1、Designation: D 5513 99 (Reapproved 2004)Standard Practice forMicrowave Digestion of Industrial Furnace Feedstreams andWaste for Trace Element Analysis1This standard is issued under the fixed designation D 5513; the number immediately following the designation indicates the year oforiginal adoption o
2、r, 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 describes the multi-stage microwave di-gestion of typical indus
3、trial furnace feedstream materials usingnitric, hydrofluoric, hydrochloric, and boric acids for thesubsequent determination of trace metals.1.2 This practice has been used successfully on samples ofcoal, coke, cement raw feed materials, and waste-derived fuelscomposed primarily of waste paint-relate
4、d material in prepa-ration for measuring the following trace elements: Ag, As, Ba,Be, Cd, Cr, Hg, Pb, Sb, and Tl. This practice may be applicableto elements not previously listed.1.3 This practice is also effective for other waste materials(for example, flyash, foundry sand, alum process residue,cem
5、ent kiln dust, etc.).1.4 This standard does 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 t
6、o use. Specific hazardstatements are given in Section 7.2. Referenced Documents2.1 ASTM Standards:2D 1193 Specifications for Reagent Water2.2 Other Document:40 CFR 266, Subpart H, Hazardous Waste Burned inBoilers and Industrial Furnaces, Latest Revision33. Summary of Practice3.1 A weighed portion of
7、 the feedstream material is com-bined with concentrated nitric acid in apolytetrafluoroethylene-lined digestion vessel, and heated in amicrowave digestion unit. Following a programmed heatingcycle, the vessel is vented and specified quantities of hydrof-luoric and hydrochloric acids are added, and t
8、he mixtureundergoes further microwave heating. Following this heatingcycle, the vessel is vented and a specified quantity of boric acidsolution is added, and the mixture undergoes a final microwaveheating. Following this final heating cycle, the vessel is vented,the contents are quantitatively trans
9、ferred to a volumetric flaskand brought to volume. Typically, the only undissolved mate-rial is particulate carbon. If particulate matter is observed,filtration or centrifugation may be needed. The digested sampleis ready for analysis.4. Significance and Use4.1 The U.S. Environmental Protection Agen
10、cy Regula-tions, 40 CFR, require that boilers, cement kilns, and otherindustrial furnaces utilizing waste-derived fuel adhere to spe-cific guidelines in assessing potential metals emissions. Acommon approach for estimating potential emissions is per-forming total metals analysis on all feedstream ma
11、terials. Thispractice describes a multi-stage microwave-assisted digestionprocedure that solubilizes trace elements for spectroscopicanalyses.5. Apparatus5.1 Microwave Digestion UnitEquipped with an auto-matic turntable, pressure and/or temperature controller, andclosed perfluoroalkoxy (PFA)-lined d
12、igestion vessels equippedwith pressure relief/rupture membrane fittings or equivalentpressure relief device. The unit should comply with applicablefederal or state standards, or both, for microwave leakage. Theuser must follow specific manufacturers instructions for sys-tem installation.NOTE 1The di
13、gestion unit used in developing this practice wasequipped with a pressure controller, automatic turntable, exhaust fan, andprogramming capacity. The unit delivers 1000 W of power at 100 %output. The lined digestion vessels consist of a high-strength polymericvessel body and cap, inner PFA liner and
14、rupture membrane housing, andPFA vent stem. These vessels have a maximum operating pressure of 200psig. There are a number of suitable lab grade microwave systemsavailable to the user that meet these minimum specifications. The usermust follow specific manufacturers instructions for using digestionv
15、essels.1This practice is under the jurisdiction of ASTM Committee D34 on WasteManagement and is the direct responsibility of Subcommittee D34.01.06 onAnalytical Methods.Current edition approved March 10, 1999. Published May 1999. Originallypublished as D 5513 94. Last previous edition D 5513 94 (199
16、8).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 Standardization Documents Order Desk, Bldg
17、. 4 Section D, 700Robbins Ave., Philadelphia, PA 19111-5094, Attn: NPODS.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.2 Analytical BalanceCapable of weighing to 0.001 g.5.3 LabwareHigh-density volumetric polyethylene orpolypropy
