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Metal & Metalloid Particulates In Workplace Atmospheres (Atomic Absorption)
[160 KB
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25 pages]
Related Information: Chemical Sampling -
Cadmium,
Copper Fume (as Cu),
Iron Oxide Fume,
Lead, Inorganic (as Pb),
Magnesium,
Manganese Fume (as Mn),
Nickel, Soluble Compounds (as Ni),
Potassium Hydroxide,
Sodium Hydroxide,
Zinc
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Method no.: |
ID-121 |
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Control no.: |
T-ID121-FV-02-0202M |
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Matrix: |
Air, Wipe, or Bulk |
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OSHA Permissible Exposure
Limits: |
See Table 1 |
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Collection Procedure: |
Personal air samples are collected on
mixed-cellulose ester filters using a calibrated sampling pump. Wipe or
bulk samples are collected using grab sampling techniques. |
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Recommended Sampling Rate: |
2 L/min |
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Recommended Air Volumes: |
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Time Weighted Average Samples: |
480 to 960 L |
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Short-Term Exposure Limit Samples: |
30 L |
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Ceiling Samples: |
10 L* |
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Analytical Procedure: |
Samples are desorbed or digested using
water extractions or mineral acid digestions. Elemental analysis of the
prepared sample solutions is performed by atomic absorption or emission
spectroscopy. |
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Detection Limits: |
See Table 2 |
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Precision and Accuracy: |
See Table 3 |
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Method Classification: |
Validated Analytical Method |
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Date (Date Revised): |
1985 (February 2002) |
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* Alternate air volumes may
be necessary to achieve good analytical sensitivity. |
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Commercial
manufacturers and products mentioned in this method are for descriptive
use only and do not constitute endorsements by USDOL-OSHA. Similar
products from other sources can be substituted.
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Division of Physical Measurements and Inorganic Analyses
OSHA Technical Center
Sandy City, Utah |
1. Introduction
This method can determine the amount of specific metal and metalloid particulates in the workplace
atmosphere. The airborne particulates are collected on filters using calibrated sampling pumps. These
samples are then analyzed using flame atomic absorption or emission spectrometry. This method can also
determine specific metals and metalloids contained in wipe and bulk samples. The identification and
quantification of the particulate is directly determined as the element. The elements are:
Aluminum (Al) |
Gold (Au) |
Potassium (K) |
Antimony (Sb) |
Hafnium (Hf) |
Selenium (Se) |
Barium (Ba) |
Indium (In) |
Silver (Ag) |
Bismuth (Bi) |
Iron (Fe) |
Sodium (Na) |
Cadmium (Cd) |
Lead (Pb) |
Tellurium (Te) |
Calcium (Ca) |
Lithium (Li) |
Thallium (Tl) |
Cesium (Cs) |
Magnesium (Mg) |
Tin (Sn) |
Chromium (Cr) |
Manganese (Mn) |
Titanium (Ti) |
Cobalt (Co) |
Molybdenum (Mo) |
Yttrium (Y) |
Copper (Cu) |
Nickel (Ni) |
Zinc (Zn) |
|
Platinum (Pt) |
Zirconium (Zr) |
For some analytes, there are alternate methods or procedures which may be more sensitive, accurate, or
specific. When a separate OSHA method or procedure exists, that method shall take precedence over this
method unless special circumstances render it inapplicable. Elements or compounds having alternate
methods or stopgap procedures are:
Element or Compound |
OSHA Method No. |
Aluminum oxide |
ID-198SG or ID-109SG |
Barium sulfate |
ID-204 |
Cadmium |
ID-189 |
Hexavalent chromium (chromic
acid/chromates) |
ID-215 (Version 2) |
Ferrovanadium |
ID-125G |
Vapors (i.e. Ni(CO)4, H2Se, TeF6, C5H4Mn(CO)3] |
In-House Methods |
Organic tin compounds |
ID-102SG |
Platinum (soluble) |
ID-130SG |
Selenium |
ID-133SG |
Solders |
ID-206 |
Stibine |
NIOSH 6008, In House |
Tetraethyl lead and tetramethyl lead |
In-House Method |
Titanium dioxide |
ID-204 |
Welding fumes |
ID-125G |
Zinc oxide |
ID-143 |
Depending on advances in technology or changes in exposure limits, substances may be added or
deleted from the above lists.
1.1 History
Air and wipe samples containing metal and metalloid particulate have always been analyzed at
the OSHA Salt Lake City Analytical Laboratory using atomic absorption or emission
spectrometry.8.1 Constituents in bulk samples have been determined semi-quantitatively
using this technique.
1.2 Principle
Air samples of the workplace are taken using calibrated sampling pumps with cassettes
containing either mixed cellulose ester (MCE) or polyvinyl chloride (PVC) filters. These
samples are prepared in the laboratory using concentrated (concd) acids or extracted with
deionized water if a soluble fraction is required. The sample solution is diluted to a known volume after any necessary matrix
modifiers are added. The sample is then aspirated into the flame
of an atomic absorption or emission spectrophotometer (AAS or AES) and the molecules in the
sample solution are subjected to the following processes:
1) nebulization
2) desolvation
3) liquefaction
4) vaporization
5) atomization
6) excitation (atoms converted from "ground" to excited state)
7) ionization
The absorption or emission of light occurring during processes 5 and 6 is then measured at the
characteristic wavelength for the element of interest.
For absorption, a hollow cathode lamp or an electrodeless discharge lamp (EDL) is used as the
light source. A double beam spectrophotometer is normally used where the lamp radiation
alternately passes through and around a flame into which the sample is being aspirated. The
sample is atomized and the metal or metalloid atoms absorb light from the source at their
characteristic wavelengths. This absorption is proportional to the concentration of the element
present in the sample solution. A monochromator isolates the characteristic radiation of the
element being analyzed. A photosensitive device then measures the intensity of the transmitted
radiation from the two light paths to determine the amount of absorbance occurring in the flame.
For emission, a light source is not used. The sample is introduced into the flame, atomized and
excited, and then the light emission from excitation is isolated and measured. The intensity of
the light emitted is proportional to the concentration of the element present.
The following flames are used in this method for absorption or emission:
a) Air/Acetylene mixture (Air/C2H2)
b) Nitrous oxide/Acetylene mixture (N2O/C2H2)
c) Air/Hydrogen mixture (Air/H2)
The use of a specific flame is dependent on the respective element's analytical stability,
sensitivity, and interferences.
1.3 Advantages and Disadvantages
1.3.1 This analytical method is specific for the element to be determined and does not
distinguish different compounds. When an analysis for a compound is requested, an
elemental analysis is performed on the sample. A gravimetric factor is then applied
to calculate the compound value (Note: For some compounds, additional analytical
procedures (i.e. ion chromatography or X-ray diffraction) can be used to confirm the
presence of the particular compound.
1.3.2 The analysis will also not differentiate between different particle size ranges, such as
dusts and fumes.
1.3.3 Metallic analytes having Permissible Exposure Limits (PELs) designated as the
soluble form (i.e., iron soluble salts, nickel, etc.) can be analyzed using this method.
Samples for soluble analytes are extracted with deionized water and an elemental
analysis is performed on the extract.
1.3.4 Some compounds may not dissolve using the digestion procedures described herein.
In these cases, an alternative digestion method should be used.
1.3.5. Several elements can be determined from the same filter sample using this method;
however, digestion procedures may solubilize only certain metals. If a combination
of metals is requested on the same filter, all of the metals must be soluble in the
digestion procedure used.
1.3.6 The equipment used is inexpensive and does not require specialized training.
1.4 Use of Metal and Metalloid Compounds in Industry
Metals, their alloys, and compounds are used in a wide variety of industries. In certain
operations (e.g., welding, smelting, grinding, etc.), particulate matter containing metals and their
compounds may be released into the workplace atmosphere. These substances pose a potential
health hazard to workers exposed to them.8.2-8.4 Further documentation regarding industrial
use, toxicity, and physical properties may be found in NIOSH criteria documents for the
particular substance.
2. Analytical Range and Sensitivity
This method uses detection limit, linearity, and sensitivity terms which are characteristic of atomic
absorption. These terms are further defined in Appendix A. Any detection limits, linear ranges, and
sensitivities mentioned in this method are for analyses using the primary analytical wavelength, a flow
spoiler, an Air/C2H2 flame, and a hollow cathode lamp unless otherwise noted.
2.1 The qualitative detection limits listed in Table 2 were taken from reference 8.5. The analytical
detection limits8.1 listed were determined from routine laboratory analyses using the
definition listed in Appendix A. These limits are approximate since they are dependent on
instrument performance and optimization, sample characteristics, and the range of standards
analyzed.
2.2 The upper linear range for each element is also given in Table 2. These ranges were taken from
reference 8.6. Instrument response is linear to greater concentrations if an alternate wavelength
is used; however, the detection limit may also increase. Samples can be diluted to bring the
concentration of the element(s) within the linear range. The upper linear range for most elements
is usually found near 0.25 to 0.30 absorbance units (ABS).
2.3 The sensitivity for each element is also listed in Table 2. These values are for a nebulizer which
has been optimized to give an ABS of 0.25 for an aqueous solution containing 5 µg/mL
Cu.8.6 The actual sensitivity obtained will depend on the particular instrument and flame used,
the sample matrix, and instrument operating parameters.
3. Method Performance - Precision and Recoveries
Listed in Table 3 are data compiled from quality control (QC) samples which were spiked with aqueous
solutions of various analytes and then analyzed in single blind tests. Each analyte was spiked onto an
individual MCE filter, allowed to dry, and then prepared and analyzed along with survey samples
previously taken by industrial hygienists. These samples were analyzed from 1986 to 1989. Due to the
limited number of survey samples received for a few substances, QC samples were not prepared and
analyzed for all analytes included in this method.
