ASTM D5954-98(2006)
(Test Method)Standard Test Method for Mercury Sampling and Measurement in Natural Gas by Atomic Absorption Spectroscopy
Standard Test Method for Mercury Sampling and Measurement in Natural Gas by Atomic Absorption Spectroscopy
SIGNIFICANCE AND USE
This test method can be used to measure the level of mercury in natural gas streams for purposes such as determining compliance with regulations, studying the effect of various abatement procedures on mercury emissions, checking the validity of direct instrumental measurements, and verifying that mercury concentrations are below those required for natural gas processing and operation.
Adsorption of the mercury on gold-coated beads can remove interferences associated with the direct measurement of mercury in natural gas. It preconcentrates the mercury before analysis thereby offering measurement of ultra-low average concentrations in a natural gas stream over a long span of time. It avoids the cumbersome use of liquid spargers with on-site sampling, and eliminates contamination problems associated with the use of potassium permanganate solutions.3 ,4 ,5
SCOPE
1.1 This test covers the determination of total mercury in natural gas at concentrations down to 1 ng/m3. It includes separate procedures for both sampling and atomic absorption spectrophotometric determination of mercury. The procedure detects both inorganic and organic forms of mercury.
1.2 The values stated in SI units are to be regarded as the standard.
This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: D5954 − 98(Reapproved 2006)
Standard Test Method for
Mercury Sampling and Measurement in Natural Gas by
Atomic Absorption Spectroscopy
This standard is issued under the fixed designation D5954; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope abatement procedures on mercury emissions, checking the
validity of direct instrumental measurements, and verifying
1.1 This test covers the determination of total mercury in
3 that mercury concentrations are below those required for
natural gas at concentrations down to 1 ng/m . It includes
natural gas processing and operation.
separate procedures for both sampling and atomic absorption
spectrophotometric determination of mercury. The procedure 4.2 Adsorption of the mercury on gold-coated beads can
detects both inorganic and organic forms of mercury. remove interferences associated with the direct measurement
of mercury in natural gas. It preconcentrates the mercury
1.2 The values stated in SI units are to be regarded as the
before analysis thereby offering measurement of ultra-low
standard.
average concentrations in a natural gas stream over a long span
1.3 This standard does not purport to address all of the
of time. It avoids the cumbersome use of liquid spargers with
safety concerns, if any, associated with its use. It is the
on-site sampling, and eliminates contamination problems as-
responsibility of the user of this standard to establish appro- 3,4,5
sociated with the use of potassium permanganate solutions.
priate safety and health practices and determine the applica-
5. Apparatus
bility of regulatory limitations prior to use.
5.1 Atomic Absorption Spectrophotometer, equipped with a
2. Referenced Documents
10-cm-long path quartz absorption cell and a mercury source
2.1 ASTM Standards:
lamp (EDLor other high intensity lamp). It must be capable of
D1193 Specification for Reagent Water
collecting and integrating data over a 30- to 60-s time window.
Background capabilities are strongly recommended.
3. Summary of Test Method
NOTE 1—Detection sensitivity may vary significantly depending on the
3.1 Mercury in a gas stream is adsorbed onto gold-coated
type of spectrophotometer and its accessories.
silica beads and subsequently directly desorbed by heat into a
5.2 Rotameter or Other Flow Measurement Device capable
long path-length quartz cell connected to an atomic absorption
of attaining and regulating air at approximately 500 mL/min.
spectrophotometer. Mercury atoms are detected by measuring
their absorbance of light from a mercury source lamp at a 5.3 Rotameter or Other Flow Measurement Device capable
of attaining and regulating the natural gas sample at approxi-
characteristic wavelength. The mercury concentration is ob-
tained from the absorbance peak area by comparison to mately 1000 to 2500 mL/min.
standards prepared at the time of analysis.
5.4 Dry or Wet Positive Displacement Test Meter, or other
calibrated total flow measurement device for measuring the
4. Significance and Use
volume of the sample.
4.1 This test method can be used to measure the level of
5.5 TFE-Fluorocarbon Tubing, to make connections to the
mercury in natural gas streams for purposes such as determin-
atomic absorption spectrophotometer. The size should be
ing compliance with regulations, studying the effect of various
appropriate for the quartz absorption cell.
5.6 Quartz Tubing, 12 cm long, ⁄4-in. outside diameter, to
ThistestmethodisunderthejurisdictionofASTMCommitteeD03onGaseous
be used for sorbent (gold-coated silica) packing.
Fuels and is the direct responsibility of Subcommittee D03.05 on Determination of
Special Constituents of Gaseous Fuels.
Current edition approved Dec. 1, 2006. Published February 2007. Originally Schroeder,W.H.,“SamplingandAnalysisofMercuryanditsCompoundsinthe
approved in 1996. Last previous edition approved 1998 as D5954–98. DOI: Atmosphere,” Environmental Science & Technology , 16, 1982, 394A–399A.
