WATER POLLUTION CONTROL RESEARCH SERIES
16020 GFR 07/71
Interaction Of Nitrilotriacetic Acid
With Suspended And Bottom Material
U.S. ENVIRONMENTAL PROTECTION AGENCY
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WATER POLLUTION CONTROL RESEARCH SERIES
The Water Pollution Control Research Series describes the
results and progress in the control and abatement of pollution
in our Nation's waters. They provide a central source of
Information on the research, development and demonstration
activities in the Environmental Protection Agency, through
inhouse research and grants and contracts with Federal,
State, and local agencies, research institutions, and
industrial organizations.
Inquiries pertaining to Water Pollution Control Research
Reports should be directed to the Chief, Publications Branch
(Water), Research Information Division, R&M, Environmental
Protection Agency, Washington, B.C. 20460.
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INTERACTION OF NITRILOTRIACETIC ACID
WITH
SUSPENDED AND BOTTOM MATERIAL
by
Division of Analytical Chemistry
Institute for Materials Research
National Bureau of Standards
Washington, D. C. 20234
for the
ENVIRONMENTAL PROTECTION AGENCY
Program No. 16020 GFR
July 1971
For sate by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 • Price 45 cents
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EPA Review Notice
This report has "been reviewed by the Environmental Protection
Agency and approved for publication. Approval does not
signify that the contents necessarily reflect the views and
policies of the Environmental Protection Agency nor does
mention of trade names or commercial products constitute
endorsement or recommendation for use.
ii
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ABSTRACT
An experimental investigation was made of the possible
interaction of residual concentrations of nitrilotriacetic
acid in surface waters with metallic elements contained
in sediments and bottom materials. Samples of bottom
materials from typical bodies of surface waters were
analyzed for their major, minor, and trace constituents.
Eight representative samples of these were equilibrated
with distilled water and with water containing 20 ppm of
NTA and the resulting solutions were analyzed by three
analytical techniques. Elements showing essentially no
increased solubility in the presence of NTA were: barium,
antimony, molybdenum, strontium, chromium, silver, tin,
iron, lead, cadmium, copper, and mercury. Elements showing
small increases in solubility were: nickel, zinc,
manganese, and cobalt. Calcium and magnesium concentrations
were increased somewhat above their normal relatively high
concentrations.
This report was submitted in fulfillment of Project No.
16020 GFR under sponsorship of the Water Quality Office,
Environmental Protection Agency.
111
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CONTENTS
Section Page
I Conclusions 1
II Recommendations 3
III Introduction 5
IV Description of Samples 7
V Equilibration Procedure 13
VI Analytical Methods 15
VII Results 19
VIII Acknowledgements 29
IX References 31
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TABLES
No. Page
1 Catalogue of Bottom Material Samples 8
2 Emission Spectrographic Analysis of
Bottom Materials 9
3 Spectrochemical Determination of
Selected Elements in Freeze-dried
Sediments 10
4 Determination of Selected Elements in
Bottom Materials by NAA 11
5 Analytical Conditions for the
Determination of Trace Elements by AAS 15
6 Determinations of Copper and Mercury in
Equilibrates by AAS, NAA, and IDMS 219
7 Determinations of Lead and Cadmium in 71
Equilibrates by AAS and IDMS Zi
8 Determinations of Nickel and Zinc in
Equilibrates by AAS and IDMS 22
9 Determination of Manganese in Equilibrates
by AAS and NNA 23
10 Determination of Barium, Antimony,
Molybdenum, Strontium, Chromium, Silver,
Tin, and Iron by IDMS 24
11 Determinations of Calcium and Magnesium in
Equilibrates by AAS 25
12 Determination of Cobalt in Equilibrates by
NAA 26
vi
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SECTION I
CONCLUSIONS
The possible interaction of residual concentrations of
nitrilotriacetic acid in natural waters with sediments
and bottom materials has been investigated. Analysis of
the aqueous phase, with and without residual concentra-
tions of NTA, equilibrated with representative bottom
materials shows no interaction in a majority of cases
and slight interactions in four cases.
Metallic elements that show essentially no increased
solubility in the presence of 20 ppm of NTA are: barium,
antimony, molybdenum, strontium, chromium, silver, tin,
iron, lead, cadmium, copper, and mercury. Elements
showing somewhat increased solubility in the presence
of residual concentrations NTA are the following: nickel,
zinc, manganese, and cobalt. All of the latter elements
except calcium and magnesium were present in the ordinary
water at sub parts-per-million levels and their concen-
trations never increased by more than 2 or 3 fold in the
presence .of NTA. Magnesium and calcium, as expected, were
found to be present at the multi parts-per-million level
and the small increases caused by the NTA were again
considered to be of little practical significance.
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SECTION II
RECOMMENDATIONS
The present study indicates that residual concentrations
of NTA in surface waters do not markedly increase the
solubility of sediments in natural waters. However, the
studies were carried out in an empirical manner and no
effort was made to understand the complex physicochemical
equilibra involved.
A more definitive understanding of NTA interactions is
very desirable. Such studies should systematically
investigate the effects of variation of concentration,
pH, and temperature. The ultimate fate and possible modes
of disappearance of NTA by other means than biodegradation
need to be investigated. The speciation of selected
elements in the aqueous environment - ionic, complex,
sediment - should be investigated, particularly as it is
influenced by intrusions of complexants such as NTA.
Because there is always the possibility that environmental
incidents can occur, the effects of massive concentrations
of NTA should be studied and threshold limits, if any,
should be established.
