ASTM D5086-95

NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
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Designation: D 5086 – 95 An American National Standard
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 D 5086; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope D 1356 Terminology Relating to Sampling and Analysis of
Atmospheres
1.1 This test method is applicable to the determination of
D 2777 Practice for Determination of Precision and Bias of
calcium, magnesium, potassium, and sodium in atmospheric
Applicable Methods of Committee D-19 on Water
wet deposition (rain, snow, sleet, and hail) by flame atomic
D 4453 Practice for Handling of Ultra-Pure Water Samples
absorption spectrophotometry (FAAS). (1)
D 4691 Practice for Measuring Elements in Water by Flame
1.2 The concentration ranges are listed below. The range
Atomic Absorption Spectrophotometry
tested was confirmed using the interlaboratory collaborative
D 5012 Guide for Preparation of Materials Used for the
test (see Table 1 for a statistical summary of the collaborative
Collection and Preservation of Atmospheric Wet Deposi-
test).
tion
MDL Range of Method Range Tested
E 131 Terminology Relating to Molecular Spectroscopy
(mg/L) (2) (mg/L) (mg/L)
E 275 Practice for Describing and Measuring Performance
Calcium 0.009 0.03–3.00 0.168–2.939
of Ultraviolet, Visible, and Near Infrared Spectrophotom-
Magnesium 0.003 0.01–1.00 0.039–0.682
eters
Potassium 0.003 0.01–1.00 0.029–0.499
Sodium 0.003 0.01–2.00 0.105–1.84
E 380 Practice for the International System of Units (SI)
(the Modernized Metric System)
1.3 The method detection limit (MDL) is based on single
E 694 Specification for Laboratory Glass Volumetric Appa-
operator precision (2) and may be higher or lower for other
ratus
operators and laboratories. Many workers have found that this
test method is reliable at lower levels than were tested, but the
3. Terminology
precision and bias data presented are insufficient to justify their
3.1 Definitions—For definitions of terms used in this test
use at lower levels.
method, refer to Terminologies D 883, D 1129, E 131, D 1356,
1.4 This standard does not purport to address all of the
and Practices D 4691, E 275, and E 380.
safety concerns, if any, associated with its use. It is the
3.1.1 method detection limit, MDL—the minimum concen-
responsibility of the user of this standard to establish appro-
tration of an analyte that can be reported with 99 % confidence
priate safety and health practices and determine the applica-
that the value is above zero based on a standard deviation of
bility of regulatory limitations prior to use. Specific precau-
greater than seven repetitive measurements of a solution
tionary statements are given in Note 1, Note 2, and Note 6 and
containing the analyte at a concentration near the low standard.
Section 9.
The analyte concentration of this solution should not be greater
2. Referenced Documents than five times the estimated MDL. (3)
2.1 ASTM Standards:
4. Summary of Test Method
D 883 Terminology Relating to Plastics
4 4.1 A solution containing the metal(s) of interest is aspirated
D 1129 Terminology Relating to Water
as a fine mist into a flame where it is converted to an atomic
D 1193 Specification for Reagent Water
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
This test method is under the jurisdiction of ASTM Committee D-22 on
Sampling and Analysis of Atmospheres and is the direct responsibility of Subcom-
distinct line source of light, usually a hollow cathode lamp
mittee D22.06 on Atmospheric Deposition.
specific to the metal of interest, a beam passed through the
Current edition approved Jan. 15, 1995. Published March 1995. Originally
published as D 5086 – 90. Last previous edition D 5086 – 90.
The boldface numbers in parentheses refer to a list of references at the end of
this test method. Annual Book of ASTM Standards, Vol 11.03.
3 6
Annual Book of ASTM Standards, Vol 08.01. Annual Book of ASTM Standards, Vol 03.06.
