EMISSION MEASUREMENT TECHNICAL INFORMATION CENTER
CONDITIONAL TEST METHOD
Prepared by Emission Measurement Branch EMTIC CTM-012.WPF
Technical Support Division, OAQPS, EPA June 30, 1992
Determination of Metals Emissions from Stationary Sources
Note: This conditional method (CTM-012.WPF) replaces the EMTIC
"Interim" test method for metals emissions from stationary
sources (ITM-001). The current version of the method reflects
the slated-to-be proposed "Method 29 - Determinarion of Metals
Emissions from Stationary Sources" which will be proposed in
conjunction with additional standards regulating municipal waste
combustors. A copy of Method 29 (dated 6/30/93) is contained in
Docket A-90-45, item II-B-12.
1. Applicability and Principle
1.1 Applicability. This method is applicable to the
determination of total chromium (Cr), cadmium (Cd), arsenic (As),
nickel (Ni), manganese (Mn), beryllium (Be), copper (Cu), zinc
(Zn), lead (Pb), selenium (Se), phosphorus (P), thallium (Tl),
silver (Ag), antimony (Sb), barium (Ba), and mercury (Hg)
emissions from stationary sources. This method may also be used
for determining particulate emissions when the prescribed
procedures and precautions are followed. Changes in the
procedures to further facilitate particulate determination may
affect the front-half mercury determination.
1.2 Principle. A stack sample is withdrawn isokinetically
from the source, with particulate emissions collected in the
probe and on a heated filter and gaseous emissions collected in
solutions of acidic hydrogen peroxide and acidic potassium
permanganate. The recovered samples are digested, and
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appropriate fractions are analyzed for mercury by cold vapor
atomic absorption spectroscopy (CVAAS) and for Cr, Cd, Ni, Mn,
Be, Cu, Zn, Pb, Se, P, Tl, Ag, Sb, Ba, and As by inductively
coupled argon plasma emission spectroscopy (ICAP) or atomic
absorption spectroscopy (AAS). Graphite furnace atomic
absorption spectroscopy (GFAAS) is used for analysis of Sb, As,
DC, Pb, Se, and Tl if these elements require greater analytical
sensitivity than can be obtained by ICAP. Additionally, if
desired, the tester may use AAS for analysis of all metals if the
resulting in-stack method detection limits meet the goal of the
testing program.
2. Range, Sensitivity, Precision, and Interferences
2.1 Range. For the analysis described and for similar
analyses, the ICAP response is linear over several orders of
magnitude. Samples containing metal concentrations in the
nanograms per ml (ng/ml) to micrograms per ml (//g/ml) range in
the final analytical solution can be analyzed using this method.
Samples containing greater than approximately 50 jug/ml Cr, Pb, or
As should be diluted to that level or lower for final analysis.
Samples containing greater than approximately 20 //g/ml of Cd
should be diluted to that level before analysis.
2.2 Analytical Sensitivity. ICAP analytical detection
limits for the sample solutions (based on SW-846, Method 6010)
are approximately as follows: Sb (32 ng/ml), As (53 ng/ml),
Ba (2 ng/ml), Be (0.3 ng/ml), Cd (4 ng/ml), Cr (7 ng/ml),
Cu (6 ng/ml), Pb (42 ng/ml), Mn (2 ng/ml), Ni (15 ng/ml),
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P (75 ng/ml), Se (75 ng/ml), Ag (7 ng/ml), Tl (40 ng/ml), and
Zn (2 ng/ml). The actual method detection limits are sample
dependent and may vary as the sample matrix may affect the
limits. The analytical detection limits for analysis by direct
aspiration AAS (based on SW-846, Method 7000 series) are
approximately as follows: Sb (200 ng/ml), As (2 ng/ml), Ba
(100 ng/ml), Be (5 ng/ml), Cd (5 ng/ml), Cr (50 ng/ml), Cu
(20 ng/ml), Pb (100 ng/ml), Mn (10 ng/ml), Ni (40 ng/ml),
Se (2 ng/ml), Ag (10 ng/ml), Tl (100 ng/ml), and Zn (5 ng/ml).
The detection limit for mercury by CVAAS is approximately
0.2 ng/ml. The use of GFAAS can give added sensitivity compared
to direct aspiration AAS for the following metals: Sb (3 ng/ml),
As (1 ng/ml), Be (0.2 ng/ml), Cd (0.1 ng/ml), Cr (1 ng/ml), Pb
(1 ng/ml), Se (2 ng/ml), and Tl (1 ng/ml).
2.3 In-stack Detection Limit.
2.3.1 Using (1) the procedures described in this method,
(2) the analytical detection limits described in the previous
paragraph, (3) a volume of 300 ml (Fraction 1) for the front-half
and 150 ml (Fraction 2A) for the back-half samples, and (4) a
stack gas sample volume of 1.25 m3, the corresponding in-stack
method detection limits are presented in Table 29-1 and
calculated using Eq. 29-1.
A x B/C = D Eq. 29-1
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where:
A = Analytical detection limit, //g/ml.
B = Volume of sample prior to aliquotting for
analysis, ml.
C = Stack sample volume, dsm3.
D = In-stack detection limit, jug/m3.
Values in Table 29-1 are calculated for the front- and back-half
and/or the total train.
2.3.2 To ensure optimum sensitivity in the measurements,
the concentrations of target metals in the solutions are
suggested to be at least ten times the analytical detection
limits. Under certain conditions, and with greater care in the
analytical procedure, this concentration can be as low as
approximately three times the analytical detection limit. In all
cases, on at least one sample (run) in the source test and for
each metal analyzed, repetitive analyses, method of standard
additions (MSA), serial dilution, or matrix spike addition, etc.,
shall be used to establish the quality of the data.
2.3.3 Actual in-stack method detection limits will be
determined based on actual source sampling parameters and
analytical results as described above. If required, the method
in-stack detection limits can be made more sensitive than those
shown in Table 29-1 for a specific test by using one or more of
the following options:
2.3.4 A 1-hour sampling run may collect a stack gas
sampling volume of about 1.25 m3. If the sampling time is
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Table 29-1. In-stack method detection limits.
Front-half
Metal
Back-half
Fraction 1
Probe and Filter
Back-half
Fraction 2
Impingers 1-3
Fractions
"Hg, only"
Impincters 4-6
Total Train
Antimony
Arsenic
Barium
Beryllium
Cadmium
Chromium
Copper
Lead
Manganese
Mercury
Nickel
Phosphorus
Selenium
Silver
Thallium
Zinc
7.7 (0.7)*
12.7 (0.3)*
0.5
0.07 (0.05)*
1.0 (0.02)*
1.7 (0.2)*
1.4
10.1 (0.2)*
0.5 (0.2)*
0.6**
3.6
18
18 (0.5)*
1.7
9.6 (0.2)*
0.5
3.8 (0.4)*
6.4 (0.1)*
0.3
0.04 (0.03)*
0.5 (0.01)*
0.8 (0.1)*
0.7
5.0 (0.1)*
0.2 (0.1)*
3.0** 2.0**
1.8
9
9 (0.3)*
0.9
4.8 (0.1)*
0.3
11.5 (1.1)*
19.1 (0.4)*
0.8
0.11 (0.08)*
1.5 (0.03)*
2.5 (0.3)*
2.1
15.1 (0.3)*
0.7 (0.3)*
5.6**
5.4
27
27 (0.8)*
2.6
14.4 (0.3)*
0.8
( )* Detection limit when analyzed by GFAAS.
** Detection limit when analyzed by CVAAS, estimated for back-Half and
total Train.
Note: Actual method in-stack detection limits will be determined based
on actual source sampling parameters and analytical results as described
earlier in this section.
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increased and 5 m3 are collected, the in-stack method detection
limits would be one fourth the values shown in Table 29-1 (with
this change, the method is four times more sensitive than a
1-hour run. Larger sample volumes (longer runs) would make it
even more sensitive.
2.3.5 The in-stack detection limits assume that all of the
sample is digested (except the aliquot for mercury) and the final
liquid volumes for analysis are 300 ml (Fraction l) for the
front-half and 150 ml (Fraction 2A) for the back-half sample. If
the front-half volume is reduced from 300 to 30 ml, the front-
half in-stack detection limits would be one tenth the values
shown above (ten times more sensitive). If the back-half volume
is reduced from 150 to 25 ml, the in-stack detection limits would
be one sixth the above values. Matrix effect checks are
necessary on sample analyses and typically are of greater
significance for samples that have been concentrated to less than
the normal original sample volume. Reduction to a volume of less
than 25 ml may not allow redissolving of the residue and may
increase interference by other compounds.
2.3.6 When both of the above modifications are used
simultaneously on one sample, the resultant improvements are
multiplicative. For example, where stack gas volume is increased
by a factor of five and the total liquid sample digested volume
of both the front- and back-halves is reduced by a factor of six,
the in-stack method detection limit is reduced by a factor of
thirty (the method is thirty times more sensitive). Conversely,
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reducing stack sample volume and increasing sample liquid volume
will increase in-stack detection limits (the method would then be
less sensitive). The front-half and back-half samples (Fractions
1A and 2A) can be combined proportionally (see Section 1.2) prior
to analysis. The resultant liquid volume (excluding the mercury
fractions, which must be analyzed separately) is recorded.
Combining the sample in this manner does not allow the point of
capture in the train to be determined. The in-stack method
detection limit then becomes a single value for all metals except
mercury (due to exclusion of the mercury fraction). This
discussion assumes no blank correction. Blank corrections are
discussed later in this method.