18、lene flasks/sample containers are recommended forthis practice. The user should be mindful of the qualitylimitations associated with volumetric non-glass labware.6. Reagents and Materials6.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intend
19、ed thatall reagents conform to the specifications of the Committee onAnalytical Reagents of the American Chemical Society wheresuch specifications are available.4Other grades may be used,provided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use without lesseni
20、ng the accuracy ofthe determination.6.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean meeting the numericalrequirements of Type II water as defined by SpecificationsD 1193.6.3 Boric Acid Solution (20 g/L)Dissolve 20 g of boricacid (H3BO3) in water and dilu
21、te to 1 L. It may be necessaryto place solution on a combination hot plate/magnetic stirrerand with the aid of a stir bar, allow the solution to mix undergentle heat until boric acid is fully in solution.6.4 Hydrochloric Acid, 37 %, (sp. gr. 1.200), HCl.6.5 Hydrofluoric Acid, 48 %, (sp. gr. 1.150),
22、HF.6.6 Nitric Acid, 70 %, (sp. gr. 1.400), HNO3.7. Hazards57.1 It is recommended that all operations involving concen-trated acids be performed in a laboratory fume hood.7.2 Hydrochloric acid is a highly corrosive chemical that isreactive with metals and most alkaline chemicals. Imperviousgloves and
23、 chemical goggles are required for handling. Seematerial safety data sheet (MSDS) for additional information.7.3 Hydrofluoric acid is a highly corrosive chemical that isreactive with metals and water or steam. Additionally, HFspecifically attacks silicate glass making certain fume hoodenclosures sus
24、ceptible to damage. Impervious gloves andchemical goggles are required for handling. See MSDS foradditional information.7.4 Nitric acid is a highly corrosive chemical that is reactivewith metals and most organic materials. Impervious gloves andchemical goggles are required for handling. See MSDS for
25、additional information.7.5 Some samples undergoing microwave digestion canexhibit a rapid pressure rise within the digestion vessel. Thepotential exists for this type of sample to rupture the rupturemembrane and liberate corrosive gases. Because of this, themicrowave unit must be vented to a fume ho
26、od for properevacuation of vapors.8. Sample8.1 Although feedstream materials are generally pulverizedpowders or liquids, the homogeneity of some feedstreammaterials can be uncertain. The laboratory sample should bethoroughly mixed or homogenized prior to withdrawing aportion for analysis. This pract
27、ice assumes that non-liquidfeedstreams are pulverized powders at the time of samplepreparation.NOTE 2If a non-liquid feedstream material is not in the form of apulverized powder, it may need to be reduced in particle size to passthrough a No. 100 sieve.9. Calibration and Standardization9.1 Although
28、equipment manufacturers specify generalpower output ratings for microwave digestion units, it isimportant to verify the actual power output of a specific unit. Itis recommended that this microwave power check procedurebe performed monthly.9.1.1 Power Check Procedure at 100 % Instrument Power:9.1.1.1
29、 Remove from the instrument cavity the turntable,drive lug, and all vessels.9.1.1.2 Adjust the instrument cavity exhaust to minimum airflow (refer to the manufacturers instructions).9.1.1.3 Program the instrument for 4-min time and 100 %power.9.1.1.4 Transfer 2000 6 2 mL of room temperature (19 to25
30、C) water into a 2-L polypropylene beaker.9.1.1.5 Measure and record the initial water temperature (Ti)to the nearest 0.1C.9.1.1.6 Place the beaker in the right front corner of theinstrument cavity (as you face the front of the instrument). Thisposition closely approximates the position of a digestio
31、n vesselduring processing.9.1.1.7 Heat the water for the programmed time.9.1.1.8 When the heating cycle is complete, immediatelyremove the beaker from the cavity, thoroughly stir the water toensure even heat distribution, and measure the final tempera-ture (Tf) to the nearest 0.1C.9.1.1.9 Calculate
32、the delivered power in accordance withthe following equations:Power watts!5DT 3 35 W/C! (1)where:DT = Tf Ti.W/C = K 3 Cp 3 Mtwhere:W = watts,K = 4.2, the factor for converting thermo-chemicalcalories/s to joules to watts.Cp = 1.0, the heat capacity for water, cal g1degree1,M = mass of water, g (1 mL
33、 H2O = 1 g), andt = time, s.9.1.1.10 If the calculated power is not within the specifica-tions of the unit, do a second test beginning at 9.1.1.1 forconfirmation before contacting the manufacturer.4Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC.
