ASTM D5543-21

Standard Test Method for Low-Level Dissolved Oxygen in Water

SIGNIFICANCE AND USE
5.1 Dissolved oxygen is detrimental in certain boiler and steam cycles because it may accelerate corrosion. Concentrations above 10 μg/L are unacceptable in many high-pressure boiler systems. The efficiency of dissolved oxygen removal from boiler feedwater by chemical or mechanical means, or both, is determined by measuring the concentration before and after the process. The measurement is also made to check for air leakage into the boiler system.  
5.2 The oxygen treatment method for boiler corrosion reduction requires injection of oxygen into the boiler feedwater. The resulting oxygen level is monitored for control purposes.
SCOPE
1.1 This test method covers the rapid determination of low-level (  
1.2 This test method may be applicable to electronic-grade, pharmaceutical-grade, and other high-purity waters, although these were not addressed in the collaborative study.  
1.3 It is the user’s responsibility to ensure the validity of this test method for waters of untested matrices.  
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.5 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.  
1.6 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: 30-Jun-2021
• 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

Relations

• Refers: ASTM D1129-13(2020)e2 - Standard Terminology Relating to Water
• Effective Date: 01-May-2020
• Refers: ASTM D1066-18e1 - Standard Practice for Sampling Steam
• Effective Date: 01-Aug-2018
• Refers: ASTM D1066-18 - Standard Practice for Sampling Steam
• Effective Date: 01-Aug-2018
• Refers: ASTM D5463-18 - Standard Guide for Use of Test Kits to Measure Inorganic Constituents in Water
• Effective Date: 01-May-2018
• Refers: ASTM D5463-13 - Standard Guide for Use of Test Kits to Measure Inorganic Constituents in Water
• Effective Date: 01-Jan-2013
• Refers: ASTM D2777-12 - Standard Practice for Determination of Precision and Bias of Applicable Test Methods of Committee D19 on Water
• Effective Date: 15-Jun-2012
• Refers: ASTM D1066-11 - Standard Practice for Sampling Steam
• Effective Date: 15-Jun-2011
• Refers: ASTM D3370-10 - Standard Practices for Sampling Water from Closed Conduits
• Effective Date: 01-Dec-2010
• Refers: ASTM D1129-10 - Standard Terminology Relating to Water
• Effective Date: 01-Mar-2010
• Refers: ASTM D5463-08 - Standard Guide for Use of Test Kits to Measure Inorganic Constituents in Water
• Effective Date: 01-Oct-2008
• Refers: ASTM D3370-08 - Standard Practices for Sampling Water from Closed Conduits
• Effective Date: 01-Oct-2008
• Refers: ASTM D5540-08 - Standard Practice for Flow Control and Temperature Control for On-Line Water Sampling and Analysis
• Effective Date: 01-Oct-2008
• Refers: ASTM D2777-08 - Standard Practice for Determination of Precision and Bias of Applicable Test Methods of Committee D19 on Water
• Effective Date: 15-Jan-2008
• Refers: ASTM D3370-07 - Standard Practices for Sampling Water from Closed Conduits
• Effective Date: 01-Dec-2007
• Refers: ASTM D1066-06 - Standard Practice for Sampling Steam
• Effective Date: 15-Dec-2006

Overview

ASTM D5543-21 is the internationally recognized standard method for the rapid determination of low-level dissolved oxygen in water. Developed by ASTM International, this standard focuses on measuring dissolved oxygen in concentrations below 100 μg/L (ppb), particularly in water used in high-pressure boiler and steam cycles. The presence of dissolved oxygen at such low levels is critically important, as even concentrations above 10 μg/L can accelerate corrosion in boilers, threatening system efficiency and longevity.

This test method is applicable to thermal-cycle steam condensate, deaerated boiler feedwater, boiler water, and deaerated deionized water. While primarily targeted at the power generation and industrial sectors, the method may also be suitable for electronic-grade, pharmaceutical-grade, and other high-purity waters, subject to validation by users.

