ASTM D4185-06(2011)
(Practice)Standard Practice for Measurement of Metals in Workplace Atmospheres by Flame Atomic Absorption Spectrophotometry
Standard Practice for Measurement of Metals in Workplace Atmospheres by Flame Atomic Absorption Spectrophotometry
SIGNIFICANCE AND USE
The health of workers in many industries is at risk through exposure by inhalation to toxic metals. Industrial hygienists and other public health professionals need to determine the effectiveness of measures taken to control workers' exposures, and this is generally achieved by making workplace air measurements. Exposure to some metal-containing particles has been demonstrated to cause dermatitis, skin ulcers, eye problems, chemical pneumonitis, and other physical disorders (1).
AAS is capable of quantitatively determining most metals in air samples at the levels required by federal, state, and local occupational health and air pollution regulations. The analysis results can be used for the assessment of workplace exposures to metals in workplace air.
SCOPE
1.1 This practice covers the collection, dissolution, and determination of trace metals in workplace atmospheres, by flame atomic absorption spectrophotometry.
1.2 The sensitivity, detection limit, and optimum working concentration for 23 metals are given in Table 1.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. (Specific safety precautionary statements are given in Section 9.)
TABLE 1 AAS Instrumental Detection Limits and Optimum Working Concentration for 23 Metals ElementDetection Limit, μg/mL
(approximately three times
standard deviation of blank)AOptimum Linear Range
Upper Limit,
μg/mLTLV, mg/m3 (elements, compound classes, and oxides)B Ag0.00150.1 (metal) 0.01 (soluble compounds as Ag) Al0.04502.0 (soluble salts and alkyls not otherwise classified) 10 (metal dust and oxide) 5 (pyro powder and welding fume) Ba0.01100.5 (soluble compounds) Bi0.0310No Limit expressed for this element Ca0.00212 (oxide as CaO) Cd0.000810.01 (elemental and compoundstotal dust) 0.002 (elemental compoundsrespirable fraction) Co0.00950.02 (elemental and inorganic) 0.1 (carbonyl and hydrocarbonyl) Cr0.00350.5 (metal and Cr III compounds) 0.05 (water soluble Cr VI compounds) 0.01 (insoluble Cr VI compounds) Cu0.00250.2 (fume) 1 (dust and mists as Cu) Fe0.00555 (iron oxide fume) 5 (soluble salts as Fe) In0.03500.1 (metal and compounds) K0.0031No Limit expressed for this element Li0.00081No Limit expressed for this element Mg0.00020.510 (as MgO fume) Mn0.00250.2 (elemental and inorganic compounds) Na0.00030.5No Limit expressed for this element Ni0.00650.05 (elemental, soluble and insoluble compounds) Pb0.02100.15 (inorganic compounds, fume, dust) Rb0.0035No Limit expressed for this element Sr0.0035No Limit expressed for this element Tl0.02500.1 (soluble compounds) V0.061000.05 (pentoxide, respirable dust or fume, as V2O5) Zn0.002110 (oxide dust as ZnO) 5 (oxide fume as ZnO)
A These detection limits represent ideal laboratory conditions; variability due to sampling, digestion, reagents, and sample handling has not been taken into account.
B Threshold Limit Values of Airborne Contaminants and Physical Agents adopted by ACGIH for 1994–1995. Values are elemental concentrations except as noted.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D4185 − 06 (Reapproved 2011)
Standard Practice for
Measurement of Metals in Workplace Atmospheres by
Flame Atomic Absorption Spectrophotometry
This standard is issued under the fixed designation D4185; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3.2.1 blank signal—that signal which results from all added
reagents and a clean membrane filter prepared and analyzed
1.1 This practice covers the collection, dissolution, and
exactly in the same way as the samples.
determination of trace metals in workplace atmospheres, by
3.2.2 instrumental detection limit—that concentration of a
flame atomic absorption spectrophotometry.
givenelementwhichproducesasignalthreetimesthestandard
1.2 The sensitivity, detection limit, and optimum working
deviation of the reagent blank signal.
concentration for 23 metals are given in Table 1.
3.2.3 working range for an analytical precision better than
1.3 This standard does not purport to address all of the
3%—therangeofsampleconcentrationsthatwillabsorb10to
safety concerns, if any, associated with its use. It is the
70 % of the incident radiation (0.05 to 0.52 absorbance units).
