ASTM D6414-23

Standard Test Methods for Total Mercury in Coal and Coal Combustion Residues by Acid Extraction or Wet Oxidation/Cold Vapor Atomic Absorption

SIGNIFICANCE AND USE
5.1 The emission of mercury during coal combustion can be an environmental concern.  
5.2 When representative test specimens are analyzed according to one of these procedures, the total mercury is representative of concentrations in the sample.
SCOPE
1.1 These test methods cover procedures to determine the total mercury content in a sample of coal or coal combustion residue.  
1.2 The values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are provided for information only and are not considered standard.  
1.3 Warning:   Mercury has been designated by many regulatory agencies as a hazardous material that can cause serious medical issues. Mercury, or its vapor, has been demonstrated to be hazardous to health and corrosive to materials. Caution should be taken when handling mercury and mercury containing products. See the applicable product Safety Data Sheet (SDS) for additional information. Users should be aware that selling mercury and/or mercury containing products into your state or country may be prohibited by law.  
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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.5 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: 31-Dec-2022
• ICS: 73.040 - Coals
• Technical Committee: D05 - Coal and Coke
• Drafting Committee: D05.29 - Major Elements in Ash and Trace Elements of Coal

Relations

• Refers: ASTM D7582-24 - Standard Test Methods for Proximate Analysis of Coal and Coke by Macro Thermogravimetric Analysis
• Effective Date: 01-Apr-2024
• Refers: ASTM D121-15(2024) - Standard Terminology of Coal and Coke
• Effective Date: 01-Mar-2024
• Refers: ASTM D3180-15(2023) - Standard Practice for Calculating Coal and Coke Analyses from As-Determined to Different Bases
• Effective Date: 01-Dec-2023
• Refers: ASTM D7582-15(2023) - Standard Test Methods for Proximate Analysis of Coal and Coke by Macro Thermogravimetric Analysis
• Effective Date: 01-Dec-2023
• Refers: ASTM D121-15 - Standard Terminology of Coal and Coke
• Effective Date: 01-Sep-2015
• Refers: ASTM D3180-15 - Standard Practice for Calculating Coal and Coke Analyses from As-Determined to Different Bases
• Effective Date: 01-Jan-2015
• Refers: ASTM E691-13 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-May-2013
• Refers: ASTM D3180-12 - Standard Practice for Calculating Coal and Coke Analyses from As-Determined to Different Bases
• Effective Date: 01-Apr-2012
• Refers: ASTM E691-11 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-Nov-2011
• Refers: ASTM D3173-11 - Standard Test Method for Moisture in the Analysis Sample of Coal and Coke
• Effective Date: 01-Apr-2011
• Refers: ASTM D7582-10e1 - Standard Test Methods for Proximate Analysis of Coal and Coke by Macro Thermogravimetric Analysis
• Effective Date: 01-Jun-2010
• Refers: ASTM D7582-10 - Standard Test Methods for Proximate Analysis of Coal and Coke by Macro Thermogravimetric Analysis
• Effective Date: 01-Jun-2010
• Refers: ASTM D7582-09 - Standard Test Methods for Proximate Analysis of Coal and Coke by Macro Thermogravimetric Analysis
• Effective Date: 01-Nov-2009
• Refers: ASTM D121-09a - Standard Terminology of Coal and Coke
• Effective Date: 01-Oct-2009
• Refers: ASTM D121-09 - Standard Terminology of Coal and Coke
• Effective Date: 01-Feb-2009

Overview

ASTM D6414-23 is the internationally recognized standard for determining the total mercury content in coal and coal combustion residues. Published by ASTM International, this standard specifies two main analytical test methods: acid extraction and wet oxidation followed by cold vapor atomic absorption spectrometry (CVAAS). These methods are essential for accurately measuring mercury levels, which is a critical step for environmental compliance, research, and quality control in the coal and energy industries. Mercury emissions from coal combustion are a significant environmental concern, making precise quantification vital for regulatory reporting, pollution control strategies, and health risk assessment.

Key Topics

• Scope and Applicability

  • Procedures for detecting total mercury in coal and coal combustion residues.
  • Use of SI units as the standard measurement, with parenthetical conversions for reference.

• Analytical Methods

  • Acid extraction and wet oxidation methods to solubilize mercury.
  • Application of cold vapor atomic absorption spectrometry for measurement.

• Quality Assurance

  • Incorporation of certified reference materials (CRM) for calibration and quality control.
  • Calculations for accuracy, repeatability, and mercury recovery.

• Safety and Compliance

  • Emphasis on mercury’s hazardous nature and necessary precautions.
  • Users are advised to consult Safety Data Sheets (SDS) and ensure legal compliance regarding mercury handling.

• Precision and Bias

  • Detailed coverage of repeatability and reproducibility, with data supporting the standard’s reliability.
  • Interlaboratory studies confirming the method’s validity.

Applications

The ASTM D6414-23 standard is widely applied across multiple sectors:

• Environmental Compliance

  • Power plants and industrial facilities use this test method to monitor and report mercury emissions in accordance with environmental regulations.
  • Essential for verifying compliance with national and international emission standards.

