ASTM E1787-16

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Designation: E1787 − 08 E1787 − 16
Standard Test Method for
Anions in Caustic Soda and Caustic Potash (Sodium
Hydroxide and Potassium Hydroxide) by Ion
Chromatography
This standard is issued under the fixed designation E1787; 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 determination of anionic impurities in 50 % caustic soda (sodium hydroxide) and 50 % caustic
potash (potassium hydroxide) solutions using ion chromatography (IC). Anions that can be determined at concentrations of
approximately 0.1–1000 0.1 to 1000 ug/g (ppm) include: bromide, chlorate, chloride, fluoride, nitrate, phosphate, and sulfate.
1.2 By varying the sample size, this test method can be used for anhydrous caustic soda and caustic potash products, as well
as other concentrations of liquid products.
1.3 This test method is not intended to be used to quantify chloride in caustic soda where the sodium chloride concentration
is approximately 1 %. For the most accurate determinations, it is recommended that high concentrations of chloride be analyzed
using a potentiometric titration procedure, such as the one described in Test Methods E291.
1.4 The values stated in SI units are to be regarded as standard. The values given in parentheses are for information only.
1.5 Review the current appropriate Material Safety Data Sheets (MSDS)(SDS) for detailed information concerning toxicity, first
aid procedures, and safety precautions.
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. Specific hazards statements are given in Section 8.
2. Referenced Documents
2.1 ASTM Standards:
D1193 Specification for Reagent Water
E180 Practice for Determining the Precision of ASTM Methods for Analysis and Testing of Industrial and Specialty Chemicals
(Withdrawn 2009)
E291 Test Methods for Chemical Analysis of Caustic Soda and Caustic Potash (Sodium Hydroxide and Potassium Hydroxide)
3. Summary of Test Method
3.1 Bromide, chlorate, chloride, fluoride, nitrate, phosphate and sulfate are measured in NaOH or KOH by ion chromatography.
The sample solution is diluted and injected onto a sample loop of an automated neutralization module. The sample in the loop is
pumped to a suppression device which uses electrolysis suppressor device (electrolytically or chemically regenerated) to neutralize
the hydroxide ions. The sample then is circulated through this device several times until it is completely neutralized. Anionic
constituents of the neutralized sample are concentrated on an anion concentrator column. After the concentration they are separated
into individual elution bands in the eluent on a separator column. The conductivity of the eluent is reduced with an anion
suppression device, and the anions of interest are detected using a conductivity detector. Quantitation of the anions in the sample
solution is achieved by calibrating the IC with a series of standards containing known amounts of the anions. These standards are
also passed through the neutralization device.
This test method is under the jurisdiction of ASTM Committee E15 on Industrial and Specialty Chemicals and is the direct responsibility of Subcommittee E15.01 on
General Standards.
Current edition approved April 1, 2008May 15, 2016. Published May 2008May 2016. Originally publishedapproved in 1996. Last previous edition approved in 20022008
as E1787-02.-08. DOI: 10.1520/E1787-08.10.1520/E1787-16.
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
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E1787 − 16
4. Significance and Use
4.1 Anion impurities in caustic soda and caustic potash are monitored by manufacturers and users for quality control of the
products. Anions of primary interest are chloride, chlorate, and sulfate. This test method has determined precision estimates only
for these three impurities.
5. Interferences
5.1 Substances that coelute with the anions of interest will interfere. A high concentration of one anion can interfere with
accurate quantitation of another anion if their retention times are close and resolution is affected. For example, caustic soda samples
containing large concentrations of chloride can interfere with the quantitation of small amounts of fluoride. Selection of a high
capacity anion separator column will minimize this problem.
5.2 Organic acids, surfactants, dyes, metals, etc., can cause fouling of the columns and membranes used in this test method,
resulting in interferences and decreased sensitivity. It is very important to follow the manufacturer’s recommendations for cleaning
and maintaining the various parts of the IC system.
5.3 The anion concentrator column in the neutralization module has a finite capacity for trapping anions, approximately 25
micro-equivalents per anions. Consult with manufacturer for selection of concentrator column of suitable capacity. Care should be
taken not to exceed the capacity of the column. When the capacity of the column is exceeded, the stripping of anions will not be
quantitative.
6. Apparatus
6.1 Ion Chromatograph, equipped with:
6.1.1 Conductivity Detector, Conductivity Detector,
6.1.2 Anion Separator Column, Anion Separator Column,
6.1.3 Guard Column, Guard Column,
6.1.4 100-μL Sample Loop, 100-μL Sample Loop, other sizes are permitted so long as they do not degrade the precision of the
method,
6.1.5 Autoneutralization Device, capable of neutralizing the caustic sample prior to being directed through the separator column,
6.1.6 Post-Column Chemical Suppression Device, capable of reducing background conductivity due to the eluent, and
6.1.7 Data Acquisition System, such as an integrator or computer system.
6.2 100-mL Volumetric Flasks, for preparing sample solutions.