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica- NOTE 1—Values for instrumental detection limit may vary from
instrument to instrument.
bility of regulatory limitations prior to use. (Specific safety
precautionary statements are given in Section 9.)
4. Summary of Practice
4.1 Workplaceairsamplesarecollectedonmembranefilters
2. Referenced Documents
2 and treated with nitric acid to destroy the organic matrix and to
2.1 ASTM Standards:
dissolve the metals present. The analysis is subsequently made
D1193 Specification for Reagent Water
by flame atomic absorption spectrophotometry (AAS).
D1356 Terminology Relating to Sampling and Analysis of
4.2 Samples and standards are aspirated into an appropriate
Atmospheres
D1357 Practice for Planning the Sampling of the Ambient AAS flame. A hollow cathode or electrodeless discharge lamp
for the metal being determined provides a source of character-
Atmosphere
D3195 Practice for Rotameter Calibration istic radiation energy for that particular metal. The absorption
of this characteristic energy by the atoms of interest in the
D5337 Practice for Flow RateAdjustment of Personal Sam-
pling Pumps flame is related to the concentration of the metal in the
D7035 Test Method for Determination of Metals and Met- aspirated sample. The flame and operating conditions for each
alloids in Airborne Particulate Matter by Inductively element are listed in Table 2.
Coupled Plasma Atomic Emission Spectrometry (ICP-
5. Significance and Use
AES)
5.1 The health of workers in many industries is at risk
3. Terminology
through exposure by inhalation to toxic metals. Industrial
hygienists and other public health professionals need to deter-
3.1 Definitions—For definitions of terms used in this
mine the effectiveness of measures taken to control workers’
practice, refer to Terminology D1356.
exposures, and this is generally achieved by making workplace
3.2 Definitions of Terms Specific to This Standard:
airmeasurements.Exposuretosomemetal-containingparticles
has been demonstrated to cause dermatitis, skin ulcers, eye
problems, chemical pneumonitis, and other physical disorders
This practice is under the jurisdiction ofASTM Committee D22 on Air Quality
(1).
and is the direct responsibility of Subcommittee D22.04 on WorkplaceAir Quality.
Current edition approved Oct. 1, 2011. Published October 2011. Originally
5.2 AAS is capable of quantitatively determining most
approved in 1990. Last previous edition approved in 2006 as D4185 - 06. DOI:
metals in air samples at the levels required by federal, state,
10.1520/D4185-06R11.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on Boldface numbers in parentheses refer to the list of references appended to
the ASTM website. these methods.
Copyright ©ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA19428-2959. United States
D4185 − 06 (2011)
TABLE 1 AAS Instrumental Detection Limits and Optimum Working Concentration for 23 Metals
Detection Limit, µg/mL Optimum Linear Range
3 B
Element (approximately three times Upper Limit, TLV, mg/m (elements, compound classes, and oxides)
A
standard deviation of blank) µg/mL
Ag 0.001 5 0.1 (metal) 0.01 (soluble compounds asAg)
Al 0.04 50 2.0 (soluble salts and alkyls not otherwise classified) 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 element
Ca 0.002 1 2 (oxide as CaO)
Cd 0.0008 1 0.01 (elemental and compounds—total dust)
0.002 (elemental compounds—respirable fraction)
Co 0.009 5 0.02 (elemental and inorganic) 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 Limit expressed for this element
Li 0.0008 1 No Limit expressed for this element
Mg 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 element
Ni 0.006 5 0.05 (elemental, soluble and insoluble compounds)
Pb 0.02 10 0.15 (inorganic compounds, fume, dust)
Rb 0.003 5 No Limit expressed for this element
Sr 0.003 5 No Limit expressed for this element
Tl 0.02 50 0.1 (soluble compounds)
V 0.06 100 0.05 (pentoxide, respirable dust or fume, as V O )
2 5
Zn 0.002 1 10 (oxide dust as ZnO) 5 (oxide fume as ZnO)
A
These detection limits represent ideal laboratory conditions; variability due to sampling, digestion, reagents, and sample handling has not been taken into account.