Key Topics

• Purpose and Significance
  • Ensures compliance with strict dissolved oxygen limits in boiler systems to minimize corrosion.
  • Supports both oxygen removal and oxygen treatment corrosion control methods by validating process effectiveness.
• Test Method Overview
  • Utilizes a sealed, oxygen-sensitive ampoule containing an indicator that changes color in the presence of dissolved oxygen.
  • The color intensity, interpreted via a calibrated color comparator, determines the oxygen concentration in the sample.
• Sample Collection and Integrity
  • Emphasizes a leak-free, well-purged sampling system to prevent atmospheric oxygen contamination.
  • Recommends using inert materials like stainless steel or glass for sampling lines, with minimal polymeric connections.
• Interferences and Limitations
  • Results can be affected by sample color, turbidity, oxidizing impurities, and certain metal ions or chemicals.
  • Hydrogen peroxide above 200 μg/L, boron at low pH, and some organic oxidants can cause positive bias.
  • Quality control procedures and duplicate testing are encouraged to ensure accuracy and reproducibility.

Applications

ASTM D5543-21 is widely used in industries where control of dissolved oxygen in water is critical:

• Power Generation
  • Monitoring boiler feedwater, steam condensate, and system water for oxygen content to prevent corrosion and ensure system reliability.
  • Validation of chemical or mechanical de-aeration efficiency and detection of air leaks into closed systems.
• Industrial Boilers
  • Control and optimization of oxygen injection methods used in corrosion prevention strategies.
• High-Purity Water Systems
  • Potential use in the semiconductor, pharmaceutical, and electronics industries, where water purity requirements are stringent and oxygen content must be minimized.

Other application areas include research laboratories and process water monitoring in various industrial settings.

Related Standards

For thorough implementation and compliance, users of ASTM D5543-21 should be familiar with related ASTM standards, including:

• ASTM D1066 - Practice for Sampling Steam
• ASTM D1129 - Terminology Relating to Water
• ASTM D1193 - Specification for Reagent Water
• ASTM D2777 - Practice for Determination of Precision and Bias for Water Analysis Methods
• ASTM D3370 - Practices for Sampling Water from Flowing Process Streams
• ASTM D5463 - Guide for Use of Test Kits for Inorganic Water Constituents
• ASTM D5540 - Practice for Flow and Temperature Control in On-Line Water Sampling

Practical Value

Implementing ASTM D5543-21 ensures reliable measurement of low-level dissolved oxygen, critical for protecting assets and maintaining safety in boiler operations. The method’s rapid results, reproducibility, and suitability for on-site use enhance monitoring efficiency across industrial water systems. Adherence to this standard supports regulatory compliance, minimizes operational risks, and extends equipment life through effective corrosion control.

Integrating ASTM D5543-21 with recommended sampling and quality assurance practices delivers accurate, actionable dissolved oxygen data, safeguarding industrial processes and promoting water management best practices.

