ASTM D3082-15

Standard Test Method for Boron in Water

SIGNIFICANCE AND USE
5.1 Because boron can be both essential and deleterious to plant growth, and because ingestion of large amounts can affect the central nervous system in humans, a method is required to determine its concentration in potable, natural, and wastewaters. This test method provides a means of determining the boron concentration of these waters. The holding time for the samples may be calculated in accordance with Practice D4841.  
5.2 Boric acid is used for chemical shim control of neutron flux in a nuclear reactor. This test method serves to determine if the boron concentration is within acceptable limits.
SCOPE
1.1 This test method covers the determination of boron in water and wastewaters by the curcumin colorimetric-extraction method2 in concentrations between 0.1 and 1.0 mg/L. The range can be extended by dilution of the sample.  
1.2 Only dissolved boron is determined. This test method requires that the water sample be filtered through a 0.45-μm membrane filter before analysis.  
1.3 This test method is a colorimetric method that is very sensitive to low concentrations of boron in water and requires a relatively small sample volume for analysis.  
1.4 Precision and bias were obtained on natural and wastewaters. It is the user's responsibility to ensure the validity of this test method for waters of untested matrices.  
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
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.

General Information

• Status: Published
• Publication Date: 31-Jan-2015
• ICS: 13.060.50 - Examination of water for chemical substances
• Technical Committee: D19 - Water
• Drafting Committee: D19.05 - Inorganic Constituents in Water

Relations

• Replaces: ASTM D3082-09 - Standard Test Method for Boron in Water
• Effective Date: 01-Feb-2015
• 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 D4841-88(2013) - Standard Practice for Estimation of Holding Time for Water Samples Containing Organic and Inorganic Constituents
• Effective Date: 01-Jan-2013
• Refers: ASTM D4841-88(2013)e1 - Standard Practice for Estimation of Holding Time for Water Samples Containing Organic and Inorganic Constituents
• 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 D5810-96(2011) - Standard Guide for Spiking into Aqueous Samples
• Effective Date: 01-May-2011
• Refers: ASTM E2251-11 - Standard Specification for Liquid-in-Glass ASTM Thermometers with Low-Hazard Precision Liquids
• Effective Date: 01-May-2011
• Refers: ASTM D3370-10 - Standard Practices for Sampling Water from Closed Conduits
• Effective Date: 01-Dec-2010
• Refers: ASTM E2251-10 - Standard Specification for Liquid-in-Glass ASTM Thermometers with Low-Hazard Precision Liquids
• Effective Date: 01-Nov-2010
• Refers: ASTM D1129-10 - Standard Terminology Relating to Water
• Effective Date: 01-Mar-2010
• Refers: ASTM E275-08 - Describing and Measuring Performance of Ultraviolet and Visible Spectrophotometers
• Effective Date: 15-Oct-2008
• Refers: ASTM D3370-08 - Standard Practices for Sampling Water from Closed Conduits
• Effective Date: 01-Oct-2008

Overview

ASTM D3082-15: Standard Test Method for Boron in Water is a widely-recognized international standard developed by ASTM International. This standard outlines a highly sensitive method for determining the concentration of dissolved boron in potable, natural, and wastewaters using the curcumin colorimetric-extraction technique. Boron is a trace element that can be both vital and harmful to plants and humans, making accurate detection essential for water quality management, environmental monitoring, and compliance in industrial processes.

Key Topics

• Boron Measurement: The standard defines procedures to accurately measure dissolved boron in water within the range of 0.1 to 1.0 mg/L. The measurement range can be extended by dilution.
• Sample Preparation: Water samples must be filtered through a 0.45-μm membrane filter to remove particulate matter prior to analysis, ensuring only dissolved boron is measured.
• Method Sensitivity: This colorimetric method provides high sensitivity for low concentrations and requires a small sample volume, making it efficient and practical for laboratory implementation.
• Interferences and Precautions: The method addresses potential interferences, such as nitrates above 20 mg/L and high water hardness, and suggests remedial actions (e.g., additional filtration or removing organic color).
• Quality Control: The standard emphasizes calibration and quality assurance protocols, including use of laboratory control samples, method blanks, and periodic verification with independent reference materials to ensure accuracy and reliability.
• Regulatory and Safety Considerations: Users must establish appropriate laboratory safety, health practices, and comply with any regulatory requirements.