B
Threshold Limit Values ofAirborne Contaminants and PhysicalAgents adopted byACGIH for 1994–1995. Values are elemental concentrations except as noted.
andlocaloccupationalhealthandairpollutionregulations.The closely adjacent emission lines from two different elements. In
analysis results can be used for the assessment of workplace
general, the use of multielement hollow cathode lamps is
exposures to metals in workplace air. discouraged.
6.4 Ionization interference occurs when easily ionized at-
6. Interferences
oms are being measured. The degree to which such atoms are
6.1 In AAS the occurrence of interferences is less common
ionized is dependent upon the atomic concentration and the
than in many other analytical techniques. Interferences can
presenceofothereasilyionizedatoms.Thisinterferencecanbe
occur, however, and when encountered are corrected for as
controlled by the addition of a high concentration of another
indicated in the following sections. The known interferences
easily ionized element which will buffer the electron concen-
and correction methods for each metal are indicated in Table 2.
tration in the flame.
The methods of standard additions and background monitoring
6.5 Chemical interferences occur in AAS when species
and correction (2-5) are used to identify the presence of an
present in the sample cause variations in the degree to which
interference. Insofar as possible, the matrix of sample and
atoms are formed in the flame, or when different valence states
standard are matched to minimize the possible interference.
of a single element have different absorption characteristics.
6.2 Background or nonspecific absorption can occur from
Such interferences may be controlled by adjusting the sample
particles produced in the flame which can scatter light and
matrixorbythemethodofstandardadditions (3).Also,theuse
produce an apparent absorption signal. Light scattering may be
oflanthanumasareleasingelementminimizestheinterference
encountered when solutions of high salt content are being
from the formation of involatile compounds in the flame.
analyzed. They are most severe when measurements are made
Lanthanum forms involatile compounds preferentially with the
at shorter wavelengths (for example, below about 250 nm).
interferent so that the analyte stays free.
Background absorption may also occur as the result of the
formation of various molecular species which can absorb light.
6.6 Physical interferences may result if the physical prop-
The background absorption can be accounted for by the use of
erties of the samples vary significantly. Changes in viscosity
background correction techniques (2).
and surface tension can affect the sample aspiration rate and
thus cause erroneous results. Sample dilution or the method of
6.3 Spectral interferences are those interferences which
standard additions, or both, are used to correct such interfer-
result from an atom different from the one being measured that
absorbs a portion of the radiation. Such interferences are ences. High concentrations of silica in the sample can cause
aspiration problems. No matter what elements are being
extremely rare in AAS. In some cases multielement hollow
cathode lamps may cause a spectral interference by having determined, if large amounts of silica are extracted from the
D4185 − 06 (2011)
TABLE 2 AAS Flame and Operating Conditions for Each Element
Analytical
A A
Element Type of Flame Interferences Remedy Reference
Wavelength, nm
− −2 −2 − − B
Ag Air-C H (oxidizing) 328.1 I0 ,WO , MnO ,Cl ,F (5,10)
2 2 3 4 4
C −2 B,D,E
Al N O-C H (reducing) 309.3 ionization, SO ,V (4)
2 2 2 4
D,F
Ba N O-C H (reducing) 553.6 ionization, large concentration Ca (1,4)
2 2 2
Bi Air-C H (oxidizing) 223.1 none known
2 2
D,E
Ca Air-C H (oxidizing) 422.7 ionization (slight) and chemical (1,4)
2 2
ionization
N O-C H (reducing)
2 2 2
Cd Air-C H (oxidizing) 228.8 none known
2 2
C
Co Air-C H (oxidizing) 240.7 none known
2 2
C B
Cr Air-C H (reducing) 357.9 Fe, Ni, oxidation state of Cr (4)
2 2
Cu Air-C H (oxidizing) 324.8 none known
2 2
B
Fe Air-C H (oxidizing) 248.3 high Ni concentration, Si (1,4)
2 2
x−3 B
In Air-C H (oxidizing) 303.9 Al, Mg, Cu, Zn, H PO (11)
2 2 x 4
D
K Air-C H (oxidizing) 766.5 ionization (1,4)
2 2
D
Li Air-C H (oxidizing) 670.8 ionization (12)
2 2
D,E
Mg Air-C H (oxidizing) 285.2 chemical ionization (1,4)
2 2
N O-C H (reducing)
2 2 2
Mn Air-C H (oxidizing) 279.5 Si
2 2
E
Na Air-C H (oxidizing) 589.6 ionization (1,4)
2 2
Ni Air-C H (oxidizing) 232.0 none known
2 2
−2 B
Pb Air-C H (oxidizing) 217.0 Ca, high concentration SO (9)
2 2 4
283.3
D
Rb Air-C H (oxidizing) 780.0 ionization (1,10)
2 2
D,E
Sr Air-C H (oxidizing) 460.7 ionization and chemical (1,10)
2 2
N O-C H (reducing) ionization
2 2 2
Tl Air-C H (oxidizing) 276.8 none known
2 2
Va N O-C H (reducing) 318.4 ionization
2 2 2
Zn Air-C H (oxidizing) 213.9 none known
2 2
A
Highconcentrationsofsiliconinthesamplecancauseaninterferenceformanyoftheelementsinthistableandmaycauseaspirationproblems.Nomatterwhatelements
are being measured, if large amounts of silica are extracted from the samples, the samples should be allowed to stand for several hours and centrifuged or filtered to
remove the silica.