6.3 Disposable 10-mL Syringes, for injecting solution into the IC.
6.3.1 IC Autosampler (optional), can be used as an alternative to manually injecting samples.
7. Reagents
7.1 Purity of Reagents—Reagent grade chemicals should be used in all tests. Unless otherwise indicated, all reagents must
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.
7.2 Purity of Water—References to water means Type 1 (18 MΩ-cm deionized water) conforming to Specification D1193.
7.3 Anion Stock Standards, 1000 ug/g (ppm):
7.3.1 Bromide Stock Solution (1.00 mL = 1.00 mg Bromide)—Dry sodium bromide (NaBr) for 6 h at 150°C and cool in a
desiccator. Dissolve 1.288 g of the dried NaBr in water, dilute to 1 L with water, and mix well.
7.3.2 Chlorate Stock Solution (1.00 mL = 1.00 mg Chlorate)—Dissolve 1.275 g of sodium chlorate (NaClO ) in water, dilute
to 1 L with water, and mix well.
7.3.3 Chloride Stock Solution (1.00 mL = 1.00 mg Chloride)—Dry sodium chloride (NaCl) for 1 h at 100°C and cool in a
desiccator. Dissolve 1.648 g of the dried NaCl in water, dilute to 1 L with water, and mix well.
7.3.4 Fluoride Stock Solution (1.00 mL = 1.00 mg Fluoride)—Dry sodium fluoride (NaF) at 105°C for at least 8 h 8 h and cool
in a desiccator. Dissolve 2.210 g of the dried NaF in 500 mL of water, dilute to 1 L with water, and mix well.
7.3.5 Nitrate Stock Solution (1.00 mL = 1.00 mg Nitrate)—Dry sodium nitrate (NaNO ) at 105°C for 48 h and cool in a
desiccator. Dissolve 1.371 g of the dried NaNO in water, dilute to 1 L with water, and mix well.
7.3.6 Phosphate Stock Solution (1.00 mL = 1.00 mg Phosphate)—Dissolve 1.433 g of potassium dihydrogen phosphate
(KH PO ) in water, dilute to 1 L with water, and mix well.
2 4
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),(USP), Rockville, MD.
E1787 − 16
7.3.7 Sulfate Stock Solution (1.00 mL = 1.00 mg Sulfate)—Dry sodium sulfate (Na SO ) for 1 h at 105°C and cool in a
2 4
desiccator. Dissolve 1.479 g of the Na SO in water, dilute to 1 L with water, and mix well.
2 4
7.4 Eluent—The eluent used for the anion analysis will depend on the choice of separator column selected. The eluent described
below is used with the Dionex AS-12A separator column.Follow the manufacturer’s instructions for preparation of the eluent.
7.4.1 Eluent Concentrate, 0.27 mol/L (M) Sodium Carbonate/0.03 mol/L (M) Sodium Bicarbonate (100× (100 × Concentrate)—
Dissolve 28.6 g of sodium carbonate and 2.52 g of sodium bicarbonate in a 1- L 1-L volumetric flask containing 800 mL of water.
Dilute to volume with water and mix. Store in a tightly capped polypropylene bottle.
7.4.2 Eluent, 2.7 mmol/L (mM) Sodium Carbonate/0.3 mmol/L (mM) Sodium Bicarbonate Eluent—Pipet 20.0 mL of the eluent
concentrate into a 2-L volumetric flask, dilute to the mark with water, and mix.
8. Hazards
8.1 Sodium and potassium hydroxides are caustic alkalies, which in their anhydrous or strong solution form, are hazardous
materials. In contact with the skin they produce burns that may be quite serious unless promptly treated. Their action is insidious
since they produce no immediate stinging or burning sensation, and damage may result before their presence is realized.
8.2 Eyes are particularly vulnerable to severe damage from these alkalies.
8.3 Use safety goggles or face shields and rubber gloves when handling these alkalies, and avoid spillage on clothing. These
materials rapidly attack wool and leather.
8.4 Flush away spilled caustic with water where possible, or cover with absorbent material (such as sawdust, vermiculite, or
baking soda), and sweep up and discard in accordance with all federal, state, and local health and environmental regulations. Last
traces may be neutralized with dilute acetic acid and the area washed with water.
8.5 Consult Material Safety Data Sheets (MSDS)(SDS) for chemicals listed in this test method for further information.
9. Calibration
9.1 The retention time for each anion is determined by injecting a series of standard solutions, each containing only one anion
of interest, into the IC and recording the time required for a peak to appear on the chromatogram. Retention times vary with
operating conditions. The standards, therefore, must be chromatographed
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