2.4 Precision. The precision (relative standard deviation)
for each metal detected in a method development test at a sewage
sludge incinerator are as follows: Sb (12.7 percent), As
(13.5 percent), Ba (20.6 percent), Cd (11.5 percent), Cr
(11.2 percent), Cu (11.5 percent), Pb (11.6 percent), P
(14.6 percent), Se (15.3 percent), Tl (12.3 percent), and Zn
(11.8 percent). The precision for Ni was 7.7 percent for another
test conducted at a source simulator. Beryllium, Mn, and Ag were
not detected in the tests; however, based on the analytical
sensitivity of the ICAP for these metals, it is assumed that
their precisions should be similar to those for the other metals
when detected at similar levels.
2.5 Interferences. Iron can be a spectral interference
during the analysis of As, Cr, and Cd by ICAP. Al can be a
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spectral interference during the analysis of As and Pb by ICAP.
Generally, these interferences can be reduced by diluting the
sample, but this increases the method detection limit (in-stack
detection limit). Refer to Method 6010 of Citation 1 of the
Bibliography or the other analytical methods used for details on
potential interferences to this method. The analyst must
eliminate or reduce interferences to acceptable levels. For all
GFAAS analyses, matrix modifiers should be used to limit
interferences, and standards should be matrix matched.
3. Apparatus
3.1 Sampling Train. A schematic of the sampling train is
shown in Figure 29-1. It is similar to the Method 5 train and
consists of the following components.
3.1.1 Probe Nozzle (Probe Tip) and Borosilicate or Quartz
Glass Probe Liner. Same as Method 5, Sections 2.1.1 and 2.1.2,
except that glass nozzles are required unless alternate tips are
constructed of materials that are free from contamination and
will not interfere with the sample. If a probe tip other than
glass is used, no correction to the sample test results may be
made to compensate for its effect on the sample. Probe fittings
of plastic such as Teflon, polypropylene, etc. are recommended
over metal fittings to prevent contamination; further, if
desired, a single glass piece consisting of a combined probe tip
and probe liner may be used, but such a single glass piece is not
a requirement of this methodology)
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Theriraeter
(T) Glass Filter Holder
Thermometer
Glass Probe Liner
Glass Probe Tip
Empty (Optional) I / Enpty
5'0 H03/105B H2Q2
Pi tot tenoteter
Air-tight
Dry Gas pMp
Heter
Figure 29-1, Sampling train
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3.1.2 Pitot Tube and Differential Pressure Gauge. Same as
Method 2, Sections 2.1 and 2.2, respectively.
3.1.3 Filter Holder. Glass, same as Method 5,
Section 2.1.5, except a Teflon filter support or other non-
metallic, non-contaminating support must be used in place of the
glass frit.
3.1.4 Filter Heating System. Same as Method 5,
Section 2.1.6.
3.1.5 Condenser. The following system shall be used for
condensing and collecting gaseous metals and determining the
moisture content of the stack gas. The condensing system should
consist of four to seven impingers connected in series with leak-
free ground glass fittings or other leak-free, non-contaminating
fittings. The first impinger is optional and is recommended as a
moisture trap. The second impinger (or the first HNO3/H2O2
impinger) shall be as described for the first impinger in
Method 5. The third impinger (or second HNO3/H2O2 impinger) shall
be the Greenburg Smith impinger with the standard tip described
as the second impinger in Method 5, Section 2.1.7. All other
impingers are the same as the first HNO3/H2O2 impinger previously
described. A thermometer capable of measuring to within 1°C
(2°F) shall be placed at the outlet of the last impinger. If
mercury analysis is not to be performed, the potassium
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permanganate impingers and the empty impinger preceding them are
removed.
3.1.6 Metering System, Barometer, and Gas Density
Determination Equipment. Same as Method 5, Sections 2.1.8
through 2.1.10, respectively.
3.1.7 Teflon Tape. For capping openings and sealing
connections, if necessary, on the sampling train.
3.2 Sample Recovery. Same as Method 5, Sections 2.2.1
through 2.2.8 (Probe-Liner and Probe-Nozzle Brushes or Swabs,
Wash Bottles, Sample Storage Containers, Petri Dishes, Glass
Graduated Cylinder, Plastic Storage Containers, Funnel and Rubber
Policeman, and Glass Funnel), respectively, with the following
exceptions and additions:
3.2.1 Non-metallic Probe-Liner and Probe-Nozzle Brushes or
Swabs. For quantitative recovery of materials collected in the
front-half of the sampling train. A description of acceptable
all-Teflon component brushes or swabs are to be included in EPA's
Emission Measurement Technical Information Center (EMTIC) files.
3.2.2 Sample Storage Containers. Glass bottles with
Teflon-lined caps which are non-reactive to the oxidizing
solutions, with capacities of 1000- and 500-ml shall be used for
KMnO4-containing samples and blanks. Polyethylene bottles may be
used for other sample types.
3.2.3 Graduated Cylinder. Glass or equivalent.
3.2.4 Funnel. Glass or equivalent.
3.2.5 Labels. For identifying samples.
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3.2.6 Polypropylene Tweezers and/or Plastic Gloves. For
recovery of the filter from the sampling train filter holder.
3.3 Sample Preparation and Analysis. For the analysis, the
following equipment is needed:
3.3.1 Volumetric Flasks, 100-ml, 250-ml, and 1000-ml. For
preparation of standards and sample dilutions.
3.3.2 Graduated Cylinders. For preparation of reagents.
3.3.3 ParrE Bombs or Microwave Pressure Relief Vessels with
Capping Station (CEM Corporation model or equivalent).
3.3.4 Beakers and Watch Glasses. 250-ml beakers for sample
digestion with watch glasses to cover the tops.
3.3.5 Ring Stands and Clamps. For securing equipment such
as filtration apparatus.
3.3.6 Filter Funnels. For holding filter paper.
3.3.7 Disposable Pasteur Pipets and Bulbs.
3.3.8 Volumetric Pipets.
3.3.9 Analytical Balance. Accurate to within 0.1 mg.
3.3.10 Microwave or Conventional Oven. For heating samples
at fixed power levels or temperatures.
3.3.11 Hot Plates.
3.3.12 Atomic Absorption Spectrometer (AAS). Equipped with
a background corrector.
3.3.12.1 Graphite Furnace Attachment. With Sb, As, Cd, Pb,
Se, and Tl hollow cathode lamps (HCLs) or electrodeless discharge
lamps (EDLs). Same as Bibliography Citation 1 Methods 7041 (Sb),
7060 (As), 7131 (Cd), 7421 (Pb), 7740 (Se), and 7841 (Tl).
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3.3.12.2 Cold Vapor Mercury Attachment. With a mercury HCL
or EDL. The equipment needed for the cold vapor mercury
attachment includes an air recirculation pump, a quartz cell, an
aerator apparatus, and a heat lamp or desiccator tube. The heat
lamp should be capable of raisinq the ambient temperature at the
quartz cell by 10°C such that no condensation forms on the wall
of the quartz cell. Same as Method 7470 in Citation 2 of the
Biblioqraphy.
3.3.13 Inductively Coupled Argon Plasma Spectrometer. With
either a direct or sequential reader and an alumina torch. Same
as EPA Method 6010 in Citation 1 of the Biblioqraphy.
4. Reagents
4.1 Unless otherwise indicated, it is intended that all
reaqents conform to the specifications established by the
Committee on Analytical Reagents of the American Chemical
Society, where such specifications are available; otherwise, use
the best available grade.
4.2 Sampling. The reagents used in sampling are as
follows:
4.2.1 Filters. The filters shall contain less than
1.3 /xg/in.2 of each of the metals to be measured. Analytical
results provided by filter manufacturers are acceptable.
However, if no such results are available, filter blanks must be
analyzed for each target metal prior to emission testing. Quartz
or glass fiber filters without organic binders shall be used.
The filters should,^ exhibit at least 99.95 percent efficiency
13
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(<0.05 percent penetration) on 0.3-/U dioctyl phthalate smoke
particles. The filter efficiency test shall be conducted in
accordance with ASTM Standard Method D2986-71 (incorporated by
reference). For particulate determination in sources containing
sulfur dioxide (SO2) or sulfur trioxide (S03), the filter
material must be of a type that is unreactive to S02 or S03/ as
described in Method 5. Quartz fiber filters meeting these
requirements are recommended.
4.2.2 Water. To conform to ASTM Specification D1193-77,
Type II (incorporated by reference). If necessary, analyze the
water for all target metals prior to field use. All target
metals should be less than 1 ng/ml.
4.2.3 Nitric Acid. Concentrated. Baker Instra-analyzed or
equivalent.
4.2.4 Hydrochloric Acid. Concentrated. Baker Instra-
analyzed or equivalent.
4.2.5 Hydrogen Peroxide, 30 Percent (V/V).
4.2.6 Potassium Permanganate.
4.2.7 Sulfuric Acid. Concentrated.
4.2.8 Silica Gel and Crushed Ice. Same as Method 5,
Sections 3.1.2 and 3.1.4, respectively.
4.3 Pretest Preparation of Sampling Reagents.
4.3.1 Nitric Acid (HNO3)/Hydrogen Peroxide (H2O2) Absorbing
Solution, 5 Percent HNO3/10 Percent H2O2. Add carefully with
stirring 50 ml of concentrated HNO3 to a 1000-ml volumetric flask
containing approximately 500 ml of water, and3 then add carefully
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with stirring 333 ml of 30 percent H2O2. Dilute to volume with
water. Mix well. The reagent shall contain less than 2 ng/ml of
each target metal.
