ASTM E2941-21

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Designation: E2941 − 14 E2941 − 21
Standard Practices for
Extraction of Elements from Ores and Related Metallurgical
Materials by Acid Digestion
This standard is issued under the fixed designation E2941; 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 practices cover the digestion of ores and related metallurgical materials, such as mine soil, waste rock and tailings, for
subsequent determination of acid-extractable contents of certain elements by such solution analytical techniques as atomic
absorption spectrometry (AAS), inductively coupled plasma atomic emission spectrometry (ICP-AES),(ICP-AES) (see Test
Method D1976), and inductively coupled plasma mass spectrometry (ICP-MS) (see Test Method D5673).
1.1.1 Contents of aluminum, antimony, arsenic, barium, beryllium, bismuth, boron, cadmium, calcium, chromium, cobalt, copper,
gallium, iron, lead, lithium, magnesium, manganese, mercury, molybdenum, nickel, phosphorus, potassium, scandium, selenium,
silver, sodium, strontium, thallium, tin, titanium, vanadium and zinc can be extracted from ores and related metallurgical materials
for determination by analytical methods for elements in solution. Other elements may be determined from extracts produced using
this practice.
1.1.2 Actual element quantification in digested solutions can be accomplished by following the various test methods under other
appropriate ASTM standards for element(s) of interest in solution.
1.1.3 The detection limit and linear content range for each element is dependent on the atomic absorption, mass spectrometry or
emission spectrometric technique employed and may be found in the manual accompanying the instrument used or ASTM standard
method for analysis of the solutions. Take into account Consider the dilution factor in content calculations due to digestion and
dilution of solid samples.
1.1.4 The extent of extraction of elements from ores and related metallurgical materials by these practices is dependent upon the
physical and mineralogical characteristics of the prepared sample and the digestion practice used.
1.2 The digestion practices appear in the following order:
Sections
Nitric Acid Microwave Digestion 7 to 14
Four-Acid Total Digestion 15 to 21.12
Four-Acid Total Digestion 15 to 21
1.3 The values stated SI units are to be regarded as the standard. No other units of measurements are included in this standard.
This test method is These practices are under the jurisdiction of ASTM Committee E01 on Analytical Chemistry for Metals, Ores, and Related Materials and isare the
direct responsibility of Subcommittee E01.02 on Ores, Concentrates, and Related Metallurgical Materials.
Current edition approved Nov. 1, 2014Oct. 1, 2021. Published January 2015October 2021. Originally approved in 2013. Last previous edition approved in 20132014 as
E2941E2941 – 14.-13. DOI: 10.1520/E2941-14.10.1520/E2941-21.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2941 − 21
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. For specific hazard statements, see SectionSections 11 and 20.
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:
D1193 Specification for Reagent Water
D1976 Test Method for Elements in Water by Inductively-Coupled Plasma Atomic Emission Spectroscopy
D5258 Practice for Acid-Extraction of Elements from Sediments Using Closed Vessel Microwave Heating
D5673 Test Method for Elements in Water by Inductively Coupled Plasma—Mass Spectrometry
E50 Practices for Apparatus, Reagents, and Safety Considerations for Chemical Analysis of Metals, Ores, and Related Materials
E135 Terminology Relating to Analytical Chemistry for Metals, Ores, and Related Materials
E882 Guide for Accountability and Quality Control in the Chemical Analysis Laboratory
2.2 Federal Standard:
CFR Title 21, Part 1030, and Title 47, Part 18
3. Terminology
3.1 Definitions—For definitions of terms used in these practices, refer to Terminology E135.
4. Significance and Use
4.1 These practices are primarily intended to test materials for compliance with compositional specifications and for monitoring.
Partial extraction of ores and related metallurgical materials can provide information on the availability of elements to leaching,
water quality changes, or other site conditions.
4.2 It is assumed that the users of these practices will be trained analysts capable of performing common laboratory procedures
skillfully and safely. It is expected that work will be performed in a properly equipped laboratory and that proper waste disposal
procedures will be followed. Appropriate quality control practices such as those described in Guide E882 shall be followed.
5. Reagents
5.1 Purity of Reagents—Reagent grade chemicals shall be used in all tests. 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 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.
5.2 Purity of Water—Unless otherwise indicated, references to water shall be understood to mean reagent water conforming to
Type I or Type II of Specification D1193. Type III or Type IV may be used if they effect no measurable change in the blank or
sample.
6. Sampling and Sample Preparation
6.1 Materials Safety—Samples shall be prepared, stored, and disposed of in accordance with the materials and safety guidelines
in Practices E50.
