.1 Dead-VolumeThis term is also used to express the extra-column volume. Strictly speaking, the term dead-volum e refers to volum es within the chrom atographic system which are not swept by themobile phase. On the other hand, mobile phase is flowing through most of the extra-columnvolum es. Due to this ambiguity the use of the term dead-volum e is discouraged.3.2.14 Liquid-Phase Film Thickness (d ,)A term used in connection with open -tubular colum ns to express the average thickness of theliquid stationary phase film coated on the inside wall of the tubing.3.2.15 Stationary-Phase Volume (V , )The volume of the liquid stationary phase or the active solid in the colum n. The volum e of anysolid support is not included. In the case of partition chrom atography with a liquid stationaryphase, it is iden tical to the Liquid-Phase Volume (V , ) .3.2.16 Mass (Weight)of the Stationary Phase W,)

The mass (weight) of the liquid stationary phase or the active solid in the column. T he mass(weight) of any solid support is not included. In the case of partition chromatography w ith aliquid stationary phase it is identical to the Liquid Phase M ass (Weight) (W,).3.2.17 Phase Ratio p)The ratio of the volume of the mobile phase to that of the stationary phase in a column:

p=v01v,In the case of open-tubular colum ns the geometric internal volum e of the tube ( V , ) is to besubstituted for Vo.

3.2.18 Specific Permeability (B o)A term expressing the resistance of an empty tube or packed column to the flow of a fluid (themobile phase). In the case of a packed columnd,' E~ d,'Bo = s

180(1 - E ) ~ 10oOIn the case of an open-tubular colum n

3.2.19 Flow Resistance Parameter (0 )This term is used to compare packing density and permeability of columns packed with differentparticles; it is dim ensionless.

where d p s the average particle diameter. In open-tubular colum ns


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834 COMM ISSIONS ON CHROMATOGRAPHY AN D ANALYTICAL NOMENCLATURE

3.3 THE CHROMATOGRAM3.3.01 Differential Chromatogram

A chrom atogram obtained with a differential detector (see Fig. 1A).3.3.02 Integral Chrom atogram

A chrom atogram obtained with an integral detector (see Fig. 1B).3.3.03 Starting Point or LineT h e p o i n t or l i n e on a c h r om a togr a ph ic p a pe r o r l a ye r whe r e the subs ta n c e to bechromatographed is applied (P in Fig. 2).3.3.04 spot

A zone in paper and thin-layer chromatography of approximately circular appearance.3.3.04.1 Spot Diameter (ST in Fig. 2)

The width of the sample com ponent spot before or after chromatography.3.3.05 BaselineThe portion of the chrom atogram recording the detector response when on ly the mobile phaseemerges from the column.

Y

@ D/FFEK/VTIAL RECORD PRODUGDBY DKFRN 7ZAL D TCTORS

IIIIIIIIIII i i

Figure 1. Typical chromatogram: A, differential record produced by differential detector; B, integralrecord produced by integral detector.


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Figure 2. Typical planar chromatogram

3.3.06 PeakTh e portion of a differential chromatogram recording the detector respon se when a singlecomponent is eluted from the column (see Fig. 1A). If separation is incomplete, two or morecomponents may be eluted as one Unresolved Peak.3.3.06.1 Peak Base (CD in Fig. 1A)The interpolation of the baseline between the extrem ities of the peak.3.3.06.2 Peak Area (CHFEGJD in F ig. 1A)The area enclosed between the peak and the peak base.3.3.06.3 Peak Maximum (E in Fig. 1A)The point on the peak at which the distance to the peak base, measured in a direction parallel to

the axis represen ting detecto r response, is a maximum.3.3.06.4 Peak Height (EB in Fig. 1A)The distance between the peak m aximum and the peak base, m easured in a direction parallel tothe axis representing detector response.3.3.06.5 Standard Deviation 0)The term in the exponent of the equation relating the width and height of a Gaussian peak:

2Y=Y,.exP*- [where y is the peak h eight at any point on the peak, yo is the peak height at maxim um, x is thedistance from the ordinate (i.e., half of the width at that point), and 0 s the standard deviation ofthe peak. In practice, the standard deviation can be calcu lated from one of the peak-width valuesspecified below.


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836 COMMISSIONS ON CHROMATOGRAPHY AN D ANAL YTICAL NOMENCLA TURE

L v b 4 r -Figure 3 Widths of a Gaussian peak at various heights, as a functionof the standard deviation of the peak.

3.3.06.6 Variance of the PeakThe square of the standard deviation (c?).3.3.07 Peak-WidthsPeak-widths represent retention dimensions (time or volume) parallel to the baseline. If thebaseline is not parallel to the axis representing time or volume, then the peak-widths are to bedrawn parallel to this axis. Three peak-width values are commonly used in chromatography (seeFig. 1A and Fig. 3).3.3.07.1 Peak-Width at Ba se (w , ) (KL n Fig. 1A and Fig. 3)The segment of the peak base intercepted by the tangents drawn to the inflection points on eitherside of the peak.3.3.07.2 Peak-Width at H alfHeight ( w , ) HJ n Fig. 1A and Fig. 3)The length of the line parallel to the peak base at 50% of the peak height that terminates at theintersection with the two limbs of the peak.

Note: The peak-width at base (w , ) may be called the base width . However, the peak widthat half height ( w , ) must never be called the half width because that has acompletely different meaning. Also, the symbol w I R should never be used instead ofwh*

3.3.07.3 Peak-Width at Inflection Points (wi) (FG in Fig. 1A and Fig. 3)The length of the line drawn between the inflection points parallel to the peak base.


