1、Designation: D 4185 06Standard Practice forMeasurement of Metals in Workplace Atmospheres byFlame Atomic Absorption Spectrophotometry1This standard is issued under the fixed designation D 4185; the number immediately following the designation indicates the year oforiginal adoption or, in the case of
2、 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 collection, dissolution, anddetermination of trace metals in workplac
3、e atmospheres, byflame atomic absorption spectrophotometry.1.2 The sensitivity, detection limit, and optimum workingconcentration for 23 metals are given in Table 1.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of th
4、e user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. (Specific safetyprecautionary statements are given in Section 9.)2. Referenced Documents2.1 ASTM Standards:2D 1193 Specification for Reagent WaterD 1
5、356 Terminology Relating to Sampling and Analysis ofAtmospheresD 1357 Practice for Planning the Sampling of the AmbientAtmosphereD 3195 Practice for Rotameter CalibrationD 5337 Practice for Flow Rate Calibration of PersonalSampling PumpsD 7035 Test Method for Determination of Metals and Met-alloids
6、in Airborne Particulate Matter by InductivelyCoupled Plasma Atomic Emission Spectrometry (ICP-AES)3. Terminology3.1 Definitions:3.1.1 For definitions of terms used in this practice, refer toTerminology D 1356.3.2 Definitions of Terms Specific to This Standard:3.2.1 blank signalthat signal which resu
7、lts from all addedreagents and a clean membrane filter prepared and analyzedexactly in the same way as the samples.3.2.2 instrumental detection limitthat concentration of agiven element which produces a signal three times the standarddeviation of the reagent blank signal.3.2.3 working range for an a
8、nalytical precision better than3%the range of sample concentrations that will absorb 10 to70 % of the incident radiation (0.05 to 0.52 absorbance units).NOTE 1Values for instrumental detection limit may vary from instru-ment to instrument.4. Summary of Practice4.1 Workplace air samples are collected
9、 on membrane filtersand treated with nitric acid to destroy the organic matrix and todissolve the metals present. The analysis is subsequently madeby flame atomic absorption spectrophotometry (AAS).4.2 Samples and standards are aspirated into an appropriateAAS flame. A hollow cathode or electrodeles
10、s discharge lampfor the metal being determined provides a source of character-istic radiation energy for that particular metal. The absorptionof this characteristic energy by the atoms of interest in theflame is related to the concentration of the metal in theaspirated sample. The flame and operatin
11、g conditions for eachelement are listed in Table 2.5. Significance and Use5.1 The health of workers in many industries is at riskthrough exposure by inhalation to toxic metals. Industrialhygienists and other public health professionals need to deter-mine the effectiveness of measures taken to contro
12、l workersexposures, and this is generally achieved by making workplaceair measurements. Exposure to some metal-containing particleshas been demonstrated to cause dermatitis, skin ulcers, eyeproblems, chemical pneumonitis, and other physical disorders(1).35.2 AAS is capable of quantitatively determin
13、ing mostmetals in air samples at the levels required by federal, state,1This practice is under the jurisdiction of ASTM Committee D22 on Air Qualityand is the direct responsibility of Subcommittee D22.04 on WorkplaceAtmospheres.Current edition approved Oct. 1, 2006. Published October 2006. Originall
14、yapproved in 1990. Last previous edition approved in 2001 as D 4185 96(2001)e1.2For 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 o
15、nthe ASTM website.3Boldface numbers in parentheses refer to the list of references appended tothese methods.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.TABLE 1 AAS Instrumental Detection Limits and Optimum Working Concentration f
16、or 23 MetalsElementDetection Limit, g/mL(approximately three timesstandard deviation of blank)AOptimum Linear RangeUpper Limit,g/mLTLV, mg/m3(elements, compound classes, and oxides)BAg 0.001 5 0.1 (metal) 0.01 (soluble compounds as Ag)Al 0.04 50 2.0 (soluble salts and alkyls not otherwise classified
17、) 10 (metal dust and oxide)5 (pyro powder and welding fume)Ba 0.01 10 0.5 (soluble compounds)Bi 0.03 10 No Limit expressed for this elementCa 0.002 1 2 (oxide as CaO)Cd 0.0008 1 0.01 (elemental and compoundstotal dust)0.002 (elemental compoundsrespirable fraction)Co 0.009 5 0.02 (elemental and inorg
18、anic) 0.1 (carbonyl and hydrocarbonyl)Cr 0.003 5 0.5 (metal and Cr III compounds) 0.05 (water soluble Cr VI compounds)0.01 (insoluble Cr VI compounds)Cu 0.002 5 0.2 (fume) 1 (dust and mists as Cu)Fe 0.005 5 5 (iron oxide fume) 5 (soluble salts as Fe)In 0.03 50 0.1 (metal and compounds)K 0.003 1 No L