• Coal and Energy Industry

  • Used in coal preparation, combustion residue analysis, and quality assurance processes to ensure products meet environmental and safety requirements.
  • Facilitates environmental impact assessments of coal-fired energy production.

• Research and Development

  • Supports academic and industrial research focused on pollution control technologies and environmental impact studies.
  • Enables data-driven decisions for mercury reduction strategies.

• Regulatory Reporting

  • Provides reliable, standardized methods for laboratories preparing documentation for government and environmental agencies.

• Health and Safety Audits

  • Assists organizations in evaluating workplace and environmental mercury exposure risks.

Related Standards

ASTM D6414-23 references and works in conjunction with several other key standards, including:

• ASTM D121 - Terminology of Coal and Coke
• ASTM D1193 - Specification for Reagent Water
• ASTM D2013 - Practice for Preparing Coal Samples for Analysis
• ASTM D3173 - Test Method for Moisture in the Analysis Sample of Coal and Coke
• ASTM D3180 - Practice for Calculating Coal and Coke Analyses From As-Determined to Different Bases
• ASTM D7582 - Test Methods for Proximate Analysis of Coal and Coke by Macro Thermogravimetric Analysis
• ASTM E691 - Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• IEEE/ASTM SI 10 - Standard for Use of the International System of Units (SI)
• ISO 5725-6:1994 - Accuracy of Measurement Methods and Results

Practical Value

Using ASTM D6414-23 ensures that laboratories and industrial operators obtain accurate, repeatable results for total mercury quantification in coal and combustion residues. Compliance with this mercury test standard supports environmental protection efforts, workplace safety, and ongoing improvements in analysis quality. The methods and practices outlined facilitate global harmonization of coal testing and reporting, vital for sustainable and lawful operation in coal-related industries.

