TA的首页ASTM D6007 Determining Formaldehyde Concentration in Air from Wood
- Scope
- Referenced Documents
1.1 This test method measures the formaldehyde concentra-
tions in air from wood products under defined test conditions of
temperature and relative humidity. Results obtained from this
small-scale chamber test method are intended to be comparable
to results obtained testing larger product samples by the large
chamber test method for wood products, Test Method E 1333.
The results may be correlated to values obtained from Test
Method E 1333. The quantity of formaldehyde in an air sample
from the small chamber is determined by a modification of the
National Institute for Occupational Safety and Health (NIOSH)
3500 chromotropic acid test procedure. Other analytical pro-
cedures may be used to determine the quantity of formaldehyde
in the air sample provided that such methods give results
comparable to those obtained by using the chromotropic acid
procedure. However, the test results and test report must be
properly qualified and the analytical procedure employed must
be accurately described.
1.2 The wood-based panel products to be tested by this test
method are characteristically used for different applications
and are tested at different relative amounts or loading ratios to
reflect different applications. This is a test method that specifies
testing at various loading ratios for different product types.
However, the test results and test report must be properly
qualified and must specify the make-up air flow, sample
surface area, and chamber volume.
1.3 Ideal candidates for small-scale chamber testing are
products relatively homogeneous in their formaldehyde release
characteristics. Still, product inhomogeneities must be consid-
ered when selecting and preparing samples for small-scale
chamber testing.
1.4 The values stated in SI units are the standard values.
Any values given in parentheses are for information only.
1.5 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 appro-
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
1 This test method is under the jurisdiction of ASTM Committee D07 on Wood
and is the direct responsibility of Subcommittee D07.03 on Panel Products.
Current edition approved April 10, 2002. Published June 2002. Originally
published as D 6007 - 96. Last previous edition D 6007 - 96.
2.1 ASTM Standards:
D 3195 Practice for Rotameter Calibration2
D 5197 Test Method for Determination of Formaldehyde
and Other Carbonyl Compounds in Air (Active Sampler
Methodology)2
D 5221 Test Method for Continuous Measurement of Form-
aldehyde in Air2
E 77 Test Methods for Inspection and Verification of Ther-
mometers3
E 220 Method for Calibration of Thermocouples by Com-
parison Techniques3
E 337 Test Method for Measuring Humidity with a Psy-
chrometer (the Measurement of Wet-Bulb and Dry-Bulb
Temperatures)2
E 691 Practice for Conducting an Interlaboratory Study to
Determine the Precision of a Test Method4
E 741 Test Method for Determining Air Change in a Single
Zone by Means of Tracer Gas Dilution5
E 1333 Test Method for Determining Formaldehyde Con-
centrations in Air and Emission Rates from Wood Products
Under Defined Test Conditions Using a Large Chamber6
2.2 U.S. Department of Housing and Urban Development
(HUD) Standards:
24 CFR 3280, Manufactured Home Construction and Safety
Standards7
2.3 NIOSH Standard:
3500 Formaldehyde Method8
2.4 Other Documents:
Minnesota Statutes Section 144.495, 325f.18, and 325F.181
Formaldehyde Gases in Building Materials9
2 Annual Book of ASTM Standards, Vol 11.03.
3 Annual Book of ASTM Standards, Vol 14.03.
4 Annual Book of ASTM Standards, Vol 14.02.
5 Annual Book of ASTM Standards, Vol 04.11.
6 Annual Book of ASTM Standards, Vol 04.10.
7 Federal Register, Vol 49, No. 155, Aug. 8, 1984, available from Superintendent
of Documents, U.S. Government Printing Office, 732 N. Capitol St., NW, Mail Stop:
SDE, Washington, DC 20401.
8 U.S. Dept. of Health and Human Services, 1989, available from Superintendent
of Documents, U.S. Government Printing Office, 732 N. Capitol St., NW, Mail Stop:
SDE, Washington, DC 20401.
9 Available from Print Communications, Dept. of Administration, 117 University
Ave., St. Paul, MN 55155.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
1
- Terminology
D 6007 – 02
4.3 This test method requires the use of a chamber of 0.02
to 1 m3in volume to evaluate the formaldehyde concentration
3.1.1 air change rate, N (N is equal to Q/V)—the ratio of
conditioned and filtered air that enters or is replaced in the
small chamber in one hour divided by the interior volume of
the small chamber, air changes per hour (ACH).