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3.3.07.4 In the case of Guassian (symmetrical) peaks, the peak-widths are related to the standarddeviation ( 0 )of the peak according to the following equations:w b = 0w i = 0w,, 2 0 2 In 2) = 2.355 Q

3.3.08 TailingAsymmetry of a peak such that, relative to the baseline, the front is steeper than the rear. Inpaper chromatography and thin-layer chromatography, it refers to the distortion of a spotshow ing a diffuse region behind the spot in the direction of flow.3.3.09 Fronting

Asym metry of a peak such that, relative to the baseline, the front is less steep than the rear. Inpaper chromatography and thin-layer chromatography, it refers to the distortion of a spot,show ing a diffuse region in front of the spot in the direction of flow.3.3.10 StepTh e portion of an integral chromatogram recording the amount of a comp onen t, or thecorresponding change in the signal from the detector as he component emerges from the column

(see Fig. IB).3.3.10.1 Step Height (NM in Fig. 1B)The distance, measured in the direction of detector response, between straight-line extensions ofthe baselines on both sides of a step.3.3.11 Internal Standard

A com pound added to a sample in known concentration to facilitate the qualitative identificationand/or quantitative determination of the sample components.3.3.12 External StandardA compound present in a standard sample of known concentration and volume which is analysedseparately from the unknown sample under identical conditions. It is used to facilitate thequalitative indentification and/or quantitative determination of the sam ple compo nents Thevolum e of the external standard (standard sample) need no t to be known if it is identical to thatof the unknown sample.3.3.13 MarkerA reference substance chromatographed with the sample to assist in identifying the com ponents.

3.4 DIFFUSIONThe diffusion coefficient ( 0 )s the am ount of a particular sub stance that diffuses across a unitarea in 1 s under the influence of a grad ient of one unit.It is usually expressed in the units cm' s- .

3.4.01

3.4.02 Diffusion Coefficient in the Stationary Phase ( Ds or D,)Th e diffusion coefficient characterizing the diffusion in the stationary phase. In partitionchromatography with a liquid stationary phase, the symbol D , may be used to express this term.

3.4.03 Diffusion Coefficient n the Mobile Phase (D , or D G )Th e d i f f us ion c oe f f i c i e n t c ha r a c te r i z ing the d i f f us ion in the m ob i l e pha se . I n ga sChromatography where the m obile phase is a g as, the sym bol D , may be used to express thisterm.


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838 COMMISSIONS O N CHROMATOGRAPHY A ND ANALYTICAL NOMENCLATURE

3.4.04 Diffusion Velocity (%)This term is used in liquid chromatography in the expression of the reduced mobile-phasevelocity (see 3.6.05.3).The diffusion velocity expresses the speed of diffusion in to the pores ofthe particles:

3.5 TEMPERATURES3.5.01 Ambient Temperature (T, )The temperature outside the chrom atographic system.3.5.02 Injection TemperatureThe temperature within the injection device.3.5.03 Separation Temperature (Tc)The t e m pe r a tu r e of the chromatographic bed under i so thermal opera t ion . In columnchromatography it is called the Column Temperature.3.5.04 Temperatures During Programm ed-Temperature Analysis3.5.04.1 Initial TemperatureThe temp erature of the chromatographic bed (column) at the start of the ana lysis. Temperatureprogramming might start imm ediately upon sample introduc tion or it can be preceded by a shortisothermal per iod (Ini t ia l Iso thermal Tempe rature) . In this case, the time of the Initial

Isothermal Perio d must also be specified.3.5.04.2 Program RateThe rate of increase of colum n temperature. The rate of temperatu re increase is usually linear(OC.min-') but it may also be non-linear. During one analysis the temperature rate may bechanged and/or the temperature programming may be interrupted by an isothermal period. Inthis case one is spe aking about Multiple Programming. In multiple programming each programmust be specified by its initial and final temperatures and program rate.3.5.04.3 Mid-Analysis Isothermal Temperature

The tem perature of the colum n in an iso therma l period during elution. The corresponding time(Mid-Analysis Isothermal Perio d) must also be specified.3.5.04.4 Final TemperatureThe h ighest temperature to which the column is programmed.3.5.04.5 Final Isothermal TemperatureTh e fina l temperature of the program if it is followed by an isothermal p eriod. Th e timecorresponding to the Final Isothermal Period must also be specified.3.5.04.6 Retention TemperatureThe column tem perature corresponding to the peak m aximum.3.5.05 Dete ctor TemperatureThe tem perature of the detector cell. In the case of a detector incorporating a flam e, it refers tothe tem perature of the detector base.


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Nomenclature for chromatography

3.6 THE MOB ILE PHASE839

3.6.01 Mobile Phase Viscosiry(q)The viscosity of the mobile phase at the temperature of the chrom atographic bed.3.6.02 Pressures3.6.02.1 Inlet Pressure (pi)The absolute pressure at the inlet of a chromatographic column.3.6.02.2 Outlet Pressure (p, )The abso lute pressure at the exit of a chrom atographic column. It is usually but not necessarilyequal to the Ambient Pressure pa , the atmospheric pressure outside the chromatographicsystem.3.6.02.3 Pressure Drop 4)The difference between the inlet and outlet pressures:

3.6.02.4 Relative Pressure ( P )The ratio of the in let and outlet pressures:

3.6.03 Mobile Phase Compressibility Correction Factor ( )A factor, applying to a hom ogeneously filled column of uniform diameter, that corrects for thecom pressib ility of the mobile phase in the column. It is also called the CompressibilityCorrecrion Factor. In gas chromatography, the correction factor can be calculated as:3 p 2 - 1 3 (p, lp0)2-12 p 3 - 1 2 ( p i i p , ) 3 - 1

j = - - - - -In liquid chromatography the compressibility of the mobile phase is negligible.Note: In form er nomenclatures the term pressure gradient correction factor was sometimes

used to express the same term. T his is, how ever, an incorrect name, because it is no tthe pressure g radient but the com pression of the mobile phase which necessitates theuse of this factor. In liquid chrom atography, where mobile phase com pression isnegligible, no correction factor has to be applied to the mo bile phase velocity;however, there is still a pressure gradient along the colum n.3.6.04 Flow RateThe vo lume of m obile phase passing through the column in unit time.3.6.04.1 The flow rate is usually measured at column outlet, at ambient pressure pa and temperature (Ta,in K); this value is indicated with the sym bol F . If a water-containing flowmeter was used forthe measuremen t (e.g., the so-called soap bubble flowm eter) then F must be corrected to dry gasconditions in order to obtain the Mobile Phase Flow Rate at Ambient Temperature ( F a ) :

where p , is the partial pressure of water vapor at ambient temperature.