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: D6414 − 23
Standard Test Methods for
Total Mercury in Coal and Coal Combustion Residues by
Acid Extraction or Wet Oxidation/Cold Vapor Atomic
Absorption
This standard is issued under the fixed designation D6414; 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 D1193 Specification for Reagent Water
D2013 Practice for Preparing Coal Samples for Analysis
1.1 These test methods cover procedures to determine the
D3173 Test Method for Moisture in the Analysis Sample of
total mercury content in a sample of coal or coal combustion
Coal and Coke
residue.
D3180 Practice for Calculating Coal and Coke Analyses
1.2 The values stated in SI units are to be regarded as
from As-Determined to Different Bases
standard. The values given in parentheses after SI units are
D7582 Test Methods for Proximate Analysis of Coal and
provided for information only and are not considered standard.
Coke by Macro Thermogravimetric Analysis
1.3 Warning: Mercury has been designated by many regu- E691 Practice for Conducting an Interlaboratory Study to
Determine the Precision of a Test Method
latory agencies as a hazardous material that can cause serious
medical issues. Mercury, or its vapor, has been demonstrated to IEEE/ASTM SI 10 Standard for Use of the International
System of Units (SI): The Modern Metric System
be hazardous to health and corrosive to materials. Caution
should be taken when handling mercury and mercury contain- 2.2 ISO Standards:
ISO 5725-6:1994 Accuracy of measurement methods and
ing products. See the applicable product Safety Data Sheet
(SDS) for additional information. Users should be aware that results-Part 6
selling mercury and/or mercury containing products into your
3. Terminology
state or country may be prohibited by law.
3.1 For definitions of terms used in this standard, refer to
1.4 This standard does not purport to address all of the
Terminology D121.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
4. Summary of Test Method
priate safety, health, and environmental practices and deter-
4.1 Test Method A—Mercury in the analysis sample is
mine the applicability of regulatory limitations prior to use.
solubilized by heating the test sample at a specified tempera-
1.5 This international standard was developed in accor-
ture in a mixture of nitric and hydrochloric acids. The acid
dance with internationally recognized principles on standard-
solutions produced are transferred into a vessel in which the
ization established in the Decision on Principles for the
mercuryisreducedtoelementalmercury.Themercuryvaporis
Development of International Standards, Guides and Recom-
determined by flameless cold-vapor atomic absorption spec-
mendations issued by the World Trade Organization Technical
trometry.
Barriers to Trade (TBT) Committee.
4.2 Test Method B—Mercury in the analysis sample is
2. Referenced Documents
solubilized by heating the test sample in a mixture of nitric and
2 4
sulfuric acids with vanadium pentoxide. The acid solutions
2.1 ASTM Standards:
D121 Terminology of Coal and Coke produced are transferred into a vessel in which the mercury is
reduced to elemental mercury. The mercury vapor is deter-
1 mined by flameless cold-vapor atomic absorption spectrom-
ThesetestmethodsareunderthejurisdictionofASTMCommitteeD05onCoal
and Coke and are the direct responsibility of Subcommittee D05.29 on Major etry.
Elements in Ash and Trace Elements of Coal.
NOTE 1—Mercury and mercury salts can be volatilized at low tempera-
Current edition approved Jan. 1, 2023. Published January 2023. Originally
tures. Precautions against inadvertent mercury loss should be taken when
approved in 1999. Last previous edition approved in 2014 as D6414 – 14. DOI:
using this method.
10.1520/D6414-23.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Available from International Organization for Standardization (ISO), 1 rue de
Standards volume information, refer to the standard’s Document Summary page on Varembé, Case postale 56, CH-1211, Geneva 20, Switzerland.
the ASTM website. Crock, J. G., Open-File Report, U.S. Geological Survey, 87–84, p.19.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6414 − 23
5. Significance and Use such specifications are available. Other grades can be used
provided it is first ascertained that the reagent is of sufficiently
5.1 The emission of mercury during coal combustion can be
high purity to permit its use without lessening the accuracy of
an environmental concern.
the determination.
5.2 When representative test specimens are analyzed ac-
8.2 Purity of Acids—Use trace metal purity grade acids or
cording to one of these procedures, the total mercury is
equivalent. Redistilled acids are acceptable.
representative of concentrations in the sample.
8.3 Purity of Water—Use water equivalent toASTMType II
reagent water of Specification D1193.
6. Apparatus
8.4 Mercury Standard Stock Solution [1000 µg ⁄mL (1000
6.1 Apparatus for Test Method A:
ppm)]—Dissolve 1.0800 g of mercury (II) oxide (HgO) in a
6.1.1 Analytical Balance, with a sensitivity of 0.1 mg.
minimum volume of HCl (1+1) and dilute to 1 L with water.
6.1.2 Atomic Absorption Spectrometer, with a flameless
Alternatively, use a commercially available stock solution
cold-vapor mercury analysis system.
specifically prepared for atomic absorption spectrometry.
