ASTM D5464-11

Standard Test Method for pH Measurement of Water of Low Conductivity

SIGNIFICANCE AND USE
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.
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.
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.
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.
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.
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 is taken in the laboratory.
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. 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 D1193.
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.

General Information

• Status: Historical
• Publication Date: 30-Apr-2011
• ICS: 13.060.50 - Examination of water for chemical substances
• Technical Committee: D19 - Water
• Drafting Committee: D19.03 - Sampling Water and Water-Formed Deposits, Analysis of Water for Power Generation and Process Use, On-Line Water Analysis, and Surveillance of Water

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: D5464 − 11
StandardTest 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 2. Referenced Documents
2
1.1 This test method is applicable to determine the pH of
2.1 ASTM Standards:
water samples with a conductivity of 2 to 100 µS/cm over the
D1129Terminology Relating to Water
pH range of 3 to 11. pH measurements of water of low
D1193Specification for Reagent Water
conductivity are problematic. Specifically, this test method
D1293Test Methods for pH of Water
avoids contamination of the sample with atmospheric gases
D2777Practice for Determination of Precision and Bias of
andpreventsvolatilecomponentsofthesamplefromescaping.
Applicable Test Methods of Committee D19 on Water
This test method provides for pH electrodes and apparatus that
D4453Practice for Handling of High Purity Water Samples
address additional considerations discussed in AnnexA2. This
D5128Test Method for On-Line pH Measurement of Water
test method also minimizes problems associated with the
of Low Conductivity
sample’s pH temperature coefficient when the operator uses
D6569Test Method for On-Line Measurement of pH
thistestmethodtocalibrateanon-linepHmonitororcontroller
(see Appendix X1).
3. Terminology
1.2 ThistestmethodcoversthemeasurementofpHinwater
3.1 Definitions—For definitions of terms used in these test
of low conductivity with a lower limit of 2.0 µS/cm, utilizing
methods, refer to Terminology D1129.
a static grab-sample procedure where it is not practicable to
3.2 Definitions:
take a real-time flowing sample.
3.3 Definitions of Terms Specific to This Standard:
NOTE1—TestMethodD5128foron-linemeasurementispreferredover
3.3.1 liquid-junction potential, n—a dc potential that ap-
this method whenever possible. Test Method D5128 is not subject to the
limited conductivity range, temperature interferences, potential KCl
pears at the point of contact between the reference electrode’s
contamination, and time limitations found with this method.
salt bridge (also known as reference junction or diaphragm)
1.3 For on-line measurements in water with conductivity of
and the sample solution.
100 µS/cm and higher, see Test Method D6569.
3.3.1.1 Discussion— Ideally, this potential is near zero and
is stable. However, in low-conductivity water this potential
1.4 Forlaboratorymeasurementsinwaterwithconductivity
may change from its value in buffer solution by an unknown
of 100 µS/cm and higher, see Test Method D1193.
3
amount, and is a zero offset (1).
1.5 The values stated in SI units are to be regarded as
standard.
4. Reagents
1.6 This standard does not purport to address all of the
4.1 Purity of Reagents—Reagent grade chemicals shall be
safety concerns, if any, associated with its use. It is the
used in all tests. Unless otherwise indicated, it is intended that
responsibility of the user of this standard to establish appro-
all reagents conform to the specifications of the Committee on
priate safety and health practices and determine the applica-
Analytical Reagents of theAmerican Chemical Society where
bility of regulatory limitations prior to use.
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 [e-mail]. 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 May 1, 2011. Published May 2011. Originally the ASTM website.
3
approved in 1993. Last previous edition approved in 2007 as D5464–07. DOI: Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
10.1520/D5464-11. this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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D5464 − 11
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such specifications are available. Other grades may be used, corrosion and scale prevention. It is sometimes used in pure
provided it is first ascertained that the reagent is of sufficiently water treatment systems between multiple pass membranes to
high purity to permit its use without lessening the accuracy of optimize performance.
the determination.
6.2 High purity water is highly unbuffered and small
4.2 Purity of Water—References to wate
...

This document is not anASTM standard and is intended only to provide the user of anASTM 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:D5464–07 Designation:D5464–11
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 ThistestmethodisapplicabletodeterminethepHofwatersampleswithaconductivityof2to100µS/cmoverthepHrange
of 3 to 11. 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 D1193.
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
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—For definitions of terms used in these test methods, refer to Terminology D1129.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 liquid-junction potential, n—adcpotentialwhichthatappearsatthepointofcontactbetweenthereferenceelectrode’ssalt
bridge (also known as reference junction or diaphragm) and the sample solution.
3.2.1.1 Discussion—Ideally,thispotentialisnearzero,zeroandisstable.However,inlow-conductivitywaterthispotentialmay
3
change from its value in 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
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 Aug. 1, 2007. Published August 2007. Originally approved in 1993. Last previous edition approved in 2001 as D5464–93 (2001). DOI:
10.1520/D5464-07.
CurrenteditionapprovedMay1,2011.PublishedMay2011.Originallyapprovedin1993.Lastpreviouseditionapprovedin2007asD5464 – 07.DOI:10.1520/D5464-11.
2
For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
3
The boldface numbers in parentheses refer to the list of references at the end of this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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D5464–11
reagents conform to the specifications of the Committee on Analytical Reagents of the American Chemical S
...