ASTM D5086-20

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Designation: D5086 − 01 (Reapproved 2013) D5086 − 20
Standard Test Method for
Determination of Calcium, Magnesium, Potassium, and
Sodium in Atmospheric Wet Deposition by Flame Atomic
Absorption Spectrophotometry
This standard is issued under the fixed designation D5086; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope
1.1 This test method is applicable to the determination of calcium, magnesium, potassium, and sodium in atmospheric wet
deposition (rain, snow, sleet, and hail) by flame atomic absorption spectrophotometry (FAAS) (1).
1.2 The concentration ranges are listed below. The range tested was confirmed using the interlaboratory collaborative test (see
Table 1 for a statistical summary of the collaborative test).
MDL Range of Method Range Tested
(mg/L) (2) (mg/L) (mg/L)
Calcium 0.009 0.03–3.00 0.168–2.939
Magnesium 0.003 0.01–1.00 0.039–0.682
Potassium 0.003 0.01–1.00 0.029–0.499
Sodium 0.003 0.01–2.00 0.105–1.84
1.3 The method detection limit (MDL) as given in 1.2 is based on single operator precisionprecision. (Detection2) and may be
higher or lower for other operators and laboratories. Many workers have found that this test method is reliable at lower levelslimits
vary by instrumentation. Laboratories may be able to achieve lower detection limits. The method detection limit for this method
as described in 1.2 than were tested, butwas determined in 1987 the (2precision ).and bias data presented are insufficient to justify
their use at lower levels.
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use. Specific warning statements are given in 8.3, 8.7, 12.1.8, and Section 9.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D883 Terminology Relating to Plastics
D1129 Terminology Relating to Water
D1193 Specification for Reagent Water
D1356 Terminology Relating to Sampling and Analysis of Atmospheres
D2777 Practice for Determination of Precision and Bias of Applicable Test Methods of Committee D19 on Water
D4453 Practice for Handling of High Purity Water Samples
D4691 Practice for Measuring Elements in Water by Flame Atomic Absorption Spectrophotometry
This test method is under the jurisdiction of ASTM Committee D22 on Air Quality and is the direct responsibility of Subcommittee D22.03 on Ambient Atmospheres
and Source Emissions.
Current edition approved Oct. 1, 2013March 15, 2020. Published October 2013April 2020. Originally approved in 1990. Last previous edition approved in 20082013 as
D5086 – 01 (2013).(2008). DOI: 10.1520/D5086-01R13.10.1520/D5086-20.
The boldface numbers in parentheses refer to a list of references at the end of this test method.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’sstandard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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TABLE 1 Interlaboratory Precision and Bias for Calcium, Magnesium, Potassium, and Sodium Determined from Analyte Spikes of
Synthetic Atmospheric Wet Deposition Samples
Amount Mean 95 % 95 %
A B
Number of S S Bias, Bias, Significant
t o
Element Added, Recovery, Reproducibility Repeatability
Observations mg/L % at 5 % Level
mg/L mg/L Limit Limit
Ca 18 0.168 0.160 0.0062 0.017 0.0063 0.018 −0.008 −4.76 yes
21 0.382 0.332 0.027 0.076 0.011 0.031 −0.030 −7.85 yes
19 0.769 0.722 0.018 0.050 0.0091 0.025 −0.047 −6.11 yes
21 1.448 1.334 0.038 0.106 0.025 0.070 −0.114 −7.87 yes
20 2.939 2.770 0.047 0.132 0.037 0.104 −0.169 −5.75 yes
Mg 18 0.039 0.037 0.0033 0.0092 0.0016 0.0045 −0.002 −5.13 yes
17 0.089 0.090 0.0061 0.017 0.0019 0.0053 0.001 1.12 no
15 0.178 0.180 0.0057 0.016 0.0029 0.0081 0.002 1.12 no
17 0.336 0.336 0.014 0.039 0.0038 0.011 0.00 0.00 no
17 0.682 0.696 0.012 0.034 0.0037 0.010 0.014 2.05 yes
K 16 0.029 0.043 0.0036 0.010 0.0032 0.0090 0.014 48.3 yes
16 0.065 0.068 0.0046 0.013 0.0012 0.0034 0.003 4.62 yes
15 0.130 0.132 0.013 0.036 0.0038 0.011 0.002 1.54 no
17 0.246 0.239 0.020 0.056 0.010 0.028 −0.007 −2.84 no
17 0.499 0.507 0.025 0.070 0.014 0.039 0.008 1.60 no
Na 18 0.225 0.219 0.014 0.039 0.0056 0.016 −0.006 −2.67 no
22 0.105 0.104 0.0010 0.027 0.0021 0.0059 −0.001 −0.95 no
20 0.239 0.235 0.0053 0.015 0.0038 0.011 −0.004 −1.67 yes
17 0.481 0.475 0.0070 0.020 0.0046 0.013 −0.006 −1.24 yes
18 0.906 0.856 0.0087 0.024 0.0073 0.020 −0.050 −5.52 yes
22 1.84 1.85 0.041 0.115 0.021 0.059 0.01 0.54 no
A
Between laboratory precision, reproducibility.