4.3.2 Acidic Potassium Permanganate (KMn04) Absorbing
Solution, 4 Percent KMn04 (W/V), 10 Percent H2S04 (V/V). Prepare
fresh daily. Mix carefully, with stirring, 100 ml of
concentrated H2S04 into approximately 800 ml of water, and add
water with stirring to make a volume of 1 liter: this solution
is 10 percent H2SO4 (V/V). Dissolve, with stirring, 40 g of KMn04
into 10 percent H2S04 (V/V) and add 10 percent H2SO4 (V/V) with
stirring to make a volume of 1 liter: this is the acidic
potassium permanganate absorbing solution. Prepare and store in
glass bottles to prevent degradation. The reagent shall contain
less than 2 ng/ml of Hg.
Precaution: To prevent autocatalytic decomposition of the
permanganate solution, filter the solution through Whatman 541
filter paper. Also, due to the potential reaction of the
potassium permanganate with the acid, there may be pressure
buildup in the sample storage bottle; these bottles shall not be
fully filled and shall be vented to relieve excess pressure and
prevent explosion potentials. Venting is reguired, but should
not allow contamination of the sample; a No. 70-72 hole drilled
in the container cap and Teflon liner has been used.
4.3.3 Nitric Acid, 0.1 N. Add with stirring 6.3 ml of
concentrated HNO3 (70 percent) to a flask containing
approximately 900 ml of water. Dilute to 1000 ml with water.
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Mix well. The reagent shall contain less than 2 ng/ml of each
target metal.
4.3.4 Hydrochloric Acid (HC1), 8 N. Make the desired
volume of 8N HCl in the following proportions. Carefully add
with stirring 690 ml of concentrated HCl to a flask containing
250 ml of water. Dilute to 1000 ml with water. Mix well. The
reagent shall contain less than 2 ng/ml of Hg.
4.4 Glassware Cleaning Reagents.
4.4.1 Nitric Acid, Concentrated. Fisher ACS grade or
equivalent.
4.4.2 Water. To conform to ASTM Specifications D1193-77,
Type II.
4.4.3 Nitric Acid, 10 Percent (V/V). Add with stirring
500 ml of concentrated HNO3 to a flask containing approximately
4000 ml of water. Dilute to 5000 ml with water. Mix well.
Reagent shall contain less than 2 ng/ml of each target metal.
4.5 Sample Digestion and Analysis Reagents.
4.5.1 Hydrochloric Acid, Concentrated.
4.5.2 Hydrofluoric Acid, Concentrated.
4.5.3 Nitric Acid, Concentrated. Baker Instra-analyzed or
equivalent.
4.5.4 Nitric Acid, 50 Percent (V/V). Add with stirring
125 ml of concentrated HNO3 to 100 ml of $/ater. Dilute to 250 ml
with water. Mix well. Reagent shall contain less than 2 ng/ml
of each target metal.
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4.5.5 Nitric Acid, 5 Percent (V/V). Add with stirring 50
ml of concentrated HN03 to 800 ml of water. Dilute to 1000 ml
with water. Mix well. Reagent shall contain less than 2 ng/ml
of each target metal.
4.5.6 Water. To conform to ASTM Specifications D1193-77,
Type II.
4.5.7 Hydroxylamine Hydrochloride and Sodium Chloride
Solution. See Citation 2 of the Bibliography for preparation.
4.5.8 Stannous Chloride. See Citation 2 of the
Bibliography for preparation.
4.5.9 Potassium Permanganate, 5 Percent (W/V). See
Citation 2 of the Bibliography for preparation.
4.5.10 Sulfuric Acid, Concentrated.
4.5.11 Nitric Acid, 50 Percent (V/V).
4.5.12 Potassium Persulfate, 5 Percent (W/V). See
Citation 2 of the Bibliography for preparation.
4.5.13 Nickel Nitrate, Ni(N03)2-6H20.
4.5.14 Lanthanum Oxide, La203.
4.5.15 Hg Standard (AAS Grade), 1000 /zg/ml.
4.5.16 Pb Standard (AAS Grade), 1000 //g/ml.
4.5.17 As Standard (AAS Grade), 1000 jug/ml.
4.5.18 Cd Standard (AAS Grade), 1000 //g/ml.
4.5.19 Cr Standard (AAS Grade), 1000 ng/ml.
4.5.20 Sb Standard (AAS Grade), 1000 //g/ml.
4.5.21 Ba Standard (AAS Grade), 1000 /xg/ml.
4.5,^2 Be Standard (AAS Grade), 1000
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4.5.23 Cu Standard (AAS Grade), 1000 /Ltg/ml.
4.5.24 Mn Standard (AAS Grade), 1000 jug/ml.
4.5.25 Ni Standard (AAS Grade), 1000 /Ltg/ml.
4.5.26 P Standard (AAS Grade), 1000 /Ltg/ml.
4.5.27 Se Standard (AAS Grade), 1000
4.5.28 Ag Standard (AAS Grade), 1000
4.5.29 Tl Standard (AAS Grade), 1000 jug/ml.
4.5.30 Zn Standard (AAS Grade), 1000 /Ltg/ml.
4.5.31 Al Standard (AAS Grade), 1000 jug/ml.
4.5.32 Fe Standard (AAS Grade), 1000 /Ltg/ml.
4.5.33 The metals standards may also be made from solid
chemicals as described in Citation 3 of the Bibliography.
Citations 1, 2, or 4 of the Bibliography should be referred to
for additional information on mercury standards.
4.5.34 Mercury Standards and Quality Control Samples.
Prepare fresh weekly a 10 /Ltg/ml intermediate mercury standard by
adding 5 ml of 1000 /ig/ml mercury stock solution to a 500-ml
volumetric flask; dilute with stirring to 500 ml by first
carefully adding 20 ml of 15 percent HNO3 and then adding water
to the 500-ml volume. Mix well. Prepare a 200 ng/ml working
mercury standard solution fresh daily: add 5 ml of the 10 /ig/ml
intermediate standard to a 250-ml volumetric flask, and dilute to
250 ml with 5 ml of 4 percent KMnO4, 5 ml of 15 percent HNO3, and
then water. Mix well. At least six separate aliquots of the
working mercury standard solution should be used to prepare the
standard curve. These aliquots should contain 0.0, 1.0, 2.0,
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3.0, 4.0, and 5.0 ml of the working standard solution containing
0, 200, 400, 600, 800, and 1000 ng mercury, respectively.
Quality control samples should be prepared by making a separate
10 pig/ml standard and diluting until in the range of the
calibration.
4.5.35 ICAP Standards and Quality Control Samples.
Calibration standards for ICAP analysis can be combined into four
different mixed standard solutions as shown below.
MIXED STANDARD SOLUTIONS FOR ICAP ANALYSIS
Solution Elements
I As, Be, Cd, Mn, Pb, Se, Zn
II Ba, Cu, Fe
III Al, Cr, Ni
IV Ag, P, Sb, Tl
Prepare these standards by combining and diluting the appropriate
volumes of the 1000 //g/ml solutions with 5 percent HNO3. A
minimum of one standard and a blank can be used to form each
calibration curve. However, a separate quality control sample
spiked with known amounts of the target metals in quantities in
the mid-range of the calibration curve should be prepared.
Suggested standard levels are 25 /ig/ml for AL, Cr and Pb,
15 jug/ml for Fe, and 10 /Ltg/ml for the remaining elements.
Prepare any standards containing less than 1 /Ltg/ml of metal on a
daily basis. Standards containing greater than 1 /Ltg/ml of metal
should be stable for a minimum of 1 to 2 weeks.
4.5.36 Graphite Furnace AAS Standards. Sb, As, Cd, Pb, Se,
and Tl. Prepare a 10 /jg/ml standard by adding 1 ml of 1000 /Ltg/ml
standard to a 100-ml volumetric flask. Dilute with stirring to
19
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100 ml with 10 percent HNO3. For graphite furnace AAS, the
standards must be matrix matched. Prepare a 100 ng/ml standard
by adding 1 ml of the 10 jug/ml standard to a 100-ml volumetric
flask, and dilute to 100 ml with the appropriate matrix solution.
Other standards should be prepared by diluting the 100 ng/ml
standards. At least five standards should be used to make up the
standard curve. Suggested levels are 0, 10, 50, 75, and
100 ng/ml. Quality control samples should be prepared by making
a separate 10 /Lig/ml standard and diluting until it is in the
range of the samples. Any standards containing less than 1 /^g/ml
of metal should be prepared on a daily basis. Standards
containing greater than 1 /ng/ml of metal should be stable for a
minimum of 1 to 2 weeks.
4.5.37 Matrix Modifiers.
4.5.37.1 Nickel Nitrate, 1 Percent (V/V). Dissolve 4.956 g
of Ni(N03)2• 6H20 in approximately 50 ml of water in a 100-ml
volumetric flask. Dilute to 100 ml with water.
4.5.37.2 Nickel Nitrate, 0.1 Percent (V/V). Dilute 10 ml
of the 1 percent nickel nitrate solution from Section 4.5.37.1
above to 100 ml with water. Inject an egual amount of sample and
this modifier into the graphite furnace during AAS analysis for
As.
4.5.37.3 Lanthanum. Carefully dissolve 0.5864 g of La203 in
10 ml of concentrated HN03, and dilute the solution by adding it
with stirring to approximately 50 ml of water. Dilute to 100 ml
with water, and mix well. Inject an equal amount of sample and
20
-------
this modifier into the graphite furnace during AAS analysis for
Pb.
