1、Designation: D5513 15Standard Practice forMicrowave Digestion of Industrial Furnace Feed Streamsand Waste for Trace Element Analysis1This standard is issued under the fixed designation D5513; the number immediately following the designation indicates the year oforiginal adoption or, in the case of r
2、evision, 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 describes the multi-stage microwave di-gestion of typical industrial furnace feed s
3、tream 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-related material in prepa
4、-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 listed above.1.3 This practice is also effective for other waste materials(for example, flyash, foundry sand, alum process residue,cement kiln dust, etc.).1.4
5、 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.5 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-p
6、riate safety and health practices and determine the applica-bility of regulatory limitations prior to use. Specific hazardstatements are given in Section 7.2. Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent Water2.2 Other Document:40 CFR 266 Subpart H, Hazardous Waste Burned
7、in Boilersand Industrial Furnaces, Latest Revision33. Summary of Practice3.1 A weighed portion of the feed stream material iscombined with concentrated nitric acid in apolytetrafluoroethylene-lined digestion vessel, and heated in amicrowave digestion unit. Following a programmed heatingcycle, the ve
8、ssel is vented and specified quantities of hydro-fluoric and hydrochloric acids are added, and the 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
9、. Following this final heating cycle, the vessel is vented,the contents are quantitatively transferred 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 digest
10、ed sampleis ready for analysis.4. Significance and Use4.1 The U.S. Environmental Protection AgencyRegulations, 40 CFR 266 , require that boilers, cement kilns,and other industrial furnaces utilizing waste-derived fuel ad-here to specific guidelines in assessing potential metals emis-sions. A common
11、approach for estimating potential emissionsis performing total metals analysis on all feed stream materials.This practice describes a multi-stage microwave-assisted di-gestion procedure that solubilizes trace elements for spectro-scopic analyses.5. Apparatus5.1 Microwave Digestion UnitEquipped with
12、an auto-matic turntable, pressure and/or temperature controller, andclosed perfluoroalkoxy (PFA)-lined digestion vessels equippedwith pressure relief/rupture membrane fittings or equivalentpressure relief device. The unit should comply with applicableregional, federal, or state standards for microwa
13、ve leakage.The user must follow specific manufacturers instructions forsystem installation.NOTE 1The digestion unit used in developing this practice wasequipped with a pressure controller, automatic turntable, exhaust fan, andprogramming capacity. The unit delivered 1000 W of power at 100 %output. T
14、he lined digestion vessels consisted of a high-strength polymericvessel body and cap, inner PFA liner and rupture membrane housing, andPFA vent stem. These vessels have a maximum operating pressure of 2001This practice is under the jurisdiction of ASTM Committee D34 on WasteManagement and is the dir
15、ect responsibility of Subcommittee D34.01.06 onAnalytical Methods.Current edition approved Sept. 1, 2015. Published September 2015. Originallyapproved in 1994. Last previous edition approved in 2009 as D5513 99 (2009).DOI: 10.1520/D5513-15.2For referenced ASTM standards, visit the ASTM website, www.
16、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. 4 Section D, 700Robbins Ave., Philadelphia, PA 19111-5094, At
17、tn: NPODS.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1psig. There are a number of suitable lab grade microwave systemsavailable to the user that meet these minimum specifications. The usermust follow specific manufacturers instruc
18、tions for using digestionvessels.5.2 Analytical BalanceCapable of weighing to 0.001 g (1mg).5.3 LabwareHigh-density volumetric polyethylene orpolypropylene flasks/sample containers are recommended forthis practice. The user should be mindful of the qualitylimitations associated with volumetric non-g
19、lass labware.6. Reagents and Materials6.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents conform to the specifications of the Committee onAnalytical Reagents of the American Chemical Society wheresuch specifications ar
20、e available.4Other grades may be used,provided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use without lessening the accuracy ofthe determination.6.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean meeting the numeric
21、alrequirements of Type II water as defined by SpecificationsD1193.6.3 Boric Acid Solution (20 g/L)Dissolve 20 g of boricacid (H3BO3) in water and dilute 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 u
22、ndergentle 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), 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 l
23、aboratory fume hood.7.2 Hydrochloric acid is a highly corrosive chemical that isreactive with metals and most alkaline chemicals. Imperviousgloves and chemical goggles are required for handling. Seesafety data sheet (SDS) for additional information.7.3 Hydrofluoric acid is a highly corrosive chemica
24、l that isreactive with metals and water or steam. Additionally, HFspecifically attacks silicate glass making certain fume hoodenclosures susceptible to damage. Impervious gloves andchemical goggles are required for handling. See SDS foradditional information.7.4 Nitric acid is a highly corrosive che
25、mical that is reactivewith metals and most organic materials. Impervious gloves andchemical goggles are required for handling. See SDS foradditional information.7.5 Some samples undergoing microwave digestion canexhibit a rapid pressure rise within the digestion vessel. Thepotential exists for this