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SECTION III
INTRODUCTION
Increased eutrophic activity in inland waters attributed,
in part, to widespread use of phosphate - containing
detergents has stimulated efforts to find substitute
builders. One of the more promising of these is nitrilo-
triacetic acid. NTA is a more effective chelating agent
than sodium tripolyphosphate by a factor of 1.4. Thus, a
smaller amount would be required in detergent formulations.
While it would substitute another nutrient, nitrogen for
phosphorous, the widespread use of NTA would only increase
nitrogen levels in waste waters by 3 percent.
Several objections of a different nature have been raised
to the use of NTA. It does not readily biodegrade under
anaerobic conditions and there is some evidence that NTA
facilitates the transport of cadmium and mercury across
the placental barrier of test animals with consequent
damage to the fetus, It is believed that further
research is underway to better understand the nature of
these problems.
A further potential problem is concerned with the chelating
action of NTA. Because of its slow rate of degradability
and its superior chelating action, there is the possibility
that significant amounts of NTA would accumulate in bodies
of water and interact with insoluble hazardous materials
contained in silts and sediments. It was the purpose of
the present research to investigate this situation.
The plan of the work was to use a multi-competence semi-
quantitative approach to ascertain whether residual
amounts of NTA would influence the concentrations of heavy
metals in water. For the purpose of this work, a solution
containing 20 ppm of NTA was selected as the maximum
residual level that could be expected in untreated
domestic sewage, if phosphates were completely replaced by
NTA. Such a level is, of course, higher than levels
expected to occur in bodies of water. Samples of silts
and sediments were obtained from typical bodies of surface
water and analyzed for their major, minor, and trace
constituents. Representative materials were equilibrated
with distilled water and water containing 20 ppm of NTA
and the resulting solutions were analyzed using atomic
absorbtion spectrometry, isotope-dilution spark-source
mass spectrometry, and neutron activation analysis.
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SECTION IV
DESCRIPTION OF SAMPLES
Eighteen samples of bottom material were obtained for
these measurements, selected to be representative of a
wide variety of silts and sediments. These materials
were obtained through the Chief, Contaminants
Characterization Program, Southeast Water Laboratory,
Athens, Georgia, who in turn solicited the collaboration
of colleagues in a number of EPA laboratories throughout
the country.
The samples received are listed in Table 1. They were
collected by experienced water scientists, and packaged
in glass jars or polyethylene bottles with enough water
to insure that they were moist when received. These
materials were sampled for analysis by a coring technique.
A polyethylene tube, approximately one-half inch in
diameter was forced into the settled material to provide
several core samples which were combined. These were
then freeze-dried and the dried material was carefully
mixed, prior to analysis. While visual observation
indicated non-homogeneity of the samples, it is
believed that the procedure followed provided samples
that were qualitatively representative of the bulk
material.
The samples were analyzed by a semi-quantitative emission
spectrochemical procedure which screens for 54 elements.
The procedure consisted in mixing 5 mg of the freeze-
dried material with high purity graphite and burning this
to completion on an under-cut electrode. The samples
were excited in an atmosphere of 70 percent argon -
30 percent oxygen to reduce the band structure from CN
which would otherwise cover some of the sensitive lines
of trace constituents. The results of these analyses are
given in Table 2.
Selected samples of the bottom materials were analyzed
by a more quantitative spectrographic technique. For
this purpose, the freeze-dried material was pulverized
and mixed using plastic vials and plexiglas balls. For
elements with low boiling points - Cd, Hg - a boiler-
cap technique was employed with 50 mg charges excited
with an argon - oxygen envelope around the arc and an
argon atmosphere in the shielding chamber. These
conditions gave low background and limits of detection
of 0.005 percent for cadmium and 0.0005 percent for
mercury. For the other elements, 10 mg charges were burned
