ASTM E1151-93(2011)
(Practice)Standard Practice for Ion Chromatography Terms and Relationships
Standard Practice for Ion Chromatography Terms and Relationships
ABSTRACT
This practice deals primarily with identifying the terms and relationships of those techniques that use ion exchange chromatography to separate mixtures and a conductivity detector to detect the separated components. However, most of the terms should also apply to ion chromatographic techniques that employ other separation and detection mechanisms. The apparatus to be used in the chromatography shall consist of syringe pumps, reciprocating pumps, pneumatic pumps, septum injectors, valve injectors, precolumns, concentrator columns, guard columns, separating columns, suppressor columns, conductivity suppressors, membrane suppressors, micromembrane suppressor, bulk property detectors, and solute property detectors. Chemical reagents to be used in the chemical analysis shall be of four kinds: mobile phase, stationary phase, solid support, and column packing materials. The stationary phase has two types which are the liquid phase and interactive solid phase material. Totally porous packing and pellicular packing are the two types of column packing materials.
SCOPE
1.1 This practice deals primarily with identifying the terms and relationships of those techniques that use ion exchange chromatography to separate mixtures and a conductivity detector to detect the separated components. However, most of the terms should also apply to ion chromatographic techniques that employ other separation and detection mechanisms.
1.2 Because ion chromatography is a liquid chromatographic technique, this practice uses, whenever possible the terms and relationships identified in Practice E682.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: E1151 − 93 (Reapproved 2011)
Standard Practice for
Ion Chromatography Terms and Relationships
This standard is issued under the fixed designation E1151; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope mean to imply that IC is tied only to ion exchange chroma-
tography or conductimetric detection.
1.1 This practice deals primarily with identifying the terms
and relationships of those techniques that use ion exchange 3.2 Chemically Suppressed Ion Chromatography, (Dual
chromatographytoseparatemixturesandaconductivitydetec- Column Ion Chromatography)—Inthistechnique,samplecom-
tor to detect the separated components. However, most of the ponents are separated on a low capacity ion exchanger and
termsshouldalsoapplytoionchromatographictechniquesthat detected conductimetrically. Detection of the analyte ions is
employ other separation and detection mechanisms. enhanced by selectively suppressing the conductivity of the
mobile phase through post separation ion exchange reactions.
1.2 Because ion chromatography is a liquid chromato-
graphic technique, this practice uses, whenever possible the 3.3 Single Column Ion Chromatography, (Electronically
terms and relationships identified in Practice E682. Suppressed Ion Chromatography)—In this technique sample
componentsareseparatedonalowcapacityionexchangerand
1.3 The values stated in SI units are to be regarded as
detected conductimetrically. Generally, lower capacity ion
standard. No other units of measurement are included in this
exchangers are used with electronic suppression than with
standard.
chemical suppression. Mobile phases with ionic equivalent
1.4 This standard does not purport to address all of the
conductancesignificantlydifferentfromthatofthesampleions
safety problems, if any, associated with its use. It is the
andalowelectrolyticconductivityareused,permittinganalyte
responsibility of the user of this standard to establish appro-
ion detection with only electronic suppression of the baseline
priate safety and health practices and determine the applica-
conductivity signal.
bility of regulatory limitations prior to use.
4. Apparatus
2. Referenced Documents
4.1 Pumps—Any of various machines that deliver the mo-
2.1 ASTM Standards:
bile phase at a controlled flow rate through the chromato-
E682Practice for Liquid Chromatography Terms and Rela-
graphic system.
tionships
4.1.1 Syringe Pumps, having a piston that advances at a
controlled rate within a cylinder to displace the mobile phase.
3. Descriptions of Techniques
4.1.2 Reciprocating Pumps, having one or more chambers
3.1 Ion Chromatography, (IC)—a general term for several from which mobile phase is displaced by reciprocating pis-
liquid column chromatographic techniques for the analysis of ton(s)ordiaphragm(s).Thechambervolumeisnormallysmall
ionic or ionizable compounds. Of the many useful separation compared to the volume of the column.
and detection schemes, those most widely used have been the 4.1.3 Pneumatic Pumps, employing a gas to displace the
mobile phase either directly from a pressurized container or
two techniques described in 3.2 and 3.3 in which ion exchange
separation is combined with conductimetric detection. By indirectly through a piston or collapsible container. The vol-
ume within these pumps is normally large as compared to the
describing only these two techniques, this practice does not
volume of the column.
4.2 Sample Inlet Systems, devices for introducing samples
This practice is under the jurisdiction ofASTM Committee E13 on Molecular
into the column.
Spectroscopy and Separation Science and is the direct responsibility of Subcom-
4.2.1 Septum Injectors—The sample contained in a syringe
mittee E13.19 on Separation Science.
isintroduceddirectlyintothepressurizedflowingmobilephase
Current edition approved Nov. 1, 2011. Published December 2011. Originally
by piercing an elastomeric barrier with a needle attached to a
approved in 1993. Last previous edition approved in 2006 as E1151–93(2006).
