ASTM E1151-93(2000)
(Practice)Standard Practice for Ion Chromatography Terms and Relationships
Standard Practice for Ion Chromatography Terms and Relationships
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 E 682.
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn. Contact ASTM
International (www.astm.org) for the latest information.
Designation: E 1151 – 93 (Reapproved 2000)
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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope enhanced by selectively suppressing the conductivity of the
mobile phase through post separation ion exchange reactions.
1.1 This practice deals primarily with identifying the terms
3.3 Single Column Ion Chromatography, (Electronically
and relationships of those techniques that use ion exchange
Suppressed Ion Chromatography)—In this technique sample
chromatographytoseparatemixturesandaconductivitydetec-
componentsareseparatedonalowcapacityionexchangerand
tor to detect the separated components. However, most of the
detected conductimetrically. Generally, lower capacity ion
termsshouldalsoapplytoionchromatographictechniquesthat
exchangers are used with electronic suppression than with
employ other separation and detection mechanisms.
chemical suppression. Mobile phases with ionic equivalent
1.2 Because ion chromatography is a liquid chromato-
conductancesignificantlydifferentfromthatofthesampleions
graphic technique, this practice uses, whenever possible the
andalowelectrolyticconductivityareused,permittinganalyte
terms and relationships identified in Practice E682.
ion detection with only electronic suppression of the baseline
1.3 This standard does not purport to address all of the
conductivity signal.
safety problems, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
4. Apparatus
priate safety and health practices and determine the applica-
4.1 Pumps—Any of various machines that deliver the mo-
bility of regulatory limitations prior to use.
bile phase at a controlled flow rate through the chromato-
2. Referenced Documents graphic system.
4.1.1 Syringe Pumps, having a piston that advances at a
2.1 ASTM Standards:
controlled rate within a cylinder to displace the mobile phase.
E682 Practice for Liquid Chromatography Terms and Re-
4.1.2 Reciprocating Pumps, having one or more chambers
lationships
from which mobile phase is displaced by reciprocating pis-
3. Descriptions of Techniques ton(s)ordiaphragm(s).Thechambervolumeisnormallysmall
compared to the volume of the column.
3.1 Ion Chromatography, (IC)—a general term for several
4.1.3 Pneumatic Pumps, employing a gas to displace the
liquid column chromatographic techniques for the analysis of
mobile phase either directly from a pressurized container or
ionic or ionizable compounds. Of the many useful separation
indirectly through a piston or collapsible container. The vol-
and detection schemes, those most widely used have been the
ume within these pumps is normally large as compared to the
two techniques described in 3.2 and 3.3 in which ion exchange
volume of the column.
separation is combined with conductimetric detection. By
4.2 Sample Inlet Systems, devices for introducing samples
describing only these two techniques, this practice does not
into the column.
mean to imply that IC is tied only to ion exchange chroma-
4.2.1 Septum Injectors—The sample contained in a syringe
tography or conductimetric detection.
isintroduceddirectlyintothepressurizedflowingmobilephase
3.2 Chemically Suppressed Ion Chromatography, (Dual
by piercing an elastomeric barrier with a needle attached to a
Column Ion Chromatography)—In this technique, sample
syringe. The syringe is exposed to pressure and defines the
componentsareseparatedonalowcapacityionexchangerand
sample volume.
detected conductimetrically. Detection of the analyte ions is
4.2.2 Valve Injectors—The sample contained in a syringe
(or contained in a sample vial) is injected into (or drawn into)
an ambient-pressure chamber through which the pressurized
This practice is under the jurisdiction ofASTM Committee E13 on Molecular
flowing mobile phase is subsequently diverted, after sealing
Spectroscopy and is the direct responsibility of Subcommittee E13.19 on Chroma-
against ambient pressure. The displacement is by means of
tography.
rotary or sliding motion. The chamber is a section (loop) of
Current edition approved July 15, 1993. Published September 1993.
Annual Book of ASTM Standards, Vol 14.02. tubing or an internal chamber.The chamber can be completely
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn. Contact ASTM
International (www.astm.org) for the latest information.
E 1151 – 93 (2000)
filled, in which case the chamber volume defines the sample 4.5.1 Bulk Property Detectors, measuring the change in a
volume, or it can be partially filled, in which case the syringe physical property of the liquid phase exiting the column. Thus
calibration marks define the sample volume. a change in the refractive index, conductivity, or dielectric
constant of a mobile phase can indicate the presence of eluting
4.3 Columns, tubes, containing a stationary phase and
sample components. Conductimetric parameters, symbols,
through which the mobile phase can flow.
units and definitions are given in Appendix X1.
4.3.1 Precolumns,positionedbeforethesampleinletsystem
4.5.2 Solute Property Detectors, measuring the physical or
and used to condition the mobile phase.
chemical characteristics of eluting sample components. Thus,
4.3.2 Concentrator Columns, installed in place of the
light absorption (ultraviolet, visible, infrared), fluorescence,
sample chamber of a valve injector and used to concentrate
and polarography are examples of detectors capable of re-
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.
4.3.4 Separating Columns, positioned after the sample inlet 5.1 Mobile Phase—Liquid used to sweep or elute the
system and the guard column and used to separate the sample sample components through the chromatographic system. It
components. mayconsistofasinglecomponentoramixtureofcomponents.