to completion at 20 amperes in a dc arc in the same type
atmosphere. The results are shown in Table 3.
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Table 1. Catalogue of Bottom Materials Samples
NBS Identification
Number
37913
37914
37915
37916
37917
37918
37919
37920
37921
37922
37923
37933
37934
37935
37936
37947
37950
37961
Sample Description
Hudels Basins Office Sample #3 [1]
Hudels Basins Office Sample #4 [1]
Ohio R. Cincinnati, RM. 466 (8/21/70) [2]
Houston Ship Channel 8.16 (j.g Hg/g dry wt. T-l [3]
Miss. R. 44.2 /ig Hg/g dry wt. D-6 [3]
Hg 12080 DH 42 1.5' 1091 [4]
13701, 13733, 13735 (Composite) [21
Coweeta Watershed, N. C. Shope Cr. Unpoll. Sample for Control [5]
Whitehall Watershed, Athens, Ga. Unpoll. Sample for Control [5]
Mobile R. Basin (Caustic Plant Fallout) OM-3 [5]
TombigbeeR., T-3 [5]
Potomac R. Blue Plain Mud Buoy #8 9-2-70 [4]
Coastal Sediment #2 [6]
Miss. R. 2 mi. below CBQRR Bridge Sample LMBO 7168 [7]
Miss. R. 100' off Iowa Shore Sample LMBO 7169 [7]
Coastal Sediment #3,[6]
Yaquina Bay Sample #5 [6]
West Coast Sediment #4, Received 10/6/70 FWQA Alameda, California [6]
Sample Source
[l] Hudson—Delaware Basins Office, Edison, New Jersey
[2] Analytical Quality Control Laboratory, Cincinnati, Ohio
[3] Kerr Water Research Center, Ada, Oklahoma
[4] Middle Atlantic Regional Office, Charlotteaville, Virginia
[5] Southeast Water Laboratory, Athens, Georgia
[6] Pacific Northwest Water Laboratory, Corvallis, Oregon
[?] Lake Michigan Basins Office, Chicago, Illinois
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Table 2. Emission Spectrographic Analysis of Bottom Materials
NBS Sample Percent
Designation >10 1-10 0.1-1 0.01-0.1 0.001-0.01 <0.001
37913
37914
37915
37916
37917
37918
37919
37920
37921
37922
37923
37933
37934
37935
37936
37947
37950
37961
Ca
Ca
Si
Si
Si
Si
Al, Ca,
Si
Al, Si
Al, Si
Al, Si
Al, Si
Al, Si
Al, Si
Si
Si
Ca, Si
Ca, Mg,
Si
Ca, Si
Ba, Fe, Mg,
Na, Si
Ba, Fe, Mg,
Si
Al, Ca, Fe
Al, Ca, Fe
Al, Ca, Fe
Al, Ca, Fe
Fe, Mg
Ca, Fe
Ca, Fe
Ca, Fe
Ca, Fe
Ca, Fe
Ca, Fe
Al, Ca, Fe
Al, Ca, Fe
Fe, Mg, Na,
Ti
Al, Cr, Fe,
Mn, Na, Ti
Fe, Mg, Na,
Ti
Al, As, B,
Cu, K, P,
Sn, Ti
Al, As, Cu,
K, Na, Sr,
Ti
Ba, K, Mg,
Na, Ti
Ba, K, Na,
P, Ti
Ba, K, Na,
Ti
Ba, K, Mg,
Na, Ti
Ba, Cu, K,
Na, P, Ti
Ba, K, Mg,
Na, Ti
Ba, K, Mg,
Ti
Ba, K, Mg,
Na, Ti
Ba, K, Mg,
Na, Ti
Ba, Cu, K,
Mg, Na, P,
Ti
Ba, K, Mg,
Na, Ti
Ba, K, Mg,
Na, Ti
Ba, K, Mg,
Na, Ti
Al, Ba, Cr,
Cu, Mn
Ba
Al, Ba, Cr,
Cu, Mn
Cr, Mn, Ni,
Pb, Zn
B, Cr, Hg,
Mn, Ni, Pb,
Zn
B, Cr, Mn,
Ni, Sr, Zr
B, Cr, Cu,
Mn, Ni, Pb,
Sr, Zr, Zn
B, Cr, Mn,
Ni, Sr, Zn,
Zr
B, Cr, Mn,
Ni, Sr
Cr, Mn, Ni,
Pb, Sr, Zn
Cr, Mn, Ni,
Sr, V, Zr
B, Cr, Mn,
Na, Ni, Sr,
Zr
B, Cr, Hg,
Mn, Ni, Sr,
V, Zr
B, Cr, Mn,
Ni, Sr
B, Cr, Mn,
Ni, Pb, Sr,
Zn
B, Cr, Cu,
Mn, Ni, Pb,
Sr, Zn, Zr
B, Cr, Mn,
Ni, Sr, Zn,
Zr
Mn, Sr,
Ni, Sr,
Cu, Sr
Ni, Sr
Mo
Mo
Cu, Pb
Cu, Pb
Cu, Pb
Ag, In
Cu, Pb
Cu, Pb
Cu, Pb
Cu, Pb
Ag
Cu, Pb
Cu, Pb
Co, V
Co, Ni,
Sn, V
V, Co
Ag, Be, In,
Sn
Ag, Be, In,
Sn
Ag, Bi, In,
Mo, Sn
Ag, Be, In,
Mo, Sn
Ag, Be, In,
Mo, Sn
Ag, In, Mo,
Sn
Be, Mo, Sn
Ag, Be, In,
Mo, Sn
Ag, Be, In,
Mo, Sn
Ag, Be, In,
Mo, Sn
Ag, Be, In,
Mo, Sn
Be, In, Mo,
Sn
Ag, Bi, In,
Mo, Sn
Ag, Be, In,
Sn
Ag, Be, In
Ag, Mo, Pb,
Sn
Ag, Mo, Pb
Ag, Mo, Pb,
Sn
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Table 3. Spectrochemical Determination of Selected Elements in Freeze-Dried Sediments
Sample No.
NBS 37914
NBS 37916
NBS 37920
NBS 37921
NBS 37922
NBS 37923
Estimated
limit of
detection of
these runs
Ag Be Bi
.0005
.0001
< .0001
<.0001
<.0001
<.0001
<.0001 <.0002 .001
Cd Cr
.05
.05
.01
.008
.01
.01
.005 .0002
Cu
>.l
.01
.002
.002
.005
.002
<.0001
Ge Hg In
.02 .002
.002 .002
- - —
.001 .002
.02 -?
- - -
.0005 .0005 .001
Pb
.04
.02
.002
.001
.003
<.001
.0005
Sn V
.008
.01
.01
.005
.01
.01
.001
Zn
.04
.15
-
—
.008
—
.005
Note: Values are as weight percent metallic element in freeze—dried sample; — , not detected;
<, less than; > , greater than, not measured quantitatively.
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All of the samples were examined by nondestructive
neutron activation analysis for the selected elements,
mercury, arsenic, copper, manganese, and vanadium. The
samples were sealed in medical grade polyethylene vials,
packed in a hexagonal array with a 1 ml water standard
in the center, and irradiated for 1 minute. The samples
were then allowed to decay for 3 days to reduce the
activity of sodium-24. The samples were then transferred
to a 4 dram preweighed polyvial, weighed, and counted
for 15 minutes on a 60 cc GeLi detector. Comparisons
were made with the standard solution to provide the semi-
quantitative results given in Table 4.