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: D5543 − 21
Standard Test Method for
Low-Level Dissolved Oxygen in Water
This standard is issued under the fixed designation D5543; 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 D2777 Practice for Determination of Precision and Bias of
Applicable Test Methods of Committee D19 on Water
1.1 This test method covers the rapid determination of
D3370 Practices for Sampling Water from Flowing Process
low-level (<100 µg/L) dissolved oxygen in thermal-cycle
Streams
steamcondensate,deaeratedboilerfeedwater,boilerwater,and
D5463 Guide for Use of Test Kits to Measure Inorganic
deaerated deionized water. Color comparators allow the esti-
Constituents in Water
mation of concentrations ranging from 0 to 100 µg/L (ppb)
D5540 Practice for Flow Control and Temperature Control
oxygen.
for On-Line Water Sampling and Analysis
1.2 This test method may be applicable to electronic-grade,
pharmaceutical-grade, and other high-purity waters, although 3. Terminology
these were not addressed in the collaborative study.
3.1 Definitions:
1.3 Itistheuser’sresponsibilitytoensurethevalidityofthis 3.1.1 For definitions of terms used in this standard, refer to
test method for waters of untested matrices. Terminology D1129.
1.4 The values stated in SI units are to be regarded as
4. Summary of Test Method
standard. No other units of measurement are included in this
4.1 The tip of a partially evacuated sealed ampoule is
standard.
broken while submerged in a flowing water sample. The
1.5 This standard does not purport to address all of the
sample is drawn into the ampoule where it reacts instanta-
safety concerns, if any, associated with its use. It is the
neously with the oxygen-sensitive indicator (leuco form of
responsibility of the user of this standard to establish appro-
RhodazineD)toproduceareddishvioletcolorwhoseintensity
priate safety, health, and environmental practices and deter- 3
is proportional to the concentration of dissolved oxygen.
mine the applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accor-
5. Significance and Use
dance with internationally recognized principles on standard-
5.1 Dissolved oxygen is detrimental in certain boiler and
ization established in the Decision on Principles for the
steam cycles because it may accelerate corrosion. Concentra-
Development of International Standards, Guides and Recom-
tions above 10 µg/L are unacceptable in many high-pressure
mendations issued by the World Trade Organization Technical
boiler systems. The efficiency of dissolved oxygen removal
Barriers to Trade (TBT) Committee.
from boiler feedwater by chemical or mechanical means, or
both, is determined by measuring the concentration before and
2. Referenced Documents
after the process. The measurement is also made to check for
2.1 ASTM Standards:
air leakage into the boiler system.
D1066 Practice for Sampling Steam
5.2 The oxygen treatment method for boiler corrosion
D1129 Terminology Relating to Water
reduction requires injection of oxygen into the boiler feedwa-
D1193 Specification for Reagent Water
ter. The resulting oxygen level is monitored for control
purposes.
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 6. Interferences
Water-Formed Deposits, Analysis of Water for Power Generation and Process Use,
6.1 Color, turbidity, and oxidizing impurities interfere in
On-Line Water Analysis, and Surveillance of Water.
Currentedition approvedJuly 1,2021.PublishedJuly 2021.Originallyapproved this test method to yield high results. If the sample is colored
in 1994. Last previous edition approved in 2015 as D5543 – 15. DOI: 10.1520/
D5543-21.
2 3
For referenced ASTM standards, visit the ASTM website, www.astm.org, or Spokes, G. N., Dissolved Oxygen in Water Measurement and Standardization,
