ASTM D5464-16
(Test Method)Standard Test Method for pH Measurement of Water of Low Conductivity
Standard Test Method for pH Measurement of Water of Low Conductivity
SIGNIFICANCE AND USE
6.1 pH measurement of low conductivity water is frequently applied to power plant water and condensed steam samples for corrosion and scale prevention. It is sometimes used in pure water treatment systems between multiple pass membranes to optimize performance.
6.2 High purity water is highly unbuffered and small amounts of contamination can change the pH significantly. Specifically, high purity water rapidly absorbs CO2 gas from the atmosphere, which lowers the pH of the sample. The sample container and accompanying pH measurement technique minimize exposure of the high purity water sample to the atmosphere.
6.3 The high purity water sample may contain volatile trace components that will dissipate from the sample if exposed to the atmosphere. The sample container used in this test method will prevent these losses.
6.4 High purity water has a significant solution temperature coefficient. For greatest accuracy the sample to be measured should be close to the temperature of the sample stream and appropriate compensation should be applied.
6.5 When the preferred Test Method D5128, which requires a real-time, flowing sample, cannot be utilized for practical reasons such as physical plant layout, unacceptable loss of water, location of on-line equipment sample points, or availability of dedicated test equipment, this method offers a viable alternative. The most significant difference between the two test methods is that Test Method D5128 obtains a real-time pH measurement from a flowing sample and this method obtains a time delayed pH measurement from a static grab sample.
6.6 pH measurements of low conductivity water are always subject to interferences (7.1 – 7.5) and Test Method D5128 is more effective in eliminating these interferences especially with regard to contamination. This static grab sample method is more prone to contamination and temperature-induced errors because of the time lag between the sampling in the plant and sample pH reading which i...
SCOPE
1.1 This test method is applicable to determine the pH of water samples with a conductivity of 2 to 100 μS/cm over the pH range of 3 to 11 and is frequently used in power generation low conductivity samples. pH measurements of water of low conductivity are problematic. Specifically, this test method avoids contamination of the sample with atmospheric gases and prevents volatile components of the sample from escaping. This test method provides for pH electrodes and apparatus that address additional considerations discussed in Annex A2. This test method also minimizes problems associated with the sample's pH temperature coefficient when the operator uses this test method to calibrate an on-line pH monitor or controller (see Appendix X1).
1.2 This test method covers the measurement of pH in water of low conductivity with a lower limit of 2.0 μS/cm, utilizing a static grab-sample procedure where it is not practicable to take a real-time flowing sample.
Note 1: Test Method D5128 for on-line measurement is preferred over this method whenever possible. Test Method D5128 is not subject to the limited conductivity range, temperature interferences, potential KCl contamination, and time limitations found with this method.
1.3 For on-line measurements in water with conductivity of 100 μS/cm and higher, see Test Method D6569.
1.4 For laboratory measurements in water with conductivity of 100 μS/cm and higher, see Test Method D1293.
1.5 The values stated in SI units are to be regarded as standard.
1.6 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 and health practices and determine the applicability of regulatory limitations prior to use.
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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: D5464 − 16
Standard Test Method for
1
pH Measurement of Water of Low Conductivity
This standard is issued under the fixed designation D5464; 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 priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
1.1 This test method is applicable to determine the pH of
water samples with a conductivity of 2 to 100 µS/cm over the
2. Referenced Documents
pHrangeof3to11andisfrequentlyusedinpowergeneration
2
2.1 ASTM Standards:
low conductivity samples. pH measurements of water of low
D1129Terminology Relating to Water
conductivity are problematic. Specifically, this test method
D1193Specification for Reagent Water
avoids contamination of the sample with atmospheric gases
D1293Test Methods for pH of Water
andpreventsvolatilecomponentsofthesamplefromescaping.
D2777Practice for Determination of Precision and Bias of
This test method provides for pH electrodes and apparatus that
Applicable Test Methods of Committee D19 on Water
address additional considerations discussed in AnnexA2. This
D3370Practices for Sampling Water from Closed Conduits
test method also minimizes problems associated with the
D4453Practice for Handling of High Purity Water Samples
sample’s pH temperature coefficient when the operator uses
D5128Test Method for On-Line pH Measurement of Water
thistestmethodtocalibrateanon-linepHmonitororcontroller
of Low Conductivity
(see Appendix X1).
D6569Test Method for On-Line Measurement of pH
1.2 ThistestmethodcoversthemeasurementofpHinwater
3. Terminology
of low conductivity with a lower limit of 2.0 µS/cm, utilizing
a static grab-sample procedure where it is not practicable to
3.1 Definitions of Terms—For definitions of terms used in
take a real-time flowing sample.
this test method, refer to Terminology D1129.
NOTE1—TestMethodD5128foron-linemeasurementispreferredover
3.2 Definitions:
this method whenever possible. Test Method D5128 is not subject to the
limited conductivity range, temperature interferences, potential KCl
3.3 Definitions of Terms Specific to This Standard:
contamination, and time limitations found with this method.
