ASTM E1511-93(2017)
(Practice)Standard Practice for Testing Conductivity Detectors Used in Liquid and Ion Chromatography
Standard Practice for Testing Conductivity Detectors Used in Liquid and Ion Chromatography
SIGNIFICANCE AND USE
5.1 This practice is intended to describe the performance of a conductivity detector independent of the chromatographic system in terms that the analyst can use to predict overall system performance when the detector is coupled to the column and other chromatography system components.
5.2 Although it is possible to observe each of the several characteristics of a detector under different and unique conditions, it is the intent of this practice that a complete set of detector specifications should be obtained at the same operating conditions, including the setup used for testing, flow rates, and temperatures. It should be noted that to specify a detector's capability completely, its performance should be measured at several sets of conditions within the useful range of the detector. The terms and tests described in this practice are sufficiently general so that they may be used at whatever conditions may be chosen for other reasons.
SCOPE
1.1 This practice covers the testing of the performance of conductivity detectors used as the detection component of a liquid or ion chromatography system.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
General Information
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Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E1511 − 93 (Reapproved 2017)
Standard Practice for
Testing Conductivity Detectors Used in Liquid and Ion
Chromatography
This standard is issued under the fixed designation E1511; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope conductivity detectors, there is little practical value in knowing
the constant as long as the detector is properly calibrated for
1.1 This practice covers the testing of the performance of
conductivity.
conductivity detectors used as the detection component of a
3.2.2 conductance—the conductance (G) of a solution is the
liquid or ion chromatography system.
inverse of the resistance measured between two electrodes in a
1.2 The values stated in SI units are to be regarded as
cell, expressed in units of siemens (S), equal to inverse ohms.
standard. No other units of measurement are included in this
3.2.2.1 Discussion—The term resistance refers specifically
standard.
to the dc resistance to ionic current, independent of the
1.3 This standard does not purport to address all of the
capacitive reactance at the interfaces between the electrodes
safety concerns, if any, associated with its use. It is the
and the solution.
responsibility of the user of this standard to establish appro-
3.2.3 conductivity—since the conductance is dependent on
priate safety, health, and environmental practices and deter-
both the conductive properties of the solution and on the
mine the applicability of regulatory limitations prior to use.
dimensions of the electrodes and the cell, the conductivity (κ)
1.4 This international standard was developed in accor-
of the solution is defined to be independent of electrode and
dance with internationally recognized principles on standard-
cell dimensions. Specifically,
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
κ 5 G (1)
A
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
where:
1 = the distance between two planer disk electrodes, and
2. Referenced Documents
A = the electrode’s surface area.
2.1 ASTM Standards:
3.2.3.1 Discussion—In liquid and ion chromatography, cell
E1151 Practice for Ion Chromatography Terms and Rela-
dimensions are commonly measured in centimetres, so the
tionships
units of κ are S/cm. (Alternatively, the SI units of S/m may be
3. Terminology
used. S/m = 100 S ⁄cm.)
3.1 See Practice E1151. 3.2.4 drift—the average slope of the noise envelope ex-
pressed in nano siemens per centimetre per hour as measured
3.2 Definitions:
over a period of 1 h.
3.2.1 cell constant—the cell constant (K) of a conductivity
3.2.5 equivalent conductivity—of an ionic solute, the con-
cell is equal to 1/A, so κ = G K.
tribution of the solute to the total conductivity of the solution,
3.2.1.1 Discussion—If the cell constant of the flow-through
measured in microsiemens per centimetre, divided by its
cell used is equal to one, then the conductivity equals the
concentration in milliequivalents/litre.
conductance. Although the cell constant is often specified for
3.2.6 flow dependence rate—the change in measured con-
ductivity as a function of flow rate.
This practice is under the jurisdiction of ASTM Committee E13 on Molecular
Spectroscopy and Separation Science and is the direct responsibility of Subcom-
3.2.7 limiting equivalent conductivity—of an ionic solute, its
mittee E13.19 on Separation Science.
equivalent conductivity extrapolated to infinite dilution.
Current edition approved Oct. 1, 2017. Published October 2017. Originally
3.2.8 linear range—of a conductivity detector for a given
approved in 1993. Last previous edition approved in 2010 as E1511 - 93(2010).
DOI: 10.1520/E1511-93R17.
solute in a specific solvent, the concentration range of solute
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
for which the detector response factor is within 5 % of the
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
response factor in the middle of the range as determined from
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. the linearity plot specified in Section 11.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E1511 − 93 (2017)
3.2.8.1 Discussion—The lower limit may be limited by 4. Summary of Practice
noise, and the upper limit by deviation from linearity. (The
4.1 Four different tests are performed to characterize a
upper limit may instead be limited by the maximum full-scale
detector.
deflection on the detector’s least sensitive output range.)