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.
Available from U.S. Government Printing Office Superintendent of Documents, 732 N. Capitol St., NW, Mail Stop: SDE, Washington, DC 20401, http://
www.access.gpo.gov.
Reagent Chemicals, American Chemical Society Specifications, American Chemical Society, Washington, DC. DC, www.chemistry.org. For suggestions on the testing
of reagents not listed by the American Chemical Society, see the United States Pharmacopeia and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC),
Rockville, MD.MD, www.usp.org.
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6.2 Prepared Sample—Dry a representative portion of the gross sample at 80 °C to constant mass in order to minimize sulfide
mineral oxidation. Pulverize or grind the laboratory sample until at least 95 % passes a 150-μm sieve. Fine grinding to 95 %
passing a 53-μm sieve is recommended for procedures using a single acid digestion.
NITRIC ACID MICROWAVE DIGESTION
7. Summary of Practice
7.1 The chemical portion of this practice involves nitricHNO acid digestion to dissociate the elements not interstitially bound in
silicate lattices.
7.2 The sample is digested with HNO in a closed fluoropolymer vessel using microwave heating to an internal pressure of 6.89
× 10 Pa.
7.3 This practice provides a sample suitable for analysis by atomic absorption, atomic emission, or inductively coupled plasma
mass spectrometry.AAS, ICP-AES, or ICP-MS.
8. Significance and Use
8.1 Rapid heating, in combination with temperatures in excess of the atmospheric boiling point of HNO , reduces sample
preparation or reaction times.
8.2 Little or no acids are lost to boiling or evaporation in the closed digestion vessel so additional portions of acid may not be
required. Increased blank corrections from trace impurities in acid are minimized.
8.3 HNO digestion of ores and related metallurgical materials are most useful for rapid, low-cost digestions, where metals locked
in the silica or other insoluble matrix components are not important for the results of the analysis.
9. Interferences
9.1 No interferences to the digestion of ores and related metallurgical materials using microwave heating have been observed.
9.2 Precautions should be exercised to avoid those interferences normally associated with the final determination of elements using
atomic absorption, atomic emission, or inductively coupled plasma mass spectrometry.
9.3 The HNO matrix may not be suitable for stabilizing solutions containing silver and antimony; an alternate digestion method
using a HCl or HF matrix may be required to determine some elements (i.e. (for example, silicon).
10. Apparatus
10.1 Microwave Heating System—A laboratory microwave heating system capable of delivering a minimum of 570 W of
microwave energy. The system should be capable of 1 % power adjustments and 1 s time adjustment. The microwave cavity should
be fluoropolymer coated and equipped with exhaust ventilation sufficient to provide ten chamber exchanges per minute. The cavity
shall have a 360° oscillating turntable to ensure even sample heating, and be capable of holding digestion vessels. Safety interlocks,
to shut off magnetron power output, shall be contained in the cavity door-opening mechanism. The system shall comply with
Department of Health and Human Services Standards under Code of Federal Regulations, Part 1030.10, Subparts (C) (1), (C) (2),
and (C) (3), for microwave leakage. The system should have Federal Communications Commission (FCC) type approval for
operations under FCC Rule Part 18.
10.1.1 Digestion Vessels—A vessel of 100-mL capacity. The vessel shallbe shall be transparent to microwave energy and have an
operating capability to withstand an internal pressure of at least 8.27 × 10 Pa, and a temperature of 200 °C. The vessel shall
contain a safety pressure relief valve, a rupture disc, pressure venting system, or be connected to an external safety relief valve
that will prevent possible vessel rupture or ejection of the vessel cap.
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10.1.2 Pressure Control Vessel—A vessel of 100 mL capacity, transparent to microwave energy, with a port for connection to a
pressure control device and capable of withstanding an internal pressure of at least 8.27 × 10 Pa and temperature of 200 °C.
10.1.3 Pressure Control Device—An externally or internally operated device to control the pressure within the digestion vessels.
3 5
The controller shall be capable of 6.89 × 10 Pa adjustments, controlling up to 8.27 × 10 Pa and be equipped with an external
pressure relief valve if a non-venting control vessel is used.
10.2 Other commercially available laboratory microwave heating systems may be used so long as they can be shown to providing
they provide comparable safety and performance. Follow manufacturers instruction for use.
11. Hazards
11.1 For hazards to be observed in the use of reagents and apparatus in this practice, refer to Practices E50.
11.2 Operate and maintain the microwave system in accordance with the manufacturer’s recommended safety precautions. Do not
operate the microwave system in
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