ASTM D5391-23

Standard Test Method for Electrical Conductivity and Resistivity of a Flowing High Purity Water Sample

SIGNIFICANCE AND USE
5.1 Conductivity measurements are typically made on samples of moderate to high ionic strength where contamination of open samples in routine laboratory handling is negligible. Under those conditions, standard temperature compensation using coefficients of 1 to 3 % of reading per degree Celsius over wide concentration ranges is appropriate. In contrast, this test method requires special considerations to reduce trace contamination and accommodates the high and variable temperature coefficients of pure water samples that can range as high as 7 % of reading per degree Celsius. In addition, measuring instrument design performance must be proven under high purity conditions.  
5.2 This test method is applicable for detecting trace amounts of ionic contaminants in water. It is the primary means of monitoring the performance of demineralization and other high purity water treatment operations. It is also used to detect ionic contamination in boiler waters, microelectronics rinse waters, pharmaceutical process waters, etc., as well as to monitor and control the level of boiler and power plant cycle chemistry treatment chemicals. This test method supplements the basic measurement requirements for Test Methods D1125, D2186, and D4519.  
5.3 At very low levels of alkaline contamination, for example, 0–1 μg/L NaOH, conductivity is suppressed, and can actually be slightly below the theoretical value for pure water. (1 and 2)4 Alkaline materials suppress the highly conductive hydrogen ion concentration while replacing it with less conductive sodium and hydroxide ions. This phenomenon is not an interference with conductivity or resistivity measurement itself but could give misleading indications of inferred water purity in this range if it is not recognized.
SCOPE
1.1 This test method covers the determination of electrical conductivity and resistivity of high purity water samples below 10 μS/cm (above 0.1 Mohm-cm). It is applicable to both continuous and periodic measurements but in all cases, the water must be flowing in order to provide representative sampling. Static grab sampling cannot be used for such high purity water. Continuous measurements are made directly in pure water process lines, or in side stream sample lines to enable measurements on high temperature or high pressure samples, or both.  
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

• Status: Published
• Publication Date: 31-Mar-2023
• ICS: 13.060.60 - Examination of physical properties of water
• 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)

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: D5391 − 23
Standard Test Method for
Electrical Conductivity and Resistivity of a Flowing High
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Purity Water Sample
This standard is issued under the fixed designation D5391; 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.
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1. Scope tivity of Water (Withdrawn 2023)
D1129 Terminology Relating to Water
1.1 This test method covers the determination of electrical
D1192 Guide for Equipment for Sampling Water and Steam
conductivity and resistivity of high purity water samples below
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in Closed Conduits (Withdrawn 2003)
10 μS/cm (above 0.1 Mohm-cm). It is applicable to both
D1193 Specification for Reagent Water
continuous and periodic measurements but in all cases, the
D2186 Test Methods for Deposit-Forming Impurities in
water must be flowing in order to provide representative
3
Steam (Withdrawn 2014)
sampling. Static grab sampling cannot be used for such high
D2777 Practice for Determination of Precision and Bias of
purity water. Continuous measurements are made directly in
Applicable Test Methods of Committee D19 on Water
pure water process lines, or in side stream sample lines to
D3370 Practices for Sampling Water from Flowing Process
enable measurements on high temperature or high pressure
Streams
samples, or both.
D3864 Guide for On-Line Monitoring Systems for Water
1.2 The values stated in SI units are to be regarded as
Analysis
standard. No other units of measurement are included in this
D4519 Test Method for On-Line Determination of Anions
standard.
and Carbon Dioxide in High Purity Water by Cation
Exchange and Degassed Cation Conductivity
1.3 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
3. Terminology
responsibility of the user of this standard to establish appro-
3.1 Definitions—For definitions of other terms used in these
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use. test methods, refer to Terminology D1129.
3.1.1 electrical conductivity—refer to Test Methods D1125.
1.4 This international standard was developed in accor-
dance with internationally recognized principles on standard-
3.1.2 electrical resistivity—refer to Test Methods D1125.
ization established in the Decision on Principles for the
3.2 Definitions of Terms Specific to This Standard:
Development of International Standards, Guides and Recom-
3.2.1 cell constant, n—the ratio of the length of the path, L
mendations issued by the World Trade Organization Technical
2
(cm), and the cross-sectional area of the solution, A (cm ),
Barriers to Trade (TBT) Committee.
between the electrodes of a conductivity/resistivity cell, with
−1
units of cm .
2. Referenced Documents
2 3.2.1.1 Discussion—In high purity water measurements, the
2.1 ASTM Standards:
−1
cell constant is normally between 0.001 and 0.1 cm to
D1066 Practice for Sampling Steam
−1
prevent electrical interference. This is lower than the 1 cm of
D1125 Test Methods for Electrical Conductivity and Resis-
the standard centimetre cube and is taken into account by direct
reading instrument ranges that are matched with specific cell
constants.
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This test method is under the jurisdiction of ASTM Committee D19 on Water
and is the direct responsibility of Subcommittee D19.03 on Sampling Water and
4. Summary of Test Method
Water-Formed Deposits, Analysis of Water for Power Generation and Process Use,
On-Line Water Analysis, and Surveillance of Water. 4.1 Conductivity or resistivity is measured with a cell and
Current edition approved April 1, 2023. Published April 2023. Originally
temperature sensor or compensator in a flowing, closed system
approved in 1993. Last previous edition approved in 2014 as D5391 – 14 which
to prevent trace contamination from wetted surfaces and from
was withdrawn January 2023 and reinstated in April 2023. DOI: 10.1520/D5391-23.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
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Standards volume information, refer to the standard’s Document Summary page on The last approved version of this historical standard is referenced on
the ASTM website. www.astm.org.
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D5391 − 23
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