1、Designation: E2941 13Standard Practice forNitric Acid-Extraction of Elements from Ores and RelatedMetallurgical Materials by Closed Vessel MicrowaveHeating1This standard is issued under the fixed designation E2941; the number immediately following the designation indicates the year oforiginal adopti
2、on or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice covers the digestion of ores and relatedmetallurgical materi
3、als, such as mine soil, waste rock andtailings, for subsequent determination of nitric acid-extractablecontents of certain elements by such solution analytical tech-niques as atomic absorption, atomic emission (see MethodD1976), and inductively coupled plasma mass spectroscopy(see Method D5673).1.1.
4、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, vanadiu
5、m and zinc can be extractedfrom ores and related metallurgical materials for determinationby analytical methods for elements in solution. Other elementsmay be determined from extracts produced using this practice.1.1.2 Actual element quantification can be accomplished byfollowing the various test me
6、thods under other appropriateASTM standards for element(s) of interest in solution.1.1.3 The detection limit and linear content range for eachelement is dependent on the atomic absorption or emissionspectrometric technique employed and may be found in themanual accompanying the instrument used or AS
7、TM standardmethod for analysis of the solutions. Take into account the 100fold dilution due to digesting a 1-g sample to final volume of100 mL.1.1.4 The extent of extraction of elements from ores andrelated metallurgical materials by this method is dependentupon the physical and mineralogical charac
8、teristics of theprepared sample.1.2 The values stated SI units are to be regarded as thestandard. No other units of measurements are included in thisstandard.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user
9、of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. For specific hazardstatements, see Section 9.2. Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent WaterD1976 Test Method for Elements
10、in Water by Inductively-Coupled Argon Plasma Atomic Emission SpectroscopyD5258 Practice for Acid-Extraction of Elements from Sedi-ments Using Closed Vessel Microwave HeatingD5673 Test Method for Elements in Water by InductivelyCoupled PlasmaMass SpectrometryE50 Practices for Apparatus, Reagents, and
11、 Safety Consid-erations for Chemical Analysis of Metals, Ores, andRelated MaterialsE135 Terminology Relating to Analytical Chemistry forMetals, Ores, and Related MaterialsE882 Guide for Accountability and Quality Control in theChemical Analysis Laboratory2.2 Federal Standard:3CFR Title 21, Part 1030
12、, and Title 47, Part 183. Terminology3.1 DefinitionsFor definitions of terms used in thispractice, refer to Terminology E135.4. Summary of Practice4.1 The chemical portion of this practice involves nitric aciddigestion to dissociate the elements not interstitially bound insilicate lattices.1This tes
13、t method is under the jurisdiction of ASTM Committee E01 onAnalytical Chemistry for Metals, Ores, and Related Materials and is the directresponsibility of Subcommittee E01.02 on Ores, Concentrates, and Related Metal-lurgical Materials.Current edition approved Oct. 1, 2013. Published October 2013. DO
14、I: 10.1520/E2941-13.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from U.S. Government Printing
15、Office Superintendent of Documents,732 N. Capitol St., NW, Mail Stop: SDE, Washington, DC 20401, http:/www.access.gpo.gov.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14.2 The sample is digested with HNO3in a closed fluoropo-lymer v
16、essel using microwave heating to an internal pressureof 6.89 105Pa.4.3 This practice provides a sample suitable for analysis byatomic absorption, atomic emission or inductively coupledplasma mass spectrometry.5. Significance and Use5.1 These test methods are primarily intended to test mate-rials for
17、 compliance with compositional specifications and formonitoring. Partial extraction of ores and related metallurgicalmaterials can provide information on the availability of ele-ments to leaching, water quality changes, or other site condi-tions.5.2 Rapid heating, in combination with temperatures in
18、excess of the atmospheric boiling point of HNO3, reducessample preparation or reaction times.5.3 Little or no acids are lost to boiling or evaporation in theclosed digestion vessel so additional portions of acid may notbe required. Increased blank corrections from trace impuritiesin acid are minimiz