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM EPRI PWR Plant Chemists’ Meeting, San Diego, CA, Nov. 17–20, 1992. Copies
Standards volume information, refer to the standard’s Document Summary page on obtainable from CHEMetrics Inc., 4295 Catlett Rd., Midland, VA 22728, https://
the ASTM website. www.chemetrics.com.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5543 − 21
or turbid or contains oxidizing impurities, the amount of
interference that may be contributed by such effects must be
determined independently prior to using this test method.
6.2 Easily reduced metal ions may interfere in this test
method to cause high results. For example, 100 µg/L (ppb)
+2
Cu may appear as 5 µg/L (ppb) dissolved oxygen, and 100
+3
µg/L Fe may appear as 7 µg/L dissolved oxygen. However,
+2 +3
less than 50 µg/L Cu or Fe cause less than 1-µg/L
interference.
6.3 Hydrogen peroxide alone in concentrations up to 200
µg/L does not affect the measurement of 1.5 µg/L of dissolved
oxygen.Above 200 µg/Lhydrogen peroxide, there is a positive
interference of 3.3 µg/L dissolved oxygen per 100 µg/L excess
over 200 µg/L hydrogen peroxide.
6.4 The following interferences occur in the presence of
2200 mg/L boron present as boric acid: (1) at pH levels below
pH 6, recovery can be as low as 80 %; (2) added hydrogen
peroxide at a concentration of 0.1 mg/L yields a positive
interference of 10 µg/L dissolved oxygen; and (3) added
hydrogen peroxide in a concentration range from 0.5 to 650
FIG. 1 Sampling Tube for Use with Ampoules to Measure Dis-
mg/L yields a positive interference of 20 to 25 µg/L.
solved Oxygen in a Flowing Water Sample
NOTE 1—Measurements of 0 to 100 µg/L of dissolved oxygen are
unaffectedbythepresenceof2200mg/LboronpresentasboricacidatpH
9. Precautions
6 and above in the absence of hydrogen peroxide.
9.1 Users should review the manufacturer’s kit instructions
6.5 Benzoquinone, an oxidation product of hydroquinone,
before use.
interferes with this test method. One hundred micrograms per
litreofbenzoquinonemayappearas33µg/Ldissolvedoxygen.
10. Sampling
6.6 Reducing agents such as hydrazine and sulfite do not
10.1 Collect the samples in accordance with Practices
interfere at 5-mg/L (ppm) levels in the sample.
D5540, D1066, and D3370.
10.2 Sampling is the most critical part of any dissolved
6.7 Ampoules must be protected from light to prevent
oxygen test. The sample stream must be completely leak-free,
darkening. Follow the manufacturer’s storage recommenda-
since even the smallest leak can elevate the oxygen level in the
tions.
sample and cause large errors in the results. New or intermit-
6.8 Color comparator tubes must be protected from light to
tentlyusedsamplingsystemsmustbepurgedforaminimumof
prevent fading. Follow the manufacturer’s storage recommen-
4 h. Sample streams that are used routinely may require only a
dations.
few minutes of purging.
10.3 With water under pressure, connect a tube of inert
7. Apparatus
material to the inlet and extend the tube outlet to the bottom of
7.1 Color Comparator, for 0, 2, 4, 6, 8, 12, 16, and 20 µg/L
the plastic sampling tube. Clamps may be attached to the tube
(ppb) of oxygen.
to hold it vertical, or it can be attached to a vertical rod or pipe
above a sink, drain, or bucket. Use stainless steel, Type 304 or
7.2 Color Comparator, for 0, 5, 10, 15, 20, 25, 30, and 40
316, or glass tubing with short neoprene connections. Do not
µg/L (ppb) of oxygen.
use copper tubing, long sections of neoprene tubing, or other
7.3 Color Comparator, for 0, 10, 20, 30, 40, 60, 80, and 100
types of elastomeric polymeric materials. If the water being
µg/L (ppb) of oxygen.
sampled is above ambient temperature, the sample line shall
containasuitablecoolingcoiltocoolittoambienttemperature
7.4 Sampling Tube. See Fig. 1.
to prevent introduction of atmospheric oxygen into the test
ampoule at the time of analysis. Establish a flow rate ranging
