ASTM D5996-16

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Designation: D5996 − 05 (Reapproved 2009) D5996 − 16
Standard Test Method for
Measuring Anionic Contaminants in High-Purity Water by
On-Line Ion Chromatography
This standard is issued under the fixed designation D5996; 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 on-line analysis of high-purity water by the ion chromatography technique. This test method is
applicable for measuring various anionic contaminants in high-purity water, typically in the range of 0.01 to 100 μg/L. This test
method is used to determine the concentration of acetate, formate, chloride, fluoride, phosphate, nitrate, and sulfate in a
continuously flowing sample. The range of the test method is only as good as the reagent water available for preparing standards.
At extremely low concentrations, <1.0 μg/L, preparing standards is difficult, and extra care must be taken in their preparation. The
sample may have to be conditioned from higher pressures and temperatures to conditions that are suitable for use by on-line
instruments.
1.2 Online sample analysis of flowing streams does not lend itself to collaborative studies due to the nature of the sample and
the possibility of contamination that may result from handling the sample as part of the collaborative study. Therefore this standard
test method is not based on the results of a collaborative study but is intended to provide the best possible guidance for doing this
type of analysis.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
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.
2. Referenced Documents
2.1 ASTM Standards:
D1066 Practice for Sampling Steam
D1129 Terminology Relating to Water
D1192 Guide for Equipment for Sampling Water and Steam in Closed Conduits (Withdrawn 2003)
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 Closed Conduits
D3864 Guide for On-Line Monitoring Systems for Water Analysis
D4453 Practice for Handling of High Purity Water Samples
D5542 Test Methods for Trace Anions in High Purity Water by Ion Chromatography
D5810 Guide for Spiking into Aqueous Samples
D5847 Practice for Writing Quality Control Specifications for Standard Test Methods for Water Analysis
3. Terminology
3.1 For definitions of terms used in this test method, refer to Terminology D1129.
3.1 Definitions:
3.1.1 For definitions of terms used in this standard, refer to Terminology D1129.
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
Water-Formed Deposits, Analysis of Water for Power Generation and Process Use, On-Line Water Analysis, and Surveillance of Water.
Current edition approved Oct. 1, 2009Feb. 15, 2016. Published November 2009June 2016. Originally approved in 1996. Last previous edition approved in 20052009 as
D5996 – 05.D5996 – 05 (2009). DOI: 10.1520/D5996-05R09.10.1520/D5996-16.
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.
The last approved version of this historical standard is referenced on www.astm.org.
*A Summary of Changes section appears at the end of this standard
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D5996 − 16
3.2 Definitions of Terms Specific to This Standard:
3.2.1 analytical column, n—a column used to separate the anions of interest.
3.2.2 analytical column set, n—a combination of one or more guard columns followed by one or more analytical columns.
3.2.3 anion suppressor device, n—a device that is placed between the analytical columns and the detector. Its purpose is to
inhibit detector response to the ionic constituents in the eluant, so as to lower the detector background and at the same time enhance
detector response to the ions of interest.
3.2.3.1 Discussion—
Its purpose is to inhibit detector response to the ionic constituents in the eluant, so as to lower the detector background and at the
same time enhance detector response to the ions of interest.
3.2.4 breakthrough volume, n—the maximum sample volume that can be passed through a concentrator column before the least
tightly bound ion of interest is eluted. All of the columns in series contribute to the overall capacity of the analytical column set.
3.2.4.1 Discussion—
All of the columns in series contribute to the overall capacity of the analytical column set.
3.2.5 concentrator column, n—an ion exchange column used to concentrate the ions of interest and thereby increase method
sensitivity.
3.2.6 eluant, n—the ionic mobile phase used to transport the sample through the analytical column.
3.2.7 guard column, n—a column used before the analytical column to protect it from contaminants, such as particulate matter
or ionic species that may chemically foul the resins and degrade their performance.
3.2.8 ion chromatography, n—a form of liquid chromatography in which ionic constituents are separated by ion exchange
followed by a suitable detection means.
3.2.9 resolution, n—the ability of an analytical column to separate constituents under specific test conditions.