DOI: 10.1520/E1151-93R11.
syringe. The syringe is exposed to pressure and defines the
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
sample volume.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
4.2.2 Valve Injectors—The sample contained in a syringe
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. (or contained in a sample vial) is injected into (or drawn into)
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E1151 − 93 (2011)
an ambient-pressure chamber through which the pressurized 4.5 Detectors—Devices that respond to the presence of
flowing mobile phase is subsequently diverted, after sealing eluted sample components. Detectors may be divided either
against ambient pressure. The displacement is by means of according to the type of measurement or the principle of
rotary or sliding motion. The chamber is a section (loop) of detection.
tubing or an internal chamber.The chamber can be completely
4.5.1 Bulk Property Detectors, measuring the change in a
filled, in which case the chamber volume defines the sample
physical property of the liquid phase exiting the column. Thus
volume, or it can be partially filled, in which case the syringe
a change in the refractive index, conductivity, or dielectric
calibration marks define the sample volume.
constant of a mobile phase can indicate the presence of eluting
sample components. Conductimetric parameters, symbols,
4.3 Columns, tubes, containing a stationary phase and
units and definitions are given in Appendix X1.
through which the mobile phase can flow.
4.3.1 Precolumns,positionedbeforethesampleinletsystem 4.5.2 Solute Property Detectors, measuring the physical or
chemical characteristics of eluting sample components. Thus,
and used to condition the mobile phase.
4.3.2 Concentrator Columns, installed in place of the light absorption (ultraviolet, visible, infrared), fluorescence,
and polarography are examples of detectors capable of re-
sample chamber of a valve injector and used to concentrate
selected sample components. sponding in such a manner.
4.3.3 Guard Columns, positioned between the sample inlet
system and the separating columns and used to protect the 5. Reagents
separator column from harmful sample components.
5.1 Mobile Phase—Liquid used to sweep or elute the
4.3.4 Separating Columns, positioned after the sample inlet
sample components through the chromatographic system. It
system and the guard column and used to separate the sample
mayconsistofasinglecomponentoramixtureofcomponents.
components.
5.2 Stationary Phase—Active immobile material within the
4.3.5 Suppressor Columns, positioned after the separating
column and a type of post column reactor where the conduc- column that delays the passage of sample components by one
of a number of processes or their combination. Inert materials
tivity of the mobile phase is selectively reduced to enhance
sample detection. that merely provide physical support for the stationary phase
are not part of the stationary phase. The following are three
4.4 Postcolumn Reactors, reaction systems in which the
types of stationary phase:
effluent from the separating columns is chemically or physi-
5.2.1 Liquid Phase—A stationary phase that has been
cally treated to enhance the detectability of the sample com-
sorbed (but not covalently bonded) to a solid support. Differ-
ponents.
encesinthesolubilitiesofthesamplecomponentsintheliquid
4.4.1 Conductivity Suppressors, post column reactors in
and mobile phase constitute the basis for their separation.
which the conductivity of the mobile phase is reduced through
5.2.2 Interactive Solid—Astationary phase that comprises a
reactions with ion exchangers. Conductivity suppressors are
relatively homogeneous surface on which the sample compo-
differentiated by their type (cationic or anionic), by their form
+ +
nents sorb and desorb effecting a separation. Examples are
(H ,Na , etc.), and by their method of regeneration (batch or
silica, alumina, graphite, and ion exchangers. In ion chroma-
continuous).
tography the interactive material is usually an ion exchanger
4.4.2 Suppressor Columns—Tubular reactors packed with
that has ionic groups that are either ionized or capable of
ionexchangers.Suppressorcolumnsrequirebatchregeneration
dissociation into fixed ions and mobile counter-ions. Mobile
when the breakthrough capacity of the column is exceeded.
ionic species in an ion exchanger with a charge of the same
4.4.3 Membrane Suppressors—Reactors made from tubular
sign as the fixed ions are termed “co-ions.” An ion exchanger
shaped ion exchange membranes. On the inside of the tube
with cations as counter-ions is termed a “cation exchanger,”
flows the mobile phase; a regenerative solution surrounds the
and an ion exchanger with anions as counter-ions is termed an
tube. These membrane suppressors can be in the form of an
“anion exchanger.” The ionic form of an ion exchanger is
opened tube, hollow fiber suppressors, or a flattened tube for
determinedbythecounter-ion,forexample,ifthecounter-ions
higher capacity. Tubular membranes can be packed with inert
arehydrogenionsthenthecationexchangerisintheacidform
materials to reduce band broadening.
or hydrogen form, or if the counter-ions are hydroxide ions
4.4.4 Micromembrane Suppressor—Reactors made from
thentheanionexchangerisinthebaseformorhydroxideform.