3.1.2 equilibrium concentration, Ceq—is that Csmeasured
when Qequals zero, ppm.
3.1.3 loading ratio, L—(L is equal to A/V) the total exposed
surface area, excluding panel edges, of the product being tested
divided by the test chamber’s interior volume, m2/m3.
3.1.4 make-up air flow, Q—the quantity of conditioned and
filtered air fed into the chamber per unit time, m3/h.
3.1.5 mass transfer coeffıcient, K—a measure of the perme-
ability of the emitting surface of a wood based panel product,
m/h. Kis calculated as follows:10
~Q/A!~Cs!
in air using the following controlled conditions:
4.3.1 Conditioning of specimens prior to testing,
4.3.2 Exposed surface area of the specimens in the test
chamber,
4.3.3 Test chamber temperature and relative humidity,
4.3.4 The Q/A ratio, and
4.3.5 Air circulation within the chamber.
- Interferences
negative interference when present at an 8:1 excess over
formaldehyde. Modifications in the analytical procedure shall
be made when relatively high phenol to formaldehyde concen-
trations (8:1) are anticipated.11,12
- Apparatus
K 5
~Ceq2 Cs!
(1)
6.1 Test Chamber—The interior volume of the small cham-
3.1.6 N/L ratio—(N/L is equivalent to Q/A) the ratio of air
flow through the chamber to sample surface area, m/h, as
follows:
Q/V
N/L 5A/V5 ~Q/V! 3 ~V/A! 5 Q/A (2)
3.1.7 Q/A ratio—the ratio of air flow through the chamber
(Q) to sample surface area ( A), m/h.
3.1.8 sample surface area, A—the total area of all sample
faces exposed in the chamber, m2.
3.1.9 steady state concentration, Cs—the interval when the
formaldehyde concentration is not changing with time (ex-
pressed in parts of formaldehyde per million parts air (ppm))
under the defined environmental test parameters.
3.1.10 volume of closed system, V—the interior volume of
the test chamber, m
3
.
- Significance and Use
lished for wood panel building products made with urea-
formaldehyde adhesives and permanently installed in homes or
used as components in kitchen cabinets and similar industrial
products. This test method is intended for use in conjunction
with the test method referenced by HUD Rules and Regula-
tions 24 CFR 3280 for manufactured housing and by Minne-
sota Statutes Section 144.495 for housing units and building
materials. This test method provides a means of testing smaller
samples and reduces the time required for testing.
4.2 Formaldehyde concentration levels obtained by this
small-scale method may differ from expected in full-scale
indoor environments. Variations in product loading, tempera-
ture, relative humidity, and air exchange will affect formalde-
hyde emission rates and thus likely indoor air formaldehyde
concentrations.
10 Christensen, R. L., and Anderson, W. H., Measuring Formaldehyde Concen-
trations Using a Small Scale Chamber, Proceedings 23rd International
Particleboard/Composite Materials Symposium, W.S.U., 1989.
2
ber shall be from 0.02 to 1 m3. The interior of the test chamber
shall be free of refrigeration coils that condense water and
items such as humidifiers with water reservoirs since water has
the potential for collecting formaldehyde and thus influencing
test results. The interior surfaces of the small chamber,
including any sample support system, shall be a nonadsorbent
material. Stainless steel, aluminum, and polytetrafluoroethyl-
ene (PTFE) have been found appropriate as chamber lining
materials. All joints except for doors used for loading and
unloading specimens should be sealed. Doors shall be self-
sealing.
6.2 Make-Up Air:
6.2.1 The make-up air shall come from a filtered dust-free
environment and contain not more than 0.02 ppm of formal-
dehyde. This can be accomplished by passing make-up air
through a filter bed of activated carbon, activated alumina
impregnated with potassium permanganate, or other materials
capable of absorbing, or oxidizing formaldehyde.
6.2.2 Make-up air for the chamber must pass through a
calibrated air flow measuring device.
6.2.3 Air Circulation—Low speed mixing fans or multi-port
inlet and outlet diffusers are two techniques that have been
used successfully to ensure mixing of the chamber air over all
sample surfaces.
6.2.4 Air Sampling Port—The exhaust flow (that is, cham-
ber outlet) is normally used as the sampling point, although
separate sampling ports in the chamber can be used. The
sampling system shall be constructed of a material to minimize
adsorption (for example, glass, stainless steel), and the system
should be maintained at the same temperature as the test
chambers.
6.3 Examples of acceptable reagents, materials, and equip-
ment are provided in Appendix X1.