4.5.38 Whatman 541 Filter Paper (or equivalent). For
filtration of digested samples.
5. Procedure
5.1 Sampling. The complexity of this method is such that,
to obtain reliable results, testers and analysts should be
trained and experienced with the test procedures, including
source sampling, reagent preparation and handling, sample
handling, safety equipment, analytical calculations, reporting,
and specific descriptions throughout this method.
5.1.1 Pretest Preparation. Follow the same general
procedure given in Method 5, Section 4.1.1, except that, unless
particulate emissions are to be determined, the filter need not
be desiccated or weighed. All sampling train glassware should
first be rinsed with hot tap water and then washed in hot soapy
water. Next, glassware should be rinsed three times with tap
water, followed by three additional rinses with water. All
glassware should then be soaked in a 10 percent (V/V) nitric acid
solution for a minimum of 4 hours, rinsed three times with
water, rinsed a final time with acetone, and allowed to air dry.
All glassware openings where contamination can occur should be
covered until the sampling train is assembled for sampling.
5.1.2 Preliminary Determinations. Same as Method 5,
Section 4.1.2.
21
-------
5.1.3 Preparation of Sampling Train.
5.1.3.1 Follow the same general procedures given in
Method 5, Section 4.1.3, except place 100 ml of the HN03/H2O2
solution (Section 4.2.1) in each of the two impingers as shown in
Figure 29-1 (normally the second and third impingers). Place
100 ml of the acidic KMn04 absorbing solution (Section 4.2.2) in
each of the two impingers as shown in Figure 29-1, and transfer
approximately 200 to 300 g of preweighed silica gel from its
container to the last impinger. Alternatively, the silica gel
may be weighed directly in the impinger just prior to train
assembly.
5.1.3.2 Several options are available to the tester based
on the sampling reguirements and conditions. The use of an empty
first impinger can be eliminated if the moisture to be collected
in the impingers will be less than approximately 100 ml. If
necessary, use as applicable to this methodology the procedure
described in Section 7.1.1 of Method 101A, 40 CFR Part 61,
Appendix B, to maintain the desired color in the last
permanganate impinger.
5.1.3.3 Retain for reagent blanks volumes of the HNO3/H202
solution per Section 5.2.16 of this method and of the acidic
KMnO4 solution per Section 5.2.17. These reagent blanks should
be labeled and analyzed as described in Section 7. Set up the
sampling train as shown in Figure 29-1. If mercury analysis is
not desired, delete the empty impinger and the two permanganate
impingers following the HNO3/H2O2 impingers. If necessary to
22
-------
ensure leak-free sampling train connections, Teflon tape or other
non-contaminating material should be used instead of silicone
grease to prevent contamination. Precaution: Extreme care
should be taken to prevent contamination within the train.
Prevent the mercury collection reagent (acidic KMn04) from
contacting any glassware of the train which is washed and
analyzed for Mn. Prevent H202 from mixing with the acidic KMnO,.
5.1.3.4 Mercury emissions can be measured, alternatively,
in a separate train using EPA Method 101A with the modifications
for processing the permanganate containers as described in the
precaution in Section 4.3.2 and the note in Section 5.2.11 of
this method). This alternative method is applicable for
measurement of mercury emissions, and it may be of special
interest to sources which must measure both mercury and manganese
emissions.
5.1.4 Leak-Check Procedures. Follow the leak-check
procedures given in Method 5, Section 4.1.4.1 (Pretest Leak-
Check), Section 4.1.4.2 (Leak-Checks During the Sample Run), and
Section 4.1.4.3 (Post-Test Leak-Checks).
5.1.5 Sampling Train Operation. Follow the procedures
given in Method 5, Section 4.1.5. For each run, record the data
required on a data sheet such as the one shown in Figure 5-2 of
Method 5.
5.1.6 Calculation of Percent Isokinetic. Same as Method 5,
Section 4.1.6.
23
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5.2 Sample Recovery.
5.2.1 Begin cleanup procedures as soon as the probe is
removed from the stack at the end of a sampling period. The
probe should be allowed to cool prior to sample recovery. When
it can be safely handled, wipe off all external particulate
matter near the tip of the probe nozzle and place a rinsed, non-
contaminating cap over the probe nozzle to prevent losing or
gaining particulate matter. Do not cap the probe tip tightly
while the sampling train is cooling; a vacuum may form in the
filter holder with the undesired result of drawing liquid from
the impingers onto the filter.
5.2.2 Before moving the sampling train to the cleanup site,
remove the probe from the sampling train and cap the open outlet.
Be careful not to lose any condensate that might be present. Cap
the filter inlet where the probe was fastened. Remove the
umbilical cord from the last impinger and cap the impinger. Cap
off the filter holder outlet and impinger inlet. Use non-
contaminating caps, whether ground-glass stoppers, plastic caps,
serum caps, or Teflon tape to close these openings.
5.2.3 Alternatively, the train can be disassembled before
the probe and filter holder/oven are completely cooled if this
procedure is followed: Initially disconnect the filter holder
outlet/impinger inlet and loosely cap the open ends. Then
disconnect the probe from the filter holder or cyclone inlet and
loosely cap the open ends. Cap the probe tip and remove the
umbilical cord as previously described.
24
-------
5.2.4 Transfer the probe and filter-impinger assembly to a
cleanup area that is clean and protected from the wind and other
potential causes of contamination or loss of sample. Inspect the
train before and during disassembly and note any abnormal
conditions. The sample is recovered and treated as follows (see
schematic in Figures 29-2a and 29-2b). Assure that all items
necessary for recovery of the sample do not contaminate it.
5.2.5 Container No. 1 (Filter). Carefully remove the
filter from the filter holder and place it in its identified
petri dish container. Acid-washed polypropylene or Teflon coated
tweezers or clean, disposable surgical gloves rinsed with water
and dried should be used to handle the filters. If it is
necessary to fold the filter, make certain the particulate cake
is inside the fold. Carefully transfer the filter and any
particulate matter or filter fibers that adhere to the filter
holder gasket to the petri dish by using a dry (acid-cleaned)
nylon bristle brush. Do not use any metal-containing materials
when recovering this train. Seal the labeled petri dish.
5.2.6 Container No. 2 (Acetone Rinse). NOTE: Perform this
section only if determination of particulate emissions are
desired in addition to metals emissions. Ensuring that dust on
the outside of the probe or other exterior surfaces does not get
into the sample, guantitatively recover particulate matter and
25
-------
Probe Liner Front Half of Filter Filter Support 1st Impinger 2nd A 3rd
and Nozzle Filter Housing
Einae with Brush
and Back Half £Effl.JPty at ImpLflgBrs
of Filter Housing beginning I^H]J03/H2O2^
with Gar ef ully RinsE
of test ^
three ueac
Tire Heosure
acetone nonmetallic brush rCfflOVC filter times with impinger impinger
and rinse with from support ° • tN HNQ3 contents contents
acetone with TeflOfl-
Bruch liner
brush ft rinse
with acetone
Check liner to see
if parciculate
rcoiDvedi if not !
repeat step above
coated tweezers
and place in
petri dish
Brush loose
p articulate
onto filter
Seal petrd. dish
with tajie
Einse three
muse cnrea Rinse three
times witli
times with
0.1M HH03
0 . IN
HNOQ
FE AR I
Empty the Empty the
cnntainer container
Hinse three Rinse three
times with times with
0.1H HN03 0.1N HH03
BI
I
(3)* C23 CO W
Hiunher in psreatheses indicates container number
Figure 29-Za. Sample recovery scheme,
26
-------
4th Impinger
& 5th
Last Impinger
and 6th impingers
C Acidified KMn04)
Measure
Impinger
contents
I
Empty the
impinger No. 4
contents into
container
Rinse witii
100 ml
0.IN HN03
0.IN HN03
I
Empty the
impingers
Nos. 5 & 6
contents into
container
Rinse three
times -with
permanganate
reagent, then
with water
Remove any
residue with
25 ml 8N
HC1 solution
Weigh for
moisture
Discard
KMn04
C5EO
8N HG1
(SO)
Figure 29-2b. Sample recovery scheme
28b
27
-------
any condensate from the probe nozzle, probe fitting, probe liner,
and front half of the filter holder by washing these components
with 100 ml of acetone and placing the wash in a glass container.
NOTE; The use of exactly 100 ml is necessary for the subsequent
blank correction procedures. Distilled water may be used instead
of acetone when approved by the Administrator and shall be used
when specified by the Administrator; in these cases, save a water
blank and follow the Administrator's directions on analysis.
Perform the acetone rinse as follows: Carefully remove the probe
nozzle and clean the inside surface by rinsing with acetone from
a wash bottle and brushing with a non-metallic brush. Brush
until the acetone rinse shows no visible particles, after which
make a final rinse of the inside surface with acetone.
5.2.7 Brush and rinse the sample exposed inside parts of
the fitting with acetone in a similar way until no visible
particles remain. Rinse the probe liner with acetone by tilting
and rotating the probe while squirting acetone into its upper end
so that all inside surfaces will be wetted with acetone. Allow
the acetone to drain from the lower end into the sample
container. A funnel may be used to aid in transferring liquid
washings to the container. Follow the acetone rinse with a non-
metallic probe brush. Hold the probe in an inclined position,
squirt acetone into the upper end as the probe brush is being
pushed with a twisting action through the probe. Hold a sample
container underneath the lower end of the probe, and catch any
acetone and particulate matter which is brushed through the probe
28
-------
three times or more until no visible particulate matter is
carried out with the acetone or until none remains in the probe
liner on visual inspection. Rinse the brush with acetone, and
quantitatively collect these washings in the sample container.