4. Interferences
Interferences occur at the analytical level and can be characterized as chemical, matrix, ionization,
spectral, or as background absorption.
4.1 Chemical or condensed phase interferences occur when the element of interest combines with
another species in the flame, thus altering the number of atoms available for emission or
absorption. This can result in either a positive or negative bias (usually negative) in the results
obtained. Chemical interferences can be controlled by using a hotter flame, or by the addition of
a releasing agent which inhibits the reaction between the metal and the interfering species.
4.2 Matrix interferences occur when the physical characteristics (viscosity, surface tension, etc.) of
the sample and standard solutions differ considerably. This may occur when samples contain
large amounts of dissolved salts or acid, when different solvents are used for samples and
standards, or when the temperatures of samples and standards are appreciably different. To control this, samples and standards must be matrix
matched, or the sample must be diluted until any
matrix effect becomes insignificant.
4.3 Ionization interferences occur when the flame temperature is sufficiently high to ionize the atoms
of interest. This changes the absorption spectrum of the analyte and effectively removes atoms
from the flame, causing a loss of sensitivity. Ionization interferences are controlled by adding
large amounts (usually >0.1%) of an easily ionized metal such as Na, K, Cs, or rubidium (Rb).
The excess electrons released in the flame greatly reduces the degree of ionization of the metal
being determined.
4.4 Spectral interferences occur when an element other than the one analyzed absorbs at the same
wavelength. This causes a positive bias in the results obtained when the interfering element is
present in the samples. In this case, an alternate line should be used. Spectral interferences also
occur when a multielement hollow cathode lamp is used which contains elements with absorbing
wavelengths close to one another and the analytical slit width used is wide enough to allow the
wavelengths of more than one element to pass. If the sample contains two or more of these
elements, a positive bias will occur. To resolve this, a single element lamp, an alternate
wavelength, or in certain cases, a narrower slit width can be used.
4.5 Background absorption interferences include flame absorption, molecular absorption, and light
scattering:
a) Flame absorption is most severe below 250 nm. This absorption can be controlled by careful
optimization of fuel and oxidant flow rates. Other mechanisms of control are: Use of
flames which are more transparent at these wavelengths (i.e., Air/H2 or argon/hydrogen
flames), or deuterium arc background correction (DABC).
b) Molecular absorption is controlled by using hotter flames to break down molecular species
or by DABC.
c) Light scattering occurs at shorter wavelengths when samples have a large salt content; this is
controlled using DABC.
4.6 Large amounts of silicates or other particulates may interfere and may also
cause aspiration problems.8.7 If present, they should be removed by filtration. The particulate should then be
re-digested and analyzed to ensure the analyte(s) of interest have been completely extracted.
4.7 This analytical method is normally not compound-specific. Compounds are only determined as
the element, and a significant positive bias can occur when any sample has additional analytes
containing the same element. Other analytical procedures may be necessary to identify a
specific compound. An assessment of the industrial operation sampled may also provide
information regarding the potential existence of other analytes that could cause a positive bias.
4.8 Potential interferences for several of the elements determined by this method are listed in Appendix B.
5. Sampling
5.1 Equipment - Air Filter Samples
5.1.1 Mixed cellulose ester (MCE) filters (0.8 µm pore size), cellulose backup pads, and
cassettes, 37-mm diameter (part no. MAWP 037 A0, Millipore Corp., Bedford, MA).
Filters and cassettes having a 25-mm diameter can also be used.
5.1.2 Gel bands (Omega Specialty Instrument Co., Chelmsford, MA) for sealing cassettes.
5.1.3 Sampling pumps capable of sampling at 2 liters per minute (L/min).
5.1.4 Assorted flexible tubing.
5.1.5 Stopwatch and bubble tube or meter for pump calibration.
5.2 Equipment - Wipe Samples
5.2.1 Smear tabs (part no. 225-24, SKC Inc., Eighty Four, PA), or wipe filters (Whatman
no. 41 or no. 42 filters, Whatman Labsales Inc., Hillsboro, OR).
5.2.2 Deionized water.
5.2.3 Scintillation vials, 20-mL (part no. 74515 or 58515, Kimble, Div. of Owens-Illinois
Inc., Toledo, OH) with polypropylene or Teflon cap liners. Metal cap liners should
not be used.
5.3 Equipment - Bulk Samples
5.3.1 High-volume sampling pump with appropriate sized MCE collection filters.
5.3.2 Scintillation vials, 20-mL (same as Section 5.2.3).
5.4 Sampling Procedure - Air Filter Samples
5.4.1 Place a MCE filter and a cellulose backup pad in each two- or three-piece cassette.
Seal each cassette with a gel band.
5.4.2 Calibrate each personal sampling pump with a prepared cassette in-line to
approximately 2 L/min.
5.4.3 Attach prepared cassettes to calibrated sampling pumps (the backup pad should face the
pump) and place in appropriate positions on the employee or workplace area.
5.4.4 Collect the samples at approximately 2 L/min for the recommended sampling times
(unless otherwise noted):
Time Weighted Average Samples | 240 to 480 min |
Short-Term Exposure Limit Samples | 15 min |
Ceiling Samples | 5 min* |
The analytical sensitivity of a specific analyte may dictate the use of a different sampling time.
* When determining compliance with the Ceiling PEL for sodium hydroxide, take 15-min samples.
5.4.5 Place plastic end caps on each cassette after sampling. Attach an OSHA-21 seal
around each cassette in such a way as to secure the end caps.
5.5 Sampling Procedure - Wipe Samples
Certain analytes may have a skin designation (See Table 1).
5.5.1 Wear clean, impervious, disposable gloves when taking each wipe sample.
5.5.2 Moisten the wipe filters with deionized water prior to use.
5.5.3 If possible, wipe a surface area covering 100 cm².
5.5.4 Fold the wipe sample with the exposed side in.
5.5.5 Transfer the wipe sample into a 20-mL scintillation vial and seal with vinyl or
electrical tape. Securely wrap an OSHA-21 seal length-wise from vial top to bottom.
5.6 Sampling Procedure - Bulk Samples
5.6.1 In order of laboratory preference, bulk samples may be one of the following:
1) a high-volume (>1,000 L) filter sample of the workplace area,
2) a representative settled dust (rafter) sample,
3) a sample of the bulk material in the workplace.
5.6.2 If possible, transfer the bulk material or filter into a 20-mL scintillation vial and seal
with vinyl or electrical tape. Securely wrap an OSHA-21 seal length-wise from vial
top to bottom.
5.7 Shipment
5.7.1 Submit at least one blank sample with each set of air or wipe samples. Blank filter
samples should be handled in the same manner as other samples, except that an air or
wipe sample is not taken.
5.7.2 The type of bulk sample should be stated on the OSHA 91A and cross-referenced to
the appropriate air sample(s). Bulk samples should be shipped with Material Safety
Data Sheets (if available) and should be sent separately from air samples. Check
current mailing restrictions and ship bulks to the laboratory by an appropriate
method.
5.7.3 Send all samples to the laboratory with the OSHA 91A paperwork requesting the
specific analyte(s) of interest. If analysis of a mixture of different elements or
compounds is necessary, contact the lab to ascertain which analytes can be analyzed
together.
6. Analysis
6.1 Safety Precautions
6.1.1 Care should be exercised when handling any acidic solutions. Acid solution contact
with work surfaces should be avoided. If any acid contacts the eyes, skin, or clothes,
flush the area immediately with copious amounts of water. Medical treatment may
be necessary.
6.1.2 All work with concd acids is potentially hazardous. Always wear safety glasses and
protective clothing. Prepare all mixtures, samples, or dilutions in an exhaust hood.
To avoid exposure to acid vapors, do not remove any beakers from the hoods until
they have returned to room temperature.
6.1.3 Extra care should be used when handling perchloric acid (HClO4). Perchloric acid
should only be used in a hood that has been approved for HClO4 use. In this hood:
a) Organic reagents should not be used or stored near HClO4.
b) A water washdown system for the ducts and work surface must be installed and
periodically used.
c) Precautions should be taken to ensure that explosions or spontaneous ignition of
sample material from HClO4 is prevented.
Working with HClO4 is very hazardous. Be sure to wear safety glasses, a labcoat,
and gloves. Always add nitric acid (HNO3) with HClO4. When digesting backup
pads or other samples with HClO4, watch them carefully since there is a chance they
could ignite. Always keep HNO3 nearby when using HClO4. In the event of sample
media ignition, quickly douse the sample with a small portion of HNO3.
6.1.4 Care should be exercised when using laboratory glassware. Chipped pipettes,
volumetric flasks, beakers, or any glassware with sharp edges exposed should not be
used.
6.1.5 Pipetting is always performed using an automatic pipet or pipette bulb, never by
mouth.
6.1.6 Before using any instrument, the operator should consult the Standard
Operating Procedure (SOP)8.8 and any instrument manuals.
6.1.7 Since metallic elements and other toxic substances are vaporized during flame
operation, it is imperative that an exhaust hood is installed and used directly above
the burner chamber of the spectrometer. Always ensure the exhaust system is
operating before proceeding with the analysis.
6.2 Equipment
6.2.1 Atomic absorption spectrophotometer consisting of a(an):
Nebulizer and burner head.
Pressure-regulating devices capable of maintaining constant oxidant and fuel
pressures.
Optical system capable of isolating the desired wavelength of radiation.