6.1.3 Digestion Vessels, 100 mL to 250 mL bottles with an
8.5 Mercury Standard Solution (100 ng/mL)—Prepare the
O-ring seal and screw cap. Bottle must be compatible for use
mercury standard solution fresh daily. Dilute 5 mL of the
with aqua regia. Polycarbonate and high density polyethylene
mercury standard stock solution to 500 mL with deionized
(HDPE) are acceptable. Bottles and cap assemblies shall be
water. Further dilute 10 mLof this intermediate solution to 1 L
washed in 1+1 hydrochloric acid (HCl) then dried before each
with deionized water.
use.
8.6 Nitric Acid—Concentrated (HNO , sp. gr. 1.42).
NOTE 2—Other bottle and cap assemblies may be used provided they
8.7 Hydrochloric Acid—Concentrated (HCl, sp. gr. 1.19).
are compatible for use with aqua regia at a temperature of 80 °C.
8.8 Sodium Chloride/Hydroxylamine Sulfate Solution—
6.1.4 Heat Source, a water bath capable of maintaining a
Dissolve 12 g 6 0.01 g of sodium chloride and 12 g 6 0.01 g
temperature of 80 °C.
of hydroxylamine sulfate in water and dilute to 100 mL.
6.1.5 Syringe and Filter,a20cm syringe and a 1 µm pore
8.9 Potassium Permanganate Solution (5 %)—Dissolve 5 g
size polytetrafluoroethylene (PTFE) filter to fit syringe.
of potassium permanganate (KMnO ) in water and dilute to
6.2 Apparatus for Test Method B:
100 mL.
6.2.1 Analytical Balance, with a sensitivity of 0.1 mg.
8.10 Stannous Chloride Solution (100 g/L)—Dissolve 100 g
6.2.2 Atomic Absorption Spectrometer, with a flameless
of stannous chloride dihydrate (SnCl ·2 H O) in 300 mL of
2 2
cold-vapor mercury analysis system.
concentrated hydrochloric acid (HCl, sp. gr. 1.19) and CAU-
6.2.3 Digestion Vessels, 16 mm by 150 mm disposable glass
TIOUSLY dilute to 1 L with water. This solution is stable for
test tubes.
approximately one week if refrigerated.
6.2.4 Heat Source, an aluminum block with 18-mm holes to
8.11 Certified Reference Material (CRM)—Use Certified
accommodate the disposable test tubes. The block shall be
Reference Material (CRM) coals with dry-basis mercury val-
capable of slowly reaching and maintaining a final temperature
ues for which confidence limits are issued by a recognized
of 150 °C. The block can be heated by placing it on a hot plate
certifying agency such as the National Institute of Standards
or it can contain its own internal heating elements.
andTechnology (NIST). It is recommended that the user verify
thevaluewiththecertifyingagencybeforeusingtheCRMcoal
7. Sample
for quality control purposes.
7.1 Prepare the analysis sample in accordance with Practice
9. Procedure
D2013 by pulverizing the material to pass a 250 µm (No. 60
U.S. standard sieve).
9.1 Preparation of Test Solution A (Extraction Step):
9.1.1 Determine the mass of a test specimen of approxi-
7.2 Analyze separate test specimens for moisture in accor-
mately1gofthe sample into a digestion bottle. Record the
dance with Test Method D3173 or Test Method D7582.
mass (m ) to the nearest 0.0001 g.
s
9.1.2 Quantitatively add 2 mL of concentrated nitric acid
Test Method A for the Analysis of Mercury by Using Acid
(8.6) and 6 mL of concentrated hydrochloric acid (8.7)tothe
Extraction
digestion bottle and secure the cap.
8. Reagents
Reagent Chemicals, American Chemical Society Specifications, American
8.1 Purity of Reagents—Reagent grade chemicals shall be
Chemical Society, Washington, DC. For suggestions on the testing of reagents not
used.Unlessotherwiseindicated,itisintendedthatallreagents
listed by the American Chemical Society, see Analar Standards for Laboratory
shall conform to the specifications of the Committee on
Chemicals,BDHLtd.,Poole,Dorset,U.K.,andtheUnitedStatesPharmacopeiaand
Analytical Reagents of the American Chemical Society where National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville, MD.
D6414 − 23
9.1.3 Transfer the digestion bottle and contents to a water 9.4.2.2 Add a specified volume (Vcal) of a calibration
bath that has been heated to 80 °C and heat for 1 h. Secure the solution to the reduction flask or reduction system.
digestionbottleinsuchawayastokeepthecontentsbelowthe
NOTE 5—If an autosampler equipped with a peristaltic pump is used for
surface of the water.
delivery of both calibration and analyses sample solutions to the reduction
9.1.4 After 1 h, remove the digestion bottle and allow to
system, a specific volume is not required.
cool to room temperature.
9.4.2.3 Either manually or by means of an autosampling
NOTE 3—Caution: Carefully relieve the pressure by slowly removing
device begin the analyses of the calibration solution by adding
the cap.
enough stannous chloride solution so as to ensure complete
9.1.5 Add 36.5 mL of water and mix the contents.
reduction of the mercury in the calibration solution.
9.1.6 Add 5 mL of 5 % potassium permanganate solution
9.4.2.4 Record the absorbance of the calibration standard.
(8.9). Allow the mixture to stand for 10 min.
Repeat for each calibration standard.
9.1.7 Add 0.5 mL of the sodium chloride/hydroxylamine
9.4.3 Analysis of Test Solution A:
sulfate solution (8.8) and mix. If a pink color persists for more
9.4.3.1 Using the 20 cm syringe, draw Test SolutionAinto
than 1 min, add an additional 0.5 mL of the sodium chloride/
the syringe.
hydroxylamine sulfate solution (8.8) and mix. Note the total
9.4.3.2 Fit the syringe with a 1 µm filter.
volume and record this volume (V) for use in the final