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840

3.6.04.2

3.6.053.6.05.1

3.6.05.2

3.6.05.3

COMMISSIONS O N CHROMATOGRAPHY AN D ANALYTICAL NOMENCLATURE

In order to specify chromatographic c onditions in column chrom atography, the flow-rate(Mobile Phase Flow Rare at Column Temp erature, F , ) must be expressed at Tc (kelvin), thecolumn temperature:

VelocitiesMobile-Phase Velocity (u)The linear velocity of the m obile phase across the average cross-section of the chromatographicbed or column. It can be calculated from the column flow-rate at column temperature (F , ) , thecross-section al area of the colum n ( A c )and the interparticle porosity (E):u = F , / ( E A JIn practice the mobile phase velocity is usually calculated by dividing the column length (L) bythe retention time of an unretained compound r,; see 3.7.03):u = L I t ,In gas chromatography, due to the co mp ressibility of the carrier gas, the linea r velocity will bedifferen t at differen t longitudinal positions in the column. T here fore two terms must bedistinguished:The Carrie r Ga s Velocity at Column Outlet u,) can be o btained as above, from the carrier gasflow rate measured at column outlet:u0= F , I (E A,)The Average Linear Ca rrie r Ga s Velocity (0) s obtained from uo, by correcting it for gascompressibility:i i u o j

The ave rage linear carrier gas velocity can a lso be obtained by dividing column length (L)by theretention time of an unretained compound r,):R = wt,In liquid chromatography where m obile phase compression is negligible,2 = uReduced Mobile Phase Velocity (u)A term used mainly in liquid chromatograph y. It comp ares the mo bile phase velocity with thevelocity of diffusion into the pores of the particles (the so-called diffusion velocity, uD: ee3.4.04):U i i l u D = i idJDMIn open-tubular chromatography:


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Nomenclature for chrom atogrephy 841

3.7 RETENTION PARAMETERS IN COLUMN CHROMATOGRAPHY3.7.01 Retention parameters may be measured in terms of chart distances or times, as well as mobilephase vo lumes; e.g., tR (time) is analogous to VR' (volum e). If recorder speed is constan t, thechart distances are directly proportional to the times ; similarily if the flow rate is cons tant, thevolumes are directly proportional to the times.

Note: In gas chromatography, or in any chromatography where the mobile phase expands inthe column, V,, VR nd VR' represent volumes under column outlet pressure. If Fc, thecarrier gas flow rate at the column outlet and corrected to column temperature (see3.6.04.2). is used in calculating the retention volumes from the retention time values,these correspond to volumes at column temperatures.

3.7.02 The various conditions under which retention volumes (times) are expressed are indicated bysuperscripts: thus, a prime ('; as in V i ) efers to correction for the hold-up volume (and time)while a circle ("; as in VRo )efers to correction for mobile-phase compression. In the case of thenet retention volume (time) both corrections should be applied: however, in order not to confusethe symbol by the use of a double supe rscript, a new symb ol (V,, t,) is used for the netretention volume (time).

3.7.03 Hold-up Volume (Tim e) (V,, t,)The volume of the mobile phase (or the corresponding time) required to elute a componen t theconcentration of which in the stationary phase is negligible compared to that in the mobilephase. In other words, this component is not retained at all by the stationary phase. Thus, thehold-up volume (time) is equal to the Retention Volume (Ti me ) of an Unretained Compound.The hold-up volum e (time) corresponds to the distance OA in Fig. 1A and it includes anyvolumes contributed by the sample injector, the detector, and connectors..

In gas chromatography this term is also called the Gas H old-up Volume (Tim e).

3.7.04 Corrected G as Hold-up Volume (V, )The gas ho ld-up volume multiplied by the compression (compressibility) correction factor ( ):V, = v, . jAssuming that the influence of extracolum n volume on V , is negligible,V, = v,(see 3.2.11.2)

3.7.05 Total Retention Volume (Tim e) (V,, t R )The vo lume of m obile phase entering the column between sample injection and the em ergenceof the peak m aximum of the sam ple component of interest (OB in Fig. la ), or the correspondingtime. It includes the hold-up volume (time):


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842 COMMISSIONS ON CHROMATOGRAPHY AND ANALYTICAL NOMENCLATURE- -3.7.06 Peak Elution Volume (Time) (V,, t,)Th e volume of mobile phase entering the column between the start of the elution and theemergence of the peak maxim um, or the corresponding time. In most of the cases, this is equalto the total retention volume (time ). There are, how ever, cases when the elution process does notstart immediately at sample introduction. For exam ple, in liquid chrom atography, sometimes the

column is washed with a l iquid af ter the app licat ion of the sam ple to displa ce cer ta incom ponen ts which are of no interest and during this treatment the sample does not m ove alongthe column. In gas chromatography, there are also cases when a liquid sample is applied to thetop of the column b ut its elution starts only after a given period. T his term is useful in suchcases.3.7.07 Adjusted Retention Volume (Time ) (V,', t, )The total elution volum e (time) minus the hold-up volume (time). It correspo nds to the d istanceAB in Fig. la:

V,' = v, - VMt = tR - tM= (VR-VM)IFc VJFc

3.7.08 Corrected Retention Volume (Tim e) VRo,Ro)The total retention volume (time) multiplied by the compression correction factor 0:V R o = V , . jt R o = V R . j / F c = V R 0 l F c

3.7.09 Net Retention Volume (Tim e) (V,, t , )The adjusted retention volume (time) multiplied by the compression correction factor 0:V ,= V i . jt N = V l ; . j / F c = V N I F c

3.7.10 In liquid chromatography, the compression of the mobile phase is negligible and thus, thecom pression correction factor does not apply. For this reason, the total and corrected retentionvolumes (times) are identical (V, = VRo ; R = tN) and so are the adjusted and net retentionvolumes (times) (Vl;= V N ; l; = t N ) .3.7.1 1 Specific Retention Volumes3.7.1 1 . 1 The specific retention volum e at column temperature (Vp )The net retention volume per gram of stationary phase (stationary liquid, active solid or solvent-free gel (W,) :

v;= V N I W S3.7.11.2 Specific retention volume a t 0 O ( V , )

The value of V, corrected to 0 OC:273.15K V,, 273.15K

where T, is the column temperature (in kelvin).