Adjustable slit.
Light measuring and amplifying device.
Display, strip chart, or computer interface for indicating the amount of absorbed or
emitted radiation.
Deuterium Arc Background Corrector. This is usually required for determinations
at short (<250 nm) wavelengths.
Light source for absorption:
a) Hollow cathode lamp for the specific element or multielement (Note: Please
see specific limitations of multielement lamps in Appendix B)
b) Electrodeless Discharge Lamp (EDL) for the specific element. This type
of lamp may provide better sensitivity and detection limits for some
elements, especially Se, Sn, and Sb. If used, a separate EDL power supply
is usually necessary.
6.2.2 Oxidant: Compressed, filtered air free from water, oils and other contaminants.
6.2.3 Nitrous oxide (N2O).
6.2.4 Fuel (Use flash arrestors when using flammable gases. Consult with the
manufacturer for appropriate use.):
a) Acetylene, commercially available acetylene dissolved in acetone.
CAUTION: Do not use grades of acetylene that contain solvents other than acetone. These
solvents may damage PVC tubing in some instruments. Do not use acetylene
when the tank pressure drops below 520 kPa (75 psi).
b) Hydrogen is used as the fuel in the determination of certain elements.
6.2.5 Pressure regulators, Two-stage.
6.2.6 Flash arrestors (model 6103, Matheson Gas Products, East Rutherford, NJ).
6.2.7 Glassware
a) Conical beakers, 125- and 250-mL
b) Volumetric flasks, Class A: 10-, 25-, 50- and 100-mL
c) Pipettes, Class A: Assorted sizes
6.2.8 Forceps.
6.2.9 Exhaust hood and hotplate, or microwave digestion system (model no. MDS-81,
CEM Corp., Matthews, NC).
6.2.10 Filtering apparatus consisting of MCE filters, 0.45-µm pore size, 47-mm diameter
(cat. no. HAWP 047 00, Millipore Corp., Bedford, MA) and filtering apparatus (cat.
no. XX15 047 00, Millipore).
6.2.11 Analytical balance (0.01 mg).
6.3 Reagents (All chemicals should be reagent grade or better. Many of the chemicals listed below are
only used in specific instances. Specific reagents are listed within the additional procedures in
Table 4 and also in Table 5.)
6.3.1 Deionized water (DI H2O) with a specific conductance of less than 10 µS.
6.3.2 Ammonium fluoride (NH4F) solutions (used for specific insoluble compounds, see AP 6,
Table 4).
a) Ammonium fluoride, 1 M: Dissolve 37.04 g NH4F and dilute to 1 L in DI
H2O. Store in a polyethylene bottle.
b) Ammonium fluoride, 0.1 M in 4% HNO3: Carefully add 40 mL
concd HNO3
and 100 mL of the 1 M NH4F solution to 500 mL DI H2O and dilute to 1 L
in a polyethylene volumetric flask. Store in a polyethylene bottle since
acidic solutions of NH4F may form small amounts of HF and etch glass
containers.
6.3.3 Hydrogen peroxide (H2O2), 30% (used for digestions of Cr, see AP 5, Table 4).
6.3.4 Mineral acids (used for digestions)
CAUTION: Refer to Section 6.1.2. before using acids
a) Hydrochloric acid (HCl), concd (36.5 to 38%).
b) Hydrofluoric acid (HF), concd (49%).
c) Nitric acid (HNO3), concd (69 to 71%).
d) Perchloric acid (HClO4), concd (69 to 72%). Please see Section
6.1.3 before
using HClO4.
e) Sulfuric acid (H2SO4), concd
(95 to 98%).
f) Acid mixture for platinum digestions: Prepare a mixture of HCl/HNO3 by slowly
and carefully adding 82 mL concd HCl to 18 mL concd HNO3 (CAUTION: Do
not store this solution; dispose of properly after use).
6.3.5 Mineral acids (used for dilutions or cleaning glassware)
CAUTION: Refer to Section 6.1.2. before using acids.
a) Nitric acid, 1:1 HNO3/DI H2O mixture: Carefully add a measured volume of
concd HNO3 to an equal volume of DI H2O.
b) Nitric acid, 4% v/v: Carefully add 40 mL concd HNO3 to 500 mL DI H2O and
dilute to 1 L.
c) Nitric acid 10% v/v: Carefully add 100 mL of concd HNO3 to 500 mL of DI H2O
and then dilute to 1 L.
d) Nitric and hydrochloric acid v/v mixture (4% HNO3 /
X% HCl, where X% is listed below): Carefully add the appropriate amount of concd
HCl to 500 mL of DI H2O:
4% HCl | 40 mL |
16% HCl | 160 mL |
32% HCl | 320 mL |
Then carefully add 40 mL concd HNO3 and dilute to 1 L with DI H2O.
6.3.6 Chemical or ionization interference suppressants
a) Aluminum ion, 5,000 µg/mL: Dissolve 69.52 g aluminum nitrate
(Al(NO3)3·9H2O) and dilute to 1 L in DI H2O.
b) Potassium ion, 5,000 µg/mL: Dissolve 9.54 g potassium chloride (KCl) in DI
H2O and dilute to 1 L.
c) Sodium ion, 5,000 µg/mL: Dissolve 12.71 g sodium chloride (NaCl) in DI H2O
and dilute to 1 L.
6.3.7 Stock standard solutions
Commercially available aqueous standards are used. Expiration dates for
standards should be followed. If there is no expiration date, dispose of after 1
year. As an alternative, standards can be prepared using the procedures
described in the SOP8.8 or instrument manufacturer manuals (i.e., 8.6, 8.9, 8.10).
6.4 Glassware Preparation
6.4.1 Place the conical beakers in an exhaust hood and add approximately 10 mL of a 1:1
HNO3/DI H2O mixture in each 125- or 250-mL
conical beaker. Apply moderate
heat until refluxing occurs. Decant the acid mixture into a waste container and
allow the beakers to cool before removing from the hood. Rinse the beakers
thoroughly with DI H2O.
6.4.2 Rinse all volumetric flasks with 10% v/v HNO3 and then rinse thoroughly with DI
H2O.
6.5 Working Standards
6.5.1 Dilute stock standard solutions to the appropriate ranges using a diluent that will
match the sample matrix. Use information in Tables 1 and 2 as guides for the ranges;
use Table 5 for matrices. The standard concentrations should bracket the expected
sample concentrations and the standard/sample matrices should match.
6.5.2 Store standards in appropriate containers. Protect Ag standards from light by storing
them in actinic or brown plastic bottles. Store standards containing NH4F in
polyethylene containers.
6.6 Sample Preparation
Note: Always prepare blank samples with every sample set. Prepare an
additional blank media sample any time an extra procedure is used
(i.e. wiping out the particulate contained inside a cassette with
an MCE filter or preparing a contaminated backup pad). This
blank media should be from the same manufactured lot as the
prepared filter or backup pad.
6.6.1 Preparation of air and wipe samples
Use 125-mL conical beakers for air samples and smear tabs; use 250-mL beakers
for large wipe samples. Carefully transfer any loose dust from the cassette into
a labeled beaker. Using forceps transfer the sample filter into the same
digestion beaker. If the backup pad appears contaminated, include it with the
sample filter. If there is loose dust present, rinse the cassette top (and ring,
if present) with a small amount of DI H2O and pour the water into the beaker
with the sample filter. Wipe out the cassette top (and ring, if present)
interior surface with a clean Smear Tab (or 1×2 inch section of Ghost Wipe) that
has been moistened with DI H2O and place it in the same digestion beaker with
the rinse and sample filter. Similarly wipe out the cassette bottom interior
surface if the cassette contains loose dust or if the backup pad is
contaminated. Ensure that blank samples are prepared and analyzed using the same
materials and procedures as used for air samples.
If the backup pad appears to be discolored, it may be due to leakage of air
around the filter during sampling.
6.6.2 Preparation of bulk samples
Review any available material safety data sheets to determine safe bulk handling. The
safety data may also offer a clue as to the aliquot amount needed for adequate detection of
the element(s) of interest.
Measure by volume or weight an appropriate aliquot of any liquid bulk sample.
Weigh the appropriate amount of any solid bulk sample.
Note: Aliquot amounts of bulks are dependent on the analytical sensitivity, detection limit,
and solubility of the material used. If uncertain, a 20- to 50-mg aliquot of a solid material
can be taken as a starting point. Make sure the aliquot taken is representative of the entire
bulk sample. If necessary, use a mortar and pestle to grind any nonhomogenous particulate
bulk samples in an exhaust hood.
After measuring, transfer the aliquot to a 250-mL conical beaker.