The results given in Table 2, Table 3, and Table 4 are
in qualitative agreement and are also in quantitative
agreement consistent with the analytical uncertainties
and evident inhomogeneity of the materials.
On the basis of these analyses, samples identified by
the NBS numbers 37914, 37915, 37916, 37920, 37922,
37933, 37934, and 37935 respectively, were considered to
be representative and were used in the equilibration
experiments.
Table 4. Determination of Selected Elements in Bottom Materials by NAA
Sample No.
37913
37914
37915
37916
37917
37918
37919
37920
37921
37922
37923
37933
37934
37935
37936
Mercury Vanadium
Manganese
Percent
Arsenic Copper
.035
.11
< .00005
.0009
< .00006
.0002
.0006
< .00005
<. 00008
.022
<. 00007
<.0001
.0002
.0002
.0003
.0054
.0021
.0050
<.0010
.011
.012
.008
.010
<.001
.011
.009
.14
.04
.07
.04
.11
.09
.11
.09
.21
.02
.09
1.1
.28
.0023
.0024
.0039
.0015
.0033
<.0002
.0015
<.0004
.0010
.0013
<.0004
.0011
<.0003
.16
.13
.008
.018
.013
.028
.009
.023
.013
.014
.010
11
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SECTION V
EQUILIBRATION PROCEUDRE
Selected samples of the bottom materials were equilibrated
with water and with water containing NTA for study of
possible chelation. Approximately 50 ml of the moist
material was removed from the containers in several
increments in order to obtain a representative sample
and transferred to 500 ml polyethylene jars. Approxi-
mately 450 ml of distilled water or water containing
NTA were added to each jar.
The NTA, Eastman Lot 701, was said to have a minimum
assay of 97 percent by titration. It was used without
further purification. Eighty milligram quantities were
weighed, dissolved in 4 liters of distilled water, and
used as the 20 ppm equilibrating solution.
The original intention was to adjust the pH of the water
in the jars so that equilibrations would be made at pH
values of 5.0, 7.0, and 9.0, respectively. However,
this proved to be infeasible. The bottom material was
found to have considerable buffer capacity so that large
amounts of acid, or alkali were required to adjust to
the desired pH values. Also the rate of approach to
pH equilibrium was frequently slow and departures from
the adjusted pH values often occurred during the
equilibration process. It was also quite evident that
the addition especially of acid but also of base to
produce changes in pH could itself produce abnormal
solubility effects. Accordingly, most of the equili-
brations were made at the natural pH values related to
the particular bottom material used.
The equilibrations were made by shaking the material
with water, using a heavy-duty, box-type mechanical
shaker. Shaking was continued for at least three hours
at room temperature (25.0 ° ± 0.2 °C), after which the
samples were allowed to settle for at least 16 hours.
Because the solutions were always cloudy, the supernatant
liquid was decanted into clean certrifuge tubes and
centrifuged at 2000 rpm (800 g) for 30 minutes, after
which it was transferred to 125 ml glass-stoppered
erlenmeyer flasks.
Sample 37922 would not clarify under the above described
conditions. Accordingly, it was necessary to use a
super-centrifuge which had a capacity of 16 tubes, each
of 3 ml volume. At 7,000 rpm (6000 g) the supernatant
liquid appeared to be essentially clear.
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SECTION VI
ANALYTICAL METHODS
Three analytical methods, atomic absorption spectroscopy
(AAS), isotope-dilution solid-source mass spectrometry
(IDMS), and neutron activation analysis (NAA) were used
to analyze the equilibrated solutions. The objective
was to investigate a large number of ions for possible
solubility influences, rather than to obtain highly
accurate data on a limited number of ions. Accordingly,
semi-quantitative measurements were made which would give
relative information in each specific case. The details
of each method are described in the following sections.
A. Atomic Absorption Spectrometry (AAS)
Atomic absorption spectrometry was used to determine
the concentrations of nine elements (calcium, cadmium,
copper, mercury, magnesium, manganese, nickel, lead, and
tin) in the equilibrated solutions [1,2]. The instrument
used was a Perkin-Elmer Model 403 with a premixed laminar
flow burner for either an air-acetylene or nitrous
oxide-acetylene burner head. This instrument is equipped
with a deuterium arc lamp for background correction.
However, the total solids in the solutions were low and
background corrections were not necessary. The analytical
conditions used for the measurements are given in Table 5.
Table 5. Analytical Conditions for the Determination of Trace Elements by AAS
Hollow Cathode Lamp, Scale Expansion Range of
Element Wave Length Current Factor Calibration Curve
°A raAa
Ca 4227 20 1.0 1.0 - 10.0
Cd 2288 8 2.5 0.1 - 1.0
Cu 3247 15 7.0 0.1 - 1.0
Hgb 2537 6 — 0.001- 0.04
Mg 2852 15 — 2.0 - 10.0
Mn 2795 20 5 0.1-1.0
Ni 2320 15 10 0.1 - 1.0
Pb 2833 6 5.0 0.2 - 1.0
Zn 2138 12 6.0 0.1 - 1.0
a Westinghouse HC1 were used for all elements except for Cu
b Flameless atomic absorption spectrometry
15
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Equilibrated water samples were analyzed without pretreatment
Several of the solutions were cloudy and solids were
observed to settle out on standing. No attempt was made
to redisperse the solids. Rather, portions of the super-
natant were withdrawn with a pipette, for analysis.
In natural water there are relatively few interferences
encountered by atomic absorption spectrometry. Phosphate
and sulfate are known to interfere in the determination
of calcium and magnesium, however, under the test
conditions, these anions either did not extract or were
so low in concentration that no interferences were observed.