4 7
Annual Book of ASTM Standards, Vol 11.01. Annual Book of ASTM Standards, Vol 14.02.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
D 5086
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.
flame. Light from the source beam, less whatever intensity was 6. Interferences
absorbed by the atoms of the metal of interest, is isolated by the
6.1 A chemical interference can prevent, enhance, or sup-
monochromator and measured by the photodetector. The
press the formation of ground state atoms in the flame. For
amount of light absorbed by the analyte is quantified by
example, in the case of calcium determinations, the presence of
comparing the light transmitted through the flame to light
phosphate or sulfate can result in the formation of a salt that
transmitted by a reference beam. The amount of light absorbed
hinders proper atomization of the solution when it is aspirated
in the flame is proportional to the concentration of the metal in
into the flame. This decreases the number of free, ground state
solution. The relationship between absorption and concentra-
atoms in the flame, resulting in lowered absorbance values.
tion is expressed by Beer’s Law:
Aluminum can cause a similar interference when measuring
log ~I /I! 5 abc 5 A (1) magnesium. The addition of appropriate complexing agents,
o
such as lanthanum, to the sample solution reduces or eliminates
where:
chemical interferences and may increase the sensitivity of this
I = incident radiant power,
o
test method.
I = transmitted radiant power,
6.2 Alkali metals, such as potassium and sodium, can
a = absorptivity (constant for a given system),
undergo ionization in an air-acetylene flame resulting in a
b = sample path length,
decrease in ground state atoms available for measurement by
c = concentration of absorbing species, and
atomic absorption. The addition of a large excess of an easily
A = absorbance.
ionizable element, such as cesium, will eliminate this problem,
The atomic absorption spectrophotometer is calibrated with
since cesium will be preferentially ionized. The preferential
standard solutions containing known concentrations of the
ionization of the cesium results in an enhanced atomic absorp-
element(s) of interest. The concentration of each analyte in the
tion signal for both potassium and sodium.
unknown sample is determined from contructed calibration
6.3 If a sample containing low concentrations of the metal
curves.
being measured is analyzed immediately after a sample having
5. Significance and Use
a concentration exceeding the concentration of the highest
calibration standard, sample carryover will result in elevated
5.1 This test method may be used for the determination of
readings due to residual metal from the previous sample. To
calcium, magnesium, potassium, and sodium in atmospheric
wet deposition samples. prevent this interference, routinely aspirate water for about 15
s after a high concentration sample. Depending on the concen-
5.2 Emphasis is placed on the easily contaminated quality of
atmospheric wet deposition samples due to the low concentra- tration of metal in the last sample analyzed, it may be
necessary to rinse for longer time periods. Complete purging of
tion levels of dissolved metals commonly present.
the system is ascertained by aspirating water until the absor-
5.3 Annex A1 represents cumulative frequency percentile
bance readout returns to the baseline.
concentration plots of calcium, magnesium, potassium, and
sodium obtained from analyses of over five thousand wet 6.4 Atmospheric wet deposition samples are characterized
deposition samples. These data may be used as an aid in the by low ionic strength and rarely contain enough salts to cause
selection of appropriate calibration standard concentrations. (4) interferences due to non-specific background absorbance. The
D 5086
use of background correction techniques is not necessary and chemicals for all solutions. All reagents shall conform to the
will decrease the signal to noise ratio and lessen precision. specifications of the Committee on Analytical Reagents of the
American Chemical Society (ACS) where such specifications
7. Apparatus 8
are available.
7.1 Atomic Absorption Spectrophotometer—Select a 8.2 Purity of Water—Unless otherwise indicated, references
double-beam instrument having a dual grating monochromator,
to water shall be understood to mean reagent water as defined
photodetector, pressure-reducing valves, adjustable spectral by Type II of Specification D 1193. Point of use 0.2 μm filters
bandwidth, and a wavelength range of 190 to 800 nm.
are recommended for all faucets supplying water to prevent the
Peripheral equipment may include a strip chart recorder or a
introduction of bacteria and/or ion exchange resins into re-
suitable data system.
agents.