19、ed.5.4 It is assumed that the users of this practice will betrained analysts capable of performing common laboratoryprocedures skillfully and safely. It is expected that work will beperformed in a properly equipped laboratory and that properwaste disposal procedures will be followed. Appropriate qua
20、l-ity control practices such as those described in Guide E882must be followed.6. Interferences6.1 No interferences to the digestion of ores and relatedmetallurgical materials using microwave heating have beenobserved.6.2 Precautions should be exercised to avoid those interfer-ences normally associat
21、ed with the final determination ofelements using atomic absorption, atomic emission, or induc-tively coupled plasma mass spectrometry.6.3 The HNO3matrix may not be suitable for stabilizingsolutions containing silver and antimony, an alternate digestionmethod using a HCl matrix may be required to det
22、ermine someelements.7. Apparatus7.1 Microwave Heating SystemA laboratory microwaveheating system capable of delivering a minimum of 570 W ofmicrowave energy. The system should be capable of 1 %power adjustments and 1 s time adjustment. The microwavecavity should be fluoropolymer coated and equipped
23、withexhaust ventilation sufficient to provide ten chamber exchangesper minute.The cavity must have a 360 oscillating turntable toensure even sample heating, and be capable of holding diges-tion vessels. Safety interlocks, to shut off magnetron poweroutput, must be contained in the cavity door openin
24、g mecha-nism. The system must comply with Department of Health andHuman Services Standards under Code of Federal Regulations,Part 1030.10, Subparts (C) (1), (C) (2), and (C) (3), formicrowave leakage. The system should have Federal Commu-nications Commission (FCC) type approval for operationsunder F
25、CC Rule Part 18.7.1.1 Digestion VesselsA vessel of 100-mL capacity. Thevessel must be transparent to microwave energy and be capableof withstanding a minimum internal pressure of 8.27 105Pa,and a temperature of 200 C. The vessel must contain a safetypressure relief valve, a rupture disc, pressure ve
26、nting system,or be connected to an external safety relief valve that willprevent possible vessel rupture or ejection of the vessel cap.7.1.2 Pressure Control VesselAvessel of 100 mLcapacity,transparent to microwave energy, with a port for connection toa pressure control device and capable of withsta
27、nding aminimum internal pressure of 8.27 105Pa and temperature of200 C.7.1.3 Pressure Control DeviceAn externally or internallyoperated device to control the pressure within the digestionvessels. The controller must be capable of 6.89 103Paadjustments, controlling up to 8.27 105Pa and be equippedwit
28、h an external pressure relief valve if a non-venting controlvessel is used.7.2 Other commercially available laboratory microwaveheating systems may be used so long as they can be shown toprovide comparable safety and performance. Follow manufac-turers instruction for use.8. Reagents8.1 Purity of Rea
29、gentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of the commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.4Other grades may beused provided
30、it is first ascertained that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination.8.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean reagent water conformingto Type I or Type II of Specification D119
31、3. Type III or TypeIV may be used if they effect no measurable change in theblank or sample.9. Hazards9.1 Operate and maintain the microwave system in accor-dance with the manufacturers recommended safety precau-tions. Do not operate the microwave system in a fume hoodwhere it is surrounded by acid
32、fumes that can cause corrosionof the equipment. Vent acid fumes generated inside the cavityfrom the cavity to a fume hood. Place the digestion vessels ina fume hood to remove vapors released when a vessel isopened.9.2 Perform the digestion in accordance with the manufac-turers recommended safety pre
33、cautions.4Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States P
34、harmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.E2941 1329.3 Use of other domestic and commercial microwavesystems not designed for nitric acid digestion of samples maynot be suitable for use with this practice.10. Sampling10.1 Materials SafetySamples must
35、 be prepared, stored,and disposed of in accordance with the materials and safetyguidelines in Practices E50.10.2 Prepared SampleDry a representative portion of thegross sample at 80 C to constant mass in order to minimizesulfide mineral oxidation. Pulverize or grind the laboratorysample until at lea
