1、Designation: D 4309 02 (Reapproved 2007)Standard Practice forSample Digestion Using Closed Vessel Microwave HeatingTechnique for the Determination of Total Metals in Water1This standard is issued under the fixed designation D 4309; the number immediately following the designation indicates the year
2、oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice covers the general considerations forquant
3、itative sample digestion for total metals in water usingclosed vessel microwave heating technique. This practice isapplicable to surface, saline, domestic, and industrial waste-water.1.2 Because of the differences among various makes andmodels of satisfactory instruments, no detailed operating in-st
4、ructions can be provided. Instead, the analyst should followthe instructions provided by the manufacturer of the particularinstrument.1.3 This practice can be used with the following ASTMstandards, providing the user determines precision and biasbased on this digestion practice: Test Methods D 857,
5、TestMethods D 858, Test Methods D 1068, Specification D 1192,Test Methods D 1687, Test Methods D 1688, Test MethodsD 1691, Test Methods D 1886, Practices D 3370, Test MethodsD 3557, Test Methods D 3559, Practice D 3919, Test MethodsD 4190, Practice D 4453, and Practice D 4691.1.4 This standard does
6、not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user 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 Se
7、ction 9.2. Referenced Documents2.1 ASTM Standards:2D 857 Test Method for Aluminum in WaterD 858 Test Methods for Manganese in WaterD 1068 Test Methods for Iron in WaterD 1129 Terminology Relating to WaterD 1192 Guide for Equipment for Sampling Water andSteam in Closed Conduits3D 1193 Specification f
8、or Reagent WaterD 1687 Test Methods for Chromium in WaterD 1688 Test Methods for Copper in WaterD 1691 Test Methods for Zinc in WaterD 1886 Test Methods for Nickel in WaterD 3370 Practices for Sampling Water from Closed ConduitsD 3557 Test Methods for Cadmium in WaterD 3559 Test Methods for Lead in
9、WaterD 3856 Guide for Good Laboratory Practices in Laborato-ries Engaged in Sampling and Analysis of WaterD 3919 Practice for Measuring Trace Elements in Water byGraphite Furnace Atomic Absorption SpectrophotometryD 4190 Test Method for Elements in Water by Direct-Current Plasma Atomic Emission Spec
10、troscopyD 4453 Practice for Handling of Ultra-Pure Water SamplesD 4691 Practice for Measuring Elements in Water by FlameAtomic Absorption Spectrophotometry2.2 U.S. Code of Federal Regulations:4CFR 1.030.10 Code of Federal Regulations, Volume 212.3 Federal Communications Commission Standard:4Code of
11、Federal Regulations, Volume 47, FCC Rule Part 182.4 U.S. EPA Method:5U.S. EPAMethod: Methods for ChemicalAnalysis of Waterand WasteMarch 1979, “Total Metals Digestion Proce-dure” 4.1.3, page Metals 6U.S. EPA Method: SW 846 Method 3015 Microwave As-sisted Acid Digestion of Aqueous Samples and Extract
12、s3. Terminology3.1 DefinitionsFor definitions of terms used in this prac-tice, refer to Terminology D 1129.4. Summary of Practice4.1 A representative aliquot of a homogeneous sample isdigested with acid in a closed microwave transparent vessel,1This practice is under the jurisdiction of ASTM Committ
13、ee D19 on Water andis the direct responsibility of Subcommittee D19.05 on Inorganic Constituents inWater.Current edition approved June 15, 2007. Published June 2007. Originallyapproved in 1991. Last previous edition approved in 2002 as D 4309 02.2For referenced ASTM standards, visit the ASTM website
14、, 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.3Withdrawn.4Available from Office of the Federal Register, National Archives RecordsAdministration, Superintendent
15、of Documents, U.S. Government Printing Office,Washington, DC 20401.5Available from National Technical Information Service (NTIS), 5285 PortRoyal Rd., Springfield, VA 22161, http:/www.ntis.gov.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United
16、States.using microwave heating. The digestate or a filtered digestateis then analyzed by direct aspiration or injection by flameatomic absorption spectrophotometry (FAAS), inductivelycoupled plasma emission techniques (ICP), direct currentplasma emission techniques (DCP), or graphite furnace atomica
17、bsorption spectrophotometry (GFAAS), or a combination ofmethods.5. Significance and Use5.1 The analysis of many types of water for metals usingflame atomic absorption spectrophotometry, inductivelycoupled plasma emission spectrophotometry, direct currentplasma emission spectrophotometry, or graphite
18、 furnaceatomic absorption spectrophotometry necessitates the use of adigestion practice in order to ensure the proper statisticalrecovery of the metals from the sample matrix. The use ofclosed vessel microwave techniques will speed the completerecovery of metals from the water matrices and eliminate