7.1.1 Burner—Use a long-path, single slot, air-acetylene
8.3 Acetylene (Fuel)—Minimum acceptable acetylene pu-
burner head supplied by the manufacturer of the spectropho-
rity is 99.5 % (v/v). Change the cylinder when the pressure
tometer.
reaches 517 kPa (75 psig) if the acetylene is packed in acetone.
7.1.2 Hollow Cathode Lamps—Single element lamps are
Pre-purified grades that contain a proprietary solvent can be
recommended. Multi-element lamps are available but are not
used to 207 kPa (30 psig) before replacement. Avoid introduc-
recommended. They have a shorter lifespan, are less sensitive,
ing these solvents into the instrument. Damage to the instru-
require a higher operating current, and increase the chances of
ment’s plumbing system can result. To prevent solvent carry-
spectral interferences.
over, allow acetylene cylinders to stand for at least 24 h before
7.1.3 Monochromator—To increase the sensitivity for cal-
use.
cium and potassium measurements, a monochromator
NOTE 1—Caution: Acetylene is a highly flammable gas. Follow the
equipped with a blaze grating in the range of 500 to 600 nm is
precautions in 9.3-9.6 regarding safe operating pressures, suitable plumb-
recommended. For the analysis of magnesium and sodium, a
ing, and operator safety.
blaze grating in the range of 200 to 250 nm is adequate.
8.4 Cesium Solution (Ionization Suppressant)—Dissolve
7.1.4 Photomultiplier Tube—A wide spectral range (160 to
126.7 g cesium chloride (CsCl), dried at 105°C for 1 h, in water
900 nm) photomultiplier tube is recommended. Select a red-
and dilute to 1 L. Store at room temperature in a high density
sensitive photomultiplier tube to detect potassium at 766.5 nm
polyethylene or polypropylene container.
and to increase sensitivity for calcium at 422.7 nm.
8.5 Hydrochloric Acid (1+1)—Carefully add one volume of
7.2 Volumetric Pipets—Maintain a set of Class A volumetric
concentrated hydrochloric acid (HCl, sp gr 1.19) to an equal
pipets (see Specification E 694) to be used only when making
volume of water.
dilute calibration solutions for the analysis of atmospheric wet
8.6 Hydrochloric Acid (1+19)—Carefully add 50 mL of
deposition samples. Alternatively, disposable tip pipets may be
concentrated hydrochloric acid (HCl, sp gr 1.19) to 900 mL of
used.
water and dilute to 1 L.
7.3 Volumetric Flasks—Maintain a set of Class A volumet-
8.7 Lanthanum Solution (Releasing Agent)—In a glass 1 L
ric flasks (see Specification E 694) to be used only when
volumetric flask, place 117.3 g of lanthanum oxide (La O ),
2 3
making dilute calibration solutions for the analysis of atmo-
dried at 105°C for 1 h. Wet with water and add HCl (1+1) in
spheric wet deposition samples.
small increments until a total of 500 mL of HCl (1+1) has been
7.3.1 The first time any glassware is used for making stock
added. Cool the solution between additions. Dilute to 1 L with
solutions and standards, clean with HCl (1+1) and rinse
water. Store at room temperature in a high density polyethylene
thoroughly with water before use.
or polypropylene container.
7.3.2 Store clean glassware filled with water and covered.
NOTE 2—Caution: Dissolving lanthanum oxide in hydrochloric acid is
7.4 Laboratory Facilities—Laboratories used for the analy-
a strongly exothermic reaction; use extreme caution when dissolving the
sis of atmospheric wet deposition samples should be free from
reagent. Refer to 9.1 for proper safety precautions when preparing this
external sources of contamination.
solution.
7.4.1 The use of laminar flow clean air workstations is
8.8 Oxidant (air)—The air may be provided by a compres-
recommended for sample processing and preparation to avoid
sor or commercially bottled supply. Remove oil, water, and
the introduction of airborne contaminants. If a clean air
other foreign matter from the air using a filter re
...