ASTM D3718-85a(2010)
(Test Method)Standard Test Method for Low Concentrations of Chromium in Paint by Atomic Absorption Spectroscopy
Standard Test Method for Low Concentrations of Chromium in Paint by Atomic Absorption Spectroscopy
SIGNIFICANCE AND USE
The permissible level of heavy metals in certain coatings is specified by governmental regulatory agencies. This test method provides a fully documented procedure for determining low concentrations of chromium present in both water- and solvent-reducible coatings to determine compliance.
SCOPE
1.1 This test method covers the determination of the content of chromium (including chromium oxide) in the range between 0.005 and 1.0 % present in the solids of liquid coatings or in dried films obtained from previously coated substrates. There is no reason to believe that higher levels could not be determined by this test method, provided that appropriate dilutions and adjustments in specimen size and reagent quantities are made.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
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 hazard statements are given in Section 7.
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Standards Content (Sample)
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Designation: D3718 − 85a (Reapproved2010)
Standard Test Method for
Low Concentrations of Chromium in Paint by Atomic
Absorption Spectroscopy
This standard is issued under the fixed designation D3718; 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.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope potassium permanganate and sulfuric acid in a polytetrafluo-
roethylene (PTFE)-lined acid decomposition vessel at an
1.1 This test method covers the determination of the content
elevated temperature. The chromium in the filtered digestion
of chromium (including chromium oxide) in the range between
mixture is determined by atomic absorption spectroscopy.
0.005 and 1.0 % present in the solids of liquid coatings or in
dried films obtained from previously coated substrates. There
4. Significance and Use
is no reason to believe that higher levels could not be
4.1 The permissible level of heavy metals in certain coat-
determined by this test method, provided that appropriate
ingsisspecifiedbygovernmentalregulatoryagencies.Thistest
dilutions and adjustments in specimen size and reagent quan-
methodprovidesafullydocumentedprocedurefordetermining
tities are made.
low concentrations of chromium present in both water- and
1.2 The values stated in SI units are to be regarded as
solvent-reducible coatings to determine compliance.
standard. No other units of measurement are included in this
standard.
5. Apparatus
1.3 This standard does not purport to address all of the
5.1 Atomic Absorption Spectrophotometer , consisting of an
safety concerns, if any, associated with its use. It is the
atomizer and either a single- or three-slot burner; gas pressure-
responsibility of the user of this standard to establish appro-
regulating and metering devices for nitrous oxide (N O) and
priate safety and health practices and determine the applica-
acetylene; a chromium hollow cathode lamp with a regulated
bility of regulatory limitations prior to use. Specific hazard
constant current supply; a monochromator and associated
statements are given in Section 7.
optics; a photosensitive detector connected to an electronic
amplifier; and a readout device.
2. Referenced Documents
5.2 Muffle Furnace, maintained at 500 6 10°C.
2.1 ASTM Standards:
5.3 Force-Draft Oven, maintained at 105 6 2°C.
D1193 Specification for Reagent Water
D2832 GuideforDeterminingVolatileandNonvolatileCon-
5.4 Acid Decomposition Vessel, with PTFE digestion cup.
tent of Paint and Related Coatings
5.5 Hot Plate, with variable surface temperature control
over the range from 70 to 200°C.
3. Summary of Test Method
5.6 Volumetric Flasks, 50, 100 and 1000-mL.
3.1 The sample of liquid coating or dried film is prepared
for analysis by dry ashing at 500°C followed by digestion with
5.7 Pipets, 5, 10, 15, and 20-mL capacity.
5.8 Filter Paper, ashless, medium filtering 15-cm.
This test method is under the jurisdiction of ASTM Committee D01 on Paint
5.9 Paint Shaker.
and Related Coatings, Materials, andApplications and is the direct responsibility of
Subcommittee D01.21 on Chemical Analysis of Paints and Paint Materials.
Current edition approved June 1, 2010. Published June 2010. Originally
approved in 1978. Last previous edition approved in 2005 as D3718 – 85a (2005). The sole source of supply of an acid decomposition cup, (Catalog Number
DOI: 10.1520/D3718-85AR10. 4745), known to the committee at this time is the Parr Instrument Co., 211
For referenced ASTM standards, visit the ASTM website, www.astm.org, or Fifty-third St., Moline, IL 61265. If you are aware of alternative suppliers, please
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM provide this information toASTM International Headquarters. Your comments will
Standards volume information, refer to the standard’s Document Summary page on receive careful consideration at a meeting of the responsible technical committee,
the ASTM website. which you may attend.