After the brushing, make a final acetone rinse of the probe as
described above.
5.2.8 It is recommended that two people clean the probe to
minimize sample losses. Between sampling runs, keep brushes
clean and protected from contamination. Clean the inside of the
front-half of the filter holder by rubbing the surfaces with a
non-metallic nylon bristle brush and rinsing with acetone. Rinse
each surface three times or more if needed to remove visible
particulate. Make a final rinse of the brush and filter holder.
After all acetone washings and particulate matter have been
collected in the sample container, tighten the lid so that
acetone will not leak out when shipped to the laboratory. Mark
the height of the fluid level to determine whether or not leakage
occurred during transport. Label the container clearly to
identify its contents.
5.2.9 Container No. 3 (Probe Rinse). Keep the probe
assembly clean and free from contamination during the probe
rinse. Rinse the probe nozzle and fitting, probe liner, and
front-half of the filter holder thoroughly with 100 ml of
0.1 N HNO3, and place the wash into a sample storage container.
NOTE: The use of exactly 100 ml is necessary for the subsequent
blank correction procedures. Perform the rinses as applicable
29
-------
and generally as described in Method 12, Section 5.2.2. Record
the volume of the combined rinse. Mark the height of the fluid
level on the outside of the storage container and use this mark
to determine if leakage occurs during transport. Seal the
container, and clearly label the contents. Finally, rinse the
nozzle, probe liner, and front-half of the filter holder with
water followed by acetone, and discard these rinses.
5.2.10 Container No. 4 (Impingers 1 through 3, HN03/H202
Impingers and Moisture Knockout Impinger, when used, Contents and
Rinses). Due to the potentially large quantity of liquid
involved, the tester may place the impinger solutions from
impingers 1 through 3 in more than one container. Measure the
liquid in the first three impingers to within 0.5 ml using a
graduated cylinder. Record the volume. This information is
required to calculate the moisture content of the sampled flue
gas. Clean each of the first three impingers, the filter
support, the back half of the filter housing, and connecting
glassware by thoroughly rinsing with 100 ml of 0.1 N HNO3 using
the procedure as applicable in Method 12, Section 5.2.4. NOTE:
The use of exactly 100 ml of 0.1 N HNO3 rinse is necessary for
the subsequent blank correction procedures. Combine the rinses
and impinger solutions, measure and record the volume. Mark the
height of the fluid level, seal the container, and clearly label
the contents.
5.2.11 Container Nos. 5A (0.1 N HNO3) , 5B (KMnO4/H2SO4
absorbing solution), and 5C (8 N HC1 rinse and dilution). Pour
30
-------
all the liquid, if any, from the impinger which was empty at the
start of the run and which immediately precedes the two
permanganate impingers (normally impinger No. 4) into a graduated
cylinder and measure the volume to within 0.5 ml. This
information is required to calculate the moisture content of the
sampled flue gas. Place the liquid in Sample Container No. 5A.
Rinse the impinger (No. 4) with 100 ml of 0.1 N HN03 and place
this into Container No. 5A.
5.2.12 Pour all the liquid from the two permanganate
impingers into a graduated cylinder and measure the volume to
within 0.5 ml. This information is required to calculate the
moisture content of the sampled flue gas. Place this KMnO4
solution into Container No. 5B. Using 100 ml total of fresh
acidified KMnO4 solution, rinse the two permanganate impingers
and connecting glass a minimum of three times. Pour the rinses
into Container No. 5B, carefully assuring transfer of all loose
precipitated materials from the two impingers. Using
100 ml total of water, rinse the permanganate impingers and
connecting glass a minimum of three times, and pour the rinses
into Container 5B, carefully assuring transfer of all loose
precipitated material, if any. Mark the height of the fluid
level, and clearly label the contents. Note the precaution in
Section 4.3.2. NOTE: Due to the potential reaction of KMnO«
with acid, there may be pressure buildup in the sample storage
bottles. These bottles shall not be filled completely and shall
be vented to relieve excess pressure. A No. 70-72 hole drilled
31
-------
in the container cap and Teflon liner has been used successfully.
5.2.13 If no visible deposits remain after the above
described water rinse, no further rinse is necessary. However,
if deposits do remain on the glassware, wash the impinger
surfaces with 25 ml of 8 N HC1, and place the wash in a separate
sample container labeled Container No. 5C containing 200 ml of
water as follows. Place 200 ml of water in a sample container
labeled Container No. 5C. Wash the impinger walls and stem with
the HC1 by turning the impinger on its side and rotating it so
that the HC1 contacts all inside surfaces. Use a total of only
25 ml of 8 N HC1 for rinsing both permanganate impingers
combined. Rinse the first impinger, then pour the actual rinse
used for the first impinger into the second impinger for its
rinse. Finally, pour the 25 ml of 8 N HC1 rinse carefully into
Container No. 5C. Mark the height of the fluid level on the
outside of the bottle to determine if leakage occurs during
transport.
5.2.14 Container No. 6 (Silica Gel). Note the color of the
indicating silica gel to determine whether it has been completely
spent and make a notation of its condition. Transfer the silica
gel from its impinger to its original container and seal. The
tester may use a funnel to pour the silica gel and a rubber
policeman to remove the silica gel from the impinger. The small
amount of particles that may adhere to the impinger wall need not
be removed. Do not use water or other liquids to transfer the
silica gel since weight gained in the silica gel impinger is used
32
-------
for moisture calculations. Alternatively, if a balance is
available in the field, record the weight of the spent silica gel
(or silica gel plus impinger) to the nearest 0.5 g.
5.2.15 Container No. 7 (Acetone Blank). If particulate
emissions are to be determined, at least once during each field
test, place a 100-ml portion of the acetone used in the sample
recovery process into a labeled container for use in the front-
half field reagent blank. Seal the container.
5.2.16 Container No. 8A (0.1 N HNO3 Blank). At least once
during each field test, place 300 ml of the 0.1 N HNO3 solution
used in the sample recovery process into a labeled container for
use in the front-half and back-half field reagent blanks. Seal
the container.
5.2.17 Container No. 8B (water blank). At least once
during each field test, place 100 ml of the water used in the
sample recovery process into a labeled Container No. 8B. Seal
the container.
5.2.18 Container No. 9 (5 Percent HN03/10 Percent H2O2
Blank). At least once during each field test, place 200 ml of
the 5 Percent HNO3/10 Percent H2O2 solution used as the nitric
acid impinger reagent into a labeled container for use in the
back-half field reagent blank. Seal the container.
5.2.19 Container No. 10 (Acidified KMn04 Blank). At least
once during each field test, place 100 ml of the acidified KMn04
solution used as the impinger solution and in the sample recovery
process into a labeled container for use in the back-half field
33
-------
reagent blank for mercury analysis. Prepare the container as
described in Section 5.2.11. See the note in Section 5.2.12.
5.2.20 Container No. 11 (8 N HC1 Blank). At least once
during each field test, perform both of the following. Place
200 ml of water into a sample container. Pour 25 ml of 8 N HC1
carefully with stirring into the container. Mix well and seal
the container.
5.2.21 Container No. 12 (Filter Blank). Once during each
field test, place three unused blank filters from the same lot as
the sampling filters in a labeled petri dish. Seal the petri
dish. These will be used in the front-half field reagent blank.
5.3 Sample Preparation. Note the level of the liquid in
each of the containers and determine if any sample was lost
during shipment. If a noticeable amount of leakage has occurred,
either void the sample or use methods, subject to the approval of
the Administrator, to correct the final results. A diagram
illustrating sample preparation and analysis procedures for each
of the sample train components is shown in Figure 29-3.
5.3.1 Container No. 1 (Filter). If particulate emissions
are being determined, desiccate the filter and filter catch
without added heat and weigh to a constant weight as described in
Section 4.3 of Method 5. For analysis of metals, divide the
filter with its filter catch into portions containing
approximately 0.5 g each and place into the analyst's choice of
either individual microwave pressure relief vessels or Parr*
Bombs. Add 6 ml of concentrated HNO3 and 4 ml of concentrated HF
34
-------
Container 3
Acid Probe Binsc
CLdbelcd FH3
Container 2
Acetone Probe Einsc
(Labeled AR}
Reduce to drynes:
in a tared be etc
I
Determine residm
weight in beaker
Container 4
HZOZ} Impiagcrs
CLebeled SH)
Cinclude coadensate
t if used^
U)
Ul
Acidify
sample to pH 2
with cone. HMOS
Fraction 2A
Containers 5A, SB, & 5C
tion 1
Remove 70 to 100 mi
oliijTaot for Eg
a&ftlysia by CVAAS
Fraction IB
Direct witli acid aid
pBrnangaaate at BS C i
ftetals by GFAAS'
Fraction 3A
Individually, ttu
separate digeetiojii
and snalyaea
digest with acic
and pernangfliiat
at 95 C for 2 h
and aaolyz.c
fOP Hfl by CVAAS
Fractions
3A, 3B, A 3C
*Analysis by AA3 for metals found at less than 2 ug/nl in dlgestac* solution,
if desired, Or analyze for each netal by AAS* if desired.
Figure 29-3. Sample preparation and analysis scheme,
35
-------
to each vessel. For microwave heating, microwave the sample
vessels for approximately 12-15 minutes in intervals of 1 to 2
minutes at 600 Watts. For conventional heating, heat the ParrR
Bombs at 140°C (285°F) for 6 hours. Then cool the samples to
room temperature, and combine with the acid digested probe rinse
as required in Section 5.3.3, below. NOTES;
5.3.1.1 Suggested microwave heating times are approximate
and are dependent upon the number of samples being digested.