19、sample contamination from external sources.6. Interferences6.1 No interferences have been observed using microwaveheating.6.2 Precautions should be exercised to avoid those interfer-ences normally associated with the particular analytical methodfor metals determination.6.3 This practice will not tot
20、ally solubilize solid silicatesthat are suspended in or settle out of the water sample.7. Apparatus7.1 Laboratory Microwave Heating System, capable of de-livering 575 to 1000 W of power. The unit should be capableof 1 % power adjustment and 1 s time adjustment. The ovencavity should be fluorocarbon-
21、coated or coated with a materialthat has equivalent acid resistance and microwave propertiesand be equipped with exhaust ventilation at 2.8 m3/min (100ft3/min) for acid vapor protection of the unit and operator. Theunit must have a rotating or alternating turntable, capable ofholding 1 to 14 digesti
22、on vessels, to ensure even sampleheating. Safety interlocks, to shut off magnetron power output,must be contained in the oven door opening mechanism. Theunit may contain a temperature control device capable ofcontrolling vessel temperatures to 200C and/or a pressurecontrol device capable of controll
23、ing vessel pressures to aminimum 100 psig.7.1.1 The unit must comply with U.S. Health and HumanServices Standards under CFR Part 1030.10, sub parts (C) (1),(C) (2), and (C) (3), for microwave leakage. The unit shouldhave FCC-type approval for operations under FCC Rule Part18.7.2 Closed Vessel, capab
24、le of holding 100 mL of solution.The vessel must be transparent to microwave energy andcapable of withstanding internal pressures of 100 psig andtemperatures of 200C. The vessel must contain a safetypressure relief valve, rupture disc, pressure venting system orbe connected to an external safety rel
25、ief valve that will preventpossible vessel rupture or ejection of the vessel cap.7.3 Apparatus, to seal the vessel system to the manufactur-ers specified requirement.8. Reagents8.1 Purity of ReagentsReagent grade chemicals shall beused in this practice. Unless otherwise indicated, it is intendedthat
26、 all reagents shall conform to the specifications for theCommittee on Analytical Reagents of the American ChemicalSociety, where such specifications are available.6Other gradesmay be used, provided it is first ascertained that the reagent isof sufficiently high purity to permit its use without lesse
27、ningthe accuracy of the determination.8.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean reagent water conformingto Specification D 1193, Type I. Other reagent water types maybe used provided it is first ascertained that the water is ofsufficiently high pur
28、ity to permit its use without adverselyaffecting the bias and precision of the method. Type II waterwas used for the data shown in Appendix 1.8.3 Hydrochloric Acid (sp gr 1.19) (HCl).8.4 Nitric Acid (sp gr 1.42) (HNO3).8.5 Nitric Acid (1 + 1)Add 1 volume of HNO3(sp gr 1.42)to 1 volume of water.9. Ha
29、zards9.1 The microwave unit should be operated in accordancewith the manufacturers recommended operating and safetyprecautions. CautionIt is not recommended to place amicrowave unit in a fume hood, where it is surrounded by acidfumes, which can cause corrosion of the equipment. Acidfumes generated i
30、nside the oven cavity should be air sweptaway from the oven cavity to a hood.9.2 PrecautionThe closed vessel should be operated inaccordance with the manufacturers recommended operatingand safety instructions.10. Procedure10.1 Power Temperature Controlprocedure for 7 to 12vessel digestions:NOTE 1For
31、 fewer than seven samples, see 10.2.10.1.1 Perform an instrument power check as outlined inAnnex A1.10.1.2 Refer to ASTM test methods for sampling andanalysis (such as Guide D 3856) to determine any samplepreservation requirements.10.1.3 Transfer 50.0 mL of a representative aliquot of thewell-mixed
32、sample into a clean vessel (see Note 2). If thesample is to be analyzed by ICP, DCP, or FAAS, add 3 mL ofHNO3(sp gr 1.42) and 2 mL of HCl (sp gr 1.19). If the sampleis to be analyzed by GFAAS, add 5 mL of HNO3(sp gr 1.42)(see Note 3). Install a safety pressure relief valve and cap onthe vessel and s
33、eal to the manufacturers recommended torque.Weigh the vessel, record the weight, and place in the micro-wave instrument turntable. Attach a vent tube, if required, bythe manufacturers operating instructions.6Reagent Chemicals, American Chemical Society Specifications , AmericanChemical Society, Wash
34、ington, 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 Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.D 4309 02