4. Summary of Test Method
4.1 A continuously flowing sample is injected into the instrument through a sample injection valve. The sample is pumped
through a concentrator column where the anions of interest are collected on ion-exchange resin. After a suitable volume of sample
has been passed through the concentrator column, sample flow is diverted and an eluant is pumped through the concentrator
column to remove the trapped anions. This eluant then flows through an analytical column set where the anions are separated based
on the retention characteristic of each anion relative to the eluant used. The eluant stream containing the anions of interest passes
through a suppressor device where the cations from the eluant are exchanged for hydrogen ions, converting the anions to their acid
form. After the suppressor device, the eluant solution passes through a conductivity detector where the separated anions are
detected. Detection limits for the anions are enhanced because the anions are in the acid form rather than the salt.
4.2 The anions are identified based on the retention time as compared to known standards. By measuring peak height or area
and comparing the detector response to known standards, the anions can be quantified.
5. Significance and Use
5.1 In the power-generation industry, high-purity water is used to reduce corrosion from anions, such as sulfate, chloride, and
fluoride. These anions are known to be detrimental to materials of construction used in steam generators, reactor vessel internals
and recirculation piping, heat exchangers, connective piping, and turbines. Most electric generating plants try to control these
anions to <1.0 μg/L in the steam generator feed water. Some nuclear power plants have been able to control anion contaminants
at less than 0.02 μg/L.
5.2 These anions and others cause low product yields in semiconductor manufacturing. They are also monitored and controlled
at similarly low levels as in the electric power industry.
5.3 Low molecular weight organic acids (acetate, formate, propionate) have been detected in steam generator feed water. These
low molecular weight organic materials are believed to be high-temperature degradation products of chemicals used to control
cycle water pH and organic contaminants in cycle makeup water.
5.4 In the semiconductor industry, anion contaminants may come from the breakdown of low molecular weight organic
materials by ultraviolet light radiation, which is frequently used to produce bacteria-free water. These organic compounds may also
contribute to low product yield.
5.5 The production of high-purity water for process makeup and use frequently employs the use of demineralizers to remove
unwanted anion contaminants. Also in the electric power industry, demineralizers are used in the process stream to maintain low
D5996 − 16
levels of these contaminants. As such, it is important to monitor this process to ensure that water quality standards are being met.
These processes can be monitored for the above-mentioned anions.
5.6 On-line measurements of these contaminants provide a greater degree of protection of the processes by allowing for frequent
on-line measurement of these species. Early detection of contaminant ingress allows for quicker corrective action to locate, reduce,
or eliminate, or combination thereof, the source. Grab samples will not provide the same level of protection because of their
intermittent nature and the longer time required to obtain and then analyze the sample.
5.7 Additionally, on-line monitoring significantly reduces the potential for contamination of high-purity water samples, a
significant problem when sampling and testing high-purity water.
6. Interferences
6.1 When working with low concentration samples, blanks, and standards, contamination can be a serious problem. Extreme
care must be exercised in all phases of this test method.
6.2 Improper sample line material or sample lines that have not been properly conditioned can give results that may not be truly
representative of the process stream. Absorption/desorption of anions on sample line wall deposits can change analytical results.
Maintaining a minimum sample flow of 1.8 m/s (6 ft/s) will minimize deposit buildup on sample line walls, reducing the potential
for absorption/desorption of anions.
6.3 A single anion present at a concentration significantly higher than other anions could mask closely adjacent peaks on the
chromatogram.
6.4 Low breakthrough volumes may be experienced when continuously monitoring for anions in water that has had its pH raised
by ammonia, morpholine, or other additives. This interference can be eliminated by taking the sample from the effluent of a cation
resin column.
6.5 Identification of the anion is based on retention time of the anion of interest. An interfering anion having the same retention
time as one of the anions of interest will result in erroneously high values for that anion.
6.6 When loading a concentrator column, high concentrations of interfering anions may cause low breakthrough volumes of
other anions. These interfering anions may act as an eluant and displace other anions from the concentrator column. See Annex
A1 to determine breakthrough volume. Do not load a sample volume greater than 80 % of the breakthrough volume.
7. Apparatus
7.1 Ion chromatograph with the following components:
7.1.1 Eluant Introduction System—The wetted portion of the eluant pump should be nonmetallic or of a corrosion-resistant
metal to prevent contamination of the chromatography columns.