19、imit expressed for this elementLi 0.0008 1 No Limit expressed for this elementMg 0.0002 0.5 10 (as MgO fume)Mn 0.002 5 0.2 (elemental and inorganic compounds)Na 0.0003 0.5 No Limit expressed for this elementNi 0.006 5 0.05 (elemental, soluble and insoluble compounds)Pb 0.02 10 0.15 (inorganic compou
20、nds, fume, dust)Rb 0.003 5 No Limit expressed for this elementSr 0.003 5 No Limit expressed for this elementTl 0.02 50 0.1 (soluble compounds)V 0.06 100 0.05 (pentoxide, respirable dust or fume, as V2O5)Zn 0.002 1 10 (oxide dust as ZnO) 5 (oxide fume as ZnO)AThese detection limits represent ideal la
21、boratory conditions; variability due to sampling, digestion, reagents, and sample handling has not been taken into account.BThreshold Limit Values of Airborne Contaminants and Physical Agents adopted by ACGIH for 19941995. Values are elemental concentrations except as noted.TABLE 2 AAS Flame and Ope
22、rating Conditions for Each ElementElement Type of FlameAnalyticalWavelength, nmInterferencesARemedyAReferenceAg Air-C2H2(oxidizing) 328.1 I03,WO42, MnO42,Cl,F B(5,10)AlCN2O-C2H2(reducing) 309.3 ionization, SO42,VB,D,E(4)Ba N2O-C2H2(reducing) 553.6 ionization, large concentration CaD,F(1,4)Bi Air-C2H
23、2(oxidizing) 223.1 none knownCa Air-C2H2(oxidizing) 422.7 ionization (slight) and chemicalionizationD,E(1,4)N2O-C2H2(reducing)Cd Air-C2H2(oxidizing) 228.8 none knownCoCAir-C2H2(oxidizing) 240.7 none knownCrCAir-C2H2(reducing) 357.9 Fe, Ni, oxidation state of CrB(4)Cu Air-C2H2(oxidizing) 324.8 none k
24、nownFe Air-C2H2(oxidizing) 248.3 high Ni concentration, SiB(1,4)In Air-C2H2(oxidizing) 303.9 Al, Mg, Cu, Zn, HxPO4x3 B(11)K Air-C2H2(oxidizing) 766.5 ionizationD(1,4)Li Air-C2H2(oxidizing) 670.8 ionizationD(12)Mg Air-C2H2(oxidizing) 285.2 chemical ionizationD,E(1,4)N2O-C2H2(reducing)Mn Air-C2H2(oxid
25、izing) 279.5 SiNa Air-C2H2(oxidizing) 589.6 ionizationE(1,4)Ni Air-C2H2(oxidizing) 232.0 none knownPb Air-C2H2(oxidizing) 217.0283.3Ca, high concentration SO42 B(9)Rb Air-C2H2(oxidizing) 780.0 ionizationD(1,10)Sr Air-C2H2(oxidizing) 460.7 ionization and chemicalD,E(1,10)N2O-C2H2(reducing) ionization
26、Tl Air-C2H2(oxidizing) 276.8 none knownVa N2O-C2H2(reducing) 318.4 ionizationZn Air-C2H2(oxidizing) 213.9 none knownAHigh concentrations of silicon in the sample can cause an interference for many of the elements in this table and may cause aspiration problems. No matter whatelements are being measu
27、red, if large amounts of silica are extracted from the samples, the samples should be allowed to stand for several hours and centrifuged or filteredto remove the silica.BSamples are periodically analyzed by the method of additions to check for chemical interferences. If interferences are encountered
28、, determinations must be made bythe standard additions method or, if the interferent is identified, it may be added to the standards.CSome compounds of these elements will not be dissolved by the procedure described here. When determining these elements, one should verify that the types ofcompounds
29、suspected in the sample will dissolve using this procedure (see 12.2).DIonization interferences are controlled by bringing all solutions to 1000 ppm cesium (samples and standards).E1000-ppm solution of lanthanum as a releasing agent is added to all samples and standards.FIn the presence of very larg
30、e calcium concentrations (greater than 0.1 %) a molecular absorption from CaOH may be observed. This interference may be overcomeby using background corrections when analyzing for barium.D4185062and local occupational health and air pollution regulations. Theanalysis results can be used for the asse
31、ssment of workplaceexposures to metals in workplace air.6. Interferences6.1 In AAS the occurrence of interferences is less commonthan in many other analytical techniques. Interferences canoccur, however, and when encountered are corrected for asindicated in the following sections. The known interfer
32、encesand correction methods for each metal are indicated in Table 2.The methods of standard additions and background monitoringand correction (2-5) are used to identify the presence of aninterference. Insofar as possible, the matrix of sample andstandard are matched to minimize the possible interfer
33、ence.6.2 Background or nonspecific absorption can occur fromparticles produced in the flame which can scatter light andproduce an apparent absorption signal. Light scattering may beencountered when solutions of high salt content are beinganalyzed. They are most severe when measurements are madeat sh
34、orter wavelengths (for example, below about 250 nm).Background absorption may also occur as the result of theformation of various molecular species which can absorb light.The background absorption can be accounted for by the use ofbackground correction techniques (2).6.3 Spectral interferences are t