35、 (2007)2NOTE 2Follow the manufacturers suggested vessel cleaning instruc-tions to avoid possible sample contamination.NOTE 3Final acid concentration of this procedure is 9 %. This mayshorten graphite tube lifetime, which may cause deterioration of analyterecovery. The analyst may choose to dilute th
36、e digested solution to a loweracid percentage to increase graphite tube life.10.1.4 Repeat 10.1.3 until the turntable contains 12 vessels.Areagent blank should be digested and analyzed along with thesamples. If less than 12 samples are to be digested, fill theremaining vessels with 50 mL of water an
37、d add an equalamount of acid as added to the sample. It is critical to theprocedure that the total volume of solutions equals 660 mLduring digestion, and that each vessel contains an equal volumeof acid. This is necessary to ensure uniform heating of allvessel solutions.NOTE 4It is not necessary to
38、weigh the blank vessels containing 50mL of reagent water.10.1.5 Turn the microwave instrument exhaust on to themaximum fan speed.Activate the turntable so that it is rotatingor alternating 360.10.1.6 For instruments delivering a measured power of 575to 635 W, program the instrument time for 50 min a
39、nd thepower to 100 %. For instruments with a measured power of635 to 700 W, program the instrument time for 30 min and thepower for 100 %. These heating parameters will allow thesamples to reach a maximum temperature of 164 6 4C (referto Fig. 1). Instruments delivering greater than 700 W must beoper
40、ated at reduced powers such that the sample heating ratesmatch the heating rates in Fig. 1. Depress the start key andallow the sample mixtures to heat for the programmed time.10.1.7 At the end of the digestion period, remove the vesselsfrom the microwave and allow the sample solutions to cool toroom
41、 temperature. Shake the vessels to mix the samplesolutions and vent to atmosphere any gas pressure that may bepresent in the vessels.NOTE 5Warning: Shake the vessel with caution to prevent any rapidout-gassing of vapor or liquid causing acid burns of the exposed skin ofthe operator.10.1.8 Detach the
42、 vent tubing and remove the vessel assem-bly from the turntable. Weigh the cooled vessel system. If thereis a weight loss greater than 0.5 g, open the vessel and add anamount of reagent water equal to the weight loss. Liquid lossof less than 10 % has not been found to result in any analyteloss (see
43、Note 6). Recap the vessel and then shake the vessel tomix the sample solution.NOTE 6Samples containing large amounts of organics may experi-ence excessive loss of liquid (greater than 10 %); therefore, a study maybe required to determine if any analyte loss occurred.10.1.9 Open the vessels and filte
44、r the samples, if required, toremove silicates and other insoluble materials. Do not rinse ordilute the digested sample. Final sample volume is 55 mL (seeNote 3).NOTE 7In place of filtering, the sample after mixing may be centri-fuged or allowed to settle by gravity overnight to remove insolublemate
45、rial.10.1.10 Analyze the sample by ICP, DCP, FAAS or GFAAS,or a combination of methods, as required.10.2 Power Temperature Controlprocedure for 1 to 6vessel digestions:10.2.1 Perform an instrument power check as outlined inAnnex A2.10.2.2 Refer to individual ASTM test methods for samplingand analysi
46、s to determine any sample preservation require-ments.10.2.3 Transfer 50.0 mL of a representative aliquot of thewell-mixed sample into a clean vessel (see Note 2). If thesample is to be analyzed by ICP, DCP, or FAAS, add 3 mL ofHNO3(sp gr 1.42) and 2 mL of HCl (sp gr 1.19). If the sampleis to be anal
47、yzed by GFAAS, add 5 mL of HNO3(sp gr 1.42)(see Note 3). Install a safety pressure relief valve and cap onthe vessel and then seal to the manufacturers recommendedtorque. Weigh the vessel, record the weight, and place in themicrowave instrument turntable.Attach a vent tube, if requiredby the manufac
48、turers operating instructions.10.2.4 Repeat 10.2.3 until the turntable contains 6 evenly-spaced vessels. A reagent blank should be digested andanalyzed along with the samples. If fewer than 6 samples are tobe digested, fill remaining vessels with 50 mL of reagent waterand add an equal amount of acid
49、 to the samples. It is critical tothe procedure that the total volume of solutions equals 330 mLduring digestion, and that each vessel contains an equal volumeof acid. This is necessary to ensure uniform heating of allvessel solutions (see Note 4).10.2.5 Turn the microwave instrument exhaust on to themaximum fan speed.Activate the turntable so that it is rotatingor alternating 360.10.2.6 For instruments with a measured power of 575 to 635W, program the instrument time for 30 min and 75 % power.For instruments with a measured power of 635 to 700 W,program