10.1520/D5954-98R06. Chao, S.S., andAttari,A., “Characterization and Measurements of Natural Gas
For referenced ASTM standards, visit the ASTM website, www.astm.org, or Trace Constituents—Volume II: Survey,” Final Report GRI-94/0243.2, June 1994.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Braman, R.S., and Johnson, D.L., “Selective Absorption Tubes and Emission
Standards volume information, refer to the standard’s Document Summary page on Technique for the Determination of Ambient Forms of Mercury in Air,” Environ-
the ASTM website. mental Science & Technology, 8, 1974, pp. 996–1003.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5954 − 98 (2006)
NOTE2—Allglassandplasticwarecomingintocontactwiththesample
where such specifications are available. Other grades may be
must be acid washed with 20 % nitric acid and thoroughly rinsed with
used, provided it is first ascertained that the reagent is of
water.
sufficiently high purity to permit its use without lessening the
5.7 Quartz Tubing, approximately 24 in. long and 1-in.
accuracy of the determination.
outside diameter, to be used for the preparation of the gold-
6.2 Reagent Water—Reagent water, conforming to Type II
coated silica.
of Specification D1193, shall be used for preparation of
5.8 Quartz Wool to be used for sorbent (gold-coated silica) reagents and washing of the quartz tubing.
packing.
6.3 Gold Chloride—Dissolve2gof gold chloride
(HAuCl ·3H O)inapproximately10mLofwater(Warning—
5.9 Fused Silica or Quartz Beads, 60/80 mesh, to be used
4 2
Poison).
for the preparation of the gold-coated silica.
6.4 Sulfuric Acid, (concentrated, H SO , relative density
2 4
5.10 Tube Furnace, approximately 8 to 10 cm in length, to
1.84) (Warning—Poison).
be used for the preparation of the gold-coated silica and the
mercury desorption. It must be capable of maintaining tem-
6.5 Nitric Acid, (concentrated, HNO , relative density 1.42)
peratures up to 750 6 25°C over a 4-cm length. A Variac or
(Warning—Poison).
other temperature control device may be required.
6.6 Nitric Acid, (20 %)—Mix 1 volume of concentrated
nitric acid with 4 volumes of water.
NOTE 3—A shorter sampling tube and a shorter tube furnace may be
used as long as the specified temperature can be maintained.
6.7 Mercury, triple distilled (Warning—Poison).
5.11 Silicone Tubing, ⁄4-in. inside diameter for connections.
6.8 Mercury Standard Stock Solution, (1000 µg/mL)—
1 1
5.12 Stainless Steel Tubing, ⁄4- and ⁄8-in outside diameter, Dissolve 1.080 g of mercury (II) oxide (HgO) in a minimal
various lengths, for connections. amount of HCl (1 + 1). Dilute to 1 L with water.
6.9 Mercury Standard Intermediate Solution, (10 µg/mL)—
5.13 Gastight Tube Fittings, ⁄4-in. nylon or TFE-
Add 10.00 mL of the mercury standard stock solution to
fluorocarbon construction, gastight end-cap type, plus one
approximately 500 mL of water. Add 0.5 mL of concentrated
stainless steel “T” fitting.
nitric acid and dilute to 1 L with water. Prepare this standard
5.14 Precision Gastight Syringe, 500 µL, equipped with a
solution daily.
needle with a side port opening.
6.10 Mercury Standard Working Solution, (100 ng/mL)—
NOTE 4—A digital syringe is recommended for better accuracy and
Add 1.00 mL of the mercury standard intermediate solution to
precision in calibration.
approximately 50 mL of water. Add 0.05 mL of concentrated
5.15 Septum Material, GC grade, low bleed type, made
nitric acid and dilute to 100 mL with water. If micropipets are
from silicone.
not available, this standard may be prepared by serial dilution
of the mercury standard intermediate solution. Prepare this
5.16 Water Bath or Constant Temperature Apparatus, ca-
standard solution daily.
pable of regulating a sealed vial of mercury to 26 6 0.05°C.
6.11 Air, PP grade, or carbon filtered.
5.17 Sealed Vial of Mercury, prepared from a 250-mL glass
6.12 Hydrogen, PP grade (Warning—Flammable).
bottle with a TFE-fluorocarbon septum cap and triple distilled
elemental mercury.
6.13 Nitrogen, PP grade.
5.18 Thermocouple, for monitoring tube furnace tempera-
6.14 Sulfur Impregnated Carbon,usedtofiltercarriergases.
tures.
7. Procedure for the Preparation of the Gold-Coated
5.19 Heating Tape, capable of maintaining a temperature of
Beads
50 to 60°C, to heat trace tubing from the outlet end of the
7.1 Soak the silica beads in concentrated sulfuric acid
sampling tube to the inlet port of the AAS cell. A Variac or
overnighttoremoveanycoatingorcontamination.Silicabeads
other temperature control device may be required.
used for GC operations are often deactivated by silanization
5.20 Stainless Steel 6-Port Switching Valve, ⁄8in.forcarrier
and this coating must be removed. Wash thoroughly with
gas control (optional).
reagent water and dry.