35、hose interferences whichresult from an atom different from the one being measured thatabsorbs a portion of the radiation. Such interferences areextremely rare in AAS. In some cases multielement hollowcathode lamps may cause a spectral interference by havingclosely adjacent emission lines from two di
36、fferent elements. Ingeneral, the use of multielement hollow cathode lamps isdiscouraged.6.4 Ionization interference occurs when easily ionized at-oms are being measured. The degree to which such atoms areionized is dependent upon the atomic concentration and thepresence of other easily ionized atoms
37、. This interference can becontrolled by the addition of a high concentration of anothereasily ionized element which will buffer the electron concen-tration in the flame.6.5 Chemical interferences occur in AAS when speciespresent in the sample cause variations in the degree to whichatoms are formed i
38、n the flame, or when different valence statesof a single element have different absorption characteristics.Such interferences may be controlled by adjusting the samplematrix or by the method of standard additions (3). Also, the useof lanthanum as a releasing element minimizes the interferencefrom th
39、e formation of involatile compounds in the flame.Lanthanum forms involatile compounds preferentially with theinterferent so that the analyte stays free.6.6 Physical interferences may result if the physical prop-erties of the samples vary significantly. Changes in viscosityand surface tension can aff
40、ect the sample aspiration rate andthus cause erroneous results. Sample dilution or the method ofstandard additions, or both, are used to correct such interfer-ences. High concentrations of silica in the sample can causeaspiration problems. No matter what elements are beingdetermined, if large amount
41、s of silica are extracted from thesamples, they shall be allowed to stand for several hours andcentrifuged or filtered to remove the silica.6.7 This procedure describes a generalized method forsample preparation, which is applicable to the majority ofsamples. There are some relatively rare chemical
42、forms of afew of the elements listed in Table 1 that will not be dissolvedby this procedure. If such chemical forms are suspected, resultsobtained using this procedure shall be compared with thoseobtained using an appropriately altered dissolution procedure.Alternatively, the results may be compared
43、 with values ob-tained using a technique that does not require dissolving thesample (for example, X-ray fluorescence or neutron activationanalysis).7. Apparatus7.1 Sampling Apparatus:7.1.1 Cellulose Ester or Cellulose Nitrate Membrane Fil-ters, with a pore size of 0.8 m mounted in a 25-mm or 37-mmdi
44、ameter two- or three-piece filter holder.NOTE 2Appropriate workplace air samplers are described in TestMethod D 7035. The background metal content of the filters should beminimal (see Annex A1 of Test Method D 7035).7.1.2 Portable, Battery-Operated Personal SamplingPumps, equipped with a flow-monito
45、ring device (rotameter,critical orifice) or a constant-flow device and capable ofdrawing 15 L/min of air through the 0.8-m filter membranesfor a period of 8 h.7.2 Analytical Apparatus:7.2.1 Atomic Absorption Spectrophotometer, equipped withair/acetylene and nitrous oxide/acetylene burner heads.7.2.2
46、 Hollow Cathode or Electrodeless Discharge Lamp, foreach element to be determined.7.2.3 Deuterium Continuum Lamp.7.2.4 Compressed AirAppropriate pressure reducingregulator with base connections (see instrument manufacturersinstructions).7.2.5 Acetylene Gas and RegulatorA cylinder of acety-lene equip
47、ped with a two-gage, two-stage pressure-reducingregulator with hose connections. (See instrument manufacturerinstructions.)7.2.6 Nitrous Oxide Gas and RegulatorA cylinder ofnitrous oxide equipped with a two-gage, two-stage pressure-reducing regulator and hose connections. Heat tape with thetemperatu
48、re controlled by a rheostat may be wound around thesecond stage regulator and hose connection to preventfreeze-up of the line. (See instrument manufacturer instruc-tions.)7.2.7 Beakers, Phillips or Griffin, 125-mL, borosilicateglass.7.2.8 Centrifuge Tubes, 15-mL, graduated, borosilicateglass.7.2.9 M
49、iscellaneous Borosilicate Glassware (Pipets andVolumetric Flasks)All pipets and volumetric flasks shall becalibrated Class A volumetric glassware.8. Reagents8.1 Purity of ReagentsReagent 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,D4185063where such specifications are available.4Other grades may beused provided that it can be demonstrated that they are ofsufficiently high purity to permit the