Twelve to 15 minute heating times have been found to be
acceptable for simultaneous digestion of up to 12 individual
samples. Sufficient heating is evidenced by sorbent reflux
within the vessel.
5.3.1.2 If the sampling train uses an optional cyclone, the
cyclone catch should be prepared and digested using the same
procedures described for the filters and combined with the
digested filter samples.
5.3.2 Container No. 2 (Acetone Rinse). Note the level of
liguid in the container and confirm on the analysis sheet whether
or not leakage occurred during transport. If a noticeable amount
of leakage has occurred, either void the sample or use methods,
subject to the approval of the Administrator, to correct the
final results. Measure the liguid in this container either
volumetrically within 1 ml or gravimetrically within 0.5 g.
Transfer the contents to an acid-cleaned, tared 250-ml beaker and
evaporate to dryness at ambient temperature and pressure. If
particulate emissions are being determined, desiccate for
36
-------
24 hours without added heat, weigh to a constant weight according
to the procedures described in Section 4.3 of Method 5, and
report the results to the nearest 0.1 mg. Redissolve the residue
with 10 ml of concentrated HNO3. Quantitatively combine the
resultant sample, including all liquid and any particulate
matter, with Container No. 3 before beginning Section 5.3.3.
5.3.3 Container No. 3 (Probe Rinse). The pH of this sample
shall be 2 or lower. If the pH is higher, the sample should be
acidified by careful addition with stirring of concentrated HN03
to pH 2. The sample should be rinsed into a beaker with water,
and the beaker should be covered with a ribbed watch glass. The
sample volume should be reduced to approximately 20 ml by heating
on a hot plate at a temperature just below boiling. Digest the
sample in microwave vessels or ParrE Bombs by quantitatively
transferring the sample to the vessel or bomb, carefully adding
the 6 ml of concentrated HNO3, 4 ml of concentrated HF, and then
continuing to follow the procedures described in Section 5.3.1.
Then combine the resultant sample directly with the acid digested
portions of the filter prepared previously in Section 5.3.1. The
resultant combined sample is referred to as Fraction 1 precursor.
Filter the combined solution of the acid digested filter and
probe rinse samples using Whatman 541 filter paper. Dilute to
300 ml (or the appropriate volume for the expected metals
concentration) with water. This dilution is Fraction 1.
Measure and record the volume of the Fraction 1 solution to
within 0.1 ml. Quantitatively remove a 50-ml aliquot and label
37
-------
as Fraction IB. Label the remaining 250-ml portion as
Fraction 1A. Fraction 1A is used for ICAP or AAS analysis.
Fraction IB is used for the determination of front-half mercury.
5.3.4 Container No. 4 (Impingers 1-3). Measure and record
the total volume of this sample (Fraction 2) to within 0.5 ml.
Remove a 75- to 100-ml aliquot for mercury analysis and label as
Fraction 2B. Label the remaining portion of Container No. 4 as
aliquot Fraction 2A. Aliquot Fraction 2A defines the volume of
2A prior to digestion. All of aliquot Fraction 2A is digested to
produce concentrated Fraction 2A. Concentrated Fraction 2A
defines the volume of 2A after digestion and is normally 150 ml.
Only concentrated Fraction 2A is analyzed for metals (except that
it is not analyzed for mercury). The Fraction 2B aliquot should
be prepared and analyzed for mercury as described in
Section 5.4.3. Aliquot Fraction 2A shall have a pH of 2 or
lower. If necessary, use concentrated HNO3 by careful addition
and stirring to lower aliquot Fraction 2A to pH 2. The sample
should be rinsed into a beaker with water and the beaker covered
with a ribbed watchglass. The sample volume should be reduced to
approximately 20 ml by heating on a hot plate at a temperature
just below boiling. Then follow either of the digestion
procedures described in Sections 5.3.4.1 and 5.3.4.2, below.
5.3.4.1 Conventional Digestion Procedure. Add 30 ml of
50 percent HNO3, and heat for 30 minutes on a hot plate to just
below boiling. Add 10 ml of 3 percent H2O2 and heat for 10 more
minutes. Add 50 ml of hot water, and heat the sample for an
38
-------
additional 20 minutes. Cool, filter the sample, and dilute to
150 ml (or the appropriate volume for the expected metals
concentrations) with water. This dilution is concentrated
Fraction 2A. Measure and record the volume of the Fraction 2A
solution to within 0.1 ml.
5.3.4.2 Microwave Digestion Procedure. Add 10 ml of
50 percent HN03 and heat for 6 minutes in intervals of 1 to 2
minutes at 600 Watts. Allow the sample to cool. Add 10 ml of
3 percent H2O2 and heat for 2 more minutes. Add 50 ml of hot
water, and heat for an additional 5 minutes. Cool, filter the
sample, and dilute to 150 ml (or the appropriate volume for the
expected metals concentrations) with water. This dilution is
concentrated Fraction 2A. Measure and record the volume of the
Fraction 2A solution to within 0.1 ml. NOTE; All microwave
heating times given are approximate and are dependent upon the
number of samples being digested at a time. Heating times as
given above have been found acceptable for simultaneous digestion
of up to 12 individual samples. Sufficient heating is evidenced
by solvent reflux within the vessel.
5.3.5 Container Nos. 5A, 5B, and 5C (Impingers 4, 5,
and 6). Keep these samples separate from each other and measure
and record the volumes of 5A and 5B separately to within 0.5 ml.
Dilute sample 5C to 500 ml with water. These samples 5A, 5B, and
5C are referred to respectively as Fractions 3A, 3B, and 3C.
Follow the analysis procedures described in Section 5.4.3.
Because the permanganate rinse and water rinse have the
39
-------
capability to recover a high percentage of the mercury from the
permanganate impingers, the amount of mercury in the HC1 rinse
(Fraction 3C) may be very small, possibly even insignificantly
small. However, as instructed in this method, add the total of
any mercury measured in and calculated for the HC1 rinse
(Fraction 3C) to that for Fractions IB, 2B, 3A, and 3B for
calculation of the total sample mercury concentration.
5.3.6 Container No. 6 (Silica Gel). Weigh the spent silica
gel (or silica gel plus impinger) to the nearest 0.5 g using a
balance. (This step may be conducted in the field.)
5.4 Sample Analysis. For each sampling train, seven
individual samples are generated for analysis. A schematic
identifying each sample and the prescribed sample preparation and
analysis scheme is shown in Figure 29-3. The first two samples,
labeled Fractions 1A and IB, consist of the digested samples from
the front-half of the train. Fraction 1A is for ICAP or AAS
analysis as described in Sections 5.4.1 and/or 5.4.2.
Fraction IB is for determination of front-half mercury as
described in Section 5.4.3. The back-half of the train was used
to prepare the third through seventh samples. The third and
fourth samples, labeled Fractions 2A and 2B, contain the digested
samples from the moisture knockout, if used, and HNO3/H202
Impingers 1 through 3. Fraction 2A is for ICAP or AAS analysis.
Fraction 2B will be analyzed for mercury. The fifth through
seventh samples, labeled Fractions 3A, 3B, and 3C, consist of the
impinger contents and rinses from the empty and permanganate
40
-------
impingers 4, 5, and 6. These samples are analyzed for mercury as
described in Section 5.4.3. The total back-half mercury catch is
determined from the sum of Fraction 2B and Fractions 3A, 3B,
and 3C.
5.4.1 ICAP Analysis. Fraction 1A and Fraction 2A are
analyzed by ICAP using Method 6010 or Method 200.7 (40 CFR 136,
Appendix C). Calibrate the ICAP, and set up an analysis program
as described in Method 6010 or Method 200.7. The quality control
procedures described in Section 7.3.1 shall be followed.
Recommended wavelengths for use in the analysis are listed below.
Element Wave 1 ength (nm)
Aluminum 308.215
Antimony 206.833
Arsenic 193.696
Barium 455.403
Beryllium 313.042
Cadmium 226.502
Chromium 267.716
Copper 324.754
Iron 259.940
Lead 220.353
Manganese 257.610
Nickel 231.604
Phosphorous 214.914
Selenium 196.026
Silver 328.068
Thallium 190.864
Zinc 213.856
The wavelengths listed are recommended because of their
sensitivity and overall acceptance. Other wavelengths may be
substituted if they can provide the needed sensitivity and are
treated with the same corrective techniques for spectral
interference. Initially, analyze all samples for the desired
target metals (except mercury) plus iron and aluminum. If iron
and aluminum are present, the sample may have to be diluted so
41
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that each of these elements is at a concentration of less than
50 ppm to reduce their spectral interferences on arsenic,
cadmium, chromium, and lead. NOTE: When analyzing samples in a
HF matrix, an alumina torch should be used; since all front-half
samples will contain HF, use an alumina torch.
5.4.2 AAS by Direct Aspiration and/or Graphite Furnace. If
analysis of metals in Fraction 1A and Fraction 2A using graphite
furnace or direct aspiration AAS is desired, Table 29-2 should be
used to determine which techniques and methods should be applied
for each target metal. Table 29-2 should also be consulted to
determine possible interferences and techniques to be followed
for their minimization. Calibrate the instrument according to
Section 6.3 and follow the quality control procedures specified
in Section 7.3.2.