26、type of sample to rupture the rupturemembrane and liberate corrosive gases. Because of this, themicrowave unit must be vented to a fume hood for properevacuation of vapors.8. Sample8.1 Although feed stream materials are generally pulverizedpowders or liquids, the homogeneity of some feed streammater
27、ials can be uncertain. The laboratory sample should bethoroughly mixed or homogenized prior to withdrawing aportion for analysis. This practice assumes that non-liquid feedstreams are pulverized powders at the time of sample prepa-ration.NOTE 2If a non-liquid feed stream material is not in the form
28、of apulverized powder, it may need to be reduced in particle size to passthrough a No. 100 sieve.9. Calibration and Standardization9.1 Although equipment manufacturers specify generalpower output ratings for microwave digestion units, it isimportant to verify the actual power output of a specific un
29、it. Itis recommended that this microwave power check procedurebe performed monthly.9.1.1 Power Check Procedure at 100 % Instrument Power:9.1.1.1 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 ma
30、nufacturers 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 to25C) 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 ri
31、ght front corner of theinstrument cavity (as you face the front of the instrument). Thisposition closely approximates the position of a digestion 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 c
32、avity, 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 the delivered power in accordance withthe following equations:Power watts! 5 T 3 35 W/C! (1)where:T = Tf Ti.W/C =K 3 Cp 3 Mtwhere:W = watts,4Reagent Chemica
33、ls, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For Suggestions on the testing of reagents notlisted by the American Chemical Society, see Annual Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National F
34、ormulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.5This information taken from the NIOSH Guide to Chemical Hazards, U.S.Depart. of Health and Human Services, June 1990.D5513 152K = 4.2, the factor for converting thermo-chemicalcalories/s to joules to watts.Cp = 1.0, the heat capacit
35、y for water, cal g1degree1,M = mass of water, g (1 mL 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.10. ProcedureNOTE 3Many microwave digestion units
36、are capable of handling up to12 digestion vessels at a time. The number of vessels processed affects therequired program settings. The microwave program examples given inAnnex A1 and Annex A2 were developed to accommodate 10 pressurevessels and have been proven effective in field testing. A maximump
37、ressure of 140 psi for a minimum time at pressure of 10 min is generallysufficient for sample digestion.Acomplete digestion can be verified by theuser by processing reference materials and calculating analyte recoveries.10.1 Process coal, coke, cement raw feed, and othergeologic/inorganic materials
38、as follows:10.1.1 Weigh 0.5 g of the feed stream material directly in aPFA digestion vessel liner and record the mass to the nearest0.01 g.10.1.2 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 re
39、action is observed,allow the reaction to subside prior to performing 10.1.3.10.1.3 Place pressure controller cap assembly on the vesselbody, and hand tighten to achieve a firm fit. Do not over tightenbecause this can damage the sealing surface and threads.10.1.4 Be sure the pressure relief/rupture m
40、embrane screw-type fitting houses a new rupture membrane, and is tightened tofinger-tightness. Do not over tighten because this can poten-tially deform the rupture membrane and damage the threads. Ifa rupture membrane bursts during the digestion, stop thedigestion and remove the vessel with the rupt
41、ured membranefrom the turntable and resume digestion. Discard the sample inthe removed vessel.10.1.5 Place the vessel in the microwave turntable. Insertthe pressure sensing tubing from the pressure controller intothe pressure controller cap assembly and tighten to finger-tightness. Be sure that the
42、pressure sensing tubing is com-pletely filled with water (from the pressure controller unit tothe pressure control vessel) prior to inserting this 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 a
43、ssembly is tightened to firmness.Evenly distribute the digestion vessels in the turntable toensure uniform heating of all vessels.10.1.7 It is recommended that a blank and a certifiedreference standard or a matrix spike be processed with eachbatch of samples of similar composition. Generally, a batc
44、h isconsidered to be samples that are processed together by thesame method, reagents, and the same manipulation. The userwill need to determine 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
45、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 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
46、 the vessels in alaboratory fume hood or the microwave oven cavity by slowlyunscrewing the pressure relief/rupture membrane fitting. Ventthe pressure 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 tu
47、bing with water toremove any trace of acid. This is an important step, becausedamage will occur to the pressure controller if an acidicsolution 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 polyethyl
48、ene 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 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 k
49、nown 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 volume for each acid.10.1.9.3 Recap the digestion vessels, making sure the pres-sure relief/rupture membrane fitting is tightened to finger-tightness. 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