9.4.3.3 Filter a volume equivalent to Vcal ofTest SolutionA
calculations.
into the reduction flask or reduction system.
9.2 Preparation of Reagent Blank—Prepare a reagent blank
NOTE6—Alaboratorycentrifugemayalsobeusedtoseparatethesolids
by repeating the procedure in 9.1 but without the test specimen
from the test solution.
of the sample.
9.4.3.4 Determine the absorbance (As) of the Test Solution
9.3 Preparation of Control Sample:
A using the procedure described in 9.4.2.
9.3.1 Prepare a test specimen of a CRM coal for analysis
9.4.3.5 Using 10 % HCl, dilute test solutions with mercury
using the procedure described in 9.1. Record the expected
absorbances greater than the highest calibration standard to
value of mercury, the certified value in the coal, as CRME.
give an estimated absorbance equivalent to the 3 ng⁄mL
9.3.2 Alternatively,determinethemassofatestspecimenof
calibration standard and reanalyze.
1 g of a CRM.After the addition of the nitric and hydrochloric
9.4.3.6 Record the dilution factor as DF.
acids to the digestion bottle, add mercury standard solution
9.4.4 Analysis of the Reagent Blank—Determine the absor-
(8.5). The volume of mercury standard solution to be added
bance (Ab) of the reagent blank using the procedure described
should yield an amount of mercury approximately equivalent
in 9.4.3.
to that in the CRM coal (Note 4).
9.4.5 Analysis of the Quality Control Sample—Determine
9.3.3 Calculate the expected value of mercury CRME as
the absorbance (Aqs) of the quality control sample using the
follows
procedure described in 9.4.3.
CRME 5 ~m 3Val 1V 30.1!/m (1)
CRM CRM std CRM
Test Method B for the Analysis of Mercury by Using Wet
where:
Oxidation Extraction
m = dry mass of the CRM coal used for preparation of
CRM
the quality control sample, g,
10. Reagents
Val = certified value of mercury in the quality control
CRM
10.1 Purity of Reagents—Reagent grade chemicals shall be
sample,
used.Unlessotherwiseindicated,itisintendedthatallreagents
V = volume of mercury standard solution added to the
std
shall conform to the specifications of the Committee on
digestion bottle, mL, and
Analytical Reagents of the American Chemical Society where
0.1 = the mass concentration of the mercury standard
such specifications are available. Other grades can be used
solution, µg/mL.
provided it is first ascertained that the reagent is of sufficiently
NOTE 4—A test specimen of 0.9 g dry mass of a CRM coal with 0.11
high purity to permit its use without lessening the accuracy of
g/g (110 ng/g) of mercury is measured out as a quality control sample. To
yieldanamountapproximatelyequivalenttothatpresentintheCRMcoal,
the determination.
0.9 mL of the mercury standard solution is added to the digestion bottle
10.2 Purity of Acids—Use trace metal purity grade acids or
after the addition of the nitric and hydrochloric acids. CRME calculates to
0.21 µg⁄g.
equivalent. Redistilled acids are acceptable.
9.4 Atomic Absorption Analyses:
10.3 Purity of Water—Use water equivalent to ASTM Type
9.4.1 Instrument Conditions—Follow the instrument manu-
II reagent water of Specification D1193.
facturers recommended procedure to align the optical cell in
10.4 Mercury Standard Stock Solution [1000 µg ⁄mL
the beam path of the atomic absorption spectrometer and
(1000 ppm)]—Dissolve 1.0800 g of mercury (II) oxide (HgO)
optimize the performance of the instrument and the flameless
in a minimum volume of HCl (1+1) and dilute to 1 L with
cold-vapor apparatus.
water. Alternatively, use a commercially available stock solu-
9.4.2 Instrument Calibration:
tion specifically prepared for atomic absorption spectrometry.
9.4.2.1 Prepare 50 mL of (0.5, 1, 3, 5, and 10) ng/mL (ppb)
of mercury calibration standards in a solution of 10 % HCl by 10.5 Mercury Standard Solution (100 ng/mL)—Prepare the
serial dilution of the mercury standard solution. mercury standard solution fresh daily. Dilute 5 mL of the
D6414 − 23
mercury standard stock solution to 500 mL with deionized 11.3.1 Prepare a CRM coal for analysis using the procedure
water. Further dilute 10 mLof this intermediate solution to 1 L described in 11.1. Record the certified value as CRM.
with deionized water.
11.3.2 Alternatively, determine the mass of a test specimen
of 0.15 g of a CRM.After the addition of the nitric acid (10.6),
10.6 Nitric Acid—Concentrated (HNO , sp. gr. 1.42).
add mercury standard solution (10.5) to the test tube. The
10.7 Hydrochloric Acid—Concentrated (HCl, sp. gr. 1.19).
volume of the mercury standard solution to be added should
yieldanamountofmercuryapproximatelyequivalenttothatin
10.8 Sulfuric Acid—(H SO , sp. gr. 1.83).
2 4
theCRMcoal(Note8).CalculatetheexpectedvalueCRMEof
10.9 Vanadium Pentoxide, V O —Remove traces of mer-
2 5
mercury using Eq 1.
cury by roasting the V O in a fume hood at a temperature
2 5
below 690 °C, the melting point of V O , in a porcelain dish NOTE 8—Atest specimen of 0.15 g of a CRM coal with 0.11 µg/g (110
2 5
ng/g) of mercury is measured out as a quality control sample. To yield an
using a muffle furnace or a Fisher burner.
amount approximately equivalent to that present in the CRM coal, 0.15
NOTE 7—Warning: V O is highly toxic, an irritant, and a possible mL of the mercury standard solution is added to the test tube after the
2 5
mutagen. addition of the nitric acid. CRME calculates to 0.21 µg/g.
10.10 Stannous Chloride S
...