Applications

ASTM D3082-15 is broadly used in:

• Environmental Monitoring: Ensures boron levels in natural water bodies are within safe ecological limits to protect aquatic life and crops.
• Drinking Water Testing: Monitors boron concentrations in potable water to safeguard public health by preventing excessive human exposure.
• Industrial Water Quality: Supports industries such as power generation, where boric acid serves chemical shim control in nuclear reactors, by confirming boron concentrations remain within operational standards.
• Wastewater Treatment: Assists treatment facilities in tracking and controlling boron discharges in compliance with environmental regulations.

Related Standards

For comprehensive water analysis and laboratory practice, the following ASTM standards are commonly referenced alongside D3082-15:

• ASTM D3370: Practices for Sampling Water from Closed Conduits
• ASTM D1129: Terminology Relating to Water
• ASTM D1193: Specification for Reagent Water
• ASTM D2777: Practice for Determination of Precision and Bias of Test Methods for Water
• ASTM D4841: Practice for Estimation of Holding Time for Water Samples
• ASTM D5810: Guide for Spiking into Aqueous Samples
• ASTM D5847: Practice for Writing Quality Control Specifications for Water Analysis
• ASTM E60/E275: Practice for Analysis of Metals and Performance of Spectrophotometers

Practical Value

Implementing ASTM D3082-15 ensures consistent, accurate boron detection in water, helping organizations meet environmental regulations, protect ecosystems, manage industrial processes, and ensure public health. The method’s precision and robust quality control procedures support reliable laboratory results, making it a trusted reference for water testing laboratories and regulatory agencies globally.

Keywords: boron in water, ASTM D3082-15, curcumin colorimetric method, water analysis, dissolved boron, environmental monitoring, water quality testing, laboratory standard, wastewater, potable water, industrial water, boric acid.