B
Within laboratory precision (pooled single operator precision), repeatability.
D5012 Guide for Preparation of Materials Used for the Collection and Preservation of Atmospheric Wet Deposition
E131 Terminology Relating to Molecular Spectroscopy
E275 Practice for Describing and Measuring Performance of Ultraviolet and Visible Spectrophotometers
E694 Specification for Laboratory Glass Volumetric Apparatus
IEEE/ASTM SI-10 Standard for Use of the International System of Units (SI): The Modern Metric System
2.2 ISO Standard:
ISO 8655 Piston-Operated Volumetric Apparatus — Part 2: Piston Pipettes
3. Terminology
3.1 Definitions:
3.1.1 For definitions of terms used in this test method, refer to Terminologies D883, D1129, D1356, E131, and Practices D4691,
E275, and IEEE/ASTM SI-10.
3.1.2 method detection limit, MDL—the minimum concentration of an analyte that can be reported with 99 % confidence that
the value is above zero based on a standard deviation of greater than seven repetitive measurements of a solution containing the
analyte at a concentration near the low standard. The analyte concentration of this solution should not be greateris not a false
positive. Laboratories must perform detection limit studies or detection limit verification studies at least once every 12 months and
any time changes to the analytical system have occurred which could affect sensitivity. Laboratories must document the statistical
basis for the derived method detection limit. The procedure by which the detection limit is determined or verified must include
a statistical assessment of a minimum of seven low level standards estimated to be at three- to five-times the detection limit and
seven method blanks. Both the standards and the blanks must be processed through the entire method. One method by which this
may be achieved is by following the EPA Method “Definition and Procedure for the Determination of the Method Detection Limit,
Revision 2” than (3ten ).times the estimated MDL.
4. Summary of Test Method
4.1 A solution containing the metal(s) of interest is aspirated as a fine mist into an air acetylene flame where it is converted to
an atomic vapor consisting of ground state atoms. These ground state atoms are capable of absorbing electromagnetic radiation
over a series of very narrow, sharply defined wavelengths from a distinct line source of light, usually a hollow cathode lamp
specific to the metal of interest, passed through the flame. Light from the source beam, less whatever intensity was absorbed by
the atoms of the metal of interest, is isolated by the monochromator and measured by the photodetector. The amount of light
Available from International Organization for Standardization (ISO), ISO Central Secretariat, BIBC II, Chemin de Blandonnet 8, CP 401, 1214 Vernier, Geneva,
Switzerland, http://www.iso.org.
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absorbed by the analyte is quantified by comparing the light transmitted through the flame to light transmitted by a reference beam.
The amount of light absorbed in the flame is proportional to the concentration of the metal in solution. The relationship between
absorption and concentration is expressed by Beer’sBeer’s Law:
log~I /I! 5 abc 5 A (1)
o
where:
I = incident radiant power,
o
I = transmitted radiant power,
a = absorptivity (constant for a given system),
b = sample path length,
c = concentration of absorbing species, and
A = absorbance.
The atomic absorption spectrophotometer is calibrated with standard solutions containing known concentrations of the
element(s) of interest. The concentration of each analyte in the unknown sample is determined from contructedconstructed
calibration curves.
5. Significance and Use
5.1 This test method may be used for the determination of calcium, magnesium, potassium, and sodium in atmospheric wet
deposition samples.
5.2 Emphasis is placed on the easily contaminated quality of atmospheric wet deposition samples due to the low concentration
levels of dissolved metals commonly present.