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: D6414 − 14 D6414 − 23
Standard Test Methods for
Total Mercury in Coal and Coal Combustion Residues by
Acid Extraction or Wet Oxidation/Cold Vapor Atomic
Absorption
This standard is issued under the fixed designation D6414; 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 These test methods cover procedures to determine the total mercury content in a sample of coal or coal combustion residue.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this The values
given in parentheses after SI units are provided for information only and are not considered standard.
1.3 Warning: Mercury has been designated by many regulatory agencies as a hazardous material that can cause serious medical
issues. Mercury, or its vapor, has been demonstrated to be hazardous to health and corrosive to materials. Caution should be taken
when handling mercury and mercury containing products. See the applicable product Safety Data Sheet (SDS) for additional
information. Users should be aware that selling mercury and/or mercury containing products into your state or country may be
prohibited by law.
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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.5 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:
D121 Terminology of Coal and Coke
D1193 Specification for Reagent Water
D2013 Practice for Preparing Coal Samples for Analysis
D3173 Test Method for Moisture in the Analysis Sample of Coal and Coke
D3180 Practice for Calculating Coal and Coke Analyses from As-Determined to Different Bases
D7582 Test Methods for Proximate Analysis of Coal and Coke by Macro Thermogravimetric Analysis
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
IEEE/ASTM SI 10 Standard for Use of the International System of Units (SI): The Modern Metric System
These test methods are under the jurisdiction of ASTM Committee D05 on Coal and Coke and are the direct responsibility of Subcommittee D05.29 on Major Elements
in Ash and Trace Elements of Coal.
Current edition approved March 1, 2014Jan. 1, 2023. Published March 2014January 2023. Originally approved in 1999. Last previous edition approved in 20062014 as
D6414 - 01(2006).– 14. DOI: 10.1520/D6414-14.10.1520/D6414-23.
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.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6414 − 23
2.2 ISO StandardStandards:
ISO 5725-6:1994 Accuracy of measurement methods and results-Part 6
3. Terminology
3.1 For definitions of terms used in this standard, refer to Terminology D121.
4. Summary of Test Method
4.1 Test Method A—Mercury in the analysis sample is solubilized by heating the test sample at a specified temperature in a mixture
of nitric and hydrochloric acids. The acid solutions produced are transferred into a vessel in which the mercury is reduced to
elemental mercury. The mercury vapor is determined by flameless cold-vapor atomic absorption spectroscopy.spectrometry.
4.2 Test Method B—Mercury in the analysis sample is solubilized by heating the test sample in a mixture of nitric and sulfuric
acids with vanadium pentoxide. The acid solutions produced are transferred into a vessel in which the mercury is reduced to
elemental mercury. The mercury vapor is determined by flameless cold-vapor atomic absorption spectroscopy.spectrometry.
NOTE 1—Mercury and mercury salts can be volatilized at low temperatures. Precautions against inadvertent mercury loss should be taken when using this
method.
5. Significance and Use
5.1 The emission of mercury during coal combustion can be an environmental concern.
5.2 When representative test portionsspecimens are analyzed according to one of these procedures, the total mercury is
representative of concentrations in the sample.
6. Apparatus
6.1 Apparatus for Test Method A:
6.1.1 Analytical Balance, with a sensitivity of 0.1 mg.
6.1.2 Atomic Absorption Spectrophotometer,Spectrometer, with a flameless cold-vapor mercury analysis system.
6.1.3 Digestion Vessels, 100-100 mL to 250-mL250 mL bottles with an O-ring seal and screw cap. Bottle must be compatible for
use with aqua regia. Polycarbonate and HDPE high density polyethylene (HDPE) are acceptable. Bottles and cap assemblies shall
be washed in 1-to-1 HCl 1+1 hydrochloric acid (HCl) then dried before each use.
NOTE 2—Other bottle and cap assemblies may be used provided they are compatible for use with aqua regia at a temperature of 80°C.80 °C.
6.1.4 Heat Source, a water bath capable of maintaining a temperature of 80°C.80 °C.
6.1.5 Syringe and Filter, a 20-cm20 cm syringe and a 1-μm PTFE 1 μm pore size polytetrafluoroethylene (PTFE) filter to fit
syringe.
6.2 Apparatus for Test Method B:
6.2.1 Analytical Balance, with a sensitivity of 0.1 mg.
6.2.2 Atomic Absorption Spectrophotometer,Spectrometer, with a flameless cold-vapor mercury analysis system.
6.2.3 Digestion Vessels, 16-16 mm by 150-mm150 mm disposable glass test tubes.
Available from International Organization for Standardization (ISO), 1 rue de Varembé, Case postale 56, CH-1211, Geneva 20, Switzerland.
Crock, J. G., Open-File Report, U.S. Geological Survey, 87–84, p.19.
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6.2.4 Heat Source, an aluminum block with 18-mm holes to accommodate the disposable test tubes. The block shall be capable
of slowly reaching and maintaining a final temperature of 150°C.150 °C. The block can be heated by placing it on a hot plate or
it can contain its own internal heating elements.
7. Sample
