ASTM D6569-05

Standard Test Method for On-Line Measurement of pH¹

SIGNIFICANCE AND USE
pH is a measure of the hydrogen ion activity in water. It is a major parameter affecting the corrosivity and scaling properties of water, biological life in water and many applications of chemical process control. It is therefore important in water purification, use and waste treatment before release to the environment.
On-line pH measurement is preferred over laboratory measurement to obtain real time, continuous values for automatic control and monitoring purposes.
SCOPE
1.1 This test method covers the continuous determination of pH of water by electrometric measurement using the glass, the antimony or the ion-selective field-effect transistor (ISFET) electrode as the sensor.
1.2 This test method does not cover measurement of samples with less than 100 S/cm conductivity. Refer to Test Method D 5128.
1.3 This test method does not cover laboratory or grab sample measurement of pH. Refer to Test Method D 1293.
1.4 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: 31-May-2005
• ICS: 71.040.50 - Physicochemical methods of analysis
• 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

Relations

• Replaces: ASTM D6569-00 - Standard Test Method for On-Line Measurement of pH¹
• Effective Date: 01-Jun-2005
• Replaced By: ASTM D6569-05(2009) - Standard Test Method for On-Line Measurement of pH¹
• Effective Date: 01-May-2009
• Referred By: ASTM D1293-18 - Standard Test Methods for pH of Water
• Effective Date: 01-Jun-2005
• Referred By: ASTM E2635-22 - Standard Practice for Water Conservation in Buildings Through In-Situ Water Reclamation
• Effective Date: 01-Jun-2005
• Referred By: ASTM E70-19 - Standard Test Method for pH of Aqueous Solutions With the Glass Electrode
• Effective Date: 01-Jun-2005
• Referred By: ASTM D5464-16 - Standard Test Method for pH Measurement of Water of Low Conductivity
• Effective Date: 01-Jun-2005

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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.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:D6569–05
Standard Test Method for
1
On-Line Measurement of pH
This standard is issued under the fixed designation D 6569; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope 3.2.1 liquid junction potential—the dc potential which ap-
pears at the point of contact between the reference electrode’s
1.1 This test method covers the continuous determination of
salt bridge and the sample solution. Ideally this potential is
pH of water by electrometric measurement using the glass, the
near zero and is stable. However, in samples with extreme pH
antimony or the ion-selective field-effect transistor (ISFET)
it becomes larger by an unknown amount and is a zero offset.
electrode as the sensor.
1.2 This test method does not cover measurement of
4. Summary of Test Method
samples with less than 100 µS/cm conductivity. Refer to Test
4.1 pH is measured as a voltage between measuring elec-
Method D 5128.
trode and reference electrode elements. The sensor assembly
1.3 This test method does not cover laboratory or grab
typically includes a temperature compensator to compensate
sample measurement of pH. Refer to Test Method D 1293.
for the varying output of the measuring electrode due to
1.4 This standard does not purport to address all of the
temperature.
safety concerns, if any, associated with its use. It is the
4.2 The sensor signals are processed with an industrial pH
responsibility of the user of this standard to establish appro-
analyzer/transmitter.
priate safety and health practices and determine the applica-
4.3 The equipment is calibrated with standard pH buffer
bility of regulatory limitations prior to use.
solutionsencompassingorincloseproximitytotheanticipated
2. Referenced Documents pH measurement range.
2
2.1 ASTM Standards:
5. Significance and Use
D 1129 Terminology Relating to Water
5.1 pH is a measure of the hydrogen ion activity in water. It
D 1193 Specification for Reagent Water
is a major parameter affecting the corrosivity and scaling
D 1293 Test Methods for pH of Water
properties of water, biological life in water and many applica-
D 2777 Practice for Determination of Precision and Bias of
tions of chemical process control. It is therefore important in
Applicable Methods of Committee D-19 on Water
water purification, use and waste treatment before release to
D 3370 Standard Practices for SamplingWater from Closed
the environment.
Conduits
5.2 On-line pH measurement is preferred over laboratory
D 3864 Guide for Continual On-Line Monitoring Systems
measurement to obtain real time, continuous values for auto-
for Water Analysis
matic control and monitoring purposes.
D 5128 TestMethodforOn-LinepHMeasurementofWater
of Low Conductivity
6. Interferences
3. Terminology 6.1 Pressure and temperature variations may force process
sample into the liquid junction of non-flowing junction refer-
3.1 Definitions—For definitions of terms used in this test
ence electrodes and cause changes in the junction potential.
method, refer to Terminology D 1129, Method D 1293 and
Estimates of 0.2 to 0.5 pH errors from this source have been
Practice D 3864.
3
cited. (1)
3.2 Definitions of Terms Specific to This Standard:
6.2 Liquid junction potentials at the reference electrode can
varydependingonthecompositionofthesample.Strongacids,
bases and extremely high and low ionic strength samples
1
This test method is under the jurisdiction of ASTM Committee D19 on Water
develop liquid junction potentials different from typical cali-
and is the direct responsibility of Subcommittee D19.03 for Sampling of Water and
brating buffer solutions.(2) Where these conditions exist, the
Water-Formed Deposits, Surveillance of Water, and Flow Measurement of Water.
most stable junction potential is obtained using a flowing
CurrenteditionapprovedJune1,2005.PublishedJuly2005.Originallyapproved
in 2000. Last previous edition approved in 2000 as D 6569 – 00.
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
3
Standards volume information, refer to the standard’s Document Summary page on The boldface numbers given in parentheses refer to a list of references at the
the ASTM website. 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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D6569–05
junction reference electrode—one that requires refilling with 6.7 Coating of the measuring electrode may produce a slow
electrolyte solution. However, providing po
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