8. Reagents and Materials
from 500–1000 mL per minute to prevent the introduction of
8.1 This test method does not require the preparation of any
atmospheric oxygen during sampling.
reagents.All the necessary analytical reagents are provided by
11. Calibration and Standardization
the manufacturer in sealed ampoules.
11.1 No calibration is required.
8.2 Purity of Water—Reference to water shall mean water
that meets or exceeds the quantitative specifications forType II
NOTE 2—The color comparator standards are precalibrated by the
reagent water of Specification D1193, Section 1.1. manufacturer for measurement of dissolved oxygen in water.
D5543 − 21
11.2 A dissolved-oxygen-in-water standard may be gener- the comparator label. Estimate the concentration to within a
ated by following the procedures given in Appendix X1. half color standard interval.
12. Procedure
13. Calculation
12.1 Insert the ampoule into the sampling device, with the
13.1 The dissolved oxygen content of the sample is the
pointed end down. Allow the sample to flow at least 5 min. A
value obtained in 12.4.1. Use the average of the two resulting
15-min wait time may be necessary to achieve the best
values if two ampoules are used.
accuracy for samples with below 20 µg/Lof dissolved oxygen.
14. Precision and Bias
12.2 Gently press the ampoule toward the wall of the
sampling tube to snap off the tip (Fig. 1), and remove the 14.1 The overall precision and bias of this test method
ampoule, keeping the tip down, immediately after filling is cannot be determined by round-robin testing because of the
complete. instability of shipping solutions.
12.3 Usingaprotectiverubberfingercot,placeafingerover 14.2 This test method was evaluated for single-operator
the broken tip. (Warning—Glass may be sharp.) Invert the precision by eight laboratories, with a total of 15 operators
ampouleseveraltimestomixthecontents,allowingthebubble running a total of 200 samples in triplicate. The collaborative
to travel from end to end each time. Wipe all liquid from the test data were obtained on the samples available at the
exterior of the ampoule. laboratory site locations. These data may not apply for other
matrices.
NOTE 3—A small bubble of inert gas will remain in the ampoule to
14.2.1 The single-operator precision, S , of this test method
o
facilitate mixing.
was found to be dependent on the ampoule type and to be
NOTE 4—Due to the possibility of air leaking in during this step, it is
advisable to run tests in duplicate. It should be noted, however, that some
partly dependent on the dissolved oxygen content of the
variation in observed concentrations may be due to changes in system
sample. The data are summarized in the tables that follow.
conditions.
14.2.1.1 Thedatainthefollowingtablewereobtainedusing
12.4 Use the color comparator as illustrated in Fig. 2 to
0to20-µg/L(ppb)rangeampoulesandcomparators. Atotalof
determine the level of dissolved oxygen in the sample. Place
66sampleswasmeasuredintriplicatebyatotalof15operators
the ampoule in the center (empty) tube of the comparator, with
in 8 laboratories:
theflatenddownward.Directthetopofthecomparatortoward
Range, µg/L (ppb) 0 to 0.9 1 to 4.9 5 to 9.9 10 to 14.9 15 to 20
a source of bright, white light while viewing from the bottom.
S 0.20 1.6 2.5 1.4 3.2
o
Hold the comparator in a nearly horizontal position, and rotate
14.2.1.2 Thedatainthefollowingtablewereobtainedusing
it until the color standard below the ampoule shows the closest 6
0to40-µg/L(ppb)rangeampoulesandcomparators. Atotalof
match. Complete this color matching procedure in less than 30
78sampleswasmeasuredintriplicatebyatotalof14operators
s after snapping the tip in the sample.
in 7 laboratories:
NOTE 5—The color intensity may continue to increase after the rapid Range, µg/L (ppb) 0 to 1.9 2 to 9.9 10 to
...