5.3 Annex A1 represents cumulative frequency percentile concentration plots of calcium, magnesium, potassium, and sodium
obtained from analyses of over five thousand wet deposition samples. These data may be used as an aid in the selection of
appropriate calibration standard concentrations. (3)
6. Interferences
6.1 A chemical interference can prevent, enhance, or suppress the formation of ground state atoms in the flame. For example,
in the case of calcium determinations, the presence of phosphate or sulfate can result in the formation of a salt that hinders proper
atomization of the solution when it is aspirated into the flame. This decreases the number of free, ground state atoms in the flame,
resulting in lowered absorbance values. Aluminum can cause a similar interference when measuring magnesium. The addition of
appropriate complexing agents, such as lanthanum, to the sample solution reduces or eliminates chemical interferences and may
increase the sensitivity of this test method.
6.2 Alkali metals, such as potassium and sodium, can undergo ionization in an air-acetylene flame resulting in a decrease in
ground state atoms available for measurement by atomic absorption. The addition of a large excess of an easily ionizable element,
such as cesium, will eliminate this problem, since cesium will be preferentially ionized. The preferential ionization of the cesium
results in an enhanced atomic absorption signal for both potassium and sodium.
6.3 If a sample containing low concentrations of the metal being measured is analyzed immediately after a sample having a
concentration exceeding the concentration of the highest calibration standard, sample carryover can result in elevated readings due
to residual metal from the previous sample. To prevent this interference, routinely aspirate water for about 15 s after a high
concentration sample. Depending on the concentration of metal in the last sample analyzed, it may be necessary to rinse for longer
time periods. Complete purging of the system is ascertained by aspirating water until the absorbance readout returns to the baseline.
6.4 Atmospheric wet deposition samples are characterized by low ionic strength and rarely contain enough salts to cause
interferences due to non-specific background absorbance. The use of background correction techniques is not necessary and will
decrease the signal to noise ratio and lessen precision.
7. Apparatus
7.1 Atomic Absorption Spectrophotometer—Analytical Apparatus: Select a double-beam instrument having a monochromator,
photodetector, pressure-reducing valves, adjustable spectral bandwidth, and a wavelength range of 190 to 800 nm. Peripheral
equipment may include a strip chart recorder or a suitable data system.
7.1.1 Burner—Flame Atomic Absorption Spectrophotometer, Use a long-path, single slot, air-acetylene burner head supplied by
the manufacturer of the spectrophotometer. equipped with air/acetylene and nitrous oxide/acetylene burner heads.
7.1.2 Hollow Cathode Lamps—or Electrodeless Discharge Lamp, Single element lamps are recommended. Multi-element
lamps are available but are not recommended. They have a shorter lifespan, are less sensitive, require a higher operating current,
and increase the chances of spectral interferences.for each element to be determined.
7.1.3 Deuterium Continuum Lamp.
7.1.4 Compressed Air—Appropriate pressure reducing regulator with base connections (see instrument manufacturer’s
instructions).
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7.1.5 Monochromator—Acetylene Gas and Regulator—To increase the sensitivity for calcium and potassium measurements, a
monochromator A cylinder of acetylene equipped with a blaze grating in the range of 500 to 600 nm is recommended. For the
analysis of magnesium and sodium, a blaze grating in the range of 200 to 250 nm is adequate. two-gage, two-stage
pressure-reducing regulator with hose connections (see instrument manufacturer’s instructions).
7.1.4 Photomultiplier Tube—A wide spectral range (160 to 900 nm) photomultiplier tube is recommended. Select a red-sensitive
photomultiplier tube to detect potassium at 766.5 nm and to increase sensitivity for calcium at 422.7 nm.
7.2 Volumetric Pipets—Maintain a set of Class A volumetric pipets (see Specification E694) to be used only when making dilute
calibration solutions for the analysis of atmospheric wet deposition samples. Alternatively, variable or fixed volume piston operated
disposable tip pipets may be used.used if they comply with ISO 8655.
7.3 Volumetric Flasks—Maintain a set of Class A volumetric flasks (see Specification E694) to be used only when making dilute
calibration solutions for the analysis of atmospheric wet deposition samples.
7.3.1 The first time any glassware is used for making stock solutions and standards, clean with HCl (1+1) and rinse thoroughly
with water before use.
7.3.2 Store clean glassware filled with water and covered.
7.4 Laboratory Facilities—Laboratories used for the analysis of atmospheric wet deposition samples should be free from
external sources of contamination.