7.1 Prepare the analysis sample in accordance with Practice D2013 by pulverizing the material to pass a 250-μm (No. 60)
sieve.250 μm (No. 60 U.S. standard sieve).
7.2 Analyze separate test portionsspecimens for moisture content in accordance with Test Method D3173 or Test Method D7582.
Test Method A for the Analysis of Mercury by Using Acid Extraction
8. Reagents
8.1 Purity of Reagents—Reagent grade chemicals shall be used. Unless otherwise indicated, it is intended that 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 can 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 Acids—Use trace metal purity grade acids or equivalent. Redistilled acids are acceptable.
8.3 Purity of Water—Use water equivalent to ASTM Type II reagent water of Specification D1193.
8.4 Mercury Standard Stock Solution [1000[1000 μg ppm ⁄mL (1000 μg/mL)]—ppm)]—Dissolve 1.0800 g of mercury (II) oxide
(HgO) in a minimum volume of HCl (1+1) and dilute to 1 L with water. Alternatively, use a commercially available stock solution
specifically prepared for atomic absorption spectrometry.
8.5 Mercury Standard Solution (100 ng/mL)—Prepare the mercury standard solution fresh daily. Dilute 5 mL of the mercury
standard stock solution to 500 mL with deionized water. Further dilute 10 mL of this intermediate solution to 1 L with deionized
water.
8.6 Nitric Acid—Concentrated (HNO , sp. gr. 1.42).
8.7 Hydrochloric Acid—Concentrated (HCl, sp. gr. 1.19).
8.8 Sodium Chloride/Hydroxylamine Sulfate Solution—Dissolve 12 g 6 0.01 g of sodium chloride and 12 g 6 0.01 g of
hydroxylamine sulfate in water and dilute to 100 mL.
8.9 Potassium Permanganate Solution (5 g/100 mL)—%)—Dissolve 5 g of potassium permanganate (KMnO ) in water and dilute
to 100 mL.
8.10 Stannous Chloride Solution (100 g/L)—Dissolve 100 g of stannous chloride dihydrate (SnCl ·2 H O) in 300 mL of
2 2
concentrated hydrochloric acid (HCl, sp. gr. 1.19) and CAUTIOUSLY dilute to 1 L with water. This solution is stable for
approximately one week if refrigerated.
8.11 Certified Reference Material (CRM)—Use Certified Reference Material (CRM) coals with dry-basis mercury values for
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.
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which confidence limits are issued by a recognized certifying agency such as the National Institute of Standards and Technology
(NIST). It is recommended that the user verify the value with the certifying agency before using the CRM coal for quality control
purposes.
9. Procedure
9.1 Preparation of Test Solution A (Extraction Step):
9.1.1 Weigh Determine the mass of a test portionspecimen of approximately 1 g of the sample into a digestion bottle. Record the
weightmass (Wsm ) to the nearest 0.0001 g.
s
9.1.2 Quantitatively add 2 mL of concentrated nitric acid (8.6) and 6 mL of concentrated hydrochloric acid (8.7) to the digestion
bottle and secure the cap.
9.1.3 Transfer the digestion bottle and contents to a water bath that has been heated to 80°C80 °C and heat for 1 h. Secure the
digestion bottle in such a way as to keep the contents below the surface of the water.
9.1.4 After 1 h, remove the digestion bottle and allow to cool to room temperature.
NOTE 3—Caution: Carefully relieve the pressure by slowly removing the cap.
9.1.5 Add 36.5 mL of water and mix the contents.
9.1.6 Add 5 mL of 5 % potassium permanganate solution. solution (8.9). Allow the mixture to stand for 10 min.
9.1.7 Add 0.5 mL of the hydroxylamine sodium chloride chloride/hydroxylamine sulfate solution (8.8) and mix. If a pink color
persists for more than 1 min, add an additional 0.5 mL of the hydroxylamine sodium chloride chloride/hydroxylamine sulfate
solution (8.8) and mix. Note the total volume and record this volume (V) for use in the final calculations.
9.2 Preparation of Reagent Blank—Prepare a reagent blank by repeating the procedure in 9.1 but without the test portionspecimen
of the sample.
9.3 Preparation of Control Sample:
9.3.1 Prepare a test portionspecimen of a CRM coal for analysis using the procedure described in 9.1. Record the expected value
of mercury, the certified value in the coal, as CRME.
9.3.2 Alternatively, weigh determine the mass of a test portionspecimen of 1 g of a CRM. After the addition of the nitric and
hydrochloric acids to the digestion bottle, add mercury standard solution (8.5). The volume of mercury standard solution to be
added should yield an amount of mercury approximately equivalent to that in the CRM coal (Note 4).
9.3.3 Calculate the expected value of mercury CRME as follows
CRME 5 Wcrm*CRM1Vstandard*0.1 /Wcrm (1)
~ !
CRME 5 ~m 3Val 1V 30.1!/m (1)
CRM CRM std CRM
where:
Wcrm = dry weight of the CRM coal used for preparation of the quality control sample, g;
CRM = certified value of mercury in the quality control sample;
Vstan- = volume of mercury standard solution added to the digestion bottle, mL; and
dard
0.1 = the concentration of the mercury standard solution, μg/mL.
m = dry mass of the CRM coal used for preparation of the quality control sample, g,
CRM
Val = certified value of mercury in the quality control sample,
CRM
V = volume of mercury standard solution added to the digestion bottle, mL, and
std
0.1 = the mass concentration of the mercury standard solution, μg/mL.
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NOTE 4—A test portionspecimen of 0.9-g0.9 g dry weightmass of a CRM coal with 0.11 g/g (110 ng/g) of mercury is weighedmeasured out as a quality