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Nomenclature for chromatography a43

3.7.12 Retention Factor (k)The retention factor is a measure of the time the sample component resides in the stationaryphase relative to the time it resides in the mobile phase: it expresses how much longer a sam pleco m p o n e n t i s r e t a r d ed b y th e s ta t i o n a r y p h ase t h an i t w o u ld t ak e to t r av e lt h r o u g h t h e co lu mn w i th t h e v e lo c i t y o f t h e mo b i l e p h ase . M a th emat i ca l l y , i t i sthe ratio of the adjusted retention volume (time) and the hold-up volume (time):k = V i / V u = t i l t uIf the distribution constant (see 3.9) is independent of sam ple component concentration, then theretention fac tor is also equal to the ratio of the am ounts of a sample comp onent in the stationaryand mobile phases respectively, at equilibrium:

amoun t of compon ent in stationary phasen - ~~~~~ amount of com ponent in mobile phaseIf the fraction of the sample component in the mobile phase is R (see 3.7.13), then the fraction inthe stationary phase is (1 - R); thusk = (1 - R ) / RNote: In former nom enclatures and in the literature one may find the expression s PartitionRatio, Capacity Ratio, Capacity Factor or Mass Distribution Ratio to describe thisterm.In the literature the symbol k is often used for the retention facto r, particularly inliquid chromatography. The o riginal reason for this was to clearly distinguish it fromthe partition coefficient (distribution constant) for which the symbol K had been

utilized. Since, however, the distribution constan ts are all identified with a subscript,there is no reason to add the prime sign to this symbol. It should be emphasized thatall the recognized nomenclatures (IUPAC, BS,ASTM ) have a lways clearly identifiedthe capacity factor with the symbol k and not k.3.7.12.1 Logarithm of the Retention FactorThis term is equivalent to the R , value used in planar chromatography (see 3.8.05). Th e symbol

K s sugg ested to express log k:

3.7.13 Retardation Factor (R)The fraction of the sam ple component in the mobile phase at equilibrium ; it is related to theretention factor and other fundamental chromatography terms:R = l /(k+ 1)

3.7.14 Relative Retention Values3.7.14.1 Relative Retention (r)The ratio of the adjusted or net retention volume (time ) or retention fa ctor of a compon ent

relative to that of a standard , obtained under identical conditions:

Dep ending on the relative position of the peak correspondin g to the standa rd compo und in thechromatogram, the va lue of r may be smaller, larger or identical to unity.


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844 COMMISSIONS ON CHROMATOGRAPHY AN D ANA LYTICAL NOMENCLATURE3.7.14.2 Separation Facto r a)The relative retention value calculated for two adjacentpeaks (VR; > VR; ):

a = VR; VR; = VNz/VNl= tR; I tR; = k , / k ,By definition, the value of the separation factor is always greater than unity.The separation factor is also identical to the ratio of the corresponding distribution constants.Note: The separation factor is sometimes also called the selectivity . T he use of thisexpression is discouraged.

3.7.14.3 Unadjusted Relative R etention (rGor aGRelative retention calculated by using the total retention volumes (times) instead of the adjustedor net retention volumes (times):k;+ 1

Subscript G commem oratesE. Glueckauf, who first used this expression.3.7.14.4 Relativ e retention ( r ) and separation facto r a) alues must alwa ys be measured underisothermal conditions. On the other hand, the 'unadjusted relative retention (rGor aG) alues mayalso be obtained in programmed-temperature or gradient-elution conditions. Under suchconditions, the symbol RRT (for Relative Retention Time) has also been used to describe theunadjusted relative retention values.Using the same stationary and mobile phases and temperature, the rela tive retention andseparation factor values are reproducible between chrom atographic systems. On the other hand,the unadjusted relative retention (and relative retention time ) values are only reproducible

within a single chromatographic system.3.7.15 Retention Index; Kovdts (Retention) Index l)Th e retention index of a sample component is a number, obtained by interpolation (usuallylogarithmic), relating the adjusted retention volume (time) or the retention factor of the samplecomponent to the adjusted retention volumes (times) of two s tandards eluted before and after the

peak of the sample component.In the Kovdts Index or Kovdts Retention Index used in gas chromatography, n-alkanes serve asthe standards and logarithmic interpolation is utilized:I = 100 z1% x + 1) - 1%xzlogxi logxzwhere X efers to the adjusted retention volumes or times, z s the number of carbon atoms of then-alkane eluting before, and z 1) is the number of carbon atoms of the n-alkane eluting afterthe peak of interest:The Kovdrs (Retention) Index expresses the num ber of carbon atom s (multiplied by 100) of ahypothetical norma l alkane which wou ld have an adjusted retention volume (time) identical tothat of the peak of interest when analyzed under identical conditions .The Ko vdts Retention Index is always m easured under isotherm al conditions. In the case oftemperature-programmedgas chromatography a similar value can be calculated utilizing directnum bers instead of their logarithm. Since both the num erator and denominator contain thedifference of two values, here we can use the total retention volumes (times ). Sometim es this


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Nomenclature for chrom atography 845

value is called the Linear Reten tion Index:

where t i refers to the total retention times (chart distances) m easured under the conditions oftemperature programming. T he value of IT will usually differ from the value of I measured forthe same compound under isothermal conditions, using the same two phases.3.8 RETENTION PARAMETERS IN PLANAR CHROMATOGRAPHY

3.8.01 Mobile-P hase FrontThe leading edg e of the mo bile phase as i t traverses the plana r media. In all form s ofdevelopment except radial, the mobile phase front is essentially a straight line parallel to themobile phase surface . It is also called the Liquid Front or Solvent Front.3.8.02 Mobile-Phase Distance

The distance travelled by the mobile phase travelling a long the medium fro m the starting(application) front or line to the mobile phase front. It is the distance a in Fig. 2 .3.8.03 Solute DistanceThe distance travelled by the solute along the m edium from the starting (application) point orline to the center of the solute spot. If the solute spot is not circular, an imaginary circle is usedwhose diam eter is the smallest axis of the spot. It is the distance b in Fig.2.3.8.04 Retardation Factor (R ,)Ratio of the distance travelled by the center of the spot to the distance simultaneously travelled

by the mobile phase. Using the symbols of Fig. 2:R , = b l aBy definition the R , values are always less than unity. They are usually given to two decimalplaces . In order to simplify this presentation the hR, Values may be used: they correspond to theRFvalues multiplied by 100.Ideally, the R, values are identical to the R values (see 3.7.13).