11 Hakes, D., Johnson, G., and Marhevka, J., Procedure for Elimination of
Phenol Interference in the Chromotropic Acid Method for Formaldehyde, American
Industrial Hygiene Association, April 1984.
12 Technical Bulletin No. 415, National Council of the Paper Industry for Air and
Stream Improvement Inc. (NCASI), 1983.
- Hazards
native conditioning intervals may give better correlation, such
7.1 Chromotropic Acid Reagent Treatment—(See 10.3.4
and 10.3.5.) During this hazardous operation, the operator must
wear rubber gloves, apron, and a full face mask or be protected
from splashing by a transparent shield such as a hood window.
The solution becomes extremely hot during addition of sulfuric
acid. If acid is not added slowly, some loss of sample could
occur due to splattering.
7.2 Cleaning Chemicals for Glassware— Use appropriate
precautions if cleaning chemicals are considered to be hazard-
ous.
- Test Specimens
A/V) is defined as the total exposed specimen surface area,
excluding edge area, divided by the chamber volume. Alumi-
num tape shall be used to cover the edges of the specimens if
the edge exposure is greater than 5 % of the surface area,
thereby retarding formaldehyde emission from the edge. The
Q/A ratios in Table 1 are used for testing wood panel products
containing formaldehyde. Each small chamber will have a
unique value for the make-up air flow (Q) dependent on the
sample surface area used, and the type of product tested.
as seven day conditioning that parallels Test Method E 1333.
- Procedure
10.1.1 Purge the chamber by running empty or with the use
of filters designed to reduce the formaldehyde background
concentration in air, or both. The formaldehyde background
concentration in air of the empty operating chamber shall not
exceed 0.02 ppm. Clean chamber surfaces with water or
suitable solvent if formaldehyde background concentrations
approach 0.02 ppm.
10.1.2 Locate the specimens in the chamber so that the
conditioned air stream circulates over all panel surfaces.
10.1.3 Operate the chamber at 25 6 1°C (776 2°F) and 50
6 4 % relative humidity. Record the temperature, relative
humidity, and barometric pressure during the testing period.
Conduct the chamber test at a given Q/A ratio and record this
ratio in the report.
10.1.4 Specimens remain in the operating chamber until a
steady state formaldehyde concentration is reached. The time
may be estimated using the following equation:
21n ~12Ct/Cs!V
8.2 Nonstandard Sample Configuration Testing Products
with Single Surface Exposed—Some products have signifi-
cantly different formaldehyde release characteristics for each
where:
t 5
Q 1 KA
(3)
surface. In those cases, panels may be tested back-to-back with
edges taped together. The panels shall be identified as tested in
t
= time to any percent of Csless than 100 % (such as
99.9999999999, and so forth),
the back-to-back mode.
8.3 Combination Testing—Different products may be tested
in combination. Qualify the test report and note the Q/A ratio
used.
- Sample Material Handling and Specimen Conditioning
wrapped in polyethylene plastic having a minimum thickness
of 0.15 mm (6 mil) until sample conditioning is initiated. When
testing wood products that are not newly manufactured such as
after original application, installation or use, the method of
packaging and shipping the products for testing shall be fully
described. Information on the age and history of the product
shall be detailed in the test report.
9.2 Conditioning—Condition test specimens with a mini-
mum distance of 0.15 m (6 in.) between each specimen for 2 h
6 15 min at conditions of 24 6 3°C (75 6 5°F) and 50 6 5 %
relative humidity. The formaldehyde concentration in the air
within 0.3 m (12 in.) of where panels are conditioned shall be
not more than 0.1 ppm during the conditioning period. Alter-
TABLE 1 Q/A Ratios, 62 %
Test Method
E 1333 N/L or Q/A (m/h) Product Type
L (m2/m3)
0.95 0.526 hardwood plywood wall paneling
0.43 1.173 particleboard flooring panels,
industrial particleboard panels,
industrial hardwood plywood panels
0.26 1.905 medium density fiberboard (MDF)
0.13 3.846 particleboard door core
3
Ct= concentration at time, t,
Cs= steady state formaldehyde concentration,
A = product surface area, m2,
V = chamber volume, m3,
K = mass transfer coefficient, m/h, and
−1n = negative natural log.
It is necessary to know the range of K for the product
involved. If K is unknown, a conservative estimate based on
the literature may be used.10Alternatively, back to back air
tests giving replicate values within the error of the analytical
method may be used.