6. Reagents
Reagent Chemicals, American Chemical Society Specifications , American
Chemical Society, Washington, DC. For suggestions on the testing of reagents not
6.1 Purity of Reagents—Reagent grade chemicals shall be
listed by the American Chemical Society, see Analar Standards for Laboratory
used in all tests. Unless otherwise indicated, it is intended that
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
all reagents shall conform to the specifications of the Commit-
and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,
tee onAnalytical Reagents of theAmerican Chemical Society, MD.
D5954 − 98 (2006)
7.2 Add 50 g of acid washed silica beads to 10 mL of gold natural gas sample should flow from the sampling point (with
chloride solution. This will result in a 2 % loading of gold on a pressure regulator) into the first sampling tube (Tube 1),
the silica substrate. Add a minimal amount of water, if followed by the second tube (Tube 2), and finally the rotameter
necessary, to form a slurry. Heat on a hot plate with stirring flow control device.
until most of the water evaporates. Let the beads air-dry until
9.2 The distance from the sampling point to the sampler
the apparent moisture is evaporated. The color may change
should be minimized because mercury is easily absorbed on
from yellow to a yellowish orange.
tubing lines and sampling equipment. The entire sampling
7.3 Pack the coated beads into the 1-in. outside diameter
system must be passivated with the sample gas before any
quartz tube with quartz wool plugs at either end and begin
sampling, especially if low levels of mercury are expected.
heating using a tube furnace with a nitrogen purge. Slowly
Stainlesssteeltubingmustbeusedforconnectionsupstreamof
raisethetemperaturefromambientto170°Ctodrythoroughly.
the pressure regulator. High density TFE-fluorocarbon or
A heat gun may be used to remove condensed moisture
stainless steel tubing is preferred for connections downstream
downstream of the furnace. The color of the beads will begin
of the regulator. Flexible silicone tubing may be used to make
to turn orange and then purplish. This may take 1 to2hto
short connections to sampling tubes. Any pumps, metering
complete depending on how much moisture is present.
valves, and so forth or other flow- and pressure-controlling
devices should be located downstream of the sampler if
NOTE 5—Caution: Moisture and oxygen must be removed and the
beads completely dry before hydrogen gas is introduced. possible. The entire sampling line should be heated to prevent
condensation, especially when a pressure reduction device is
7.4 Switch the gas to hydrogen and slowly raise the tem-
used to step down the pressure for sampling.
perature to 250°C to reduce the gold ion to metallic gold. As
the temperature rises, HCl vapors are generated from the tube
9.3 Ascertain that the sample can be obtained at a pressure
and may appear as a smoky haze. A yellowish haze may be
not exceeding 15 psig (10 psig is preferable) and a flow of 1 to
seen on the inside walls of the quartz tube. The reaction is
2.5 L/min (2 L/min is preferable). Pressure- and flow-control
complete when this haze either disappears or does not change
devices may be required. A total flow volume measurement
over a 15- to 20-min period. Do not allow the temperature of
device, such as a dry test meter, can be used to record the exact
the furnace to rise above 250°C since gold chloride will
amounts of gas sampled for more accurate sampling.
sublimate at 265°C. This procedure may take 2 to3hto
9.4 Using a calibrated rotameter, installed upstream of the
complete.
total flow measurement device, determine an approximate flow
NOTE6—Caution:Thegasstreamexitingfromthetubefurnaceshould
control setting for the selected flow at the applied pressure.
be directed into a flask containing water to absorb the HCl gas generated
Thiswillsavetimewhensettingupthesamplingtubesandwill
as the gold ion is reduced.
condition the sampling system.
7.5 Raise the furnace temperature to approximately 400°C
over a 10-min period. Switch the gas to nitrogen and continue
9.5 Remove the fitting on one end of each tube and join the
heating up to 500 to 550°C for an additional 10 min. Remove
two tubes end-to-end with a short piece of silicone tubing.
the quartz tube from the furnace and allow to cool under the
9.6 Connect the back end of the sampling tube assembly
nitrogen purge.
(Tube 2) to the rotameter and connect the front end of the
8. Procedure for the Preparation of the Sampling Tubes sampling tube assembly (Tube 1) to the sampling point.
Carefully open the sampling valve and quickly adjust the flow
8.1 Washeach ⁄4-in.outsidediameterquartztubewith20 %
control (and pressure if necessary) to obtain the required
HNO , rinse with water, and dry in an oven at 105°C.
flowrate.Recordthetimeandflowdataatthestartofsampling.
8.2 Place a 1-cm length of quartz wool at one end of a tube.
Mark the direction the sample gas flowed through the tube.
8.3 Add 0.5 g of the gold-coated beads to a quartz tube
9.7 Flow the sample through the sampling tube for the
(oriented vertically) and gently tap the contents to eliminate air
desired amount of time, periodically checking that the flow is
spaces. The final length of gold-coated beads should be
staying close to what it originally was and adjusting it if
approximately 2.5 cm and centered within the tube.
necessary. Typical volumes of gas range from 50 to 100 L. A
8.4 Add a final 1-cm length of quartz wool to the opposite
smaller volume of gas should be used for a sample containing
end of the tube.
a high concentration of mercury.The optimal r
...
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