6.6.3 Extraction or digestion - all samples
Consult Tables 4 and 5 to determine the reagents used during extraction or digestion
for each element to be analyzed. Some elements (Ba, Sn, etc.) or compounds are not
digested with concd HNO3, but are prepared using alternate procedures (APs) listed in
Table 4. These elements or compounds and their AP numbers are:
|
Ag |
AP 1 |
LiH |
AP 7 |
Te |
AP 1 |
Al (soluble) |
AP 2 |
MgO |
AP 3 |
TiO2 |
AP 8 |
Al (pyro powders) |
AP 3 |
Na cmpds |
AP 7 |
Tl (soluble) |
AP 2 |
Au |
AP 4 |
Ni (soluble) |
AP 2 |
Y |
AP 3 |
Ba (soluble) |
AP 2 |
Mo (soluble) |
AP 2 |
Zr |
AP 6 |
Ca cmpds |
AP 3 |
Mo (insoluble) |
AP 3 |
|
Cr (II or III) |
AP 2 |
Pb |
AP 1 |
|
Cr (metal) |
AP 5 |
Pt (metal) |
AP 4 |
|
CsOH |
AP 7 |
Sb |
AP 1 |
|
Fe (soluble) |
AP 2 |
Se |
AP 1 |
|
Hf |
AP 6 |
Sn (inorganic) |
AP 4 |
|
KOH |
AP 7 |
SnO |
AP 4 |
|
|
For the element or compounds listed above, follow the APs recommended and then
proceed with Section 6.6.2. For other elements or compounds, follow the procedures
a, b, or c listed below:
a) All MCE air filters and smear tabs requiring HNO3 digestion
Place the beakers in an exhaust hood and add 3 to 5 mL concd HNO3 to cover the
filter. Place the beakers on a hot plate and heat the samples until about 1 mL
remains. Add a second portion of approximately 1 to 2 mL of concd HNO3. Apply
heat until the appropriate amount of HNO3 remains in the beaker (1 mL of HNO3 will
give a 4% HNO3 matrix when diluted to 25 mL final volume).
b) Large wipe, PVC filters, or backup pads
Place the beakers in an exhaust hood and add the following amount of concd HNO3 to
the beakers:
Large wipes and backup pads 10 to 15 mL
PVC filters 3 to 5 mL
Place the beakers on a hot plate and heat the samples until about 1 mL remains. Add
2 mL of concd HClO4 along with a second portion of 2 mL HNO3, heat the sample,
and then remove when about 1 mL remains. (Note: Please see Section 6.1.3. before
using HClO4.)
As an alternative, an extraction of the backup pad or wipe sample using only HNO3
may be used. Add HNO3 to the media, digest on a hotplate, and continue to add
HNO3 until the solution becomes clear. Remove the beaker from the hotplate when
the appropriate amount of HNO3 remains.
c) Bulk samples
Add 10 to 30 mL HNO3, place the beaker on a hot plate, and digest the bulk sample
until the material dissolves and the appropriate amount of solution remains (about 1
mL if diluting samples to 25 mL, 2 mL if 50 mL final volume, etc. After dilution
this will give a final volume of 4% HNO3). If necessary, use other acids, or use a
microwave digestion system to facilitate digestion [For further information regarding
microwave digestion, see the Standard Operating Procedure].8.11
6.6.4 Filtration - all samples
1) Samples Previously Extracted:
Samples extracted with DI H2O should normally be filtered. If particulate is
present, filter the extract through a 0.45-µm MCE filter. Save the extract as the
soluble portion. If necessary, digest the particulate on both filters using
procedure (a) above or the applicable AP to prepare the remaining insoluble
material for additional analyses. To control for potential contamination, prepare
blank samples in the same fashion as the filtered samples.
2) Samples Previously Digested:
If particulate matter is present after digesting, cool the sample, add
approximately 10 mL DI H2O, then filter the solution through a 0.45-µm MCE
filter. Save the filtrate. Repeat digestion procedure (a) above for the filter
containing the particulate.
6.6.5 Dilution - all samples
Allow all digested samples to cool to room temperature in an exhaust hood before
proceeding. Additional sample or filtrate treatment may be required for certain
elements. Perform any special sample treatments recommended in Table 5, and then
quantitatively transfer each sample and each filtrate solution to individual volumetric
flasks. Add any reagents necessary to achieve the final solution concentrations listed
in Table 5 for specific analytes. Dilute to volume with DI H2O and then mix well.
Solution volumes are dependent on the following factors:
a) The amount of sample the industrial hygienist has collected (air volume and/or
filter loading).
b) The detection limit of the analytical method.
c) The PEL of the analyte.
d) The number of analytes requested.
Air samples are normally diluted to 25 mL unless one or more of the above factors
suggests an alternate volume should be used. For routine analysis, at least 1/10 of
the OSHA PEL should be detectable. Final solution volumes can be estimated using
the following equation:
FV Factor = |
0.1 × PEL × air volume QnDL × GF |
Where:
PEL |
= |
Permissible Exposure Limit (in mg/m3) |
Air Vol |
= |
Air Volume taken (in L) |
QnDL |
= |
Quantitative Detection Limit (in µg/mL) |
GF |
= |
Gravimetric Factor (if required - some factors are listed in Table 6) |
Quantitative detection limits are listed in Table 2.
The FV factor assists in determining the final volume. Sample solution volumes
normally used are: 5-, 10-, 25-, 50-, or 100-mL. Final volumes of 50- and 100-mL
are normally reserved for wipe or bulk samples. If possible, FV should always be
larger than the final solution volume. For example, if a sample has a 200-L air
volume, a PEL of 0.05 mg/m3, a GF of 1, and a QnDL of 0.09 µg/mL, then:
FV Factor = 11.1
and a final volume should be 10-mL. Due to the limited amount of solution available
for analysis and the potential for sample loss during transfer, 5-mL solution volumes
are only used when absolutely necessary.
6.7 Instrument Setup and Analysis
6.7.1 Set up the AAS or AES according to the SOP8.8 or the manufacturer's
instructions. Use the flame and wavelength recommended in Table 7. If alternate
conditions are necessary, consult the instrument manufacturer's manual for other
settings and operating procedures. Install an EDL or hollow cathode lamp for the
element of interest and allow it to warm up for 10-20 min or until
the energy output stabilizes. Optimize conditions such as lamp position, burner
head alignment, fuel and oxidant flow rates, etc. See the SOP8.8 or specific instrument manuals for
details.
6.7.2 Aspirate and measure the ABS of a standard solution for the element of interest. The
standard concentration should be within the linear range for the element. Compare
the ABS to an expected sensitivity value (Note: Some values are listed in Table 7;
these were adapted from reference 8.6 or obtained at the OSHA laboratory). Then
aspirate the smallest standard to be used and assure the ABS reading is above the
background level of the instrument.
6.7.3 Make any adjustments necessary for the particular analysis, such as: scale expansion,
burner head rotation, background correction, or alternate wavelength.
6.7.4 Aspirate and measure the ABS of a prepared standard solution, then determine the
baseline by aspirating DI H2O and measuring the ABS.
6.7.5 Analyze standards, samples, and blanks. Repeat the baseline determination after
each solution is analyzed. The baseline readings will assist in correcting any
instrument drift. If more than one solution has been prepared for a sample (i.e.
filtrate and sample, or soluble and insoluble portions), analyze each for all requested
elements. Standards must bracket the sample concentrations. Analyze a standard
after every four or five samples. Standard readings should be within 10 to 15% of
the readings obtained at the beginning of the analysis.
6.7.6 If any samples exceed the linear range, they should be diluted. When diluting a
sample, be sure that the diluted sample has the same matrix as the original sample
and standards. If a number of samples must be diluted, it may be more advantageous
to use a less sensitive wavelength.
6.8 Analytical Recommendations
6.8.1 When a fresh standard is prepared, analyze the old and new standards and compare
results to verify the new standard is correct. If two or more stock solutions are
available for working standard preparations, rotate the preparation from one stock
solution to the next to verify the quality.
6.8.2 Keep a permanent record of all standard preparation and comparison data. Assign
and follow expiration dates for all standards.
6.8.3 Always analyze blank samples along with the other samples. Treat blanks in the
same fashion as samples, including any filtration steps.
6.8.4 When analyzing for Ag, carry-over from a large concentration sample or standard to
the next sample can occur, causing erroneous readings. To remedy this, aspirate 4%
HNO3 instead of water between samples.
6.8.5 In this method, many different matrices are used to digest and keep analytes in
solution. Occasionally, during multiple element analysis of the same sample, matrix
effects can occur if standards are not matrix-matched with samples. Also, it is
sometimes necessary to prepare samples in a matrix substantially different from
recommendations. If these conditions occur, one or two standards should be
prepared in the same matrix to determine any matrix effects. A reagent blank should
also be prepared and analyzed to determine any effect on the background signal. If a
significant difference is noted in the analytical signals for the two different matrices,
a full set of standards should always be prepared in the sample matrix and analyzed
with the samples.
7. Calculations
7.1 Subtract each baseline ABS from the corresponding standard ABS, and plot the net ABS versus
the standard concentrations. Using a least squares method, determine the equation for the best
curve fit.
7.2 Subtract each baseline ABS from the corresponding sample or blank ABS, and use the standard
curve to calculate the concentration of each analyte in µg/mL.
7.3 Calculate the concentration for each air sample as:
C = |
[(A × SA × D × GF) - (B × SB × GF)] air volume |
Where:
C |
= |
analyte (mg/m3) |
A |
= |
concn of analyte in the sample solution (µg/mL) |
B |
= |
concn of analyte in the blank solution (µg/mL) |
SA |
= |
sample solution volume (mL) |
SB |
= |
blank solution volume (mL) |
D |
= |
dilution factor (if any) |
GF |
= |
gravimetric factor (if any; see Table 6) |
Air Vol |
= |
air volume sampled (L) |
7.4 For wipe or bulk samples, calculate the total amount (in µg) of analyte in each sample using the
equation above. An air volume is not used. Convert bulk sample analytes to % composition
using:
analyte % (w/w) = |
(C) (100%) (sample wt) (1,000 µg/mg) |
(Bulk Samples) |
Where:
C |
= |
analyte amount (µg) |
Sample wt |
= |
aliquot (in mg) of bulk taken in Section 6.6. |
7.5 Reporting Results to the Industrial Hygienist
For those samples only extracted with DI H2O, report the sample results as the soluble fraction of
the sample.
If more than one solution exists for a sample, and it is not necessary to report results separately,
then combine these results. An example is a sample that was filtered due to insoluble particulate.