10.2 Air Sampling—Purge air sampling lines for 1 min. At
the sampling station, bubble air through a single impinger
containing 20 mL of a 1 % sodium bisulfite (NaHSO3) solu-
tion. A filter trap may be placed between the impinger and the
flowmeter. Set a calibrated flowmeter to maintain an average
airflow of 1 6 0.05 L/min for 30 min with time measured
accurately to within 5 s. Following air sampling, analyze the
collection solution.
10.3 Analysis of Air Samples:
10.3.1 Pipet 4 mL of the NaHSO3solution from the im-
pinger into each of three 16 by 150-mm screwcap test tubes for
triplicate analysis of each impinger sample.
10.3.2 Pipet 4 mL of 1 % NaHSO3into a 16 by 150-mm
screwcap test tube to act as a reagent blank.
10.3.3 Add 0.1 mL of 1 % chromotropic acid reagent to
each test tube. Shake tube after addition.
10.3.4 Slowly and carefully pipet 6.0 mL concentrated
sulfuric acid (H2SO4) into each test tube (Warning—See 7.1.)
and allow to flow down the side of test tube. Allow the
volumetric pipet to drain. Do not blow out. Before placing caps
D 6007 – 02
on test tubes, check the condition of the polytetrafluoroethyl-
ene (PTFE) cap liners to make sure they are clean and not
deteriorated.
11.2.1 Calculate the concentration of formaldehyde in air in
the small chamber as follows:
Ct3 24.47
10.3.5 Slowly and gently agitate test tubes to affect mixing.
Mixing is complete when there is no sign of stratification.
Caution needs to be taken due to the exothermic chemical
where:
Cs5
Vs3 30.03
(6)
reaction. Rapid mixing will cause heating and a pressure
increase which may break the test tube. Vent test tubes to
release pressure.
10.3.6 If absorbance readings exceed 1.0 or if spectropho-
tometric analysis is performed within 2 h, heat capped test
tubes to 95°C or place capped test tubes in a boiling water bath
for 15 6 2 min to ensure that the chemical reaction is
completed. Remove tubes from water bath and allow to cool to
room temperature.
10.4 Absorbance Readings:
10.4.1 Standardize the spectrophotometer using distilled
water at 580 nm in accordance with the instrument’s operating
instructions. The reagent blank shall be read against distilled
water because an absorbance above 0.100 for the reagent blank
indicates contamination of reagent blank or improper solution
preparation. If absorbance for the reagent blank compared to
distilled water is greater than 0.100, repeat the entire standard-
ization procedure.
10.4.2 Zero the instrument using the reagent blank if the
absorbance is not greater than 0.100 (compared to distilled
water as zero). Alternatively, the instrument may be left zeroed
on distilled water, and the absorbance of the reagent blank
subtracted from the absorbance of the standard solutions.
10.4.3 Read and record absorbance at 580 nm for each test
tube prepared (see A4.6-A4.9). If the absorbance of the
specimen solution is found to fall outside the preferred
absorbance range (>1.0), steps 10.3.1-10.3.4 may be repeated
using an appropriate dilution of each impinger solution.
- Calculation
at standard conditions as follows:
V 3 P 3 298
Cs= parts of formaldehyde per million parts air, ppm,
30.03 = molecular weight of formaldehyde, and
24.47 = µL of formaldehyde gas in 1 µmol at 101 kPa and
298 K.
Round calculated formaldehyde concentrations to the near-
est 0.01 ppm. Round up to the nearest 0.01 ppm any value at
or in excess of 0.005 ppm. Round down all values below 0.005
to the nearest 0.01 ppm.
11.3 When the chamber temperature differs from 25 by 1⁄4
°C (77 by 1⁄2 °F) or more, adjust the formaldehyde concentra-
tions obtained to a standard temperature of 25°C (77°F) using
a formula developed by Berge, et al.13Annex A1 contains a
table of conversion factors for use at different observed test
temperatures as calculated using this formula. The observed
test temperature is the average temperature for the total period
of 15 min prior to air sampling plus the time of air sampling.
11.4 The small chamber formaldehyde concentration in air
shall be adjusted to a concentration at 50 % relative humidity
when the difference in relative humidity from 50 % is greater
than or equal to 1 % (see Annex A2).
- Report
12.1.1 Test number.
12.1.2 Title of report shall state if standard face and back
configuration testing (see 8.1) or if nonstandard configuration
testing (see 8.2) was performed.