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: D5543 − 15 D5543 − 21
Standard Test Method for
Low-Level Dissolved Oxygen in Water
This standard is issued under the fixed designation D5543; 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 covers the rapid determination of low-level (<100 μg/L) dissolved oxygen in thermal-cycle steam condensate,
deaerated boiler feedwater, boiler water, and deaerated deionized water. Color comparators allow the estimation of concentrations
ranging from 0 to 100 μg/L (ppb) oxygen.
1.2 This test method may be applicable to electronic-grade, pharmaceutical-grade, and other high-purity waters, although these
were not addressed in the collaborative study.
1.3 It is the user’suser’s responsibility to ensure the validity of this test method for waters of untested matrices.
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.5 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.6 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.
2. Referenced Documents
2.1 ASTM Standards:
D1066 Practice for Sampling Steam
D1129 Terminology Relating to Water
D1193 Specification for Reagent Water
D2777 Practice for Determination of Precision and Bias of Applicable Test Methods of Committee D19 on Water
D3370 Practices for Sampling Water from Flowing Process Streams
D5463 Guide for Use of Test Kits to Measure Inorganic Constituents in Water
D5540 Practice for Flow Control and Temperature Control for On-Line Water Sampling and Analysis
3. Terminology
3.1 Definitions—Definitions: For definitions of terms used in this test method, refer to Terminology D1129.
TheseThis test methods aremethod is under the jurisdiction of ASTM Committee D19 on Water and areis 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 Feb. 1, 2015July 1, 2021. Published May 2015July 2021. Originally approved in 1994. Last previous edition approved in 20092015 as
D5543 – 09.D5543 – 15. DOI: 10.1520/D5543-15.10.1520/D5543-21.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’sstandard’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
D5543 − 21
3.1.1 For definitions of terms used in this standard, refer to Terminology D1129.
4. Summary of Test Method
4.1 The tip of a partially evacuated sealed ampoule is broken while submerged in a flowing water sample. The sample is drawn
into the ampoule where it reacts instantaneously with the oxygen-sensitive indicator (leuco form of Rhodazine D) to produce a
reddish violet color whose intensity is proportional to the concentration of dissolved oxygen.
5. Significance and Use
5.1 Dissolved oxygen is detrimental in certain boiler and steam cycles because it may accelerate corrosion. Concentrations above
10 μg/L are unacceptable in many high-pressure boiler systems. The efficiency of dissolved oxygen removal from boiler feedwater
by chemical or mechanical means, or both, is determined by measuring the concentration before and after the process. The
measurement is also made to check for air leakage into the boiler system.
5.2 The oxygen treatment method for boiler corrosion reduction requires injection of oxygen into the boiler feedwater. The
resulting oxygen level is monitored for control purposes.
6. Interferences
6.1 Color, turbidity, and oxidizing impurities interfere in this test method to yield high results. If the sample is colored or turbid
or contains oxidizing impurities, the amount of interference that may be contributed by such effects must be determined
independently prior to using this test method.
+2
6.2 Easily reduced metal ions may interfere in this test method to cause high results. For example, 100 μg/L (ppb) Cu may appear
+3 +2
as 5 μg/L (ppb) dissolved oxygen, and 100 μg/L Fe may appear as 7 μg/L dissolved oxygen. However, less than 50 μg/L Cu
+3
or Fe cause less than 1-μg/L interference.
6.3 Hydrogen peroxide alone in concentrations up to 200 μg/L does not affect the measurement of 1.41.5 μg/L of dissolved oxygen.
Above 200 μg/L hydrogen peroxide, there is a positive interference of 3.3 μg/L dissolved oxygen per 100 μg/L excess over 200
μg/L hydrogen peroxide.
6.4 The following interferences occur in the presence of 2200 mg/L boron present as boric acid: (1) at pH levels below pH 6,
recovery can be as low as 80 %; (2) added hydrogen peroxide at a concentration of 0.1 mg/L yields a positive interference of 10
μg/L dissolved oxygen; and (3) added hydrogen peroxide in a concentration range from 0.5 to 650 mg/L yields a positive
interference of 20 to 25 μg/L.
NOTE 1—Measurements of 0 to 100 μg/L of dissolved oxygen are unaffected by the presence of 2200 mg/L boron present as boric acid at pH 6 and above
in the absence of hydrogen peroxide.
6.5 Benzoquinone, an oxidation product of hydroquinone, interferes with this test method. One hundred micrograms per litre of
benzoquinone may appear as 33 μg/L dissolved oxygen.
6.6 Reducing agents such as hydrazine and sulfite do not interfere at 5-mg/L (ppm) levels in the sample.
6.7 Ampoules must be protected from light to prevent darkening. Follow the manufacturer’smanufacturer’s storage recommen-
dations.
6.8 Color comparator tubes must be protected from light to prevent fading. Follow the manufacturer’smanufacturer’s storage
recommendations.
Spokes, G. N., Dissolved Oxygen in Water Measurement and Standardization, EPRI PWR Plant Chemists’Chemists’ Meeting, San Diego, CA, Nov. 17–20, 1992. Copies
obtainable from CHEMetrics Inc., 4295 Catlett Rd., Midland, VA 22728, https://www.chemetrics.com.
D5543 − 21
7. Apparatus
7.1 Color Comparator, for 0, 2, 4, 6, 8, 12, 16, and 20 μg/L (ppb) of oxygen.