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: D3082 − 15
Standard Test Method for
Boron in Water
This standard is issued under the fixed designation D3082; 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* D3370 Practices for Sampling Water from Closed Conduits
D4841 Practice for Estimation of Holding Time for Water
1.1 This test method covers the determination of boron in
Samples Containing Organic and Inorganic Constituents
waterandwastewatersbythecurcumincolorimetric-extraction
2 D5810 Guide for Spiking into Aqueous Samples
method in concentrations between 0.1 and 1.0 mg/L. The
D5847 Practice for Writing Quality Control Specifications
range can be extended by dilution of the sample.
for Standard Test Methods for Water Analysis
1.2 Only dissolved boron is determined. This test method
E60 Practice for Analysis of Metals, Ores, and Related
requires that the water sample be filtered through a 0.45-µm
Materials by Spectrophotometry
membrane filter before analysis.
E2251 Specification for Liquid-in-Glass ASTM Thermom-
eters with Low-Hazard Precision Liquids
1.3 This test method is a colorimetric method that is very
sensitive to low concentrations of boron in water and requires E275 Practice for Describing and Measuring Performance of
Ultraviolet and Visible Spectrophotometers
a relatively small sample volume for analysis.
1.4 Precision and bias were obtained on natural and waste-
3. Terminology
waters. It is the user’s responsibility to ensure the validity of
3.1 Definitions:
this test method for waters of untested matrices.
3.1.1 For definitions of terms used in this test method, refer
1.5 The values stated in SI units are to be regarded as
to Terminology D1129.
standard. No other units of measurement are included in this
4. Summary of Test Method
standard.
1.6 This standard does not purport to address all of the 4.1 When a water sample containing soluble boron is
safety concerns, if any, associated with its use. It is the acidified with hydrochloric acid and evaporated to dryness in
responsibility of the user of this standard to establish appro- the presence of curcumin, a red-colored complex called roso-
priate safety and health practices and determine the applica- cyanine is formed. This colored product is taken up in
bility of regulatory limitations prior to use. isopropyl alcohol and is read spectrophotometrically.
5. Significance and Use
2. Referenced Documents
5.1 Because boron can be both essential and deleterious to
2.1 ASTM Standards:
plantgrowth,andbecauseingestionoflargeamountscanaffect
D1066 Practice for Sampling Steam
the central nervous system in humans, a method is required to
D1129 Terminology Relating to Water
determine its concentration in potable, natural, and wastewa-
D1193 Specification for Reagent Water
ters. This test method provides a means of determining the
D2777 Practice for Determination of Precision and Bias of
boron concentration of these waters. The holding time for the
Applicable Test Methods of Committee D19 on Water
samples may be calculated in accordance with Practice D4841.
5.2 Boric acid is used for chemical shim control of neutron
This test method is under the jurisdiction of ASTM Committee D19 on Water
flux in a nuclear reactor. This test method serves to determine
and is the direct responsibility of Subcommittee D19.05 on Inorganic Constituents
if the boron concentration is within acceptable limits.
in Water.
Current edition approved Feb. 1, 2015. Published March 2015. Originally
6. Interferences
approved in 1972. Last previous edition approved in 2009 as D3082 – 09. DOI:
10.1520/D3082-15.
6.1 Nitrate concentrations above 20 mg/Lbegin to interfere.
This test method is similar to, but not identical with that appearing in Standard
Hardness levels about 100 mg/L as CaCO give high results
Methods for Examination of Water and Wastewater, 13th Ed., American Public
Health Association, Washington, DC, pp 69–72.
because of the turbidity caused by the insolubility of the
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
hardness salts in isopropyl alcohol. The turbidity can be
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
eliminated by filtering the final solution through a 0.45-µm
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. membrane filter before reading on the spectrophotometer.
*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
D3082 − 15
sufficiently free of interferences. The water should be analyzed using the
6.2 Organic color may be present in the sample that could
test method.
affect absorbance readings on the spectrophotometer. If an
interfering organic color is present in the sample, the following 8.3 Boron Solution, Stock (1.00 mL = 1.00 mg B)—Dry
procedure has been found useful in reducing this interference about 10 g of boric acid (H BO ) crystals in a desiccator
3 3
for some matrices. Pipet an appropriate sample aliquot into a containing a silica gel desiccant for 24 h (Note 2). Dissolve
platinum dish (Note 1). Make alkaline to litmus with NaOH 5.719 g of the dry H BO in water and dilute to 1 L. Store the
3 3
solution (20 g/L) and add 3 drops in excess. Evaporate to solution in a plastic bottle or boron-free container.
dryness on a steam or hot-water bath. If desired, organic Alternatively, certified boron stock solutions of appropriate
material may be destroyed by ignition from 500 to 550°C known purity are commercially available through chemical
before proceeding.Allow the platinum dish to cool and acidify supply vendors and may be used.