12.1.3 The manner in which materials were shipped or
stored, or both: wrapped separately in vapor retarder, wrapped
collectively in vapor retarder or in original box or container. If
materials were shipped unwrapped, or not in the original box or
container, it shall be noted in the test report. Information on age
and product history, if known, shall be described in the test
report.
where:
Vs5
101 3 ~T 1 273!
(4)
12.1.4 Name of product manufacturer or name of company
submitting material, or both, date of manufacture, and sam-
Vs= volume of air at standard conditions (101 kPa and
298 K), L,
V = volume of air sampled, L,
P = barometric pressure, kPa, and
T = temperature of sample air, °C.
11.2 Calculate total micrograms of formaldehyde collected
in each impinger sample as follows:
pling date (if known).
12.1.5 Description of test material or product shall include
generic product name, thickness, size, if surface is finished or
sealed (both surfaces should be described), and special treat-
ment (if known).
12.1.6 Specimen conditioning details to include average
temperature and range (nearest 1⁄4 °C), average relative humid-
where:
Ct5 Ca3 Fa
(5)
ity and range (nearest 1 %), and time to the nearest minute.
12.1.7 Formaldehyde background concentration in the air in
the area where specimens are conditioned (rounded to the
Ct= total formaldehyde in the sample, µg,
Ca= total quantity of formaldehyde in the sample aliquots
taken from the impinger (as determined from the
calibration curve in Annex A4), µg, and
Fa= aliquot factor 5 sampling solution volume, mL
nearest 0.01 ppm).
12.1.8 Chamber volume: nominal length, width, and height.
13 Berge, A., Mellagaard, B., Hanetho, P., and Ormstad, E. B., Formaldehyde
aliquot used, mL
4
Release from Particleboard-Evaluation of a Mathematical Model , Holz Als
Roh-und Werkstoff 38, 1980, pp. 252–255.
12.1.9 Chamber Q/L ratio.
D 6007 – 02
- Precision and Bias
12.1.10 Description of specimens as loaded into chamber
including number of specimens in charge and number of
surfaces exposed.
12.1.11 Average temperature and range (nearest 1⁄4 °C),
average relative humidity and range (nearest 1 %), and time to
the nearest minute during the sampling period.
12.1.12 Chamber formaldehyde concentration in air at test
conditions; chamber formaldehyde concentration in air cor-
rected to 25°C, 50 % relative humidity, rounded to nearest 0.01
ppm.
12.1.13 The analytical method employed if different from
the NIOSH 3500 chromotropic acid test procedure.
12.1.14 Formaldehyde background concentration of air in
chamber prior to test and formaldehyde concentration of
make-up air (rounded to the nearest 0.01 ppm).
12.1.15 Air-sampling rate and length of sample time.
12.1.16 Date of test.
13.1 A study including seven laboratories and four test
materials was conducted in accordance with Practice E 691 and
resulted in the following statements for precision and bias.
13.1.1 Repeatability—Test results indicate a repeatability
(within laboratory) precision standard deviation ranging from
0.01 to 0.02 for products emitting 0.06 to 0.24 ppm of
formaldehyde.
13.1.2 Reproducibility—Test results indicate a reproducibil-
ity (between laboratory) precision standard deviation ranging
from 0.02 to 0.05 for products emitting 0.06 to 0.24 ppm of
formaldehyde, respectively.
13.1.3 Bias—No bias statement is available for this test
method due to the lack of an acceptable homogeneous form-
aldehyde off-gassing reference material.
- Keywords
concentration in air; small chamber; small-scale test; wood
products
ANNEXES
(Mandatory Information)
A1. TEMPERATURE CONVERSION FACTORS FOR FORMALDEHYDE
A1.1 Table A1.1 is based on the Berge, et al13formula to
correct formaldehyde concentrations in air for temperature:
C 5 Co3 e2R~1/t21/to!
or
Co5 CeR~1/t21/to!
5
where:
C = test formaldehyde concentration level,
Co= corrected formaldehyde concentration level,
e = natural log base,
R = coefficient of temperature (9799),
t = actual temperature, K, and
to= corrected temperature, K.
D 6007 – 02
TABLE A1.1 Temperature Conversion Table for Formaldehyde
NOTE 1—The Berge, et al11equation is an exponential function. The
greater the variance between actual and corrected temperature, the greater
the potential error. Two horizontal lines within the table delineate the
specified test temperature ranges 25 6 1°C (77 6 2°F).