36、st 95 % passes a 150-m sieve. Fine grindingto 95 % passing a 53-m sieve, is recommended for proceduresusing a single acid digestion.11. Preparation of Apparatus11.1 The manufacturers recommended cleaning proceduremay be followed or the procedure in 11.2 through 11.4 may beused.11.2 Soak the fluoropo
37、lymer vessel parts in HNO3(1+1)cleaning solution at 60 C 6 5 C for 10 min.11.3 Remove the vessel parts from the cleaning solution andthoroughly rinse the parts with water.11.4 Allow the vessel parts to air-dry or wipe dry using aclean, soft cloth.12. Procedure12.1 Determine the power output of the m
38、icrowave usingthe procedure described in the annex to ensure that the unitmeets the minimum power requirement.12.2 Obtaina1gportion of the sample prepared in 10.2,weighed to the nearest 0.1 mg, and transfer into digestionvessels. Include an empty digestion vessel in each set as amethod blank.NOTE 1T
39、he pressure control vessel must contain1gofsamplematerial.12.3 Add 20 mL of HNO3(1 + 1) to each sample and blankdigestion vessel.12.4 Close each digestion vessel according to the manufac-turers recommended procedures.12.5 Place the closed digestion and pressure control vesselinto the instrument turn
40、table and assemble following themanufacturers suggested procedure.NOTE 2The pressure control vessel is connected to the pressurecontrol device and may be assembled into the turntable differently than thestandard digestion vessels. Refer to the manufacturers suggested proce-dure.12.6 Set the pressure
41、 control device to control the digestionvessel pressure at 6.89 105Pa.12.7 Heat the vessels to obtain an internal pressure 6.89 105Pa and maintain for 30 min. Refer to the manufacturerssuggested procedure.12.8 Allow the vessels to cool to room temperature, andthen vent excess pressure from the vesse
42、ls. Refer to themanufacturers recommended venting procedure.12.9 Remove the vessels from the turntable, place in a fumehood, and open the vessel.12.10 Filter5the contents of the digestion vessel. Wash thevessel and filter thoroughly with small portions of water,without exceeding 100 mL solution volu
43、me. Alternatively,separate the solid and liquid phases by centrifugation.12.11 Transfer the filtered solution and washes, orconcentrate, to a 100-mLvolumetric flask and dilute to volumewith water.13. Precision and Bias13.1 This practice was tested by digesting a single sampleby one laboratory during
44、 the standardization of PracticeD5258. Table 1 summarizes precision and bias of the traceelement analyses conducted on six portions of NIST RiverSediment (SRM 1645)6digested by this practice. All traceelement contents were determined by flame or graphite furnaceatomic absorption techniques.14. Keywo
45、rds14.1 atomic absorption; atomic emission; digestion; induc-tively coupled plasma mass spectrometry; microwave; minesoils; ores and related metallurgical materials; tailings; vessel;waste rock5Whatman No. 41 filter paper, available from Whatman Specialty Products, 6Just Rd., Fairfield, NJ 07004, ha
46、s been found suitable for this purpose.6NIST Standard Reference Materials, Office of Standard Reference Materials,U.S. Department of Commerce, Gaithersburg, MD 20899.E2941 133ANNEX(Mandatory Information)A1. PROCEDURE TO DETERMINE DELIVERED POWER OF MICROWAVE OVEN AT 100 % INSTRUMENT POWERA1.1 Remove
47、 the turntable, drive lug, and all vessels fromthe instrument cavity.A1.2 Adjust the instrument cavity exhaust to minimumairflow.A1.3 Program the instrument for 4 min time and 100 %power.A1.4 Transfer 2000 6 2 mL of room temperature (19 to 25C) water into a 2-L polypropylene beaker.A1.5 Measure and
48、record the initial water temperature, Ti,to the nearest 0.1 C.A1.6 Place the beaker in the right front corner of theinstrument cavity.A1.7 Heat the water for the programmed time.A1.8 When the heating cycle is complete, immediatelyremove the beaker from the cavity, thoroughly stir the water toensure
49、even heat distribution, and measure the finaltemperature, Tf, to the nearest 0.1 C.A1.9 Calculate the delivered power as follows:P 5 Tf2 Ti! 335 (A1.1)where:P = delivered power, watts,Tf= final water temperature, C, andTi= initial water temperature, C.and35 54.2 31.0 3 Mt(A1.2)where:4.2 = conversion factor for thermochemical calories to watts,1.0 = heat capacity of water, calories/g per C,M = mass of water, g, andt = heating time, s.ASTM International takes no position respecting the validity of any patent rights asserted in connectio