7.4.1 The use of laminar flow clean air workstations is recommended for sample processing and preparation to avoid the
introduction of airborne contaminants. If a clean air workstations is unavailable, samples must be capped or covered prior to
analysis.
7.4.2 A positive pressure environment within the laboratory is recommended to minimize the introduction of external sources
of contaminant gases and particulates. Windows within the laboratory should be kept closed at all times and sealed if leaks are
apparent.
7.4.3 The use of disposable tacky floor mats at the entrance to the laboratory is helpful in reducing the particulate loading within
the room.
8. Reagents and Materials
8.1 Purity of Reagents—Use reagent grade or higher grade chemicals for all solutions. better. All reagents shall conform to the
specifications of the Committee on Analytical Reagents of the American Chemical Society (ACS) where such specifications are
available.
8.2 Purity of Water—Unless otherwise indicated, references to water shall be understood to mean reagent water as defined by
Type I of Specification D1193. Point of use 0.2 μm filters are recommended for all faucets supplying water to prevent the
introduction of bacteria and/or ion exchange resins into reagents.
8.3 Acetylene (Fuel)—Minimum acceptable acetylene purity is 99.5 % (v/v). Change the cylinder when the pressure reaches 517
kPa (75 psig) if the acetylene is packed in acetone. Pre-purified grades that contain a proprietary solvent can be used to 207 kPa
(30 psig) before replacement. Avoid introducing these solvents into the instrument. Damage to the instrument’sinstrument’s
plumbing system can result. To prevent solvent carryover, allow acetylene cylinders to stand for at least 24 h before use.
(Warning—Acetylene is a highly flammable gas. Follow the precautions in 9.3 – 9.6 regarding safe operating pressures, suitable
plumbing, and operator safety.)
8.4 Cesium Solution (Ionization Suppressant)—Dissolve 126.7 g cesium chloride (CsCl), dried at 105°C for 1 h, in water and
dilute to 1 L. Store at room temperature in a high density polyethylene or polypropylene container. Alternatively, commercially
available Cesium ionization suppressants/buffers may be purchased.
8.5 Hydrochloric Acid (1+1)—(1+1, Volume to Volume)—Carefully add one volume of concentrated hydrochloric acid (HCl, sp
gr 1.19) to an equal volume of water.
8.6 Hydrochloric Acid (1+19)—(1+19, Volume to Volume)—Carefully add 50 mL of concentrated hydrochloric acid (HCl, sp
gr 1.19) to 900 mL of water and dilute to 1 L.
8.7 Lanthanum Solution (Releasing Agent)—In a glass 1 L volumetric flask, place 117.3 g of lanthanum oxide (La O ), dried
2 3
at 105°C for 1 h. Wet with water and add HCl (1+1) in small increments until a total of 500 mL of HCl (1+1) has been added.
Cool the solution between additions. Dilute to 1 L with water. Store at room temperature in a high density polyethylene or
polypropylene container. (Warning—Dissolving lanthanum oxide in hydrochloric acid is a strongly exothermic reaction; use
extreme caution when dissolving the reagent. Refer to 9.1 for proper safety precautions when preparing this solution.)
Alternatively, commercially available lanthanum releasing agent solutions may be purchased.
Reagent Chemicals, American Chemical Society SpecificationsACS Reagent Chemicals, Specifications and Procedures for Reagents and Standard-Grade Reference
Materials, , American Chemical Society, Washington, DC. For suggestions on the testing of reagents not listed by the American Chemical Society, see Analar Standards for
Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC),
Rockville, MD.
D5086 − 20
8.8 Oxidant (air)—The air may be provided by a compressor or commercially bottled supply. Remove oil, water, and other
foreign matter from the air using a filter recommended by the manufacturer. Refer to the manufacturer’smanufacturer’s guidelines
for recommended delivery pressure.
8.9 Stock Standard Solutions—Stock standard solutions may be purchased as certified solutions or prepared from ACS reagent
grade materials as detailed in 8.9.1 – 8.9.4. Store the solutions at room temperature in high density polyethylene or polypropylene
containers.
8.9.1 Calcium Solution, Stock (1.0 mL = 1.0 mg Ca)—Add 2.497 g of calcium carbonate (CaCO ), dried at 180°C for 1 h, to
approximately 600 mL of water. Add concentrated hydrochl
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