°C
Actual
(°F)
To Convert
to 25°C
(77°F)
Multiple by
°C
Actual
(°F)
To Convert
to 25°C
(77°F)
Multiply by
22.2
22.5
22.8
23.1
23.3
23.6
23.9
24.2
24.4
24.7
25.0
(72)
(72.5)
(73)
(73.5)
(74)
(74.5)
(75)
(75.5)
(76)
(76.5)
(77)
1.36
1.32
1.28
1.24
1.20
1.17
1.13
1.10
1.06
1.03
1.00
25.3
25.6
25.8
26.1
26.4
26.7
26.9
27.2
27.5
27.8
(77.5)
(78)
(78.5)
(79)
(79.5)
(80)
(80.5)
(81)
(81.5)
(82)
0.97
0.94
0.91
0.89
0.86
0.83
0.81
0.78
0.76
0.74
A2. RELATIVE HUMIDITY CONVERSION FACTORS FOR FORMALDEHYDE
A2.1 Table A2.1 is based on the Berge, et al13formula to
correct formaldehyde concentrations in air for relative humid-
ity:
TABLE A2.1 Relative Humidity Conversion Table for
Formaldehyde
or
C 5 Co@1 1 A~H 2 Ho!#
C
Co5
Actual RH % To Convert to 50 %
RH Multiply by Actual RH %
To Convert to 50 %
RH Multiply by
where:
1 1 A~H 2 Ho!
46
47
48
49
50
1.08
1.06
1.04
1.02
1.00
51
52
53
54
0.98
0.97
0.95
0.93
C = test formaldehyde concentration level,
Co= corrected formaldehyde concentration level,
A = coefficient of humidity (0.0175),
H = actual relative humidity, and
Ho= relative humidity, %.
A3. STANDARD SOLUTIONS A AND B
A3.1 Standardization of Formaldehyde Standard Solution
A (1.0 mg/mL):
A3.1.1 Pipet 2.70 mL of 37.0 % formaldehyde solution into
a 1 L volumetric flask. Dilute to mark with freshly distilled
water and mix well. This solution is stable for at least one
month.
A3.1.2 Calibrate the pH meter with standard buffer solution
of pH 9.0.
A3.1.3 Pipet two 50 mL aliquots of formaldehyde standard
A3.1.4 Place solution on magnetic stirrer. Immerse pH
electrodes into the solution and carefully titrate with 0.100 N
hydrochloric acid (HCl) to the original pH of the solution.
Record volume of HCl and corresponding pH intermittently.
Make a graph of pH versus volume of HCl.
A3.1.5 Calculate the concentration, CA, of formaldehyde
standard Solution A in milligrams per millilitre as follows:
V 3 N 3 30.03 ~ mg per milliequivalent!
Solution A into two 150-mL beakers for duplicate analysis and
add 20 mL of 1 M sodium sulfite (Na2SO3) to each beaker.
where:
CA5
50 ~mL!
Sodium sulfite solution can age, thus the 1 M sodium sulfite
solution should be adjusted to a 9.5 pH before adding to
standard Solution A aliquots.
6
V = 0.100 N HCl required at pH of 9.5 from the graph
prepared in A3.1.4, mL, and
D 6007 – 02
N = normality of HCl. The concentration of standard
Solution A will be the average of the two analyses
conducted.
A3.2 Standard Solution B:
(NaHSO3) to 100 mL in a volumetric flask using distilled
water. This standard is stable for at least one week.
A3.2.2 Calculate the concentration of formaldehyde CBin
standard Solution B in micrograms per millilitre as follows:
CA3 1000 3 1 mL
A3.2.1 Prepare formaldehyde standard Solution B by dilut-
ing 1 mL of standard Solution A and 1 g of sodium bisulfite
Cb5
A3.2.3 Record the value.
100
A4. CALIBRATION CURVE
A4.1 Prepare a 1 % sodium bisulfite (NaHSO3) solution by
dissolving 1 g of NaHSO3in a 100 mL volumetric flask and
diluting to the mark with distilled water. This solution is stable
at room temperature and should be prepared on a weekly basis.
A4.2 Label six 16 by 150 mm screwcapped test tubes 1, 2,
3, 4, 5, and 6.
A4.3 Pipet the following volumes of 1 % sodium bisulfite
solution and then standard Solution B (see Annex A3) into the
labeled test tubes:
Tube No. Volume, mL
repeat the entire standardization procedure.