42
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Table 29-2 . Applicable techniques, methods and minimization of i
Metal
Fe
Pb
Pb
tin
Hi
Se
AS
Tl
Tl
Zn
Tech.fl.iq.ue
Aspiration
Aspiration
Furnace
Aspiration
Aspiration
Furnace
Acpi.raT.don
Aspiration
Furnace
Aspiration
SW-846 Wavel ength
Method No, CGnO
7380 248,3
7420 283 . 3
7421 283.3
7460 279 . 5
7520 232 . O
7740 196. O
77fiQ 32S. 1
7840 276 , 8
7841 276.8
7950 213.9
Interferences
Cause Minimization,
Contamination
217. O nm alternate
Poor recoveries
403.1 nm alternate
352.4 nm alternstt
Fet Co., and Cr
Nonlinear response
Volatility
Adsorption & scam
Adsorption & ccatt
AgCl insoluble
Hydrochl ori c acid
or chloride
High Si , Cu . A P
Cont ami nation
Great care taken to avoid ctmtaminatio
Background correction required
Matrix modifier, add 10 ul of phosphor
acid to 1 ml of prepared sample in
sampler cup
Background correction required
Background correction required
Matrix matching or nitrous-oxide/
acetylene flame
Sample dilution or use 352.3 nm line
Spi he sampl es and reefer ence mat efi als
add nickel nitrate to minimize
volatilization
fiBactground correction is required and
Zeeman background correction can "be US'
dSsacigro-und correction is required
Avoid hydrochloric acid unless silver
!n solution as a chloride complex
Sample and standards monitored for
aspiration rate
Background correction is required
Hydrochloric acid should not be used
Background correction is required
Verify that losses are not occurring f
volatizstion by spiked samples or stan
addition.; Palladium is a suitable matr
modifier
Strontium removes Cu and phosphate
Great care taJcen to avoid contaminatio:
L
us
and
jful
.s
ir
lard
-X
1
43
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Table 29-2 cont.
Iletal
Sb
Sb
As
Ba
B*
Be
Cd
Cd
Cr
Cr
Cu
Technique
Aspiration
Furnace
Furnace
Aspiration
Aspi.ratd.oii
Furnace
Aspiration
Furnace
Aspiration
Furnace
Aspiration
SW-846
Method Ho,
7040
7041
7O6O
7080
7090
7091
7130
7131
7190
71S1
7Z10
Wavelength
(mO
217.6
217.6
193.7
553.6
234.9
2.34.9
2.2.8.8
22.8.8
3S7.9
357.9
324.7
Interferences
Cause Minimization
1000 mgXmi Pb
Hi , Cu , or acid
High Pb
Arsenic volatilize
Al-uaifiiiu
Calcium
Barium ionizakion
500 ppm Al
Bigll Mg and Si
Be in optical patt
Absorption and lig
scattering
As aoove
Excess chloride
Pipet tips
Alkali metal
200 mg/L Ca and P
Absorption a scatt
Use secondary wavelenthe of Z31.1 urn;
match sample & standards ' acid concent
tion or use nitrous oxide/acetylene fl
Secondary waveleagtJ) or Zeeman correct
t£tpiifced samples and add nickel nitrate
lution to
digestates prior to analysis
Use Zeeman background correction
High hollow cathode current and narrow
band set
2 ml of KC1 per 100 ml of sample
Add O.l« fluoride
Use method of standard additions
Optimize parameters to minimize effect
tftackoround correction is required
As above
Ammonium phosphate used as a matrix
modifier
Use cadmium-free tips
KC1 ioniaation suppressant in samples
and standards
Consult manufacturer 's literature
All calcium nitrate for a known consta
effect and to eliminate effect of phos
SEonsult manufacturer 's manual
ra-
ame
.on
3O-
s
at
phafce
44
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5.4.3 Cold Vapor AAS Mercury Analysis. Fractions IB, 2B,
3A, 3B, and 3C should be analyzed separately for mercury using
CVAAS following the method outlined in EPA SW-846 Method 7470 or
in Standard Methods for Water and Wastewater Analysis, 15th
Edition, Method 303F. Set up the calibration curve (zero to
1000 ng) as described in SW-846 Method 7470 or similar to Method
303F using 300-ml BOD bottles instead of Erlenmeyers. Dilute
separately, as described below, an aliquot sized from 1 ml to
10 ml of each original sample to 100 ml with water. Record the
amount of the aliguot used for dilution to 100 ml. If no prior
knowledge exists of the expected amount of mercury in the sample,
a 5-ml aliquot is suggested for the first dilution to 100 ml and
analysis. In determining the emission value for mercury, the
size of the sample aliquot used for dilution and analysis is
dependent upon its mercury content. The total amount of mercury
in the aliquot shall be less than 1 pq and within the range (zero
to 1000 ng) of the calibration curve. Place each sample aliquot
into a separate 300-ml BOD bottle, and add enough water to make a
total volume of 100 ml. Then analyze the sample for mercury by
adding to it sequentially the sample preparation solutions and
performing the sample preparation and analysis as described in
the procedures of SW-846 Method 7470 or Method 303F. If the
reading maximums are off-scale (because mercury in the aliquot
exceeded the calibration range), including the dilution of l-ml
aliquots of the original sample, then perform the following:
45
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dilute the original sample (or a portion of it) with 0.15 percent
HN03 (1.5 ml concentrated HN03 per liter aqueous solution) so
that when a 1- to 10-ml aliquot of the original sample is further
diluted to 100 ml and analyzed by the procedures described above,
it will yield an analysis within the range of the calibration
curve.
6. Calibration
Maintain a laboratory log of all calibrations.
6.1 Sampling Train Calibration. Calibrate the sampling
train components according to the indicated sections of Method 5:
Probe Nozzle (Section 5.1); Pitot Tube (Section 5.2); Metering
System (Section 5.3); Probe Heater (Section 5.4); Temperature
Gauges (Section 5.5); Leak-Check of the Metering System
(Section 5.6); and Barometer (Section 5.7).
6.2 Inductively Coupled Argon Plasma Spectrometer
Calibration. Prepare standards as outlined in Section 4.5.
Profile and calibrate the instrument according to the
manufacturer's recommended procedures using the above standards.
The calibration should be checked once per hour. If the
instrument does not reproduce the standard concentrations within
10 percent, the complete calibration procedures should be
performed.
6.3 Atomic Absorption Spectrometer - Direct Aspiration,
Graphite Furnace and Cold Vapor Mercury Analyses. Prepare the
standards as outlined in Section 4.5 and use to calibrate the
spectrometer. Calibration procedures are also outlined in the
46
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EPA methods referred to in Table 29-2 and in SW-846 Method 7470
or Standard Methods for Water and Wastewater Method 303F (for
mercury). Each standard curve should be run in duplicate and the
mean values used to calculate the calibration line. The
instrument should be recalibrated approximately once every 10 to
12 samples.
7. Quality Control
7.1 Sampling. Field Reagent Blanks. When analyzed, the
blanks in Container Nos. 7 through 12 produced previously in
Sections 5.2.14 through 5.2.19, respectively, shall be processed,
digested, and analyzed as follows. Digest and process one of the
filters from Container No. 12 per Section 5.3.1, 100 ml from
Container No. 7 per Section 5.3.2, and 100 ml from Container
No. 8A per Section 5.3.3. This produces Fraction Blanks 1A and
IB from Fraction Blank 1. [If desired, the other two filters may
be digested separately according to Section 5.3.1, diluted
separately to 300 ml each, and analyzed separately to produce a
blank value for each of the two additional filters. If these
analyses are performed, they will produce two additional values
for each of Fraction Blanks 1A and IB. The three Fraction Blank
1A values will be calculated as three values of M£hb in Eguation 3
of Section 8.4.3, then the three values shall be totalled and
divided by 3 to become the value MfM> to be used in computing Mt
by Equation 3. Similarly, the three Fraction Blank IB values
will be calculated separately as three values, totalled,
averaged, and used as the value for Hgfhb in Equation 8 of
\
47
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Section 8.5.3. The analyses of the two extra filters are
optional and are not a requirement of this method, but if the
analyses are performed, the results must be considered as
described above.] Combine 100 ml of Container No. 8A with 200 ml
from Container No. 9, and digest and process the resultant volume
per Section 5.3.4. This produces concentrated Fraction Blanks 2A
and 2B from Fraction Blank 2. A 100-ml portion of Container
No. 8A is Fraction Blank 3A. Combine 100 ml from Container
No. 10 with 33 ml from Container No. 8B. This produces Fraction
Blank 3B (use 400 ml as the volume of Fraction Blank 3B when
calculating the blank value. Use the actual volumes when
calculating all the other blank values). Dilute 225 ml from
Container No. 11 to 500 ml with water. This produces Fraction
Blank 3C. Analyze Fraction Blank 1A and Fraction Blank 2A per
Section 5.4.1 and/or 5.4.2. Analyze Fraction Blank IB, Fraction
Blank 2B, and Fraction Blanks 3A, 3B, and 3C per Section 5.4.3.
The analysis of Fraction Blank 1A produces the front-half reagent
blank correction values for the metals except for mercury; the
analysis of Fraction Blank IB produces the front-half reagent
blank correction value for mercury. The analysis of concentrated
Fraction Blank 2A produces the back-half reagent blank correction
values for the metals except for mercury, while separate analyses
of Fraction Blanks 2B, 3A, 3B, and 3C produce the back-half
reagent blank correction value for mercury.