with 5 mL of HCl (1 + 19). Triturate with a rubber policeman
NOTE 3—If boric acid is heated, it gradually loses water, changing first
to dissolve the residue, pour the contents into a calibrated
to metaboric acid (HBO ) and finally dehydrating completely to the
centrifuge tube, wash the platinum dish with 3 or 4 mL of
anhydrous oxide (B O ). It is important therefore that oven drying not be
2 3
used as a method of drying boric acid.
water, and add to the centrifuge tube. Dilute to the 10-mL
mark. Centrifuge to obtain a clear solution. Perform the same
8.4 Boron Solution, Standard (1.00 mL = 0.010 mg B)—
steps on a reagent blank.
Quantitatively dilute 10.0 mL of the stock boron solution to 1
L with water. Store in a plastic bottle or boron-free container.
NOTE 1—Other types of evaporating dishes may be used but must be
checked. Porcelain or ceramic-type dishes may contain boron-fluxing
8.5 Curcumin Solution—Dissolve 40 mg of finely ground
agents.
curcumin and5gof oxalic acid (H C O ·2H O) in 80 mLof
2 2 4 2
isopropylalcohol.Add4.0mLofhydrochloricacid(HCl,spgr
7. Apparatus
1.19) and make up to 100 mL with isopropyl alcohol.
7.1 All laboratory ware used in the performance of this test
NOTE 4—There are other colorimetric methods available for boron
method must either be plastic or boron-free.
testing which use other indicators (the Carmine Method).
7.2 Hot-Water Bath, with temperature control at 55 6 2°C.
8.6 Hydrochloric Acid (1 + 19)—Add 1 volume of hydro-
7.3 Spectrophotometer, suitable for use in the range of 540
chloric acid (sp gr 1.19) to 19 volumes of water.
nm. The photometric practices prescribed in this test method
8.7 Isopropyl Alcohol.
shall conform to Practice E60. Spectrophotometers shall con-
form to Practice E275. Measure absorbance using a 50-mm 8.8 Sodium Hydroxide Solution (20 g/L)—Dissolve2gof
NaOH in water and dilute to 100 mL.
cell.
7.4 Evaporating Dishes, 100 to 150 mL capacity. 8.9 Filter Paper—Purchase suitable filter paper. Typically
the filter papers have a pore size of 0.45-µm membrane.
7.5 Thermometer—AnASTM Gravity Thermometer having
Material such as fine-textured, acid-washed, ashless paper, or
a range from –20 to +102°C, as specified, and conforming to
glass fiber paper are acceptable. The user must first ascertain
the requirements for Thermometer 12C as prescribed in Speci-
that the filter paper is of sufficient purity to use without
fication E2251.
adversely affecting the bias and precision of the test method.
8. Reagents and Materials
9. Sampling
8.1 Reagent grade chemicals shall be used in all tests.
9.1 Collect the samples in accordance with Practice D1066
Unless otherwise indicated, all reagents shall conform to the
or Practices D3370.
specifications of the Committee on Analytical Reagents of the
American Chemical Society, where such specifications are
9.2 Filter the sample through a 0.45-µm membrane filter as
available. Other grades may be used, provided it is first
soon as possible after sampling.
ascertained that the reagent is of sufficiently high purity to
9.3 Samples should be collected and stored in polyethylene
permit its use without lessening the accuracy of the determi-
bottles or alkali-resistant, boron-free glass. No other preserva-
nation.
tion is required.
8.2 Purity of Water—Unless otherwise indicated, references
towatershallbeunderstoodtomeanreagentwaterconforming
10. Calibration and Standardization
to Specification D1193, Type I, II, or III water. Type I is
10.1 Prepare a series of standard boron solutions to cover
preferred and more commonly used. Type II water was
the range from 0 to 1.0 mg/L. Make up standards by diluting
specified at the time of round robin testing of this test method.
suitable volumes of the boron standard solution (1.00
NOTE 2—The user must ensure the type of reagent water chosen is
mL = 0.010 mg B) to 100 mL.
Reagent Chemicals, American Chemical Society Specifications, American
Chemical Society, Washington, DC. For Suggestions on the testing of reagents not The sole source of supply of curcumin known to the committee at this time is
listed by the American Chemical Society, see Annual Standards for Laboratory Eastman No. 1179. If you are aware of alternative suppliers, please provide this
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia information to ASTM International Headquarters. Your comments will receive
and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville, careful consideration at a meeting of the responsible technical committee, which
MD. you may attend.
D3082 − 15
TABLE 1 Interlaboratory Precision for Boron in Reagent Water by TABLE 2 Interlaboratory Precision for Boron in Natural Water and
Curcumin Colorimetric Method Waste Water (Combined Data) by Curcumin Colorimetric Method
Statistically Statistically
Amount Added, Amount Amount Added, Amount
S, mg/L S , mg/L Significant 95 S, mg/L S , mg/L Significant 95
t o t o
mg/L Found, mg/L mg/L Found, mg/L
% Level % Level
1.000 0.993 0.049 0.042 yes 1.000 0.993 0.045 0.067 no
0.600 0.581 0.040 0.025 yes 0.600 0.581 0.041 0.040 no
0.200 0.201 0.025 0.011 no 0.200 0.201 0.032 0.020 no
10.2 Develop the color complex as directed in 11.1 – 11.4.
Measure the absorbance of each standard at 540 nm in a
13.1.1 The overall precision for reagent water varies lin-
50-mm cell using a reagent blank as the reference solution to
early with the concentration of boron being measured, and it
set zero absorbanc
...