4.3.5 Suppressor Columns, positioned after the separating
5.2 Stationary Phase—Active immobile material within the
column and a type of post column reactor where the conduc- column that delays the passage of sample components by one
tivity of the mobile phase is selectively reduced to enhance
of a number of processes or their combination. Inert materials
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-
cally treated to enhance the detectability of the sample com-
5.2.1 Liquid Phase—A stationary phase that has been
ponents.
sorbed (but not covalently bonded) to a solid support. Differ-
encesinthesolubilitiesofthesamplecomponentsintheliquid
4.4.1 Conductivity Suppressors, post column reactors in
which the conductivity of the mobile phase is reduced through and mobile phase constitute the basis for their separation.
reactions with ion exchangers. Conductivity suppressors are
5.2.2 Interactive Solid—Astationaryphasethatcomprisesa
differentiated by their type (cationic or anionic), by their form
relatively homogeneous surface on which the sample compo-
+ +
(H ,Na , etc.), and by their method of regeneration (batch or
nents sorb and desorb effecting a separation. Examples are
continuous).
silica, alumina, graphite, and ion exchangers. In ion chroma-
4.4.2 Suppressor Columns—Tubular reactors packed with
tography the interactive material is usually an ion exchanger
ionexchangers.Suppressorcolumnsrequirebatchregeneration that has ionic groups that are either ionized or capable of
when the breakthrough capacity of the column is exceeded.
dissociation into fixed ions and mobile counter-ions. Mobile
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
opened tube, hollow fiber suppressors, or a flattened tube for “anion exchanger.” The ionic form of an ion exchanger is
determinedbythecounter-ion,forexample,ifthecounter-ions
higher capacity. Tubular membranes can be packed with inert
materials to reduce band broadening. arehydrogenionsthenthecationexchangerisintheacidform
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.
4.5 Detectors—Devices that respond to the presence of 5.3 Solid Support—Inert material to which the stationary
eluted sample components. Detectors may be divided either phase is sorbed (liquid phases) or covalently attached (bonded
according to the type of measurement or the principle of phases).Itholdsthestationaryphaseincontactwiththemobile
detection. phase.
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn. Contact ASTM
International (www.astm.org) for the latest information.
E 1151 – 93 (2000)
5.4 Column Packing—The column packing consists of all by the tangents drawn to the inflection points on both sides of
the material used to fill packed columns. The two types are as the peak. Peak width at half height, (HJ in Fig. X1.1) is the
follows: retention dimension drawn at 50% of peak height parallel to
5.4.1 Totally Porous Packing—One where the stationary the peak base. The peak width at inflection points, (FG in Fig.
phase is found throughout each porous particle. X1.1), is the retention dimension drawn at the inflection points
5.4.2 Pellicular Packing—One where the stationary phase (=60.7% of peak height) parallel to the peak base.
is found only on the porous outer shell of the otherwise
7. Retention Parameters, Symbols, and Units
impermeable particle. Surface agglomerated packings are con-
7.1 Retention parameters, symbols, units, and their defini-
sidered to be a type of pellicular packing.
tions or relationship to other parameters are listed in Table
X3.1.
6. Readout
6.1 Chromatogram—Graphic representation of the detector NOTE 1—The adjusted retention time, capacity ratio, number of theo-
retical plates, and relative retention times are exactly true only in an
response versus retention time or retention volume as the
isocratic, constant-flow system yielding perfectly Gaussian peak shapes.
sample components elute from the column(s) and through the
detector. An idealized chromatogram of an unretained and a 7.2 Fig.X1.1canbeusedtoillustratesomeofthefollowing
most common parameters measured from chromatograms:
retained component is shown in Fig. X1.1.
6.2 Baseline—Portion of a chromatogram recording the Retention time of unretained component, t = OA
M
Retention time, t = OB
detector response when only the mobile phase emerges from
R
the column. Adjusted retention time, t = AB
R
Capacity factor, k8 = (OB − OA)/OA
6.3 Peak—Portion of a chromatogram recording detector
response when a single component, or two or more unresolved Peak width at base, w = KL
b
Peak width at half height, w = HJ
components, elute from the column.
h
6.4 Peak Base (CD in Fig. X1.1)—Interpolation of the Peak width at inflection points,= FG =0.607(EB)
Number of theoretical plates, N=16[(OB)/
baseline between the extremities of a peak.
2 2
6.5 Peak Area (CHFEGJD in Fig. X1.1)—Area enclosed (KL)] =5.54[(OB)/(HJ)]
Relative retention, r (Note 2)=(AB)/(AB)
between the peak and the peak base.
i s
6.6 Peak Height (EB in Fig. X1.1)—Distance measured in Peak resolution, R (Note 2 and Note 3)=2[(OB) −(OB)]/
s i
j
(KL) +(KL) . (OB) −(OB)/(KL)
the direction of detector response, from the peak base to peak
i j j i j
maximum.
NOTE 2—Subscripts i, j,and srefertosomepeak,afollowingpeak,and
6.7 Peak Widths—Represent retention dimensions parallel
a reference peak (standard), respectively.
to the baseline. Peak width at base or base width, (KL in Fig.
NOTE 3—The second fraction may be used if peak resolution of two
X1.1) is the retention dimension of the peak base intercepted 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 because the fixed ions have different thermodynamic complex-
counter-ions compete to form neutral ion pairs with the fixed ation constants resulting in chromatographic selectivity be-
ions of an ion exchanger. When paired, the sample ions do not
tween ions.
movethroughtheionexchangecolumn.Separationisachieved
TABLE X1.1 Conductometric Parameters
A
Parameter Symbol Unit Definition or Relation to Other Parameters
Conductance S The reciprocal of a measure
...
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