control sample. To yield an amount approximately equivalent to that present in the CRM coal, 0.9 mL 0.9 mL of the mercury standard solution is added
to the digestion bottle after the addition of the nitric and hydrochloric acids. CRME calculates to 0.21 0.21 μg μg/g.⁄g.
9.4 Atomic Absorption Analyses:
9.4.1 Instrument Conditions—Follow the instrument manufacturers recommended procedure to align the optical cell in the beam
path of the atomic absorption spectrophotometerspectrometer and optimize the performance of the instrument and the flameless
cold-vapor apparatus.
9.4.2 Instrument Calibration:
9.4.2.1 Prepare 50 mL of 0.5,(0.5, 1, 3, 5, and 1010) ng/mL (ppb) of mercury calibration standards in a solution of 10 % HCl by
serial dilution of the mercury standard solution.
9.4.2.2 Add a specified volume (Vcal) of a calibration solution to the reduction flask or reduction system.
NOTE 5—If an autosampler equipped with a peristaltic pump is used for delivery of both calibration and analyses sample solutions to the reduction system,
a specific volume is not required.
9.4.2.3 Either manually or by means of an autosampling device begin the analyses of the calibration solution by adding enough
stannous chloride solution so as to ensure complete reduction of the mercury in the calibration solution.
9.4.2.4 Record the absorbance of the calibration standard. Repeat for each calibration standard.
9.4.3 Analysis of Test Solution A:
9.4.3.1 Using the 20-cm20 cm syringe, draw Test Solution A into the syringe.
9.4.3.2 Fit the syringe with a 1-μm1 μm filter.
9.4.3.3 Filter a volume equivalent to Vcal of Test Solution A into the reduction flask or reduction system.
NOTE 6—A laboratory centrifuge may also be used to separate the solids from the test solution.
9.4.3.4 Determine the absorbance (As) of the Test Solution A using the procedure described in 9.4.2.
9.4.3.5 Using 10 % HCl, dilute test solutions with mercury absorbances greater than the highest calibration standard to give an
estimated absorbance equivalent to the 3-ng/mL3 ng ⁄mL calibration standard and reanalyze.
9.4.3.6 Record the dilution factor as DF.
9.4.4 Analysis of the Reagent Blank—Determine the absorbance (Ab) of the reagent blank using the procedure described in 9.4.3.
9.4.5 Analysis of the Quality Control Sample—Determine the absorbance (Aqs) of the quality control sample using the procedure
described in 9.4.3.
Test Method B for the Analysis of Mercury by Using Wet Oxidation Extraction
10. Reagents
10.1 Purity of Reagents—Reagent grade chemicals shall be used. Unless otherwise indicated, it is intended that 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 can 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.
10.2 Purity of Acids—Use trace metal purity grade acids or equivalent. Redistilled acids are acceptable.
D6414 − 23
10.3 Purity of Water—Use water equivalent to ASTM Type II reagent water of Specification D1193.
10.4 Mercury Standard Stock Solution [1000[1000 μg ppm (1000 μg/mL)]—⁄mL (1000 ppm)]—Dissolve 1.0800 g of mercury (II)
oxide (HgO) in a minimum volume of HCl (1+1) and dilute to 1 L with water. Alternatively, use a commercially available stock
solution specifically prepared for atomic absorption spectrometry.
10.5 Mercury Standard Solution (100 ng/mL)—Prepare the mercury standard solution fresh daily. Dilute 5 mL of the mercury
standard stock solution to 500 mL with deionized water. Further dilute 10 mL of this intermediate solution to 1 L with deionized
water.
10.6 Nitric Acid—Concentrated (HNO , sp. gr. 1.42).
10.7 Hydrochloric Acid—Concentrated (HCl, sp. gr. 1.19).
10.8 Sulfuric Acid—H(H SO , sp. gr. 1.83).
2 4
10.9 Vanadium Pentoxide, V O —Remove traces of mercury by roasting the V O in a fume hood at a temperature below
2 5 2 5
690°C,690 °C, the melting point of V O , in a porcelain dish using a muffle furnace or a Fisher burner.
2 5
NOTE 7—Warning: V O is highly toxic, an irritant, and a possible mutagen.
2 5
10.10 Stannous Chloride Solution (100 g/L)—Dissolve 100 g of stannous chloride dihydrate (SnCl ·2H O) in 300 mL of
2 2
concentrated hydrochloric acid (HCl, sp. gr. 1.19) and CAUTIOUSLY dilute to 1 L with water. This solution is stable for
approximately one week if refrigerated.
10.11 Sodium Dichromate, 25 % (w/v) Solution—Solution, (25 % mass concentration)—Dissolve 25 g of Na Cr O ·2H O in water
2 2 7 2
and dilute to 100 mL.
10.12 Complex Reducing Solution—Dissolve 30 g of hydroxylamine hydrochloride and 30 g of sodium chloride (NaCl) in
approximately 500 mL of water. Slowly add 100 mL of concentrated sulfuric acid. Allow the solution to cool, then dilute to 1 L
with water.
10.13 Certified Reference Material (CRM)—Use Certified Reference Material (CRM) coals with dry-basis mercury values for
which confidence limits issued by a recognized certifying agency such as NIST. the National Institute of Standards and Technology
(NIST). It is recommended that the user verify the value with the certifying agency before using the CRM coal for quality control
purposes
11. Procedure
11.1 Preparation of Test Solution B:
11.1.1 Weigh Determine the mass of a test portionspecimen of 0.15 g of the test sample into a 16-16 mm by 150-mm150 mm
disposable test tube. Record the weightmass (Wsm ) to the nearest 0.0001 g.
s
11.1.2 Add approximately 0.1 g of V O , (10.9), 3.5 mL of concentrated HNO , (10.6), and 1.5 mL of concentrated H SO . (10.8).
2 5 3 2 4
Swirl to mix the contents. Place the test tube in the aluminum heating block and cover with a watch gla
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