The results from the filtrate plus results from the second particulate digestion are added together.
7.5.1 Report air sample results as mg/m3 analyte.
7.5.2 Report wipe sample concentrations as total micrograms or milligrams
analyte.
7.5.3 Report bulk sample results as approximate percent by weight analyte (note: Sample
results for bulk liquids may be reported as approximate percent by volume if
volumetric aliquots were taken during sample preparation.) Due to differences in
sample matrices between bulks and standards, bulk results are approximate.
8. References
8.1 Occupational Safety and Health Administration Analytical Laboratory: OSHA Manual of
Analytical Methods edited by R.G. Adler (Method No. I-1). Salt Lake City, UT. 1977.
8.2 Clayton, G.D. and F.E. Clayton, ed.: Patty's Industrial Hygiene and Toxicology. 3rd ed. New
York: John Wiley and Sons, 1978.
8.3 American Conference of Governmental Industrial Hygienists: Documentation of the
Threshold Limit Values and Biological Exposure Indices. 5th Ed. Cincinnati, OH: American
Conference of Governmental Industrial Hygienists, 1986.
8.4 National Institute for Occupational Safety and Health: The Industrial Environment--Its
Evaluation and Control. Washington, DC: Government Printing Office, 1973.
8.5 Slavin, S., W.B. Barnett, and H.L. Kahn: The Determination of Atomic Absorption Detection
Limits by Direct Measurement. Atomic Absorption Newsletter 11: 37-41 (1972).
8.6 Perkin-Elmer Corp.: Analytical Methods for Atomic Absorption Spectrophotometry. Norwalk,
CT: Perkin-Elmer Corp., 1973 and revised edition, 1982.
8.7 National Institute for Occupational Safety and Health: NIOSH Manual of Analytical
Methods. 2nd ed. (Method no. 173) Cincinnati, OH: National Institute for Occupational Safety
and Health, 1977.
8.8 Occupational Safety and Health Administration Technical Center: Standard Operating
Procedure for Atomic Absorption. Salt Lake City, UT. In progress (unpublished).
8.9 Fisher Scientific Company: Atomic Absorption Methods Manual. Waltham, MA: Fisher
Scientific Co., 1977.
8.10 Instrumentation Laboratory Inc.: Atomic Absorption Methods Manual. Wilmington, MA:
Instrumentation Laboratory Inc., 1975.
8.11 Occupational Safety and Health Administration Analytical Laboratory: Standard Operating
Procedure for Microwave Digestions by D. Cook. Salt Lake City, UT. 1989 (unpublished).
8.12 "Air Contaminants; Final Rule": Federal Register 54:12 (19 Jan. 1989). pp. 2923-2960 and also
54:127 (5 July 1989). pp. 28054-28061.
8.13 Occupational Safety and Health Administration Analytical Laboratory: OSHA Laboratory
Quality Control Division Data by B. Babcock, Salt Lake City, UT, 1989 (unpublished).
8.14 Slavin, Walter: Atomic Absorption Spectroscopy. New York: Interscience Publishers, 1968.
8.15 Ediger, R.D.: Atomic Absorption Analysis with the Graphite Furnace using Matrix
Modification. Atomic Absorption Newsletter. 14(5): 127-130 (1975).
Table 1 Air Contaminants - OSHA Permissible Exposure Limits* |
|
|
Transitional PEL |
---Final Rule PEL--- |
Element |
Substance Exposed to |
----(mg/m3)---- |
----(mg/m3)---- |
|
TWA |
CEILING |
TWA |
STEL |
CEILING |
|
Ag |
Metal and soluble cmpds (as Ag) |
0.01 |
|
0.01 |
|
|
Al |
Soluble salts (as Al) |
--- |
|
2 |
|
|
Pyro powders |
--- |
|
5 |
|
|
Ba |
Soluble compounds (as Ba) |
0.5 |
|
0.5 |
|
|
Bi |
Bismuth telluride (Se doped)** |
--- |
|
5 |
|
|
Ca |
Calcium oxide |
5 |
|
5 |
|
|
Calcium cyanamide |
--- |
|
0.5 |
|
|
Cd |
Fume |
0.1 |
0.3 |
0.1 |
|
0.3 |
|
Dust |
0.2 |
0.6 |
0.2 |
|
0.6 |
|
Co |
Metal dust and fume (as Co) |
0.1 |
|
0.05 |
|
|
Cobalt Carbonyl or hydrocarbonyl (as Co) |
--- |
|
0.1 |
|
|
Cr |
Cr (II or III) compounds (as Cr) |
0.5 |
|
0.5 |
|
|
Cr metal (as Cr) |
1 |
|
1 |
|
|
Cs |
Cesium hydroxide |
--- |
|
2 |
|
|
Cu |
Fumes (as Cu) |
0.1 |
|
0.1 |
|
|
Dusts and mists (as Cu) |
1 |
|
1 |
|
|
Fe |
Dicyclopentadienyl iron |
|
|
Total dust |
15 |
|
10 |
|
|
Iron oxide fume (as Fe2O3) |
10 |
|
10 |
|
|
Iron salts (soluble) (as Fe) |
1 |
|
|
Hf |
Hafnium |
0.5 |
|
0.5 |
|
|
In |
Indium and compounds (as In) |
--- |
|
0.1 |
|
|
K |
Potassium hydroxide |
--- |
|
2 |
|
|
Li |
Lithium hydride |
0.025 |
|
0.025 |
|
|
Mg |
Magnesium oxide fume |
|
|
Total particulate |
15 |
|
10 |
|
|
Mn |
Mn compounds (as Mn) |
5 |
|
5 |
|
Mn fume (as Mn) |
|
5 |
1 |
3 |
|
Manganese tetroxide (as Mn) |
--- |
|
1 |
|
|
Mo |
Soluble compounds (as Mo) |
5 |
|
5 |
|
|
Insoluble compounds (as Mo) |
|
|
Total dust |
15 |
|
10 |
|
|
Na |
Sodium bisulfite |
--- |
|
5 |
|
|
Sodium fluoroacetate |
--- |
|
0.05 |
0.15 |
|
|
Sodium hydroxide |
2 |
--- |
|
2 |
|
Sodium metabisulfite |
--- |
|
5 |
|
|
Tetrasodium pyrophosphate*** |
--- |
|
5 |
|
|
Ni |
Metal and insoluble |
|
|
compounds (as Ni) |
1 |
|
1 |
|
|
Soluble compounds (as Ni) |
1 |
|
0.1 |
|
|
Pb |
Inorganic (see Code of Federal Regulations 1910.1025) |
|
Pt |
Pt metal |
--- |
|
1 |
|
|
Sb |
Sb and compounds (as Sb) |
0.5 |
|
0.5 |
|
|
Se |
Se and compounds (as Se) |
0.2 |
|
0.2 |
|
|
Sn |
Inorganic compounds |
|
|
except oxides (as Sn) |
2 |
|
2 |
|
|
Tin oxide (as Sn) |
|
2 |
|
|
Te |
Te and compounds (as Te) |
0.1 |
|
0.1 |
|
|
Ti |
Titanium dioxide |
|
|
Total dust |
15 |
|
10 |
|
|
Tl |
+ Soluble compounds (as Tl) |
0.1 |
|
0.1 |
|
|
Y |
Yttrium |
1 |
|
1 |
|
|
Zn |
Zinc chloride fume |
1 |
|
1 |
2 |
|
|
Zinc oxide fume |
5 |
|
5 |
10 |
|
|
Zinc oxide |
|
|
Total dust |
15 |
|
10 |
|
|
|
Zinc stearate |
|
|
Total dust |
15 |
|
10 |
|
|
Zr |
Zr compounds (as Zr) |
5 |
|
5 |
10 |
|
|
* From reference 8.12 - Final Rule PELs were voided
by a court ruling and are not applicable *** Also can be analyzed for total phosphate content by ion chromatography.
+ Skin Designation |
|
Note: Compounds having total and respirable dust PELs of 15 and 5 mg/m3, respectively, are normally analyzed
gravimetrically. Elements contained in these dust samples can be identified by this or other methods, if
necessary.
Table 2 Detection Limits, Sensitivities, and Ranges |
|
Element |
Qualitative |
Analytical |
Sensitivity* |
Upper Linear Range* |
|
DL* (µg/mL) |
DL* (µg/mL) |
(µg/mL) |
(µg/mL) |
|
Ag |
0.002 |
0.005 |
0.06 |
4 |
Al+ |
0.02 |
0.3 |
1 |
50 |
Au |
0.01 |
0.05 |
0.25 |
20 |
Ba+ |
0.008 |
0.5 |
0.4 |
25 |
Bi |
0.025 |
0.2 |
0.5 |
30 |
Ca |
<0.0005 |
0.03+ |
0.08 (0.029)+ |
7 |
Cd |
0.0002 |
0.004 |
0.025 |
2 |
Co |
0.01 |
0.04 |
0.15 |
5 |
Cr |
0.003 |
0.04 (0.04) + 0.1 |
(0.31)+ |
5(10)+ |
Cs |
0.005++ |
|
0.2 |
15 |
Cu |
0.001 |
0.005 |
0.09 |
5 |
Fe |
0.005 |
0.03 |
0.12 |
5 |
Hf+ |
2.0 |
|
15 |
500 |
In |
0.02 |
0.1 |
0.7 |
50 |
K |
<0.002 |
0.02 |
0.04 |
2 |
Li |
0.0003 |
0.004 |
0.035 |
2 |
Mg |
<0.0001 |
0.01 |
0.007 |
0.5 |
Mn |
0.002 |
0.01 |
0.055 |
3 |
Mo+ |
0.02 |
0.04 |
0.5 |
60 |
Na |
<0.0002 |
0.009 |
0.015 |
1 |
Ni |
0.002 |
0.1 |
0.15 |
5 |
Pb |
0.01 |
0.05 |
0.5 |
20 |
Pt |
|
2.0 |
13 |
|
Sb** |
(0.08) |
0.1 |
1.0 |
50 |
Se** |
(0.05) |
0.3 |
0.25 |
25 |
Sn** |
(0.01) |
0.1 |
0.6 |
40 |
Te |
0.05 |
0.2 |
1.0 |
25 |
Ti+ |
0.04 |
|
1.8 |
|
Tl |
0.03 |
0.05 |
0.5 |
20 |
Y |
0.05 |
0.7 |
1.8 |
200 |
Zn |
<0.01 |
0.01 |
0.018 |
1 |
Zr+ |
1.0 |
8 |
10.0 |
800 |
* DL = Detection Limit. See Appendix A for more information regarding definitions or calculations.