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: D3082 − 09 D3082 − 15
Standard Test Method for
Boron in Water
This standard is issued under the fixed designation D3082; 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 boron in water and wastewaters by the curcumin colorimetric-extraction
method in concentrations between 0.1 and 1.0 mg/L. The range can be extended by dilution of the sample.
1.2 Only dissolved boron is determined. This test method requires that the water sample be filtered through a 0.45-μm
membrane filter before analysis.
1.3 This test method is a colorimetric method that is very sensitive to low concentrations of boron in water and requires a
relatively small sample volume for analysis.
1.4 Precision and bias were obtained on natural and wastewaters. It is the user’s responsibility to ensure the validity of this test
method for waters of untested matrices.
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
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.
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 Closed Conduits
D4841 Practice for Estimation of Holding Time for Water Samples Containing Organic and Inorganic Constituents
D5810 Guide for Spiking into Aqueous Samples
D5847 Practice for Writing Quality Control Specifications for Standard Test Methods for Water Analysis
E60 Practice for Analysis of Metals, Ores, and Related Materials by Spectrophotometry
E2251 Specification for Liquid-in-Glass ASTM Thermometers with Low-Hazard Precision Liquids
E275 Practice for Describing and Measuring Performance of Ultraviolet and Visible Spectrophotometers
3. Terminology
3.1 Definitions:
3.1.1 For definitions of terms used in this test method, refer to Terminology D1129.
4. Summary of Test Method
4.1 When a water sample containing soluble boron is acidified with hydrochloric acid and evaporated to dryness in the presence
of curcumin, a red-colored complex called rosocyanine is formed. This colored product is taken up in isopropyl alcohol and is read
spectrophotometrically.
This test method is under the jurisdiction of ASTM Committee D19 on Water and is the direct responsibility of Subcommittee D19.05 on Inorganic Constituents in Water.
Current edition approved May 15, 2009Feb. 1, 2015. Published May 2009March 2015. Originally approved in 1972. Last previous edition approved in 20032009 as
D3082 – 03.D3082 – 09. DOI: 10.1520/D3082-09.10.1520/D3082-15.
This test method is similar to, but not identical with that appearing in Standard Methods for Examination of Water and Wastewater, 13th Ed., American Public Health
Association, Washington, DC, pp 69–72.
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’s Document Summary page on the ASTM website.
*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
D3082 − 15
5. Significance and Use
5.1 Because boron can be both essential and deleterious to plant growth, and because ingestion of large amounts can affect the
central nervous system in humans, a method is required to determine its concentration in potable, natural, and wastewaters. This
test method provides a means of determining the boron concentration of these waters. The holding time for the samples may be
calculated in accordance with Practice D4841.
5.2 Boric acid is used for chemical shim control of neutron flux in a nuclear reactor. This test method serves to determine if
the boron concentration is within acceptable limits.
6. Interferences
6.1 Nitrate concentrations above 20 mg/L begin to interfere. Hardness levels about 100 mg/L as CaCO give high results
because of the turbidity caused by the insolubility of the hardness salts in isopropyl alcohol. The turbidity can be eliminated by
filtering the final solution through a 0.45-μm membrane filter before reading on the spectrophotometer.
6.2 Organic color may be present in the sample that could affect absorbance readings on the spectrophotometer. If an interfering
organic color is present in the sample, the following procedure has been found useful in reducing this interference for some
matrices. Pipet an appropriate sample aliquot into a platinum dish (Note 1). Make alkaline to litmus with NaOH solution (20 g/L)
and add 3 drops in excess. Evaporate to dryness on a steam or hot-water bath. If desired, organic material may be destroyed by
ignition from 500 to 550°C before proceeding. Allow the platinum dish to cool and acidify with 5 mL of HCl (1 + 19). Triturate
with a rubber policeman to dissolve the residue, pour the contents into a calibrated centrifuge tube, wash the platinum dish with
3 or 4 mL of water, and add to the centrifuge tube. Dilute to the 10-mL mark. Centrifuge to obtain a clear solution. Perform the
same steps on a reagent blank.
NOTE 1—Other types of evaporating dishes may be used but must be checked. Porcelain or ceramic-type dishes may contain boron-fluxing agents.
7. Apparatus
7.1 All laboratory ware used in the performance of this test method must either be plastic or boron-free.
7.2 Hot-Water Bath, with temperature control at 55 6 2°C.