3.8.05 R, ValueA logarithm ic function of the R, value:

1 - R F 1R , = log -= 1% [R 11RF3.8.06 Relative Retardation (Rre,)This term is equivalent to relative retention used in co lumn chromatography: it is the ratio of theR , value of a componen t to the R, value of a standard (reference) substance. Since the mobilephase front is com mon for the two components, the RRl value can be expressed directly as theratio of the distances travelled by the spot of the compound of interest (bi ) and the referencesubstance (bs,) respectively:

Note: In former nomenclatures the symbol Rs was used to express relative retardation inplanar chromatography . Because of its identity with the symbol for peak resolution(see 3.10.01) the symb ol Rrel s sugges ted for re la t ive re tardat ion in p lanarchromatography.


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846 COMMISSIONS ON CHROMATOGRAPHYAND ANALYTICAL NOMENCLATURE3.9 DISTRIBUTION CONSTANTSTh e distribution constant is the concentration of a comp onent in or on the stationary phasedivided by the conc entration of the component in the mobile phase. Since in chroma tography acomponent may be present in m ore than one form (e.g., associated and dissociated forms), theanalytical condition used here refers to the total amount present w ithout regard to the existenceof various forms.These terms are also called the Distribution Coefficients. How ever, the present term conform smore closely to the general usage in science.The concentration in the mo bile phase is always calculated per unit volume of the phase.Depe nding on the way the concentration in the stationary phase is expressed various forms ofthe distribution constants may exist.

3.9.01 Distribution Constant K,In the general case, the concentration in the stationary phase is exp ressed per unit volume of thephase. This term is mainly applicable to partition chromatography with a liquid stationary phasebut can also be used with a solid s tationary phase:

where Wis)and WjM ) are the amounts of component i in the stationary and m obile phases ,while V s and VM are the volumes of the stationary and mobile phases, respectively.The term Distribution Constant and the symb ol K , are recommen ded in preference to the termPartitio n CoefSicient which has been in use in partition chromatography with a liquid stationaryphase.The value of K , is related to the retention volum e (V,) of a sam ple component and the volumesof the stationary (V,) and m obile phases (V,) in the colum n:VR= VM + K,VsIn gas chromatography both VR and VM have to be corrected for gas compressibility: thereforeVRo see 3.7.08) s to be used for VR,and VG= VMo see3.2.1 1.2) is to be used for VwVRo= VG +K,. Vs

3.9.02 Distribution Constant KgIn the case of a solid stationary phase, the distribution constant may be ex pressed p er m ass(weight) of the dry solidphase:

where Wist) and WjM) are the amounts (masses) of the component i in the stationary and mobilephases, respectively, W, s the mass (weight) of the dry stationary phase, and VMis the volumeof the mob ile phase in the colum n.


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3.9.03 Distribution Constant K,In the case of adsorption chromatography with a well characterized adsorbent of known surfacearea, the concentration in the stationary phase may be expressed per unit suMace area :Wi (s) A SWim V M

K,

where Wi s)and Wim re the amounts (masses) of the com ponent i in the stationary and mobilephases, respectively, A, is the surface area of the stationary phase, and VMis the volum e of themobile phase in the column.Note: The symbols used in 3.9.01 through 3.9.03 are generalised.

3.10 TERMS EXPRESSING THE EFFICIENCY OF SEPARATION3.10.01 Peak Resolution (RJThe separation of two peaks in terms of their average peak width at base (tR2z fm):

(m tR1)-R2 1 )R , = -(wbl + wb2 ) / 2 wbl + wb2

In the case of two adjacent peaks it may be assumed that wbl= wb2, nd thus, the width of thesecond peak may be substituted for the average value:Rs (fR2 - 1) 1 b2

3.10.02 Separation Number (SN)This expresses the number of peaks which can be resolved in a given part of the chromatogrambetween the peaks of two consecutive n-alkanes with z and (z + 1) carbon atom s in theirmolecules:SN = - 1tR(r 1 Rz

whz + wh(r 1)In the G erman literature the symbolTZ Trennzahl) is comm only used to express the separationnumber.As the separation number depends on the n-alkanes used for the calculation, they always must bespecified with any given SN value.

3.10.03 Plate Number N)A number indicative of column performance, calculated from the following equations whichdepend on the selection of the peak width expression (see 3.3.07):N = ( V , / O ) = (tR/G)N = 16 ( V R /wb) = 16 tR/wb)N = 5.545 ( V R /wh) 5.545 ( t R /wh)Th e value of 5.545 stands for 8 In 2 (see 3.3.07.4) . Th ese expressions assume a Guassian(symm etrical) peak.


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848

3.10.04

3.10.05

3.10.06

COMMISSIONS O N CHROMATOGRAPHY AN D ANALYTICAL NOMENCLATURE

In these expression s the units for the quantities inside the brackets must be consistent so thattheir ratio is dimensionless: i.e., if the numerator is a volum e, then peak width m ust also beexpressed in terms of volume.Note: In forme r nomenclatures the expressions Num ber of Theo retical Plates orTheoretical Plate Num ber were used for the same term. For simplification, the

present name is suggested.EffectivePlate Number ( N , f f )A number indicative of column perform ance calculated by using the a djusted retention volume(time) instead of the total retention volum e (time). It is also called the Number of EffectivePlates:Ne, = ( V i o ) ~ (ti o ) ~Ne, = 16 ( V i wb) = 16 ( t i w ~ ) ~Ne, = 5.545 (VI; / wh )2 = 5.545 ( t i / wh)2The plate number and effective plate number are related to each o ther:

k + l

Where k s the retention factor (see 3.7.12).Notes: In the former literature the expression num ber of effective theoretical plates hadbeen used to express this term. This is incorrect since the plate num ber is eithertheoretical or effective, but cannot be both.