Analytical DLs are approximate.
** Alternate line of 231.2 nm was used with one exception: The qualitative detection limit value is for the
primary line (217.6 nm).
*** Air/H2 flame used with the exception of the qualitative detection limit determination. This value is for
Air/C2H2 flame.
+ N2O/C2H2 flame used.
++ Flame emission used to determine qualitative detection limit.
Table 3 Precision and Accuracy* |
|
Element |
CV |
% Ave Recovery |
Range** |
N |
Ag |
0.083 |
97.8 |
1-4 |
270 |
Al |
0.076 |
94.5 |
100-1500 |
27 |
Au |
--- |
--- |
--- |
|
Ba |
0.10 |
104.7 |
50-75 |
45 |
Bi |
--- |
--- |
--- |
|
Ca |
0.162 |
98.3 |
100-150 |
51 |
Cd |
0.087 |
99.5 |
10-15 |
93 |
Co |
0.052 |
99.3 |
10-15 |
39 |
Cr (Soluble) |
--- |
--- |
--- |
|
Cr (Insoluble) |
0.052 |
95.7 |
45-75 |
72 |
Cs |
--- |
--- |
--- |
|
Cu |
0.043 |
96.8 |
100-150 |
45 |
Fe |
0.084 |
98.2 |
300-400 |
69 |
Hf |
--- |
--- |
--- |
|
In |
--- |
--- |
--- |
|
K |
0.063 |
93.3 |
125-200 |
30 |
Li |
--- |
--- |
--- |
|
Mg |
0.073 |
112.1 |
100-300 |
24 |
Mn |
0.044 |
100.2 |
100-150 |
60 |
Mo (Soluble) |
--- |
--- |
--- |
|
Mo (Insoluble) |
0.075 |
91.2 |
100-250 |
27 |
Na |
0.058 |
97.5 |
100-250 |
68 |
Ni |
0.065 |
99.1 |
100-150 |
18 |
Pb |
0.047 |
99.3 |
20-40 |
300 |
Pt |
0.055 |
98.1 |
80-1800 |
24+ |
Sb |
0.081 |
98.4 |
50-75 |
36 |
Se |
0.122 |
104.9 |
20-100 |
30 |
Sn |
0.079 |
97.4 |
100-150 |
63 |
Te |
--- |
--- |
--- |
|
Tl |
--- |
--- |
--- |
|
Y |
--- |
--- |
--- |
|
Zn |
0.039 |
101.2 |
100-150 |
69 |
Zr |
--- |
--- |
--- |
|
|
CV Coefficient of Variation
* Table updated January, 19908.13
** Range (in µg) of analyte spiked onto MCE filters. Samples were
spiked with aqueous solutions of dissolved metals or their salts. All samples were prepared and analyzed
using conditions stated in the method.
+ These samples were prepared by weighing the metal on filters. A single blind study was not
performed.
Table 4 Alternate Procedures
|
1) Digest samples with HNO3. Heat until the liquid is nearly gone. Allow the samples to cool to room
temperature.
2) For 25 mL final sample solution volumes, add the following amount of concd HCl (Adjust accordingly
for alternate solution volumes):
Analyte Suspected to be Present |
Amount of HCl |
|
Sb |
|
8 mL |
|
Pb or Ag |
|
4 mL |
|
Se or Te |
|
1 mL |
3) Warm gently and swirl to dissolve the analyte. Allow samples to cool and dilute to a 25-mL volume
with DI H2O.
AP 2: Soluble Compounds of Al, Ba, Cr (II or III), Fe, Ni, Mo, Tl, Zn
|
1) Place the sample in a beaker and add an aliquot of room-temperature DI H2O into the beaker (15 mL is
typically used for a full-shift sample).
2) Place the beaker in an ultrasonic bath for approximately 10 min.
3) Filter the sample through a 0.45 µm MCE filter and transfer the filtrate to a 25-mL volumetric flask. If
an insoluble fraction is also requested, digest both sample filters according to the appropriate
procedure.
4) Add reagents to achieve the final solution concentrations listed:
Analyte Presence Suspected |
Final Concentration |
Cr (II or III), Fe, Ni, Tl, Zn (as ZnCl2) |
4% HNO3 |
|
Al, Ba |
4% HNO3/1,000 µg/mL Potassium ion |
|
Mo |
4% HNO3/1,000 µg/mL Aluminum ion |
AP 3: Al (pyro powders), Ca, Mg, Mo (insoluble), Y
|
(1) Digest the sample using the procedure described in
Section 6.6.3.a.
(2) Transfer the sample to a volumetric flask.
(3) Dilute the samples and add ionization suppressants to
achieve the final solution concentrations listed:
Analyte Suspected to be Present |
Final Concentration |
Al (pyro powders), Ca, Mg, Y |
4% HNO3/1,000 µg/mL Potassium ion |
Mo (insoluble) |
4% HNO3/1,000 µg/mL Aluminum ion |
AP 4: Au, Pt (metal), Sn, or Tin Oxide (SnO)
|
(1) For Au, Sn, or SnO, add 9 mL HCl to each beaker, swirl,
and then add 2 mL HNO3. CAUTION: Make sure the
entire filter or sample is wetted with HCl and allow the
filter/HCl solution to sit for a period of at least 2 to 3 min
before adding the HNO3.
(2) Digest the sample on a hot plate until nearly dry.
(3) Allow the samples to cool and then quantitatively
transfer the sample, using a small amount of DI H2O to
rinse the beaker, to a clean volumetric flask. Dilute to
volume, making the final solution 10% HCl. For example,
add 2.5 mL concd HCl to a sample if the total solution
volume is 25 mL.
(4) Results for either Sn or SnO are reported as total Sn.
AP 5: Cr [Samples which potentially contain Cr(VI)]
|
For samples requiring analysis of total Cr, the following procedure should be
used. This procedure avoids the loss of any Cr(VI) as chromyl chloride
(CrO2Cl2). For chromate or chromic acid analysis, see OSHA method no. ID-103.
(1) Digest the samples collected on MCE filters with HNO3
and then allow to cool to room temperature. If PVC filters
were used, digest with HNO3 plus 2 mL of HClO4 and then
allow to cool.
(2) Add 1 or 2 mL of 30% H2O2 to the cooled solution to
reduce any Cr(VI) that may be present. Let the sample sit
for several minutes.
(3) Heat approximately 5 min to boil off the H2O2 and then
allow to cool. At this stage HCl may be added if needed to
dissolve other metals.
(4) Dilute to volume with DI H2O and analyze.
NOTE: Do not add HClO4 to the sample solution if a large amount of HCl is already present [any Cr(VI) in the
sample would be lost as CrO2Cl2]. Add
concd HNO3, boil
off the HCl, and then add the HClO4.
AP 6: Elements or Compounds* which are Insoluble in Nitric Acid Digestions
|
(1) For compounds such as zirconium dioxide or hafnium dioxide, place the sample
filter in a platinum crucible, char at 300 °C, then heat the residue at 800 °C
in a muffle furnace. [As an alternative, the digestion can be performed using a
microwave digestion system.]8.11
(2) Add 1 to 2 mL of HF, swirl the solution, and then heat
on a hot plate to dissolve the residue.
(3) Evaporate the solution to approximately 0.4 mL and then
transfer to a 10-mL polyethylene volumetric flask. Dilute
to volume with a solution of 0.1 M ammonium fluoride in
4% HNO3.
Another procedure can be used for elements which do not need to be converted to
their fluoride salts:
(1) Heat the HF solution on the hot plate until the liquid is nearly gone.
(2) Add 2 to 3 mL HCl, and warm the solution until about 1
mL remains.
(3) Quantitatively transfer the solution to a 10 mL
volumetric flask and dilute to volume with the appropriate
diluents mentioned in Table 5.
(4) It is recommended to prepare quality control samples of
the substance of concern. Digest the samples and analyze
by the same procedure to check the recovery efficiency.
For platinum:
(1) Place the sample filter in a Teflon microwave digestion
vessel and add 5 mL of the "acid mixture (HCl/HNO3) for
platinum digestions" prepared in Section 6.3.4, part f).
(2) Digest the sample according to Microwave Digestion Standard Operating
Procedure8.11 or manufacturer
guidelines.
(3) Allow the sample to cool and then transfer to a 25-mL
volumetric flask. Dilute to volume with DI H2O.
* Some Zr compounds, such as the oxide and sulfate, may be
insoluble when using
the HNO3 digestion.8.6,
8.7 Hafnium dioxide may also be insoluble.
AP 7: CsOH, KOH, LiH, and Na Compounds
|
(1) Place the sample filter in a beaker and desorb with 15
mL of DI H2O for approximately 5 min.