A4.7 Zero the instrument using the reagent blank (Tube 1)
if the absorbance is not greater than 0.040 (compared to
distilled water as zero). Alternatively, the instrument may be
left zeroed on distilled water, and the absorbance of the reagent
blank subtracted from the absorbance of the standard solutions.
Recovery shall be within 65 % of reagent blank.
A4.8 Read and record absorbance at 580 nm for each
standard prepared (Tubes 2 through 6).
1
2
3
4
5
6
NaHSO3
4.0
3.9
3.7
3.5
3.3
3.0
Solution B
0
0.10
0.30
0.50
0.70
1.00
A4.9 Plot absorbance against micrograms of formaldehyde
in the color developed solution. Note the amount of formalde-
hyde in micrograms is based upon the concentration of
formaldehyde in standard Solution B, which is dependent upon
the standardization carried out on standard Solution A in Annex
A3.
A4.3.1 Note that no Solution B was added to Test Tube 1.
Test Tube 1 will be the reagent blank.
A4.4 Add 0.1 mL of 1 % chromotropic acid reagent to each
test tube. Shake tube after addition.
A4.5 Slowly and carefully pipet 6.0 mL concentrated
sulfuric acid (H2SO4) into each test tube (Warning–See 7.1.)
and allow to flow down the side of the test tube. Allow the
volumetric pipet to drain. Do not blow out. Before placing caps
on test tubes, check the condition of the polytetrafluoroethyl-
ene (PTFE) cap liners to make sure they are clean and not
deteriorated.
A4.5.1 Slowly and gently agitate test tubes to affect mixing.
Mixing is complete when there is no sign of stratification.
Carefully vent test tubes to release pressure. Rapid mixing will
cause heating and a pressure increase with the potential for
breaking the test tube. If absorbance readings exceed 1.0 or if
spectrophotometric analysis is performed within 2 h, heat
capped test tubes to 95°C or place in a boiling water bath for
15 + 2 min to ensure that the chemical reaction is complete.
After removal, allow the test tubes to cool to room temperature.
A4.6 Standardize the spectrophotometer using distilled
water at 580 nm in accordance with the instrument’s operating
instructions. The reagent blank (Tube 1) shall be read against
distilled water. A high absorbance for the reagent indicates
contamination of reagent blank or improper solution prepara-
tion. If absorbance for the reagent blank compared to distilled
water is greater than 0.040 (using a 12 mm cell path length),
7
A4.9.1 Example—If standard Solution A = 100 µg/mL then
standard Solution B = 10.00 µg/mL:
Tube 1 = 0 mL Standard Solution B
310.00 µg/mL = 0.00 µg total formaldehyde
Tube 2 = 0.10 mL Standard Solution B
310.00 µg/mL = 1.00 µg total formaldehyde
Tube 3 = 0.30 mL Standard Solution B
310.00 µg/mL = 3.00 µg total formaldehyde
Tube 4 = 0.50 mL Standard Solution B
310.00 µg/mL = 5.00 µg total formaldehyde
Tube 5 = 0.70 mL Standard Solution B
310.00 µg/mL = 7.00 µg total formaldehyde
Tube 6 = 1.00 mL Standard Solution B
310.00 µg/mL = 10.00 µg total formaldehyde
A4.9.2 The absorbance of each tube would be plotted
against the total micrograms of formaldehyde in each tube.
A4.9.3 The absorbance of each chamber impinger aliquot
specimen determined in 10.4.3 is compared to this calibration
curve, and the total micrograms of formaldehyde in the aliquot
is represented as Cain 11.2.
NOTE A4.1—The calibration curve as described in this annex is
provided as an example. If absorbance readings are outside of this range,
dilute the solution with distilled water to a concentration that is within the
calibration curve. If absorbance readings exceed 1.0, place capped test
tubes in a boiling water bath for 15 6 2 min to ensure that the chemical
reaction is completed. Vent test tubes to release pressure. Remove tubes
from water bath and allow to cool to room temperature.
A4.10 Preparation of the calibration curve (A4.3-A4.9)
D 6007 – 02
shall be repeated at least once more and the final calibration
line shall reflect the composite of the determinations (or the
curve shall be calculated using a linear least squares fitting
technique). The calibration curve may not be linear at high
formaldehyde concentrations (high absorbance readings). If the
plot in A4.9 shows the last few points deviating from linearity,
omit the points from calculations or repeat entire procedure.
Further, the curve should be frequently checked based on
changes in reagent lot numbers, past experience, data scatter-
ing, or instrument instability.