4.1.1 Noise and drift are measured while a solution is
3.2.9 long-term noise—the maximum amplitude in nano flowing through the detector cell. The test is performed using
siemens per centimetre for all random variations of the detector two different solutions: deionized water (DI) and 1 mM
output of frequencies between 2 and 60 cycles per hour. potassium chloride (KCl).
4.1.2 Linear range is determined by preparing a plot of
3.2.9.1 Discussion—Long-term noise represents noise that
response factor versus the log of solute concentration using
can be mistaken for eluting peaks.
standard solutions of KCl and hydrochloric acid (HCl) as
3.2.10 minimum detectability—of a conductivity detector,
solutes.
that concentration of solute in a specific solvent that corre-
4.1.3 Dependence of response on flow rate is measured by
sponds to twice the short-term noise.
pumping 1 mM KCl through the conductivity cell at several
3.2.10.1 Discussion—Because of the difficulty of pumping
flow rates and measuring the detector output.
solvents through the chromatographic system without any
4.1.4 Response time is measured by measuring the time
contamination of the solvents from the system, this quantity
required for the detector output to change from that measured
can only be measured with solutes retained by a column. Since
with DI water to that measured with 1 mM KCl.
minimum detectability is dependent on the chromatographic
system used, it is not measured in this practice. However, if the
5. Significance and Use
minimum detectability of a solute is measured on one system
5.1 This practice is intended to describe the performance of
with one detector, the minimum detectability can be predicted
a conductivity detector independent of the chromatographic
when other detectors are tested on the same system by
system in terms that the analyst can use to predict overall
comparing the measured values of short-term noise.
system performance when the detector is coupled to the
3.2.11 response factor—of a conductivity detector, the mea-
column and other chromatography system components.
sured conductivity response of a solute divided by the solute
5.2 Although it is possible to observe each of the several
concentration.
characteristics of a detector under different and unique
3.2.12 response time of the detector—the time required for
conditions, it is the intent of this practice that a complete set of
the output of the detector to change from 10 to 90 % of the new
detector specifications should be obtained at the same operat-
equilibrium value when the composition of the eluent is
ing conditions, including the setup used for testing, flow rates,
changed in a stepwise manner, within the linear range of the
and temperatures. It should be noted that to specify a detector’s
detector.
capability completely, its performance should be measured at
3.2.12.1 Discussion—A slow response time has the effect of
several sets of conditions within the useful range of the
limiting resolution for efficient peaks such as early eluting detector. The terms and tests described in this practice are
peaks and those from highly efficient columns or microbore sufficiently general so that they may be used at whatever
columns. Response time is generally dependent on three conditions may be chosen for other reasons.
factors: (a) cell volume, (b) volume of heat transfer tubing
6. Reagents
leading to the cell, and (c) electronic filtering of the output.
6.1 Reagent chemicals are reagent grade or better.
3.2.13 sensitivity—the detector response divided by
6.1.1 Deionized Water, (DI water), 18 M-ohm.
concentration, which is also the response factor (11.1.1).
6.1.2 Potassium Chloride, (KCl) dry powder.
3.2.13.1 Discussion—Sensitivity is therefore by definition
6.1.3 Hydrochloric Acid, (HCl) standard 0.1000 N solution.
the same for all properly calibrated conductivity detectors.
(Sensitivity is often confused with minimum detectability,
7. Preparation of Standards
which is dependent on both sensitivity and noise.) Therefore,
7.1 Potassium Chloride Standards:
the calibration of the detector should be measured, and if
7.1.1 Prepare a 10-mM KCl standard stock solution. Weigh
necessary, adjusted. Follow the manufacturer’s procedure for
out 0.7455 g KCl (desiccated) and dissolve it in 18 M-ohm DI
calibrating the detector. The procedure in Section 9 is used by
water in a 1-L plastic volumetric flask. Fill the flask to 1 L with
many manufacturers and is useful for the tests in this practice.
DI water.
3.2.14 short-term noise—the maximum amplitude in nano
7.1.2 Prepare KCl standards from the 10-mM KCl standard
siemens per centimetre for all random variations of the detector
stock solution. Using accurate Class A pipettes, pipette the
output of a frequency greater than one cycle per minute.
volumes of the 10-mM standard stock solution listed below
3.2.14.1 Discussion—Short-term noise determines the into 100-mL plastic volumetric flasks. For the 1-mM KCl
smallest signal detectable by a conductivity detector, limits the standard, fill a 100-mL plastic volumetric flask with the 10-mM
precision available for the determination of trace samples, and KCl solution and transfer to a 1-L plastic volumetric flask. Fill
may set the lower limit of linearity. to the line with DI water.