7.2 An attempt may be made to determine if the laboratory
reagents used in Section 5.3 caused contamination. They should
48
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be analyzed by the procedures in Section 5.4. The Administrator
will determine whether or not the laboratory blank reagent values
can be used in the calculation of the test results.
7.3 Quality Control Samples. The following quality control
samples should be analyzed.
7.3.1 ICAP Analysis. Follow the quality control shown in
Section 8 of Method 6010. For the purposes of a three run test
series, these requirements have been modified to include the
following: two instrument check standard runs, two calibration
blank runs, one interference check sample at the beginning of the
analysis (must be within 25 percent or analyze by standard
additions), one quality control sample to check the accuracy of
the calibration standards (must be within 25 percent of
calibration), and one duplicate analysis (must be within 10
percent of average or repeat all analyses).
7.3.2 Direct Aspiration and/or Graphite Furnace AAS
Analysis for Sb, As, Ba, Be, Cd, Cu, Cr, Pb, Ni, Mn, Hg, P, Se,
Ag, Tl, and Zn. All samples should be analyzed in duplicate.
Perform a matrix spike on at least one front-half sample and one
back-half sample or one combined sample. If recoveries of less
than 75 percent or greater than 125 percent are obtained for the
matrix spike, analyze each sample by the method of additions. A
quality control sample should be analyzed to check the accuracy
of the calibration standards. The results must be within
10 percent or the calibration repeated.
49
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7.3.3 Cold Vapor AAS Analysis for Mercury. All samples
should be analyzed in duplicate. A quality control sample should
be analyzed to check the accuracy of the calibration standards
(within 15 percent or repeat calibration). Perform a matrix
spike on one sample from the HN03 impinger portion (must be
within 25 percent or samples must be analyzed by the method of
standard additions). Additional information on quality control
can be obtained from EPA SW-846 Method 7470 or in Standard
Methods for Water and Wastewater Method 303F.
8. Calculations
8.1 Dry Gas Volume. Using the data from this test,
calculate Vn(std), the dry gas sample volume at standard conditions
as outlined in Section 6.3 of Method 5.
8.2 Volume of Water Vapor and Moisture Content. Using the
data obtained from this test, calculate the volume of water vapor
vw(Std> and the moisture content Bws of the stack gas. Use
Equations 5-2 and 5-3 of Method 5.
8.3 Stack Gas Velocity. Using the data from this test and
Equation 2-9 of Method 2, calculate the average stack gas
velocity.
8.4 Metals (Except Mercury) in Source Sample.
8.4.1 Fraction 1A, Front-Half, Metals (except Hg).
Calculate separately the amount of each metal collected in
Fraction 1 of the sampling train using the following equation:
M«, = Cal Fd Vsoln^ Eq. 29-1
where:
50
-------
Mfh = Total mass of each metal (except Hg) collected
in the front half of the sampling train
(Fraction 1) , jug.
Cal = Concentration of metal in sample Fraction 1A as
read from the standard curve, jug/ml.
Fd = Dilution factor (Fd = the inverse of the
fractional portion of the concentrated sample
in the solution actually used in the instrument
to produce the reading Cal. For example, when
2 ml of Fraction 1A are diluted to 10 ml,
Fd = 5).
vsoin,i = Total volume of digested sample solution
(Fraction 1), ml.
NOTE: If Fractions 1A and 2A are combined, proportional aliquots
must be used. Appropriate changes must be made in Equations 29-1
to 29-3 to reflect this approach.
8.4.2 Fraction 2A, Back-Half, Metals (except Hg).
Calculate separately the amount of each metal collected in
Fraction 2 of the sampling train using the following equation.
Mbh = Ca2 Fa Va Eq. 29-2
where:
Mbh = Total mass of each metal (except Hg) collected
in the back-half of the sampling train
(Fraction 2) , //g.
51
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Ca2 = Concentration of metal in sample concentrated
Fraction 2A as read from the standard curve,
(jug/ml).
Fa = Aliquot factor, volume of Fraction 2 divided by
volume of aliquot Fraction 2A (see
Section 5.3.4).
Va = Total volume of digested sample solution
(concentrated Fraction 2A), ml (see
Section 5.3.4.1 or 5.3.4.2, as applicable).
8.4.3 Total Train, Metals (except Hg). Calculate the total
amount of each of the quantified metals collected in the sampling
train as follows:
Mt = (Mfh - Mehb) + (Mbh - Mbhb) Eq. 29-3
where:
Mt = Total mass of each metal (separately stated for
each metal) collected in the sampling train,
jug.
M£hb = Blank correction value for mass of metal
detected in front-half field reagent blank, //g.
Mbhb = Blank correction value for mass of metal
detected in back-half field reagent blank, jug.
NOTE: If the measured blank value for the front half (m^) is in
the range 0.0 to A nq [where A /Ltg equals the value determined by
52
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multiplying 1.4 jug/in.2 times the actual area in in.2 of the
filter used in the emission sample], mfhb may be used to correct
the emission sample value (mfh) ; if mfhb exceeds A jug, the greater
of the two following values may be used:
I. A nq, or
II. the lesser of (a) mfhb, or (b) 5 percent of mfh.
If the measured blank value for the back-half (mbhb) is in
the range 0.0 to 1 jug, mbhb may be used to correct the emission
sample value (mbh) ; if mbhb exceeds 1 jug, the greater of the two
following values may be used: 1 jug or 5 percent of mbh.
8 . 5 Mercury in Source Sample .
8.5.1 Fraction IB, Front-Half, Mercury. Calculate the
amount of mercury collected in the front-half, Fraction 1, of the
sampling train using the following eguation:
Eq' 29~4
flB
where:
Hgfh = Total mass of mercury collected in the front-
half of the sampling train (Fraction 1), //g.
Qfh = Quantity of mercury in analyzed sample, fj,g.
Vsoin,i - Total volume of digested sample solution
(Fraction 1), ml.
VflB = Volume of Fraction IB analyzed, ml. See the
following Note.
53
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Note: VflB is the actual amount of Fraction IB analyzed. For
example, if 1 ml of Fraction IB were diluted to 100 ml to bring
it into the proper analytical range, and 1 ml of the 100-ml
dilution were analyzed, VflB would be 0.01.
8.5.2 Fractions 2B, 3A, 3B, and 3C, Back Half, Mercury.
Calculate the amount of mercury collected in Fractions 2 using
Equation 5 and in Fractions 3A, 3B, and 3C using Equation 6.
Calculate the total amount of mercury collected in the back-half
of the sampling train using Eq. 29-7.
f2B
where :
Hgbh2 = Total mass of mercury collected in Fraction 2,
/ig.
Qbh2 = Quantity of mercury in analyzed sample, /Ltg.
Vsoin,2 = Total volume of Fraction 2, ml.
V£2B = Volume of Fraction 2B analyzed, ml (see the
following note).
Note: Vf2B is the actual amount of Fraction 2B analyzed. For
example, if 1 ml of Fraction 2B were diluted to 10 ml to bring it
into the proper analytical range, and 5 ml of the 10-ml dilution
was analyzed, Vf2B would be 0.5. Use Equation 6 to calculate
separately the back-half mercury for Fractions 3A, then 3B, then
3C.
where :
54
-------
bh3 (A, B, C) / T7 p~ -5 Q _
T - (VSoln,3(A,B.C.) E(3 • 29
Hgbh3(A,B,c> = Total mass of mercury collected separately in
Fraction 3A, 3B, or 3C, jug.
,o = Quantity of mercury in separately analyzed
samples, /ug.
,o = Volume of Fraction 3A, 3B, or 3C analyzed, ml
(see note in Sections 8.5.1 and 8.5.2, and
calculate similarly) .
vsoin,3
-------
Note: If the total of the measured blank values (Hgfhb + Hgbhb) is
in the range of 0 to 6 ng, then the total may be used to correct
the sample value (Hgfh + Hgbh); if it exceeds 6 ng, the greater of
the following two values may be used: 6 jxg or 5 percent of the
sample value (Hgfh + Hgbh).
8.6 Metal Concentration in Stack Gas. Calculate each metal
separately for the Cd, total Cr, As, Ni, Mn, Be, Cu, Pb, P, Tl,
Ag, Ba, Zn, Se, Sb, and Hg concentrations in the stack gas (dry
basis, adjusted to standard conditions) as follows:
Vm(std)
Eq. 29-9
where:
Cs = Concentration of each metal in the stack gas,
mg/dscm.
K4 = 10"3 mg//ig.
Mt = Total mass of each metal collected in the
sampling train, /ng; (substitute Hgt for Mt for
the mercury calculation).
Vm(std) = Volume of gas sample as measured by the dry gas
meter, corrected to dry standard conditions,
dscm.
8.7 Isokinetic Variation and Acceptable Results. Same as
Method 5, Sections 6.11 and 6.12, respectively.
9. Bibliography
1. Method 303F in Standard Methods for the Examination of
Water Wastewater, 15th Edition, 1980. Available from the
56
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American Public Health Association, 1015 18th Street N.W.,
Washington, D.C. 20036.
2. EPA Methods 6010, 7000, 7041, 7060, 7131, 7421, 7470,
7740, and 7841, Test Methods for Evaluating Solid Waste;
Physical/Chemical Methods. SW-846, Third Edition. September
1988. Office of Solid Waste and Emergency Response, U. S.
Environmental Protection Agency, Washington, D.C. 20460.
3. EPA Method 200.7, Code of Federal Regulations, Title 40,
Part 136, Appendix C. July 1, 1987.
4. EPA Methods 1 through 5, Code of Federal Regulations,
Title 40, Part 60, Appendix A, July 1, 1991.
57
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