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D3718 − 85a (2010)
5.10 Crucibles, wide form, porcelain, approximately 30-mL hazardous to health. Care should be exercised in preparation of
capacity. a sample for test. The wearing of a respirator and rubber or
synthetic gloves is recommended. In case of contact, wash
5.11 Mortar and Pestle.
thoroughly with soap and water. Mixtures containing hexava-
5.12 Paint Draw-Down Bar.
lent chromium compounds should not be flushed down a drain
but disposed of as hazardous waste.
6. Reagents
7.3 Use only a rubber bulb aspirator for pipetting liquids.
6.1 Purity of Reagents—Reagent grade chemicals shall be
used in all tests. Unless otherwise indicated, it is intended that
8. Calibration and Standardization
all reagents shall conform to the specifications of the Commit-
8.1 Prepare 50-mL quantities of at least four standard
tee onAnalytical Reagents of theAmerican Chemical Society,
5 solutions bracketing the expected chromium concentration in
where such specifications are available. Other grades may be
the sample to be tested. To suitable aliquots of the 100-ppm
used, provided it is first ascertained that the reagent is of
chromium standard working solution, add 10 mL of the
sufficiently high purity to permit its use without lessening the
oxidizing solution with a pipet, followed by the dropwise
accuracy of the determination.
addition of reducing solution until the permanganate color has
6.2 Purity of Water—Unless otherwise indicated, references
been discharged, then dilute to 50 mL with water.
towatershallbeunderstoodtomeanreagentwaterconforming
8.2 Operational instructions for atomic absorption spectro-
to Type II of Specification D1193.
photometers vary with different models. Consult the manufac-
6.3 Chromium Standard Stock Solution (1 mg/mL)—
turer’s literature for establishing optimum conditions for the
Dissolve 3.735 g of potassium chromate (K CrO ) in 100 mL
2 4
specific instrument used.
of water and dilute to 1 L.
8.3 Turn the instrument on and set the wavelength to the
6.4 Chromium Standard Working Solution (0.1 mg/mL)—
357.9-nm chromium line. Apply the recommended current to
Pipet 10 mL of the chromium standard stock solution into a
the chromium hollow-cathode lamp. Allow the instrument to
100-mL volumetric flask and dilute to volume with water.
warm up for about 15 min and set the slit width. Adjust the
nitrous oxide and acetylene pressures and ignite the burner
6.5 Oxidizing Solution—Dissolve 0.2 g of potassium per-
according to instructions.
manganate (KMnO ) in 100 mL of H SO (1 + 1). Stir until
4 2 4
completely dissolved. The color of this solution is dark brown.
8.4 Aspirate water to rinse the atomizer chamber.Aspirate a
standard solution and make any necessary readjustment in
6.6 Reducing Solution—Dissolve1gof hydroxylamine
instrumentparameterstoobtainmaximumabsorption.Zerothe
hydrochloride (NH OH·HCl) in 100 mL of water.
instrument while aspirating reagent blank solution (6.7).Aspi-
6.7 Reagent Blank—Pipet 5 mL of oxidizing solution into
rate each of the appropriate standard solutions and record the
25 mL of water contained in a 50-mL volumetric flask. Add
corresponding instrument readings. Aspirate water between
reducing solution dropwise until the permanganate color has
each standard.
been discharged; then dilute to 50 mL with water.
8.5 Transfer a 25-mL aliquot from each of the standard
6.8 Sulfuric Acid (1+1) —Carefully add 1 volume of
solutions prepared in 8.1 to 50-mLvolumetric flasks and dilute
concentrated H SO (sp gr 1.84) to 1 volume of water.
2 4
to volume with water. Repeat the steps outlined in 8.4 for the
6.9 Sulfuric Acid (5 % volume per volume)—Carefully add
diluted aliquot solutions.
50 mL of concentrated H SO (sp gr 1.84) to 500 mL of water
2 4
8.6 Construct a calibration curve on linear graph paper by
and dilute to 1 L.
plotting the absorbance versus concentration (micrograms per
millilitre) for each set of standard solutions.
7. Hazards
NOTE1—Toobtainmaximumaccuracyoneshouldcompletecalibration
7.1 Use care in handling concentrated H SO because it is
2 4
and standardization just prior to sample analysis.
corrosiveandmaycausesevereburnsoftheskinoreyes.Refer
to suppliers
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