As a check against possible interferences the standard
addition method was used for each element. In this method
a known concentration of the analyte is added to each test
solution and the recovery determined by comparison with
a calibration curve which was prepared in water free of
interfering ions.
Standard stock solutions of each individual element were
prepared from high purity metals or salts. Then, an
appropriate dilution was made and a calibration curve
was prepared for each element using the most sensitive
ground state resonance line. The unknown solutions were
aspirated into the flame and the absorbance measured for
each element. To check the calibration curve, standard
solutions were aspirated at frequent intervals during
the determinations of the unknown solutions. Then, the
concentrations of the unknown solutions were determined
using a calibration curve prepared by means of a desk
computer.
Mercury was determined by flameless atomic absorption
using a modification of the procedure developed by Hatch
and Ott [3]. The test portion was transferred to a
reducing cell and diluted to 50 ml with a mixture of
HNO, and H-SO.. The mercury was reduced to the free metal
witn hydroxylamine hydrochloride and stannous chloride.
Then, the mercury was flushed from the reduction cell
with a flow of argon into a heatgd absorption cell and
the absorption measured at 2537 A. To correct for light
scatter or molecular absorption, the samples were 0
repeated using a non absorbing line of tungsten at 2551 A.
Also, the standard addition method was used to check for
possible losses in the method.
The precision obtained for Cd, Ni, Ca, Cu, Mg, Zn, Pb,
and Mn by AAS was from 2-4 percent. However, the precision
of the flameless technique for mercury was 10 percent.
16
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B. Isotope-Dilution Spark-Source Mass Spectrometry
(IDMS)
In an isotope dilution method, the concentration of an
element in a matrix is determined from the change produced
in its natural isotopic composition by the addition of
a known quantity of the same element, the isotopic composition
of which has been artificially altered. The concentrations
are computed from:
W K (A - B R)
r = SP SP
M (BR - A)
where C is the concentration in ppm (ug/g), W is the
weight of isotopically enriched material ("spike") added
in yg, M is the weight of sample in g, A and B are the
natural abundances of the analyte isotopes a and b, ASp
and Bsp are the abundance of isotopes a and b in the spike,
R is the measured altered ratio of isotope a to isotope b,
and K is the ratio of the natural atomic weight to the
atomic weight of the spike.
Applications of isotope dilution techniques to spark source
mass spectrometry for simultaneous, multi-element determina-
tions in metals have been described [4,5,6].
Fourteen elements were determined by this technique,
including silver, barium, cadmium, chromium, copper, iron,
mercury, molybdenum, nickel, lead, antimony, tin, strontium,
and zinc. Solutions of the enriched isotope materials
were prepared for the elements to be determined. Chemically
compatable solutions were combined and volumetric additions
of these "multiple spike" solutions were introduced into
volumetric flasks. The flasks were made to volume by
adding portions of the water (0 ppm NTA) and 20 ppm NTA
solutions that had been equilibrated with the sediments.
Aliquots of these spiked samples were pipetted into .small
quartz flasks and 0.3 ml of a 1 to 1 nitric-perchloric
acid mixture were added to each flask. The acids were of
high-purity grade. After evaporating the solutions in a
"Clean Environment Chamber" [4], the solutions were heated
further to HC1C>4 fumes. This step destroyed the NTA and
equilibrated the analytes with the enriched isotope spikes.
The residue was dissolved in distilled water and the
resulting solution was transferred to a Teflon electrolysis
cell. The isotopically altered trace elements were
electrodeposited onto two high-purity gold wire cathodes
connected in parallel. Two gold wires served as the anodes.
The cathodes were sparked in the spark source mass
spectrograph and the spectra were photographically recorded.
17
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For the initial samples, it was found that the solutions
had been "over spiked", that is, the concentrations of the
trace elements were appreciably lower than anticipated.
Consequently, to obtain suitable isotope ratios for
measurement, aliquots of the spiked samples were diluted
with known volumes of the sample solutions and the
procedures were repeated. The results were computed from
the isotope dilution equation given above except that the
concentration was computed in micrograms per milliliter
of solution. Method blank determinations were made under
the same experimental conditions and using the same volumes
of acids.
C. Neutron Activation Analysis (NAA)
Neutron activation analysis is a useful technique for
the determination of minute quantities of many elements.
Elemental Analyses are usually treated in one of two ways.
The first envolves chemical separations of the product
radioisotopes with each separated chemical species
determined individually. This type of procedure gives
maximum sensitivity with minimum interference. However,
multi-element analyses are tedious. The second procedure
envolves a minimum of chemical manipulation utilizing
high resolution gamma ray spectroscopy to identify the
individual radioactive species. This method is somewhat
less sensitive but yeilds many more elements determined
for a given expenditure of time. This type of analysis
was reported by Gills et a.1. for the determination of trace
elements in Glass [7].
The application of neutron activation analysis to the
determination of trace elements in the aquatic environment
has been described by Funk, Bhagat, and Filby [8],
Samples of river bottom sediments and NTA solutions
equilibrated with sediment were analyzed using the latter
technique to determine metal chelation effects. Mercury,
cobalt, manganese, copper, and arsenic were reported.
The analyses gave total elemental composition.
The procedure used was as follows: Samples consisting
of 5 ml of solution were sealed in 5 dram polyethylene
vials, irradiated for 30 minutes in the pool H-5 facility
at a thermal neutron flux of 2 x 1013. Cobalt wires
were used as flux monitors. After irradiation, samples
were transferred to beakers, weighed, and brought to 6
N with HC1. The solutions were passed through hydrated
antimony pentoxide (HAP) to remove sodium-24, brought
to 50 ml volume and counted on the 47 cc Ge(Li) detector.