B
Samples are periodically analyzed by the method of additions to check for chemical interferences. If interferences are encountered, determinations must be made by
the standard additions method or, if the interferent is identified, it may be added to the standards.
C
Some compounds of these elements will not be dissolved by the procedure described here. When determining these elements, one should verify that the types of
compounds suspected in the sample will dissolve using this procedure (see 12.2).
D
Ionization interferences are controlled by bringing all solutions to 1000 ppm cesium (samples and standards).
E
1000-ppm solution of lanthanum as a releasing agent is added to all samples and standards.
F
In the presence of very large calcium concentrations (greater than 0.1%) a molecular absorption from CaOH may be observed.This interference may be overcome by
using background corrections when analyzing for barium.
samples, they shall be allowed to stand for several hours and 7.1.2 Portable, Battery-Operated Personal Sampling
centrifuged or filtered to remove the silica. Pumps, equipped with a flow-monitoring device (rotameter,
critical orifice) or a constant-flow device and capable of
6.7 This procedure describes a generalized method for
drawing 1–5 L/min of air through the 0.8-µm filter membranes
sample preparation, which is applicable to the majority of
for a period of 8 h.
samples. There are some relatively rare chemical forms of a
few of the elements listed in Table 1 that will not be dissolved 7.2 Analytical Apparatus:
bythisprocedure.Ifsuchchemicalformsaresuspected,results
7.2.1 Atomic Absorption Spectrophotometer, equipped with
obtained using this procedure shall be compared with those
air/acetylene and nitrous oxide/acetylene burner heads.
obtained using an appropriately altered dissolution procedure.
7.2.2 HollowCathodeorElectrodelessDischargeLamp,for
Alternatively, the results may be compared with values ob-
each element to be determined.
tained using a technique that does not require dissolving the
7.2.3 Deuterium Continuum Lamp.
sample (for example, X-ray fluorescence or neutron activation
7.2.4 CompressedAir—Appropriatepressurereducingregu-
analysis).
lator with base connections (see instrument manufacturer’s
instructions).
7. Apparatus
7.2.5 Acetylene Gas and Regulator—A cylinder of acety-
7.1 Sampling Apparatus:
lene equipped with a two-gage, two-stage pressure-reducing
7.1.1 Cellulose Ester or Cellulose Nitrate Membrane regulator with hose connections. (See instrument manufacturer
Filters, with a pore size of 0.8 µm mounted in a 25-mm or
instructions.)
37-mm diameter two- or three-piece filter holder.
7.2.6 Nitrous Oxide Gas and Regulator—A cylinder of
nitrous oxide equipped with a two-gage, two-stage pressure-
NOTE 2—Appropriate workplace air samplers are described in Test
reducing regulator and hose connections. Heat tape with the
Method D7035. The background metal content of the filters should be
minimal (see Annex A1 of Test Method D7035). temperature controlled by a rheostat may be wound around the
D4185 − 06 (2011)
second stage regulator and hose connection to prevent 8.5.6 Stock Chromium Solution—Dissolve 3.735 g of po
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