7.1.2 Sample Injection System—The wetted portion of the sample pump should be nonmetallic or of a corrosion-resistant metal
to prevent metal contamination of the chromatography columns.
7.1.3 Anion Suppressor Device.
7.1.4 Conductivity Cell, low dead volume (1 μL). Temperature compensated or corrected flow through conductivity detector
should be capable of measuring conductivity from 0 to 1000 μS/cm. If temperature controlled conductivity detector is used,
temperature control should be at 60.5°C or better.
7.1.5 Suppressor Device Regenerant System—Some manufacturers provide integrated regenerant systems that reduce the
consumption of eluant. Electrochemical suppressor regenerant systems can be used, eliminating the need to prepare regenerant
solutions.
8. Reagents
8.1 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 of the American Chemical Society where such
specifications are available. Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high purity
to permit its use without lessening the accuracy of the determination.
8.2 Purity of Water—Unless otherwise indicated, reference to water shall be understood to mean reagent water as defined by
Specification D1193 Type 1 and shall contain less than 0.2 μg/L of the anions of interest. Freshly prepared water should be used
for making the low-level standards used for calibration. Detection limits will be limited by the purity of the water and reagents
used to make standards. The purity of the water used shall be checked by the use of Test Methods D5542.
8.3 Prepare eluant for the specific columns used and for the anions of interest in accordance with manufacturer’s directions.
Reagent Chemicals, American Chemical Society Specifications, American Chemical Society, Washington, DC. For suggestions on the testing of reagents not listed by
the American Chemical Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and National
Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville, MD.
D5996 − 16
8.4 Prepare regenerant for the specific suppressor used in accordance with the manufacturer’s directions if required.
NOTE 1—There are numerous combinations of analytical columns, suppressors, eluants, and regenerants that may be used with this test method. It is
not practicable to list all the combinations. Users should use the appropriate combination of concentrator column, analytical column, suppressor, eluant,
and regenerant to achieve the desired resolution and detection.
8.5 Fluoride Solution, Stock (1.00 mL = 1.00 mg F)—Dry sodium fluoride at 110°C for 2 6 0.5 h and cool in a desiccator.
Dissolve 2.210 g of dried salt in water and dilute to 1 L.
8.6 Acetate Solution, Stock (1.00 mL = 1.00 mg acetate)—Dissolve 1.389 g of sodium acetate in water and dilute to 1 L with
water. Store in a brown glass bottle with a TFE-fluorocarbon lined cap in a refrigerator.
8.7 Formate Solution, Stock (1.00 mL = 1 mg formate)—Dissolve 1.511 g sodium formate in water and dilute to 1 L with water.
Store in a brown glass bottle with a TFE-fluorocarbon lined cap in a refrigerator.
8.8 Chloride Solution, Stock (1.00 mL = 1.00 mg Cl)—Dry sodium chloride (NaCl) for 2 6 0.5 h at 110°C and cool in a
desiccator. Dissolve 1.648 g of the dry salt in water and dilute to 1 L.
8.9 Phosphate Solution, Stock (1.00 mL = 1.00 mg PO )—Dissolve 1.433 g of potassium dihydrogen phosphate (KH PO ) in
4 2 4
water and dilute to 1 L with water.
8.10 Sulfate Solution, Stock (1.00 mL = 1.00 mg SO )—Dry sodium sulfate for 2 6 0.5 h at 110°C and cool in a desiccator.
Dissolve 1.479 g of the dried salt in water and dilute to 1 L.
8.11 Nitrate Solution, Stock (1.00 mL = 1.00 mg NO )—Dry approximately 2 g of sodium nitrate (NaNO ) at 105°C for 48 h.
3 3
Dissolve exactly 1.371 g of the dried salt in water and dilute to 1 L with water.
8.12 Anion Intermediate Solutions—Prepare a 1000 μg/L standard of each anion by diluting 1.00 mL of each stock solution to
1 L. If acetate, formate, or phosphate are included in the standard, the solution must be prepared daily. It is recommended that these
standards be prepared separately from the rest of the anions.
8.13 Anion Working Solutions—Prepare a blank and at least three different working solutions from the anion intermediate
solution, containing the anions of interest. Prepare in dedicated volumetric flasks and transfer to sample containers in accordance
with Practice D4453. Prepare fresh daily. The range of the working solutions pr
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