Samples were compared to solution standards made by
dissolving the metal or metal oxide and diluting to a
known volume. Standards were treated in a like manner to
that of the samples.
-------
SECTION VII
RESULTS
The results of determinations of the concentrations of
selected elements in the equilibrated solutions are given
in Table 6 to Table 12. Altogether, 18 elements were
determined. Copper and mercury were determined by all
three techniques. Nickel, zinc, manganese, cadmium, and
lead were determined by two techniques, while the remainder
were determined by a single analytical competence.
In each table, the first column gives the sample number
while the second lists the pH of the equilibrated solutions.
Asterisks are used to indicate thy natural pH of the
equilibrated solutions, while the other values were obtained
by adjustment of pH by addition of acid or base during the
equilibration procedure as already described. It is
believed that only the starred values have significance
as far as natural processes are concerned. However, the
other data are presented for whatever interest they may
have .
All analytically determined concentrations were expressed
in parts-per-million (yg cm~3). The concentrations of NTA
in the solutions with which the materials were equilibrated
are likewise given in parts-per-million. The analytical
techniques used are identified as follows: AAS - atomic
absorbtion spectroscopy; IDMS - isotope-dilution spark-
source mass spectrometry; NAA - neutron activation analysis.
In addition to the tabulated data, several additional
elements were determined in specific samples. Thus,
lanthanum was found at low levels in several of the
equilibrates but showed no correlation with the presence
of NTA. Bromine was observed in relatively high
concentrations of mercury, which may be an interesting
observation.
The analytical values obtained by the several techniques
are generally consistent, considering that semi-quantitative
measurements were made. Also, there are no doubt some
differences caused by inhomogeneity of the bottom
materials, and to a lesser extent by equilibration problems.
Nevertheless, the large number of equilibrated solutions
analyzed minimizes the chance of faulty conclusions and
the satisfactory agreement where multiple techniques were
used lends confidence to those measurements where only one
technique was employed.
19
-------
Sample
No.
37914
37914
37915
37915
37915
37916
37920
37922
37922
37933
37933
37934
37935
B
B
B
37914
37914
37915
37915
37916
37920
37922
37922
37933
37933
37934
37934
37935
B
Table 6. Determination of Copper and Mercury in Equilibrates
PH
7.0
9.0*
5.0
7.0*
9.0
8.2*
7.9*
7.0
9.0*
7.0*
9.0
7.0*
7.7*
5.0
7.0
9.0
7.0
9.0*
7.0*
9.0
8.2*
7.9*
7.0
9.0*
7.0*
9.0
7.0*
9.0
7.7*
9.0
AAS
ppm
.036
.037
.12
.019
.017
.26
.031
.24
.010
.009
<.0005
<.0005
<.0005
.016
<.0005
<.0005
<.0005
<.0005
<.0005
0 ppm NTA
NAA
ppm
.039
.036
.012
.074
.060
.026
.030
.175
.033
.173
.046
.026
.028
.0019
<.0015
<.001
<.0017
<.001
<.001
.89
1.00
<.001
<.001
<.004
<.004
<.0005
IDMS AAS
ppm ppm
COPPER
.02 .035
.099
.04
.19
.04 .017
.075
.03
.29
.037
.28
.02 .024
.02 .042
MERCURY
<.01
.1
<.0005
.03 <.0005
<.0005
.2
.007
<.0005
<.0005
.2 <.0005
.01 <.0005
.01 <.0005
20 ppm NTA
NAA
ppm
.039
.034
.023
.26
.034
.089
.032
.234
.044
.190
.053
.048
.008
.029
.0019
<.0015
<.001
<.0016
<.001
<.002
.85
1.07
<.002
<.001
<.004
<.004
<.0005
.006
IDMS
ppm
.02
.02
.02
.03
.02
.03
<.01
.1
.01
.2
.2
.01
<.01
20
-------
Table 7. Determination of Lead and Cadmium Equilibrates by AAS and IDMS
Sample No.
PH
0 ppm NTA
AAS IDMS
20 ppm NTA
AAS IDMS
LEAD
37914
37915
37915
37915
37916
37920
37922
37933
37933
37934
37934
37935
37914
37915
37915
37915
37916
37922
37922
37933
37934
37934
37935
9.0*
5.0
7.0*
9.0
8.2*
7.9*
9.0*
7.0*
9.0
7.0*
9.0
7.7*
9.0*
5.0
7.0*
9.0
8.2*
7.0
9.0*
9.0
7.0*
9.0
7.7*
.08
<.05
.14
.20
<.05
.18
<.05
.11
.17
<.05
<.05
.028
.026
.024
.029
.028
.027
.06
.03
.09
.2
.11
.1
CADMIUM
<.001
.002
.001
<.001
<.005
.001
.002
<.05
<.05
.12
.20
<.05
.32
<.05
.15
.15
<.05
<.05
.031
.030
.023
.029
.024
.027
.04
.08
.06
.1
.12
.2
<.001
.007
.001
<.005
.002
.002
21
-------
Table 8. Determination of Nickel and Zinc in Equilibrates by AAS and IDMS
Sample No. pH
0 ppm NTA
AAS IDMS
20 ppm NTA
AAS IDMS
NICKEL
37914
37915
37915
37915
37916
37920
37922
37933
37933
37934
37934
37935
37914
37915
37915
37915
37916
37920
37922
37922
37933
37933
37934
37934
37935
9.0*
5.0*
7.0
9.0
8.2*
7.9*
9.0*
7.0*
9.0
7.0*
9.0
7.7*
9.0*
5.0
7.0*
9.0
8.2*
7.9*
7.0
9.0*
7.0*
9.0
7.0*
9.0
7.7*
.02
.04
.04
.02
<.01
.05
.05
.11
.04
<.01
.02
.002
.23
.39
.067
.010
.30
.030
.23
<.001
.01
<.001
•01, .03 .01 .01, .04
.11
.01 .2
.14
.06 .15 .15
.02
.14
.15
.05
•01 .07 .08
.02
•04 .14 .15
ZINC
.02, .03 .003 .004, .02
.42
.02 .1
.53
-05 .090 .07
.046
.03 .04
.52
.070
CADMIUM
.31
-08 .022 .05
.06 .01 .07
.08 .41 .5
22
-------
Table 9. Determination of Manganese in Equilibrates by AAS and NNA
Sample No.