E1511 − 93 (2017)
solutions. If no plateau is reached, then a larger sample
KCl Concentration, Volume in 100 mL DI Water,
mm mL
injection loop is needed.
0.05 0.5
8.3 If the conductivity detector has a setting for temperature
0.1 1
compensation, set it to 2.0. If not, the DI water eluent and all
0.2 2
of the test solutions should be thermostated as close as possible
0.5 5
1 100 mL in 1 L
to 25 °C. Or, the detector cell may be thermostated at a higher
2 20
temperature but be calibrated as if the cell were at 25 °C. If the
5 50
cell is thermostated, ensure that the cell temperature has
10 mM No dilution
stabilized. Refer to the manufacturer’s procedure for cell
7.2 Hydrochloric Acid Standards:
temperature stabilization. Turn off any output filtering on the
7.2.1 Prepare a 2.00-mM HCl standard stock solution by
detector. The output from the detector should be monitored on
diluting 20.0 mL of standard 0.1000 N HCl into a 1-L plastic
a strip-chart recorder, integrator, or computer. The calibration
volumetric flask and filling to the line with DI water. If
and linearity tests can be performed with a voltmeter monitor-
standard 0.1000 N HCl is not available, a 0.10-mM HCl
ing the detector output or, on some detectors, the output is
solution can be prepared by diluting 8.3 mL of 12 N (37 %)
monitored on the front panel readout.
concentration HCl into 1 L of DI water. (The concentration of
this solution will be less accurate than that prepared from
9. Calibration
0.1000 N HCl standard.)
7.2.2 Prepare the following HCl calibration standards from
9.1 Method—The detector is calibrated by adjusting the
the 2.00-mM HCl standard stock solution. Use accurate Class
detector output to 147.0 μS/cm for a 1-mM solution of
A pipettes and 100-mL plastic volumetric flasks.
potassium chloride flowing through the conductivity cell at 1
HCl Concentration, Volume in 100 mL DI Water,
mL/min.
mM mL
9.1.1 Set up the chromatographic system according to the
instructions in Section 8. Turn on the pump and ensure that the
0.02 1
0.04 2
pump is pumping smoothly.
0.1 5
9.1.2 Monitor the detector output. The conductivity should
0.2 10
0.4 20 be below 1μS/cm. If it is higher, continue flushing out the
1 50
system to remove leftover salts until the conductivity stabilizes
2 No dilution
below 1 μS/cm. (A higher reading is an indication of either an
8. Instrumentation Set-Up incompletely cleaned flow system or of poor deionized water
quality and may compromise noise and linearity tests.) Fill the
8.1 Set up the chromatographic system according to the
sample injection loop with DI water and inject. Note the
manufacturer’s recommendation. Also, passivate the conduc-
minimum conductivity reported during the elution of the DI
tivity cell using the manufacturer’s recommended procedure.
water through the detector cell. Either calibrate the detector to
Set the flow rate on the pump to 1.0 mL/min or to the flow rate
zero using the injected DI water or subtract the conductivity of
normally used in your application. Fill the eluent bottle with 18
injected DI water from all subsequent measurements.
M-ohm DI water. Connect the outlet of the pump to the
9.1.3 Fill the sample injection loop with the 1-mM KCl
injection valve, and the outlet of the injection valve directly to
standard and inject the standard. Note the maximum conduc-
the conductivity cell using as short a length of tubing as is
tivity reported during the elution through the detector cell of
practical. (Standard 0.25-mm (0.01-in.) internal diameter
the 1-mM KCl standard. It should be 147.0 μS/cm. If it is not,
HPLC tubing may be used.) Do not install any columns or
follow the manufacturer’s procedure for calibrating the con-
suppressors. To ensure smooth operation of the pump, it is
ductivity detector so that the reading will be 147.0 μS/cm.
necessary to supply more pressure than that normally provided
9.1.4 Some conductivity detectors do not report conductiv-
by the detector cell and the standard tubing alone. This is
ity directly in siemens, but instead provide a voltage output
accomplished by installing a 1-m coil of 0.25-mm internal
proportional to conductivity. Instead of adjusting the detector
diameter narrow bore tubing between the pump and the
output, calibrate these detectors by recording the known
injection valve. Increase the length or decrease the diameter of
conductivity of the calib
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