7.2 Color Comparator, for 0, 5, 10, 15, 20, 25, 30, and 40 μg/L (ppb) of oxygen.
7.3 Color Comparator, for 0, 10, 20, 30, 40, 60, 80, and 100 μg/L (ppb) of oxygen.
7.4 Sampling Tube. See Fig. 1.
8. Reagents and Materials
8.1 This test method does not require the preparation of any reagents. All the necessary analytical reagents are provided by the
manufacturer in sealed ampoules.
8.2 Purity of Water—Reference to water shall mean water that meets or exceeds the quantitative specifications for Type II reagent
water of Specification D1193, Section 1.1.
9. Precautions
9.1 Users should review the manufacturer’s kit instructions before use.
10. Sampling
10.1 Collect the samples in accordance with Practices D5540, D1066, and D3370.
10.2 Sampling is the most critical part of any dissolved oxygen test. The sample stream must be completely leak-free, since even
the smallest leak can elevate the oxygen level in the sample and cause large errors in the results. New or intermittently used
sampling systems must be purged for a minimum of 4 h. Sample streams that are used routinely may require only a few minutes
of purging.
10.2 Collect the samples in accordance with Practices D1066 and D3370.
FIG. 1 Sampling Tube for Use with Ampoules to Measure Dissolved Oxygen in a Flowing Water Sample
D5543 − 21
10.3 With water under pressure, connect a tube of inert material to the inlet and extend the tube outlet to the bottom of the sample
bottle or tube. plastic sampling tube. Clamps may be attached to the tube to hold it vertical, or it can be attached to a vertical rod
or pipe above a sink, drain, or bucket. Use stainless steel, Type 304 or 316, or glass tubing with short neoprene connections. Do
not use copper tubing, long sections of neoprene tubing, or other types of elastomeric polymeric materials. If the water being
sampled is above roomambient temperature, the sample line shall contain a suitable cooling coil to cool it to approximate room
temperature.ambient temperature to prevent introduction of atmospheric oxygen into the test ampoule at the time of analysis.
Establish a flow rate ranging from 500–1000 mL per minute to prevent the introduction of atmospheric oxygen during sampling.
10.4 Attach the feedwater source to the plastic sampling tube as described in 10.3. Clamps may be attached to the tube to hold
it vertical, or it can be attached to a vertical rod or pipe above a sink, drain, or bucket.
11. Calibration and Standardization
11.1 No calibration is required.
NOTE 2—The color comparator standards are precalibrated by the manufacturer for measurement of dissolved oxygen in water.
11.2 A dissolved-oxygen-in-water standard may be generated by following the procedures given in Appendix X1.
12. Procedure
12.1 Insert the ampoule into the sampling device, with the pointed end down. Allow the sample to flow at least 5 min. A 15-min
wait time may be necessary to achieve the best accuracy for samples with below 20 μg/L of dissolved oxygen.
12.2 Gently press the ampoule toward the wall of the sampling tube to snap off the tip, tip (Fig. 1), and remove the ampoule,
keeping the tip down, immediately after filling is complete.
12.3 Using a protective rubber finger cot, place a finger over the broken tip. (Warning—Glass may be sharp.) Invert the ampoule
several times to mix the contents, allowing the bubble to travel from end to end each time. Wipe all liquid from the exterior of
the ampoule.
NOTE 3—A small bubble of inert gas will remain in the ampoule to facilitate mixing.
NOTE 4—Due to the possibility of air leaking in during this step, it is advisable to run tests in duplicate. It should be noted, however, that some variation
in observed concentrations may be due to changes in system conditions.
12.4 Use the color comparator as illustrated in Fig. 2 to determine the level of dissolved oxygen in the sample. Place the ampoule
in the center (empty) tube of the comparator, with the flat end downward. Direct the top of the comparator toward a source of
bright, white light while viewing from the bottom. Hold the comparator in a nearly horizontal position, and rotate it until the color
standard below the ampoule shows the closest match. Complete this color matching procedure in less than 30 s after snapping the
tip in the sample.
NOTE 5—The color intensity may continue to increase after the rapid initial color reaction. However, it is the initial color reaction that is complete within
30 s, and to which the system calibrations apply.
12.4.1 Find the analytical result from the concentration value of the closest matching color standard as designated on the
comparator label. Estimate the concentration to within a half color standard interval.
13. Calculation
13.1 The dissolved oxygen content of the sample is the value obtained in 12.4.1. Use the average of the two resulting values if
two ampoules are used.
D5543 − 21
FIG. 2 Use of the Comparator
14. Precision and Bias
14.1 The overall precision and bias of this test method cannot be determined by round-robin testing because of the instability of
shipping solutions.
14.2 This test method was evaluated for single-operator precision by eight laboratories, with a total of 15 operators running a total
of 200 samples in triplicate. The collaborative test data were obtained on the samples available at the laboratory site locations.
These data may not apply for other matrices.
14.2.1 The single-operator precision, S , of this test method was found to be dependent on the ampoule type and to be partly
o
dependent on the dissolved oxygen content of t
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