37914
37914
37915
37915
37915
37916
37920
37922
37922
37933
37933
37934
37934
37935
B
B
PH
7.0
9.0*
5.0
7.0*
9.0
8.2*
7.9*
7.0
9.0
7.0*
9.0*
7.0*
9.0
7.7*
7.0
9.0
0 ppm
AAS
<.005
26
.48
.06
.06
.08
.39
.43
.03
.05
<.005
NTA
NAA
MANGANESE
.002
.006
.022
.56
.028
.041
.010
.199
.455
.492
.004
.008
.0005
.0008
20 ppm
AAS
<.005
>50
.55
<.005
.24
.12
.65
.43
.01
<.005
<.005
NTA
NAA
.015
.010
.439
.79
.041
.148
.103
.378
.765
.800
.001
.002
.0011
.0008
23
-------
Table 10. Determination of Barium, Antimony, Molybdenum, Strontium, Chromium, Silver, Tin, and
Iron in Equilibrates by IDMS
Sample No.
PH
NTA Concentration
0 ppm 20 ppm
Sample No.
PH
NTA Concentration
0 ppm 20 ppm
BARIUM
37914
37915
37922
37934
37934
37935
37914
37915
37916
37922
37934
37934
37935
9.0*
7.0*
7.0
7.0*
9.0
7.7*
9.0*
7.0*
8.2*
7.0
7.0*
9.0
7.7*
.06
.07
<.l
<.03
0.2
0.3
0.5
4
1
1.4
1
2
.06
0.1
<.l
<.03
.04
IRON
0.6
0.5
2
1
1.5
1
1
37914
37915
37916
37922
37934
37935
9.0*
7.0*
8.2*
7.0
7.0*
7.7*
CHROMIUM
0.04
.1
.03
.02
.1
0.2
.05
.1
.3
.006
.1
SILVER
37914
37915
37916
37922
37934
37935
37935
9.0*
7.0*
8.2*
7.0
9.4
7.0
7.7*
<.001
<.002
.006
<.001
<.001
<.001
<.001
MOLYBDENUM
37914
37916
37922
37934
37934
37935
9.0*
8.2*
7.0
7.0*
9.0
7.7*
0.2
.05
.03
<.003
.003
0.2
.03
<.004
.006
.002
STRONTIUM
37914
37915
37922
37934
37934
9.0*
7.0*
7.0
7.0*
9.0
1.2
0.3
.02
.2
.3
1.2
0.4
.09
.2
.3
37914
37915
37916
37922
37934
37934
37935
9.0*
7.0*
8.2*
7.0
7.0*
t
9.0
7.7*
.002
<.01
.02
<.004
<.002
.002
<.001
<.001
<.001
.001
<.001
<.001
<.001
TIN
.002
<.01
.003
<.004
.001
<.001
ANTIMONY
37914
37916
37934
37935
9.0*
8.2*
9.0
7.7*
.004
.004
.001
.001
.003
.004
.001
.001
24
-------
Table 11. Determination of Calcium and Magnesium in
Equilibrates by AAS
Sample No.
PH
NTA Concentrations
0 ppm 20 ppm
CALCIUM
37914
37915
37915
37916
37920
37922
37933
37933
37934
37934
37935
9.0*
5.0
9.0
8.2*
7.9*
9.0*
7.0*
9.0
7.0*
9.0
7.7*
147.
166.
2.4
2.1
.36
2.5
17.
3.9
59.
24.
28.
163.
209.
3.9
3.2
.68
3.2
15.
2.9
49.
29.
40.
MAGNESIUM
37914
37915
37915
37916
37920
37922
37933
37933
37934
37934
37935
9.0*
5.0
9.0
8.2*
7.9*
9.0*
7.0*
9.0
7.0*
9.0
7.7*
62.
22.
5.
6.6
.6
7.
3.8
3.
50.
24.
6.4
54.
26.
5.
7.0
1.3
9.
3.6
5.
39.
28.
8.7
25
-------
Table 12. Determination of Cobalt in Equilibrates by NAA
NTA Concentrations
Sample No.