3.3.1 liquid-junction potential, n—a dc potential that ap-
1.3 For on-line measurements in water with conductivity of pears at the point of contact between the reference electrode’s
salt bridge (also known as reference junction or diaphragm)
100 µS/cm and higher, see Test Method D6569.
and the sample solution.
1.4 Forlaboratorymeasurementsinwaterwithconductivity
3.3.1.1 Discussion—Ideally,thispotentialisnearzeroandis
of 100 µS/cm and higher, see Test Method D1293.
stable. However, in low-conductivity water this potential may
1.5 The values stated in SI units are to be regarded as
change from its value in buffer solution by an unknown
3
standard.
amount, and is a zero offset (1).
1.6 This standard does not purport to address all of the
4. Reagents
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro- 4.1 Purity of Reagents—Reagent grade chemicals shall be
used in all tests. Unless otherwise indicated, it is intended that
1
These test methods are under the jurisdiction of ASTM Committee D19 on
2
WaterandarethedirectresponsibilityofSubcommitteeD19.03onSamplingWater For referenced ASTM standards, visit the ASTM website, www.astm.org, or
and Water-Formed Deposits, Analysis of Water for Power Generation and Process contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Use, On-Line Water Analysis, and Surveillance of Water Standards volume information, refer to the standard’s Document Summary page on
Current edition approved June 1, 2016. Published June 2016. Originally the ASTM website.
3
approved in 1993. Last previous edition approved in 2011 as D5464–11. DOI: Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
10.1520/D5464-16. this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1
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D5464 − 16
all reagents conform to the specifications of the Committee on 6. Significance and Use
Analytical Reagents of theAmerican Chemical Society where
6.1 pHmeasurementoflowconductivitywaterisfrequently
4
such specifications are available. Other grades may be used,
applied to power plant water and conden
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D5464 − 11 D5464 − 16
Standard Test Method for
1
pH Measurement of Water of Low Conductivity
This standard is issued under the fixed designation D5464; 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
1.1 This test method is applicable to determine the pH of water samples with a conductivity of 2 to 100 μS/cm over the pH range
of 3 to 11. 11 and is frequently used in power generation low conductivity samples. pH measurements of water of low conductivity
are problematic. Specifically, this test method avoids contamination of the sample with atmospheric gases and prevents volatile
components of the sample from escaping. This test method provides for pH electrodes and apparatus that address additional
considerations discussed in Annex A2. This test method also minimizes problems associated with the sample’s pH temperature
coefficient when the operator uses this test method to calibrate an on-line pH monitor or controller (see Appendix X1).
1.2 This test method covers the measurement of pH in water of low conductivity with a lower limit of 2.0 μS/cm, utilizing a
static grab-sample procedure where it is not practicable to take a real-time flowing sample.
NOTE 1—Test Method D5128 for on-line measurement is preferred over this method whenever possible. Test Method D5128 is not subject to the limited
conductivity range, temperature interferences, potential KCl contamination, and time limitations found with this method.
1.3 For on-line measurements in water with conductivity of 100 μS/cm and higher, see Test Method D6569.
1.4 For laboratory measurements in water with conductivity of 100 μS/cm and higher, see Test Method D1193D1293.
1.5 The values stated in SI units are to be regarded as standard.
1.6 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 and health practices and determine the applicability of regulatory
limitations prior to use.
2. Referenced Documents
2
2.1 ASTM Standards:
D1129 Terminology Relating to Water
D1193 Specification for Reagent Water
D1293 Test Methods for pH of Water
D2777 Practice for Determination of Precision and Bias of Applicable Test Methods of Committee D19 on Water
D3370 Practices for Sampling Water from Closed Conduits
D4453 Practice for Handling of High Purity Water Samples
D5128 Test Method for On-Line pH Measurement of Water of Low Conductivity
D6569 Test Method for On-Line Measurement of pH
3. Terminology
3.1 Definitions—Definitions of Terms—For definitions of terms used in thesethis test methods,method, refer to Terminology
D1129.
3.2 Definitions:
3.3 Definitions of Terms Specific to This Standard:
3.3.1 liquid-junction potential, n—a dc potential that appears at the point of contact between the reference electrode’s salt bridge
(also known as reference junction or diaphragm) and the sample solution.
1
These test methods are under the jurisdiction of ASTM Committee D19 on Water and are the direct responsibility of Subcommittee D19.03 on Sampling Water and
Water-Formed Deposits, Analysis of Water for Power Generation and Process Use, On-Line Water Analysis, and Surveillance of Water
Current edition approved May 1, 2011June 1, 2016. Published May 2011June 2016. Originally approved in 1993. Last previous edition approved in 20072011 as
D5464 – 07.D5464 – 11. DOI: 10.1520/D5464-11.10.1520/D5464-16.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1
---------------------- Page: 1 ----------------------
D5464 − 16
3.3.1.1 Discussion—
Ideally, this potential is near zero and is stable. However, in low-conductivity water this potential may change from its value in
3
buffer solution by an unknown amount, and is a zero offset (1).
4. Reagents
4.1 Purity of Reagents—Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all
reagents conform to the specifications of the Committee on Analytical Reagents o
...
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