In form er nomenclatures the respective symbo ls n and N have been used for the platenum ber and the effective plate number. Howev er, there was often a confusion in theproper selection of lower case and cap ital letters; therefore, the pres ent usage,characterizing the effective plate number by a subscript, is suggested.Plate Height H)The column length 15) ivided by the plate number:H = L I NIt is also called the Height Equivalent to One Theoretical Plate (HETI').Effective Plate Height H, )The colum n length divided by the effective plate number:

It is a lso called the Height Equivalent to One Efective Plate.Notes: In the former literature the expression height equivalent to one effective theoreticalplate had been used to express this term. Th is is incorrect, since the plate heighr iseither theoretical or effective see3.10.04). but cannot be both.


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Nomenclature for chromatography 849In former nomenclatures the respective symbols h and H have been used for the plateheight and the effective plate height, respectively. However, there was often aconfusion in the proper selection of lower case and capital letters and also due to thefact that h (lower case letter) is also used to express the reduced plate height (see3.10.07). The present usage is suggested in order to avoid any confusion.

3.10.07 Reduced Plate Height ( h )A term used in liquid chromatography. It is the ratio of the plate height to the average particlediameter:h = H l d pFor open-tubular columns:h = H l d c

4. TERMS RELATED TO DETECTION4.1 CLASSIFICATION OF DETECTORS

4.1.01 Classification According to the Form ofResponse4.1.01.1 Differential D etectorsThese measure the instantaneous difference in the composition of the column effluent.4.1.01.2 Integral DetectorsThese measure the accumulated quantity of sample component(s) reaching the detector.4.1.02 Classification According to the Basis of Response4.1.02.1 Concentration-SensitiveDetector

A device the response of which is proportional to the concentration of a sample component inthe eluent.4.1.02.2 Mass-Flow Sensitive Detector

A device the response of which is proportional to the amount of sample component reaching thedetector in unit time.4.1.03 Classification According to Detector Selectivity4.1.03.1 Universal Detector

A detector which responds to every component in the column effluent except the mobile phase.4.1.03.2 Selective DetectorA detector which responds to a related group of sample components in the column effluent.4.1.03.3 Specific Detector

A detector which responds to a single sample component or to a limited number of componentshaving similar chemical characteristics.


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850

4.2.01

4.2.01.1

4.2.01.2

4.2.01.3

4.2.02

COMMISSIONS O N CHROMATOGRAPHY AND ANALYTICAL NOMENCLATURE

4.2 DETECTOR RESPONSEDetector Sensitivity (S)The signal output per unit concentration or unit mass of a substance in the m obile phase enteringthe detector.

In the ca lculation of detec tor sensitivity the signal outpu t of the detector is given as peak area inmV.min, A.s or AU.min (AU = absorbance unit). These values are obtained from the integratedpeak area converted to the units specified.Alternately, the peak area can also be obtained by mu ltiplying the peak he ight at max imum (inmV, A or AU) by the peak-w idth at half height (in time units). The peak area calculated in thisway will be 6% less than the true integrated peak area, assuming that the peak is G aussian.In the case of concentration-sensitivedetectors, sensitivity is calculated per unit concentration inthe mobile phase:S = A i F c l W i = E I C iwhere Ai is the integrated peak area (in mV.min or AU.min), E is the peak height (in mV orAU), C j s the concentration of the particular substance in the mob ile phase at the detector (ing . ~ m - ~ ) ,, s the mobile phase flow rate corrected to column temperature (in cm3.min-') and W iis the mass (amount) of the substance present (in mg). The dimensions of detector sensitivity aremV.cm3.mg-' or AU.cm3.mg-'.In the case of therm al-condu ctivity detectors, this sensitivity value is also called the Dimbat-Porter-Stross Sensitivity of the d etector.

In the c ase of mas s-flow sensitive de tectors, sensitivity is calculated per unit mass of the testsubstance in the m obile phase entering the detector:S = A i / W i = E i / M jwhere Ai is the integrated peak area (in A s), E . is the peak heigh t (in A ), Mi is the m ass rate ofithe test substance entering the detec tor (in g.s- ), and W i is the mass (amou nt) of test substancepresent (in g). The dim ension of detec tor sensitivity is A.s.g-' or C.g-'.Relative Detector Response Factor (f )The rela tive detector response factor expresses the sensitivity of a d etector relative to a standardsubstance. It can be expressed on an equal mole, equal volum e or equal mass (w eight) basis:

where A refers to the peak area of the compound of interest (subscript i ) and s tandard (subscriptst) respective ly, and f,, is the response factor of the standard comp ound. Usua lly, an arbitraryvalue (e.g., 1 or 100) is assigned to f .Expressing the relative molar responses and using n-alkanes as the standards, the assigned value off, is usually the number of carbon atom s of the n -alkanes m ultiplied by 100 (e.g., 600 for n-hexane).If the relative de tector response fac tor is expressed on an eq ua l mass (w eight) basis, thedeterm ined sensitivity values can be su bstituted for the peak area.


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Nomenclature for chromatography 8514.3 NOISE AND DRIFT

4.3.01 Noise N) (See Fig. 4)The amplitude expressed in volts, amp eres, or absorbance units of the envelop e of the baselinewhich inc ludes all random variations of the detector signal the frequency of which is in the orderof one or more cycles per minute. In the case of photometric detectors the amplitude may beexpressed in absorbance units per unit ce ll length.

4.3.02 Drift (see Fig.4)The average slope of the noise envelope , expressed in volts, amp eres, or absorbance units perhour. It may be actually measured for 0.5 hour and extrapo lated to on e hour.

HE .SPCIFED DRIFT FOR W6MUR I5 TWICE TH/S DPIFT

I-IrrME

Figure 4. Measurem ent of the noise and drift of a chromatographic detector.

4.4 MINIMUM DETECTA BILITYThe concen tration or mass flow of a sample component in the mobile phase that gives a detectorsignal equal to twice the no ise level. It can be calculated from the measured sensitivity (5 ) andnoise N):D = NISwhere D is the m inimum detectability, expressed either as concentration or mass-flow of thesubstance of interest in the mobile phase at the detector. Both sensitiv ity and minimumdetectability must be determined for the same substance.