37914
37914
37915
37915
37916
37920
37922
37922
37933
37933
37934
37934
37935
B
B
PH
7.0
9.0*
7.0*
9.0
8.2*
7.9*
7.0
9.0*
7.0*
9.0
7.0*
9.0
7.7*
9.0
5.0
0 ppm
.34
<.002
.010
.023
.024
.004
.028
.026
.003
.030
.054
.037
.0005
<.0005
.0005
20 ppm
.36
.005
.041
.043
.163
.023
.083
.058
.046
.039
.048
.030
.010
.0005
26
-------
A study of the analytical data leads to the conclusion that
residual concentrations of NTA have little or no effect
upon the concentration of metal ions to be expected in
bodies of water. No significant differences in concentra-
tions of the following were found: barium, antimony,
molybdenum, strontium, chromium, silver, tin, iron, lead,
copper, and mercury. Significant but small increases
were found for zinc and manganese in the solutions
containing 20 ppm of NTA. However, in both cases, less
than a two-fold increase was found and the maximum
concentration was less than one part in a million. Cobalt
was found to be solubilized by NTA but again the concentra-
tion was very small in that the highest concentration
found was less than 0.2 ppm. The element nickel appears
to be the most affected of all measured in that a three-fold
increase in solubility was noted. However, the maximum
concentration found amounted to only 0.15 ppm which is
hardly a significant level.
An element of uncertainty in this work is the amount of
NTA remaining at the conclusion of the equilibration
procedure. In a natural situation an almost inexhaustible
supply of residual NTA solution would be continuously
available but this situation is difficult to reproduce
in the laboratory. In the present experiments, it was
only possible to equilibrate with a solution containing
an initially determined level of NTA.
When the present experiments were undertaken, a reliable
method for determination of residual concentrations of
NTA was not available in this laboratory. After the work
was completed and during the preparation of this report,
an investigation of methods for NTA determination was
initiated at NBS (Program No. 16020 GVY). A polarographic
method under development in that investigation was used
to determine the concentrations of NTA remaining in
equilibrations similar to those reported here. These
determinations showed that at least 15 to 50 percent of
the initial NTA remained at the end of the equilibration
procedure. Obviously, more work needs to be done to
confirm the apparent degradation of the NTA and to
understand the equilibria involved. However, it is
evident that significant amounts of NTA remained throughout
the equilibration experiments.
27
-------
SECTION VIII
ACKNOWLEDGEMENTS
The investigations described in this report were carried
out by the following members of the staff of the
Analytical Chemistry Division, Institute for Materials
Research, National Bureau of Standards: Martha M. Darr
and Virginia C. Stewart - emission spectrographic analyses;
Theodore C. Rains and Theresa A. Rush - atomic absorption
spectroscopic analyses; Harry A. Rook and William D. Kinard
neutron activation analyses; Robert Alvarez and Paul J.
Paulsen - isotope dilution spark-source mass-spectrometric
analyses; Rolf A. Paulson - sample preparation and solution
equilibrations. John K. Taylor coordinated the
experimental work and prepared the report of the investiga-
tion.
The support of the project by the Water Quality Office,
Environmental Protection Agency and the help provided
by Mr. William T. Donaldson, the Grant Project Officer,
are Acknowledged with sincere thanks.
29
-------
SECTION IX
REFERENCES
1. Rains, T. C., ASTM Special Technical Publication 443
pp 19-36 (1969). '
2. Rains, T. C., NBS Technical Note 544, pp 58-84 (1970).
3. Hatch, W. R., and Ott, W. C., Anal. Chem. 40, pp 2085
(1968). —
4. Alvarez, R., Paulsen, P. J., and Kelleher, D. E.,
Anal. Chem. 41, pp 955 (1969).
5. Paulsen, P. J., Alvarez, R., and Kelleher, D. E.,
Spectroohim. aota 24B, pp 535 (1969).
6. Paulsen, P. J., Alvarez, R., and Mueller, C. W.,
Anal. Chem. 4_2, pp 673 (1970).
7. Gills, T. E., Marlow, W. F., and Thompson, B. A.,
Anal. Chem. 42, pp 1831 (1970).
8. Funk, W, H., Bhagat, S. K., and Filby, R. H.,
Proceedings of the Eutrophication Assessment Workshop,
Sponsored by FWPCA, Pacific Northwest Water Laboratory,
Corvallis, Oregon, June, pp 19-21 (1969).
31
-------
1
Accession Number
5
2
Subject field & Group
05A
SELECTED WATER RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
Organization
Analytical Chemistry Division, National Bureau of Standards
Title
Interaction of Nitrilotriacetic Acid with Suspended and Bottom Material
10
Authors)
Taylor, John K.
Alvarez, Robert
Paulson, Rolf A.
Rains, Theodore C.
Rook, Harry L.
16
Project Designation
EPA-WQO Project 16020 GFR
21
Note
22
Citation
23
Descriptors (Starred First)
Detergents*, Absorption*, Analytical Techniques, Neutron Activation
Analysis..
25
Identifiers (Starred First)
Nitrilotriacetic Acid, Interaction with Sediment Materials.
An experimental investigation was made of the possible interaction
of residual concentrations of nitrilotriacetic acid in surface
waters with metallic elements contained in sediments and bottom
materials. Samples of bottom materials from typical bodies of surface
waters were analyzed for their major, minor, and trace constituents.
Eight representative samples of these were equilibrated with distilled
water and with water containing 20 ppm of NTA and the resulting
solutions were analyzed by three analytical techniques. Elements
showing essentially no increased solubility in the presence of NTA
were: barium, antimony, molybdenum, strontium, chromium, silver,
tin, iron, lead, cadmium, copper, and mercury. Elements showing
small increases in solubility were: nickel, zinc, manganese, and
cobalt. Calcium and magnesium concentrations were increased somewhat
above their normal relatively high concentrations.
This report was submitted in fulfillment of Project No. 16020 GFR
under sponsorship of the Water Quality Office, Environmental Protection
Agency.
Abstractor.
in K.
Tayl
or
Institution
National
Bureau
of
Standards
WRM02 (REV JULY <««»>
WRSIC
US DEPARTMENT OF THE INTERIOR
WASHINGTON, D, C. 202«0
* SPO: I969-3S9-339
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