7.3 Spectrophotometer, suitable for use in the range of 540 nm. The photometric practices prescribed in this test method shall
conform to Practice E60. Spectrophotometers shall conform to Practice E275. Measure absorbance using a 50-mm cell.
7.4 Evaporating Dishes, 100 to 150 mL capacity.
7.5 Thermometer—An ASTM Gravity Thermometer having a range from –20 to +102°C, as specified, and conforming to the
requirements for Thermometer 12C as prescribed in Specification E2251.
8. Reagents and Materials
8.1 Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, all reagents shall 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, references to water shall be understood to mean reagent water conforming to
Specification D1193, Type I, II, or III water. Type I is preferred and more commonly used. Type II water was specified at the time
of round robin testing of this test method.
NOTE 2—The user must ensure the type of reagent water chosen is sufficiently free of interferences. The water should be analyzed using the test method.
8.3 Boron Solution, Stock (1.00 mL = 1.00 mg B)—Dry about 10 g of boric acid (H BO ) crystals in a desiccator containing
3 3
a silica gel desiccant for 24 h (Note 2). Dissolve 5.719 g of the dry H BO in water and dilute to 1 L. Store the solution in a plastic
3 3
bottle or boron-free container. Alternatively, certified boron stock solutions of appropriate known purity are commercially available
through chemical supply vendors and may be used.
NOTE 3—If boric acid is heated, it gradually loses water, changing first to metaboric acid (HBO ) and finally dehydrating completely to the anhydrous
oxide (B O ). It is important therefore that oven drying not be used as a method of drying boric acid.
2 3
8.4 Boron Solution, Standard (1.00 mL = 0.010 mg B)—Quantitatively dilute 10.0 mL of the stock boron solution to 1 L with
water. Store in a plastic bottle or boron-free container.
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 Annual 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.
D3082 − 15
8.5 Curcumin Solution—Dissolve 40 mg of finely ground curcumin and 5 g of oxalic acid (H C O ·2H O) in 80 mL of
2 2 4 2
isopropyl alcohol. Add 4.0 mL of hydrochloric acid (HCl, sp gr 1.19) and make up to 100 mL with isopropyl alcohol.
NOTE 4—There are other colorimetric methods available for boron testing which use other indicators (the Carmine Method).
8.6 Hydrochloric Acid (1 + 19)—Add 1 volume of hydrochloric acid (sp gr 1.19) to 19 volumes of water.
8.7 Isopropyl Alcohol.
8.8 Sodium Hydroxide Solution (20 g/L)—Dissolve 2 g of NaOH in water and dilute to 100 mL.
8.9 Filter Paper—Purchase suitable filter paper. Typically the filter papers have a pore size of 0.45-μm membrane. Material such
as fine-textured, acid-washed, ashless paper, or glass fiber paper are acceptable. The user must first ascertain that the filter paper
is of sufficient purity to use without adversely affecting the bias and precision of the test method.
9. Sampling
9.1 Collect the samples in accordance with Practice D1066 or Practices D3370.
9.2 Filter the sample through a 0.45-μm membrane filter as soon as possible after sampling.
9.3 Samples should be collected and stored in polyethylene bottles or alkali-resistant, boron-free glass. No other preservation
is required.
10. Calibration and Standardization
10.1 Prepare a series of standard boron solutions to cover the range from 0 to 1.0 mg/L. Make up standards by diluting suitable
volumes of the boron standard solution (1.00 mL = 0.010 mg B) to 100 mL.
10.2 Develop the color complex as directed in 11.111.1 – 11.4 through 11.4. Measure the absorbance of each standard at 540
nm in a 50-mm cell using a reagent blank as the reference solution to set zero absorbance on the spectrophotometer. Plot Read
directly in concentration if this capability is provided with the instrument or plot absorbance versus concentration on linear graph
paper. paper or using a computer. The calibration curve is linear from 0.1 to 1.0 mg/L.
11. Procedure
11.1 Pipet 1.0 mL of a clear, filtered sample containing 0.1 to 1.0 mg/L of boron into an evaporating dish (Treatment of organic
interferences discussed in 6.2). Run a blank and at least one standard in conjunction with the unknown sample. Add 4 mL of
curcumin solution to each sample and standard, and then, gently swirl to mix contents.
11.2 Place the evaporating dishes in a hot-water bath that is controlled at 55 6 2°C and evaporate to dryness. Allow 15 min
after the contents appear dry before removing. Cool to room temperature.
11.3 Add 10 mL of isopropyl alcohol to each dish and stir with a plastic rod to ensure complete dissolution of the red-colored
complex. Wash the contents of each evaporating dish into a 25-mL volumetric flask using isopropyl alcohol. Dilute to the mark
using isopropyl alcohol and mix thoroughly.
11.4 If the solution appears turbid, filter through a 0.45-μm membrane filter before reading the absorbance. Measure the
absorbance of each sample and standard at 540 nm on the spectrophotometer using the reagent blank to set zero absorbance. Record
the boron concentration as indicated
...