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852

4.5.014.5.01.1

4.5.01.2

t:

k8

s

cB

4.5.01.3

4.5.01.4

4.5.01.5

COMMISSIONS ON CHROMATOGRAPHY AND ANALYTICAL NOMENCLATURE

4.5 LINEAR AND DYNAMIC RANGESLinear RangeThe linear range of a chromatographic detector represents the range of concentrations or massflows of a substance in the mobile phase at the detector over which the sensitivity of the detectoris constant within a specified variation, usuallyf percent.The best way to present detector linear range is the Linearity Plot (see Fig. 5 ) plotting detectorsensitivity against amount injected, concentration or mass flow-rate. Here, the upper limit oflinearity can be graphically established as the amount, concentration,or mass flow-rate) at whichthe deviation exceeds the specified value (k x% window around the plot). The lower limit oflinearity is always the minimum detectable amount determined separately for the samecompound.

C O T R A T l O N OR MASS FLOW OF n /E rESTSUBSTANCE / THE M081.2 PHASE

Figure 5. Linearity plot of a chromatographic detector. The scale of the ordinate is linear:the scale of the abscissa may be either linear or logarithmic.

Alternatively, the linear range of a detector may be presented as the plot of peak area (height)against concentration or mass flow-rate of the test substance in the column effluent at thedetector (see Fig. 6). This plot may be either linear or logflog. The upper limit of linearity is thatconcentration (mass flow-rate) at which the deviation from an ideal linearity plot is greater thanthe specified percentage deviation (kx window).Numerically, the linear range can be expressed as the ratio of the upper limit of linearityobtained from the linearity plot and the minimum detectability, both measured for the samesubstance.When presenting the linear range of a detector, either as a plot or as a numerical value, the testsubstance, the minimum detectability, and the specified deviation must be stated.


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4.5.02 Dynamic Range4.5.02.1 The dyn amic range of a detector is that range of concentration or mass flow-rates of a substanceover which an increm ental change in concentration or mass flow-rate produces an increm entalchange in detector signal. Fig. 6 presents a plot used for the determination of the dynam ic rangeof a detector.4.5.02.2 The low er limit of the dynamic range is the minimum detectability. The upper limit is thehighest concentration at which a further increase in concentration (mass flow -rate) will still givean obse rvable increase in detector signal, and the dynam ic range is the ratio of the upper andlower limits. The dynamic range is greater than the linear range.4.5.02.3 Num erically the dynam ic range can be expressed as the ratio of the upper limit of the dynam icrange obtained from the plot and the m inimum detectability, both measured fo r the samesubstance.4.5.02.4 When e xpres sing the dynamic range of a detector, the test sub stance and the minimumdetectability must be stated.

1 DYNAMIC RANG /

@MENfRAmN OR AM99 FLOW OF l?tE IFST S U 8 S E W W /N tnE W S -6Figure 6. Determination of the linear and dynam ic ranges of a chromatographic detector.Such a plot is usually in a log-log scale


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854 COMMISSIONS O N CHROMATOGRAPHY AN D ANALYTICAL NOMENCLATURE

5. SPECIAL TERMINOLOGY USED IN ION-EXCHANG E CHROMATOGRAPHYThe general terms and definitions discussed in the previous chapters are also valid in ion-exchange chromatography. In addition, the following terms and definitions refer specifically to this variantof the technique.

5.1 BASIC DEFINITIONS5.1.01

5.1.02

5.1.03

5.1.04

5.1.05

5.1.06

5.1.07

5.1.08

5.1.09

5.1.10

5.2.01

5.2.02

Ion ExchangeThe process of exchang ing ions between a solution and an ion exchanger.Counter-IonsIn an ion exchanger, the mobile exchange able ions.Fixed IonsIn an ion exchanger, the non-exchan geable ions which have a charge opp osite to that of thecounter-ions.Ion-Exchange IsothermTh e concentra t ion of a counter- ion in the ion exchan ger expressed as a funct ion of i t sconcentration in the external solution under specified cond itions and at constant temperature.SorptionUptake of electrolytes or non-electrolytes by the ion exchanger through mechanisms o ther thanpure ion exchange.Sorption IsothermTh e concentration of a sorbed species in the ion exchanger, expressed as a function of itsconcentration in the external solution under specified conditions and at constant temperature.Ionogenic GroupsThe fixed g roupings in an ion exchanger which are either ionized or capable of dissociation intofixed ions and mobile counter-ions.Co-IonsThe m obile ionic species in an ion exchanger with a charge of the sam e sign as the fixed ions.Cation ExchangeThe proc ess of exchanging cations between a solution and a cation exchanger.Anion ExchangeThe process of exchanging anions between a solution and an anion exchanger.

5.2 THE MOBILE PHASESolventThe term used in classical ion exchange to express the mobile phase.External SolutionThe solution in contact with the ion exchanger which contains the ionized species before andafter exchange with the ion exchanger.


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Nomenclature for chrom atography 8555.3 THE CHROMATOGRAPHIC MEDIUM

5.3.01 Ion ExchangersA solid or liquid, inorganic or organic substance contain ing ions exchangeable with others of thesame charge, present in a solution in which the ion exchanger is considered to be insoluble.Note: It is recognized that there are cases where liquid exchangers are em ployed and w hereit may be difficult to distinguish between the separation process as belonging to ionexchange or liquid-liquid distribution, but the broad definition given here is regardedas that which is m ost appropriate.

5.3.01.1 Resin MatrixThe m olecular network of an ion exchanger which carries the ionogenic groups.5.3.01.2 Monofunctional Ion Exchanger

An ion exchanger containing only one type of ionogenic group.5.3.01.3 Bifunctional Ion ExchangerAn ion exchanger contain ing two types of ionogenic groups.5.3.01.4 Polyfunctional Ion ExchangerAn ion exchanger contain ing more than one type of ionogenic groups.5.3.01.5 Macroporous Ion ExchangerAn ion exchanger with pores that are large compared to atomic dimensions.5.3.01.6 Salt Form of an Ion ExchangerThe ionic form of an ion exch anger in which the co unter-ions are neither hydrogen norhydroxide ions. When only one valence is possible for the counter-ion, or its exact form orcharge is not known, the symbol or the name of the counter-ion without charge is used, e.g.,sodium-form or Na-form, tetramethylammonium-form, orthophosphate-form . When one of twoor more possible forms is exclusively present, the oxidation state may be indicated by a Romannumeral, e.g., Fen-form, Fem-form.