34、 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. Pharmacoepeial Convention, Inc. (USPC), Rockville,MD.5This information t
35、aken from the NIOSH Guide to Chemical Hazards, U.S.Depart. of Health and Human Services, June 1990.D 5513 99 (2004)210. ProcedureNOTE 3Many microwave digestion units are capable of handling upto 12 digestion vessels at a time. The number of vessels processed affectsthe required program settings. The
36、 microwave program examples given inAnnexes A1 and A2 were developed to accommodate 10 pressure vesselshave been proven effective in field testing. A maximum pressure of 140 psifor a minimum time at pressure of 10 min is generally sufficient for sampledigestion. A complete digestion can be verified
37、by the user by processingreference materials and calculating analyte recoveries.10.1 Process coal, coke, cement raw feed, and othergeologic/inorganic materials as follows:10.1.1 Weigh 0.5 g of the feedstream material directly in aPFA digestion vessel liner and record the mass to the nearest0.01 g.10
38、.1.2 Place the liner with sample in the digestion vesselbody and with a pipet unit, or equivalent device, slowly add 8mL HNO3to the PFA liner. If a chemical reaction is observed,allow the reaction to subside prior to performing 10.1.3.10.1.3 Place pressure controller cap assembly on the vesselbody,
39、and hand tighten to achieve a firm fit. Do not overtightenbecause this can damage the sealing surface and threads.10.1.4 Be sure the pressure relief/rupture membrane screw-type fitting houses a new rupture membrane, and is tightened tofinger-tightness. Do not overtighten because this can poten-tiall
40、y deform the rupture membrane and damage the threads. Ifa rupture membrane bursts during the digestion, stop thedigestion and remove the vessel with the ruptured membranefrom the turntable and resume digestion. Discard the sample inthe removed vessel.10.1.5 Place the vessel in the microwave turntabl
41、e. Insertthe pressure sensing tubing from the pressure controller intothe pressure controller cap assembly and tighten to finger-tightness. Be sure that the pressure sensing tubing is com-pletely filled with water (from the pressure controller unit tothe pressure control vessel) prior to inserting t
42、his line.10.1.6 Repeat 10.1.1 and 10.1.2 for three or five additionalvessels. Cap these vessels with standard vessel cap assemblies.Be sure each vessel cap assembly is tightened to firmness.Evenly distribute the digestion vessels in the turntable toensure uniform heating of all vessels.10.1.7 It is
43、recommended that a blank and a certifiedreference standard or a matrix spike be processed with eachbatch of samples of similar composition. Generally, a batch isconsidered to be samples that are processed together by thesame method, reagents, and the same manipulation. The userwill need to determine
44、 the number of samples comprising abatch based on the users quality assurance requirements.10.1.8 The samples are ready for microwave processing.Process the samples by following the Stage 1 microwaveprogram described in Annex A1. Be sure the instrument cavityexhaust is set to maximum air flow.10.1.9
45、 Following the cooling step (0 power) in Stage 1, thevessels should be cool to the touch. Additional cooling timemay be necessary if vessels remain hot. Vent the vessels in alaboratory fume hood or the microwave oven cavity by slowlyunscrewing the pressure relief/rupture membrane fitting. Ventthe pr
46、essure control vessel in the microwave in order to removethe pressure sensing tubing. Remove the vessel cap assemblies.10.1.9.1 Flush the pressure sensing tubing with water toremove any trace of acid. This is an important step, becausedamage will occur to the pressure controller if an acidicsolution
47、 from the pressure sensing tubing is allowed to migrateto the pressure controller. The flush water should be disposedof as a waste.10.1.9.2 Using a polyethylene syringe, or other equivalentcompatible device, add 4 mL of HF, and 2 mL of HCl to eachvessel. If a chemical reaction is observed, allow the
48、 reaction tosubside prior to performing 10.1.9.3.NOTE 4The user may choose to vary the amounts of HF and HClbased on prior knowledge of the sample. Samples known to be low insiliceous material may require a lesser amount of HF. In no case should theuser reduce the amount of HF or HCl below a 2-mL vo
49、lume for each acid.10.1.9.3 Recap the digestion vessels, making sure the pres-sure relief/rupture membrane fitting is tightened to finger-tighteness. Replace the digestion vessels in the turntable, andreconnect the pressure sensing tubing to the pressure controlvessel. Be sure that the pressure sensing tubing is completelyfilled with water. Place the remaining digestion vessels in theturntable.10.1.9.4 The samples are ready for microwave processing.Process the samples by following the Stage 2 microwaveprogram described in Annex A1.10.1.9.5 Following the vess