APPENDIX
(Nonmandatory Information)
X1. REAGENTS, MATERIALS, AND EQUIPMENT FOUND SUITABLE FOR USE
X1.1 Air-Sampling Apparatus
NOTE X1.1—Other apparatus and instruments may be used if equiva-
lent results are anticipated.
X1.1.1 Midget Impingers.14
X1.1.2 Rotameters, 1 L/min.15
X1.1.3 Line Filter, with desiccant (to dry the air before
entering rotameters).16
X1.1.4 Polytetrafluoroethylene (PTFE) Tubing.16
X1.1.5 Buret, 250 or 500 mL (to calibrate rotameters).16
X1.1.6 Impinger Pumps.16
X1.1.7 Film-Type Laboratory Calibrators or Bubble Tube,
for calibrating pumps and rotameters.17
X1.2 Analytical Apparatus
X1.2.1 Spectrophotometer.18
X1.2.2 Spectrochek,16for calibration of the spectrophotom-
eter.
X1.2.3 Beaker, 150 mL, low form.16
X1.2.4 Volumetric Flask, 1000 mL.16
X1.2.5 Volumetric Flask, 100 mL.16
X1.2.6 Volumetric Flasks, two, 10 mL.16
X1.2.7 Buret, 25 mL, Class A.16
X1.2.8 pH meter.16
X1.2.9 Magnetic Stirrer.16
X1.2.10 Pipet, volumetric, 4 mL.16
14 Ace Glass Stopper No. 7531-06 and 30-mL Bottle No. 7531-04, available from
Ace Glass Inc., P.O. Box 688, Vineland NJ 08360, or Lurex No. 191-4050, available
from Lurex Scientific, have been found suitable for this purpose.
15 Scott Specialty Gases, Model S2-315-2-4 with stainless steel float, available
from 7425 North Oak Park Ave., Chicago, IL 60648, have been found suitable for
this.
16 Available from scientific supply houses.
17 Available from SKC Inc., 334 Valley View Rd., Eighty Four, PA 15330-9614.
18 Milton Roy Spectronic 20 Spectrophotometer, available from scientific supply
houses, or equivalent, has been found suitable for this purpose.
8
X1.2.11 Pipet, volumetric, 50 mL, Class A.16
X1.2.12 Pipet, volumetric, 6 mL, Class A.16
X1.2.13 Pipet, long-tip Mohr type, 2 by 0.01 mL.16
X1.2.14 Pipet, Mohr, 10 by 0.1 mL.16
X1.2.15 Safety Bulb, for pipeting.16
X1.2.16 Test Tubes, 16 by 150 mm, with polytetrafluoroet-
hylene (PTFE) lined screw caps.16
X1.2.17 For repetitive analyses of sample solutions and for
added safety, use of automatic pipeting equipment may be
desirable. Use of the following have been found suitable.16
X1.2.17.1 Brinkman Dispensers, volume 0.1 to 0.5 mL (for
chromotropic acid), volume 1 to 10 mL (for sulfuric acid), and
volume to 25 mL (for distilled water).16
X1.2.17.2 Oxford Macro-Set Pipet.16
X1.2.17.3 Tips, 250, for transferring 4 mL aliquots.16
X1.3 Reagents
X1.3.1 Chromotropic Acid Reagent—Dissolve 0.10 g of
chromotropic acid (4,5-dihydroxy-2,7-naphthalene-disulfonic
acid disodium salt) in freshly distilled water and dilute to 10
mL. This solution is to be made up daily.
X1.3.2 Sulfuric Acid (H2SO4), concentrated, reagent grade.
Nitrate concentration shall be less than 10 ppm.
X1.3.3 Buffer Solution, pH 9.0.
X1.3.4 Hydrochloric Acid, (HCl) 0.100 N, standard.
X1.3.5 Sodium Sulfite Solution, 1.0 M—Dissolve 12.67 g
anhydrous sodium sulfite (Na2SO3) (ACS assay 99.5 %) in a
100-mL volumetric flask and dilute to the mark with freshly
distilled water. The correct amount to be dissolved should be
12.6/ACS assay of the anhydrous sodium sulfite actually being
used (read assay from bottle label).
X1.3.6 Formaldehyde Solution, weight 37 %.
X1.3.7 Sodium Bisulfite, (NaHSO3), reagent grade.
X1.3.8 Mild Liquid Soap.
D 6007 – 02
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