5.3.0.7 Redox PolymersPolymers containing functional groups which can be reversibly reduced or oxidized. ElectronExchanger may be used as a synonym.5.3.01.8 Redox Ion ExchangersConventional ion exc hang ers in which reversible redox co uple s hav e been introduced ascounter-ions either by sorption or complex formation. They close ly resemble redox polymers intheir behavior.5.3.02 Cation Exchanger

Ion exchanger with cations as counter-ions. The term Cation-ExchangeResin may be used in thecase of solid organic polymers.5.3.02.1 Acid Form of a Cation ExchangerThe ionic form of a cation exchanger in which the counter-ions are hydrogen ions (H-form) orthe ionogenic groups have added a proton forming an undissociated acid.


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856 COMMISSIONS O N CHROMATOGRAPHY AND ANALYTICAL NOMENCLATURE5.3.03 Anion ExchangerIon exchanger with anions as counter-ions. The term Anion-Exchange Resin may be used in thecase of solid organic polymers.5.3.03.1 Base Form of an Anion ExchangerThe ionic form of an anion exchanger in which the counter-ions are hydroxide groups OH-form) or the ionogenic groups form an uncharged base, e.g., -w.5.3.04 Ion -Exchange Membrane

A thin sheet or film of ion-exchange material which may be used to separate ions by allow ingthe preferential transport of either cations (in the case of a Cation-Exchange Membrane) oranions (in the case of an Anion-ExchangeMembrane).If the membrane material is made fromonly ion -exchanging material, it is called a Homogeneous Ion-Exchange Membrane. If the ion-exchang e material is embedded in an inert binder, it is called a Heterogeneous Ion-ExchangeMembrane.5.3.04.1 Perm-SelectivityA term used to defin e the preferential permeation of certain ionic species through ion-exchangemembranes.5.3.05 Weight-SwellingRatio in SolventMass of solvent taken up by unit mass of the dry ion exchanger. The solvent must always bespecified.5.3.06 Volume-Swelling RatioRatio of the dry swollen volume to the true dry volume of the ion exch anger.

5.4 CAPACITY VALUES5.4.01 Theoretical Specific CapacityAmount (mmol) of ionogen ic group per mass (g) of d ry ion exchanger. If not o therwise stated,the capacity should be reported per mass (g) of the H-form of a cation exchanger and of the C1-form of an anion exchanger.5.4.02 Volume Capacity ( Q , )Amount (mmol) of ionogenic group per volume (cm3) of swollen ion exchanger. The ionic formof the ion exchanger and the medium should be stated.5.4.03 Bed Volume CapacityAmo unt (mm ol) of ionogen ic group per bed volume (cm 3) (see 3.2.06) determined underspecified conditions. The conditions should always be specified.5.4.04 Practical Specific Capacity (Q,)Total amount of ions (mmole) taken up per mass (g) of dry ion exchanger under specifiedconditions. The conditions should always be specified.5.4.05 Break-ThroughCapacity ofIon-Exchange Bed (Q,)

The practical capacity of an ion exchanger bed, obtained experimentally by p assing a solutionconta ining a particular ionic or molecular species through a colu mn contain ing the ionexchanger. This is under specified conditions and is determined by measuring the amount ofspecies which has been taken up when the species is first detected in the efflue nt or when theconcentration in the effluent reaches som e arbitrarily defined value. The break-through capacitymay be expressed in m illimoles or milligrams taken up per gram of dry ion exchanger or per cm3of bed volume.


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Nomenclature for chrom atography 8575.5 DIFFUSION, SELECTIVITY AND SEPARATION

5.5.01 Diffu ion CoefJicient in the Ion Exchanger (Dex)The meaning of this term is the same as that specified in 3.4.01-3.4.02.5.5.02 Selectivity Coeflcient (km )The equilibrium coefficient obtained by application of the law of mass action to ion exch angeand characterizing quantitatively the ability of an ion exchanger to select one of tw o ions presentin the same solution. The ions involved in the exchange should be specified as subscripts.Examples:

Exchange: Mg 2' - Ca2+

In the a bove equations subscript S refers to the ion exchanger ( stationary phase ) and M to theexternal solution ( mobile phase ). For exchang es involving counter-ions differing in theircharges, the numerical value of k depend s on the choice of the concentration sca les in the ionexchang er and the external solution (molal scale, molar scale, mole fraction sca le, etc.).Concentration units must be clearly stated for an exchange of ions of d iffering charges.

-5.5.03 Corrected Selectivity CoefJicient(km* )This is calculated in a way iden tical to the selectivity coefficient except that the concen trationsin the external solutions are replaced by activities.5.5.04 Separation Factor a, )The definition of this term is identical to the definition given in 3.7.14.2. In an exchan ge ofcounter-ions of equa l charge the separation factor is equal to the selectivity coefficient (see

5.5.01), provided that only one type of ion represents the an alytical concentration (e.g., inexchanges of K+ nd Na') but not in systems where several individual species are included in theanalytical concentrations.

5.6 DISTRIBUTION CONSTANTSA Distribution Constant is the concentration of a com ponen t in the ion exchanger (the stationaryphase) d iv id ed by i t s concent ra t ion in the exte rna l so lu t ion ( th e mob i le phase) . Theconcentration in the external solution is always calculated per unit volume. Depending on theway the concentration in the ion exchanger is expressed three forms of the distribution constantmay exist.In 5.6.01 - 5.6.03, WjE) and W j are the amounts of the component i in the ion exchanger andin the external solution; VsIEand DIE are the volumes of the swollen and dry ion exchanger,respectively; and V(sol, is the volume of the external solution.


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858

5.6.01

5.6.02

5.6.03

COMMISSIONS ON CHROMATOGRAPHY A ND ANA LYTICAL NOMENCLATURE

Distribution Constant ( K JIn this case the concentration in the ion exchanger is calculated

Nomenclature for Chromatography IUPAC

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