two sizes of ion-exchange screen.Afine screen is used for the
Ionicgroupscanbecovalentlybondedtoorganicpolymers(for
mobile phase chamber and a coarse screen is used for the
example, styrene/divinylbenzene) or an inorganic material (for
regenerant chambers. The mobile phase screen is sandwiched
example, silica gel). Ion exchange parameters, symbols, units
between ion-exchange membranes, and on either side of each
and definitions are given in Appendix X2. Separation mecha-
membrane is a regenerant screen. The stack is laminated by
nisms on ion exchangers are described in Appendix X3.
pressure, causing intimate contact between screens and mem-
branes. Mobile phase passes through a hole in the upper 5.2.3 Bonded Phase—A stationary phase that comprises a
regenerant screen and membrane. It enters the screen-filled chemical (or chemicals) that has been covalently attached to a
mobile phase chamber and passes through it. It then exits solid support. The sample components sorb onto and off the
through a second set of holes in the upper membrane and bonded phase differentially to effect separation. Octadecylsilyl
regenerant screen. The regenerant flows countercurrent to the groups bonded to silica represent a typical example for a
mobile phase through the screen-filled regenerant chamber. bonded phase.
E1151 − 93 (2011)
5.3 Solid Support—Inert material to which the stationary 6.7 Peak Widths—Represent retention dimensions parallel
phase is sorbed (liquid phases) or covalently attached (bonded to the baseline. Peak width at base or base width, (KL in Fig.
phases).Itholdsthestationaryphaseincontactwiththemobile X1.1) is the retention dimension of the peak base intercepted
phase. by the tangents drawn to the inflection points on both sides of
the peak. Peak width at half height, (HJ in Fig. X1.1) is the
5.4 Column Packing—The column packing consists of all
retention dimension drawn at 50% of peak height parallel to
the material used to fill packed columns. The two types are as
the peak base. The peak width at inflection points, (FG in Fig.
follows:
X1.1), is the retention dimension drawn at the inflection points
5.4.1 Totally Porous Packing—One where the stationary
(=60.7% of peak height) parallel to the peak base.
phase is found throughout each porous particle.
5.4.2 Pellicular Packing—Onewherethestationaryphaseis
7. Retention Parameters, Symbols, and Units
found only on the porous outer shell of the otherwise imper-
7.1 Retention parameters, symbols, units, and their defini-
meableparticle.Surfaceagglomeratedpackingsareconsidered
tions or relationship to other parameters are listed in Table
to be a type of pellicular packing.
X3.1.
6. Readout
NOTE 1—The adjusted retention time, capacity ratio, number of
theoretical plates, and relative retention times are exactly true only in an
6.1 Chromatogram—Graphic representation of the detector
isocratic, constant-flow system yielding perfectly Gaussian peak shapes.
response versus retention time or retention volume as the
7.2 Fig.X1.1canbeusedtoillustratesomeofthefollowing
sample components elute from the column(s) and through the
most common parameters measured from chromatograms:
detector. An idealized chromatogram of an unretained and a
Retention time of unretained component, t = OA
M
retained component is shown in Fig. X1.1.
Retention time, t = OB
R
6.2 Baseline—Portion of a chromatogram recording the
Adjusted retention time, t = AB
R
detector response when only the mobile phase emerges from
Capacity factor, k' = (OB − OA) ⁄OA
the column.
Peak width at base, w = KL
b
6.3 Peak—Portion of a chromatogram recording detector Peak width at half height, w = HJ
h
response when a single component, or two or more unresolved
Peak width at inflection points,= FG =0.607(EB)
components, elute from the column. Number of theoretical plates, N=16[(OB)/
2 2
(KL)] =5.54[(OB)/(HJ)]
6.4 Peak Base (CD in Fig. X1.1)—Interpolation of the
Relative retention, r (Note 2)=(AB) /(AB)
i s
baseline between the extremities of a peak.
Peak resolution, R (Note 2 and Note 3)=2[(OB) −(OB)
s j i
6.5 Peak Area (CHFEGJD in Fig. X1.1)—Area enclosed
]/(KL) +(KL) . (OB) −(OB) /(KL)
i j j i j
between the peak and the peak base.
NOTE2—Subscripts i, j,and srefertosomepeak,afollowingpeak,and
6.6 Peak Height (EB in Fig. X1.1)—Distance measured in
a reference peak (standard), respectively.
the direction of detector response, from the peak base to peak
NOTE 3—The second fraction may be used if peak resolution of two
maximum. closely spaced peaks is expressed; in such as case (KL) =(KL) .
i j
APPENDIXES
(Nonmandatory Information)
X1. SEPARATION MECHANISMS
X1.1 Ion Exchange Chromatography—Sample and mobile partially ionized sample components can enter and be retained
byapartitionoradsorptionmechanism.Separationofpartially
counter-ions compete to form neutral ion pairs with the fixed
ions of an ion exchanger. When paired, the sample ions do not ionized sample components, such as weak acids, is achieved
because of their dif
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