(2) Decant the sample solution into a 25-mL volumetric
flask and add any reagents to achieve the final solution
concentrations:
Analyte Suspected to be Present |
Final Concentration |
CsOH |
DI H2O/1,000 µg/mL potassium ion |
LiH, Na cmpds |
DI H2O |
KOH |
DI H2O/1,000 µg/mL sodium ion |
For example, add 5 mL of 5,000 µg/mL potassium ion for Cs analysis and dilute to volume with DI H2O.
Add 5 mL of 5,000 µg/mL sodium ion for KOH analysis.
(3) Analyze by flame emission or atomic absorption.
(1) Digest the filter with 1 mL HNO3 and 2 mL H2SO4 in a
conical beaker and heat until about 1 mL remains.
(2) Quantitatively transfer the solution to a 25-mL
volumetric flask, add 5 mL of 5,000 µg/mL potassium ion,
then dilute to volume with DI H2O.
Table 5 Digestion or Extraction Reagents |
|
Substance |
Reagents Used |
Final Volume Concentration+ |
|
Ag |
HNO3/HCl |
4% HNO3/16% HCl |
Al (soluble cmpds) |
DI H2O |
4% HNO3/1,000 µg/mL K+ |
Al (pyro powders) |
HNO3 |
4% HNO3/1,000 µg/mL K+ |
Au |
HCl/HNO3 |
10% |
Ba (soluble cmpds) |
DI H2O |
4% HNO3/1,000 µg/mL K+ |
Bi2Te3 (Se doped) |
HNO3 |
4% HNO3 |
Ca & cmpds |
HNO3/HCl* |
4% HNO3/1,000 µg/mL K+ |
Cd |
HNO3 |
4% HNO3 |
Co & cmpds |
HNO3/HCl* |
4% HNO3 |
Cr (II or III) soluble cmpds |
DI H2O |
4% HNO3 |
Cr metal |
HNO3/H2O2/HCl* |
4% HNO3 |
CsOH |
DI H2O |
DI H2O/1,000 µg/mL K+ |
Cu |
HNO3 |
4% HNO3 |
Fe & cmpds |
HNO3/HCl* |
4% HNO3 |
Fe (soluble salts) |
DI H2O |
4% HNO3 |
Hf |
HF |
4% HF/4% HNO3/0.1 M NH4F |
In & cmpds |
HNO3 |
4% HNO3 |
KOH |
DI H2O |
DI H2O/1,000 µg/mL Na+ |
LiH |
DI H2O |
DI H2O |
MgO |
HNO3/HCl* |
4% HNO3/1,000 µg/mL K+ |
Mn & cmpds |
HNO3/HCl* |
4% HNO3 |
Mo (soluble cmpds) |
DI H2O |
4% HNO3/1,000 µg/mL Al |
Mo (insoluble cmpds) |
HNO3 |
4% HNO3/1,000 µg/mL Al |
Na & cmpds |
DI H2O |
DI H2O |
Ni metal & insoluble cmpds |
HNO3/HCl* |
4% HNO3 |
Ni (soluble cmpds) |
DI H2O |
4% HNO3 |
Pb |
HNO3/HCl |
4% HNO3/16% HCl |
Pt metal |
HCl/HNO3 |
4% HNO3/16% HCl |
Sb & cmpds |
HNO3/HCl |
4% HNO3/32% HCl |
Se & cmpds |
HNO3/HCl |
4% HNO3/4% HCl |
Sn (and SnO) |
HCl/HNO3 |
10% HCl |
Te & cmpds |
HNO3/HCl |
4% HNO3/4% HCl |
TiO2 |
HNO3/H2SO4 |
4% H2SO4/1,000 µg/mL K+ |
Tl (soluble cmpds) |
DI H2O |
4% HNO3 |
Y |
HNO3 |
4% HNO3/1,000 µg/mL K+ |
ZnCl2 |
DI H2O |
4% HNO3 |
Zn & cmpds |
HNO3 |
4% HNO3 |
Zr & cmpds |
HF |
4% HF/4% HNO3/0.1 M NH4F |
|
+ Standards should be prepared in this matrix.
* After completing the digestion with HNO3, add 1 or 2 drops of
concd HCl to facilitate particulate
dissolution.
Table 6 Gravimetric Factors |
|
Element |
Compound |
Gravimetric Factor |
|
Bi |
Bismuth telluride (Bi2Te3) |
1.916 |
Ca |
Calcium cyanamide (CaCN2) |
1.998 |
Ca |
Calcium hydroxide [Ca(OH)2] |
1.849 |
Ca |
Calcium oxide (CaO) |
1.399 |
Cs |
Cesium hydroxide (CsOH) |
1.128 |
Cr |
Chromic acid (CrO3) |
1.923 |
Fe |
Dicyclopentadienyl iron [(C5H5)2Fe] |
3.331 |
Fe |
Iron oxide (Fe2O3) |
1.430 |
Li |
Lithium hydride (LiH) |
1.145 |
Mg |
Magnesium oxide (MgO) |
1.658 |
Na |
Sodium bisulfite (NaHSO3) |
4.525 |
Na |
Sodium fluoroacetate (FCH2COONa) |
4.351 |
Na |
Sodium hydroxide (NaOH) |
1.740 |
Na |
Sodium metabisulfite (Na2S2O5) |
4.134 |
Na |
Tetrasodium pyrophosphate (Na4P2O7) |
2.891 |
Ti |
Titanium oxide (TiO2) |
1.668 |
Zn |
Zinc chloride (ZnCl2) |
2.085 |
Zn |
Zinc oxide (ZnO) |
1.245 |
Zn |
Zinc stearate [Zn(C18H35O2)2] |
9.671 |
|
Table 7 Analytical Parameters |
|
Element |
l(nm) |
Slit (nm) |
Optimization* |
Flame Used |
Comments |
Ag |
328.1 |
0.7 |
4 µg/mL=0.3 ABS |
1 |
For multielement lamps containing Cu, use 0.2 nm slit. |
Al |
309.3 |
0.7 |
50 µg/mL=0.22 ABS |
3 |
|
Au |
242.8 |
0.7 |
15 µg/mL=0.26 ABS |
1 |
|
Ba |
553.6 |
0.4 |
15 µg/mL=0.16 ABS |
3 |
|
Bi |
223.1 |
0.2 |
20 µg/mL=0.18 ABS |
1 |
|
Ca** |
422.7 |
0.7 |
4 µg/mL=0.22 ABS |
4 |
|
Cd** |
228.8 |
0.7 |
2 µg/mL=0.35 ABS |
1 |
|
Co |
240.7 |
0.2 |
5 µg/mL=.015 ABS |
2 |
|
Cr** |
357.9 |
0.7 |
2 µg/mL=0.05 ABS |
3 |
|
Cs |
852.1 |
1.4 |
10 µg/mL=0.22 ABS |
1 |
|
Cu** |
324.7 |
0.7 |
5 µg/mL=0.25 ABS |
1 |
For multielement lamps containing Ni or Fe, use 0.2 nm slit. |
Fe** |
248.3 |
0.2 |
5 µg/mL=0.18 ABS |
2 |
In the presence of Co, |
|
248.8 |
0.2 |
5 µg/mL=0.11 ABS |
2 |
do not use a multielement lamp containing Co at 248.3 nm. Use 248.8 or 372.0 nm. |
Hf |
286.6 |
0.2 |
300 µg/mL=0.2 ABS |
3 |
|
In |
303.9 |
0.7 |
25 µg/mL=0.15 ABS |
1 |
|
K |
766.5 |
1.4 |
2 µg/mL=0.3 ABS |
1 |
|
Li |
670.8 |
1.4 |
1 µg/mL=0.13 ABS |
1 |
|
Mg** |
285.2 |
0.7 |
0.3 µg/mL=0.19 ABS |
3 |
|
Mn** |
279.5 |
0.2 |
2 µg/mL=0.16 ABS |
1 |
|
Mo** |
313.5 |
0.7 |
2 µg/mL=0.20 ABS |
3 |
|
Na |
589.6 |
0.4 |
0.8 µg/mL=0.2 ABS |
1 |
|
Ni** |
232.0 |
0.2 |
5 µg/mL=0.15 ABS |
1 |
For multielement lamps containing Fe, use the secondary Ni line, 352.4 nm. |
Pb |
283.3 |
0.7 |
20 µg/mL=0.18 ABS |
1 |
|
Pt |
265.9 |
0.7 |
100 µg/mL=0.033 ABS |
3 |
|
Sb |
217.6 |
0.2 |
20 µg/mL=0.18 ABS |
1 |
For determination in 231.2 0.7 20 µg/mL=0.07 ABS 1 the presence of Pb, use the 231.2 nm line. |
Se |
196.0 |
2.0 |
20 µg/mL=0.18 ABS |
5 |
Use an EDL |
Sn |
224.6 |
0.7 |
50 µg/mL=0.28 ABS |
5 |
|
Te |
214.3 |
0.2 |
25 µg/mL=0.11 ABS |
1 |
|
Ti |
365.3 |
0.2 |
120 µg/mL=0.3 ABS |
3 |
|
Tl |
276.8 |
0.7 |
20 µg/mL=0.18 ABS |
1 |
|
Y |
410.2 |
0.2 |
100 µg/mL=0.24 ABS |
3 |
|
Zn** |
213.9 |
0.7 |
0.5 µg/mL=0.12 ABS |
1 |
In the presence of Cu, do not use a multielement lamp containing Cu. |
Zr |
360.1 |
0.2 |
400 µg/mL=0.17 ABS |
3 |
|
|
* Adapted from reference 8.6 or from laboratory determinations
** Due to the limited upper linear range, samples may have to be diluted, the burner head rotated, or an
alternate wavelength used. The burner head is routinely rotated for Fe and Mg before analysis.
Flame Types:
1. Air/Acetylene mixture, lean, blue flame
2. Air/Acetylene mixture, very lean, blue flame
3. Nitrous oxide/Acetylene mixture, rich, red flame
4. Nitrous oxide/Acetylene mixture, slightly rich, red flame
5. Air/Hydrogen mixture
For the purposes of this method, the following definitions are used:
Qualitative detection limit
The concentration (µg/mL) of an element which would yield an absorbance (ABS) equal to twice the
standard deviation of a series of measurements of an aqueous solution containing the element. The signal
obtained from the aqueous solution must be distinctly greater than the baseline.8.10 These detection
limits were taken from reference 8.5.
Analytical detection limit
The lowest concentration (µg/mL) of an element that can be reliably quantitated. This limit is the largest
value obtained from any of the three calculations:
a) Three times the smallest possible non-zero instrument reading,
b) Two times the average baseline variation, or
c) The lowest standard used to construct a concentration-response curve. One-tenth the
concentration of this standard is considered to be the detection limit if:
The average reading for this standard is within 20% of it's linear response. The linearity is
determined by the other standards used to construct the least-squares curve fit.
If the lowest standard ABS reading is more than 20% in error, then an algorithm is used and the
concentration value is increased in 10% increments until a concentration is achieved that would
display less than 20% error or until the lowest standard concentration is reached.
Sensitivity
The concentration (µg/mL) of an element in
aqueous solution which will produce an ABS of 0.0044.8.6
Linear Range
The working range of a specific analyte. The range is considered linear if doubling the concentration of a
standard results in at least a 75% increase in ABS.
Appendix B
Potential Interferences
|
Ag |
If a multielement lamp containing
Cu is used, a spectral interference may occur when determining Ag in a sample
containing Cu. A narrow slit should be used in this instance.8.6 |
|
|
Thorium (Th) is a reported
chemical interference;8.14 however, this element is extremely rare in workplace environments. Analyze the sample for Th first if both are suspected to be present. |
|
Al |
Acetic acid, fluoroborate, Fe, and Ti enhance the Al signal. Ionization should be controlled by adding an alkali salt (potassium or lanthanum) to samples and standards. |
|
Au |
Spectral interferences from Fe
have been observed. Palladium, platinum, and cyanide complexes are reported
interferences.8.6 |
|
Ba |
This element is partially ionized in the N2O/C2H2 flame. To control this interference, the samples and standards should contain 1,000 µg/mL
potassium ion.8.6 |
|
|
When analyzing using the primary Ba line (553.6 nm), background correction should be used if a large amount of Ca is present. The Ca can cause molecular absorption at this line. |
|
Ca |
Sulfate, aluminate, phosphate, and
silicate decrease sensitivity.8.14
Silicon (Si), Ti, Al, and Zr have also been reported as interferences.8.6 Using a N2O/C2H2 flame will control these interferences; however, samples and standards should contain 1,000 µg/mL potassium ion to control any ionization. |
|
|
Acetone from acetylene tanks has
been reported to decrease sensitivity. Tanks should be changed when the pressure
drops below 75 to 85 psig to prevent acetone from entering the flame.8.9 |
|
Cd |
A possible interference is Si; however, Si is not significantly soluble using the mentioned digestion procedures. |
|
Co |
A reported interference is Ni in concentrations greater than 1,500 µg/mL.8.10 Such levels of Ni are unusual in industrial environments. If a large amount is expected, samples should be analyzed for Ni first and then analyzed using an alternate Co line if Ni concentrations exceed 1,500 µg/mL. |
|
Cr |
Co, Fe, Ni, Cu, Ba, Al, Mg, Ca,
Na, and other metals have been reported as chemical interferences.8.6, 8.9,
8.10 Determining Cr in a
lean flame will control these interferences, but with a decrease in sensitivity.8.9,
8.10 The instrument should be optimized using a mixed standard containing Fe and Ni in addition to the Cr when using the Air/C2H2 flame. The above interferences are not noticed when a N2O/C2H2 flame is used. |
|
Cs |
Solutions should contain 1,000 µg/mL potassium ion to control ionization. |
|
|
Strong acids may suppress the signal; therefore, samples and standards should be matrix-matched. |
|
Cu |
Spectral interferences may occur when Ni or Fe is contained in the multielement lamp and in the sample solution. Use a single element Cu lamp or a narrow slit to circumvent this problem. |
|
|
A large amount of Zn in the sample
may interfere but can be controlled by using a lean flame.8.10 |
|
Fe |
A spectral interference may be observed if the multielement
lamp and the sample solution contain Co. An alternate line for Fe should be
used.8.6 |
|
|
Citric acid, Ni, and HNO3
may interfere but can be controlled by using a lean flame and by carefully
optimizing burner height.8.6,
8.10 Silica may also interfere,8.14 but is not appreciably soluble in the acid digestion procedures mentioned. |
|
Hf |
The presence of fluoride greatly enhances the sensitivity in the determination of Hf. Samples and standards should contain 0.1 M NH4F
to control this effect and to obtain the best sensitivity.8.6 |
|
In |
A 100-fold or greater excess of Al, Mg, Cu, Zn, or phosphate will suppress the signal. |
|
Mg |
Al, H2SO4, HNO3, Si, Ti, and HF
are reported to interfere. Addition of a suppressant (lanthanum or potassium)
will control these interferences.8.6,
8.14 Interferences can also be controlled using a N2O/C2H2 flame. |
|
Mn |
Phosphate, perchlorate, Fe, Ni,
and Co may interfere but can be controlled by using a lean flame.8.10
Tungsten (W), Mo, and Si have been reported to interfere when the pressure in
the acetylene tanks is low.8.14 |
|
Mo |
Many interferences have been reported for Mo including Fe, Mn, Ni, Cr, Si, and strontium (Sr).
Addition of Al controls these interferences.8.9,
8.10,
8.14 |
|
Na |
Ionization in the flame can occur;
an ionization suppressant should be added to the standards and samples.8.6 |
|
Ni |
A spectral interference from Fe will result when determining Ni in a sample containing Fe with a multielement lamp containing Fe. An alternate line should be used. |
|
|
Cr, Co, and Fe,8.9 or HCl and HClO4
in the presence of these metals8.10 have been reported as interferences. They are controlled by using a lean Air/C2H2
flame.8.10,
8.14 |
|
Pb |
Al, Be, Th, and Zr in a 1,000-fold
molar excess over the Pb concentration decrease sensitivity.8.14 The digestion procedure used for Pb does not solubilize a significant amount of Al, Be, or Zr for them to be a problem in the analysis. Workplace environments rarely contain significant amounts of Th along with Pb; however, if suspected to be present, the sample should also be analyzed for Th since it is very toxic. |
|
|
Phosphate, carbonate, iodide, fluoride, and acetate at a 10-fold
excess may also interfere.8.10
Sulfate and Ca in excess have also been reported as interferences.8.7 |
|
Pt |
A number of elements interfere with the determination when using an Air/C2H2
flame.8.6 These interferences are minimized when using a N2O/C2H2 flame. |
|
Sb |
A spectral interference occurs when Sb is determined at 217.6 nm in the presence of large amounts of Pb, which has an adjacent line at 217.0 nm. It has been reported that large concentrations of Cu also absorb at 217.6 nm. In either situation, the alternate 231.2 nm line for Sb
should be used.8.6,
8.7 |
|
|
Cu and Ni have been reported to suppress Sb
sensitivity, but can be controlled by using a lean flame.8.9,
8.10 |
|
Se |
Background absorption is severe at
the wavelengths used to determine Se. Background correction should be used.8.6 |
|
|
Large amounts of Ni, Co, Fe, Cu,
Mn, Pb, and other metals, if present in the sample may form selenides in the
flame, decreasing sensitivity.8.9 |
|
|
Increased sensitivity is noted when using an Air/H2 flame as compared to an Air/C2H2
flame. For greatly enhanced sensitivity, analyze Se by graphite furnace atomic
absorption using a modified matrix containing Ni.8.15 |
|
Sn |
Alkali metals and alkaline earths, Cu, Co, Zn, Al, Ti, phosphoric acid (H3PO4), and H2SO4 have been reported as interferences when Air/H2
flames are used. Interferences are reduced or eliminated in hotter flames, but
sensitivity is greatly reduced.8.6,
8.10 |
|
Te |
A spectral interference may occur when Cu is contained in the multielement
lamp and in the sample.8.14 |
|
|
Enhanced sensitivity can be
obtained for this element using graphite furnace atomic absorption analysis of
sample solutions modified to contain a Ni matrix.8.15 |
|
Ti |
Samples and standards should contain 1,000 µg/mL potassium ion to control ionization. |
|
|
The Ti signal is enhanced by many
other metals.8.6 |
|
Y |
Samples and standards should contain 1,000 µg/mL potassium ion to control ionization. |
|
|
Strong acids may suppress the signal; therefore, samples and standards should be matrix-matched. |
|
Zn |
A spectral interference may occur
if the multielement lamp and the sample contain Cu.8.14 |
|
Zr |
Fluoride, chloride, and ammonium enhance Zr sensitivity. Sulfate, nitrate, and nickel bromide decrease sensitivity. Addition of NH4F
will control these interferences.8.6 |
|
|
|