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MICROCOPY RESOLUTION TEST CHART
NATIONAL BUREAU OF STANDARDS - 1963
This paper was submitted for publication
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LEGAL NOTICE
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MASTER
RADIO-RELEASE METHODS FOR THE EVALUATION
OF ATMOSPHERIC POLLUTION. SULFUR DIOXIDE*
8. H. Ross
W. S. Lyon
Analytical Chemistry Division
Oak Ridge, Tennessee
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This paper we submitted for publication
in the open literature at least thonths
prior to the issuanco date of the Micro-
aard. Since the V.8.A.L.C. has no art-
dence that it has been published, the pa-
I por 15 being distributed in Microcard
form us a proprint.
............
Research sponsored by the U. 8. Atomic Energy Comandssion under contract
with the Union Carbide Corporation...
1. Introduction
Atmospheric pollution has grown into a problem of national concern in
recent years. Because of this, eftorts have been directed toward the deter-
mination of sulfur-bearing air pollutants, primarily sulfur dioxide. How-
ever, the exact danger level of sulfur dioxide is still disputed us was noted
in a recent article [37.
Jacobs (47 presents a survey of the methods presently being used for
airborne sulfur dioxide. Altshuller (17 reviews recent work. Stephens
and Lindstrom [67 offer a new spectrophotometric method based on the forme-
tion of the ferrous phenanthroline complex. Because of the high sensitivity
possible with the radio-release technique, we selected this method as a new
approach to the determination of sulfur dioxide.
The radio-release technique 18 potentially one of the most useful radio-
18otope analytical methods, although it has not been widely used. In addi.
tion to sensitivity, the technique has the advantages of selectivity and
speed. Also, the method often lends itself to self-contained automated sys-
tems.
The radio-release method is based upon the selective reaction of the
sought constituent with a radioactive reagent of known specific activity.
During the reaction, activity 18 released as a gas or as an easily separa-
ble chemical species. The amount of sought constituent can be calculated
from the amount of activity released, the specific activity of the reagent,
and the stoichiometry of the reaction. Alternatively, the calculations can
be avoided by reference to standard sample determinations. Richter and
Gillespie have applied the technique to the determination of dissolved oxy-
gen in water 3,57 and were able to measure lower concentrations than are
possible with other existing methods.
The present method for sulfur dioxide is based on the release of radio-
Lodine according to the reaction:
550, + 2KI*03 + 43,0 – 6,80+ 48,802 + I2*..
..iii.
*. ..
in
'
; ::-::?"
The reaction is carried out in solution by forcing air through a bubbler
train containing a basic potassium iodate solution. After the sample has
reacted, the solution 18 acidified, and the liberated lodine 18 extracted.
The activity of this solution is determined, and the amount of sulfur diox-
ides is calculated.
.
-1..
...
2. Eksperimental
2.1 Reagents and Apparatus
Analytical reagent grade chemicals were used whenever possible. The
Isotopes Division, ORNL, supplied the carrier free lodine-131 tracer as
iodide, which was converted later to KIO, reagent. Anhydrous sulfur dioxide
(99.98%) and other compressed gases were manufactured by Matheson. Distil-
·led water was used in all experiments after first being purged with argon.
A gas bubbler and extraction system was constructed as shown in Fig. 1..
Point A 18 a small glass-wool filter used to remove any particulate material
in the gas stream. Flasks B and B' are the primary and secondary reaction
bubblers; C is a final scrubber for blowby protection; D is the solvent
extraction flask. The E flasks are required for solvent and acid additions.
The complete system was constructed of glass with a minimum number of joints
and was designed so that negligible contamination of the reagents by the
atmosphere would occur.
Gas samples were introduced into the system by means of a double vented
flask connected to the input of the system. Samples can be pushed through
the system with compressed air or pulled through with a vacuum. No difference
was observed using either method.
Sulfur dioxide samples were prepared by diluting the appropriate amount,
of gas with hydroxide scrubbed air. For very dilute samples, two dilution
steps were needed.
Activity measurements were made with a 3" x 3" sodium iodide well-type
scintillation detecto: connected to a conventional high-speed scaler of ORNL
design. Counting times were adjusted for most samples so that a total count
of at least 5 x 10° was collected (0.88% counting error at 95% confidence
level).
mi'. 2.2 Procedures
Radioactive potassium iodate was prepared by the oxidation of lodide
lon with permanganate. Toree millicuries of I+5+ tracer solution was placed
in a 25-ml. reflux flask and 1.0 mg. of potassium iodide was added. A suf-
ficient amount of 0.05 N sulfuric acid was added (1f necessary) to adjust
the på to 8-7. The flask was fitted with a small reflux condenser and three
drops of a saturated potassium permanganate solution were added. Water was
added to bring the total volume to about 5 ml., and the solution was gently
i.si
refluxed. Additional permanganate was added after 10 minutes to just re-
store the purple color. Refluxing was allowed to continue for another 20
minutes. After the solution bad cooled, it was transferred to a tube and
centrifuged for five minutes. The clear solution was decanted from the
manganese dioxide precipitate into a 20-ml. beaker. The solution was heated
just to the boiling point and sufficient potassium iodato was added to satu-
rate the solution. After cooling, the crystals of potassium iodate were col.
lected and dried. The yield was 1.22 g. of material having an approximate
specific activity of 2 mc./gm.
The radio-reagent stock solution was prepared by dissolving 1.0 gm. of
the active potassium iodate in 20 ml. of water and then diluting to 100 ml.
This solution was stored in a bottle to which 100 ml. of chloroform were
added. During the useful life of the reagent, a small amount (< 0.1%) of
elemental lodine is generated in solution due to radiation decomposition.
The purpose of the chloroform is to extract any lodine formed in the reagent
80 that the reagent blank can be kept to a minimum.
A 10-normal sulfuric acid solution and sand l-aormal sodium hydroxide
solutions were prepared conventionally.
All of the experimental runs were performed by a general procedure as
follows. The 3-way stopcock was closed to all positions and one milliliter
of radioreagent and 15 ml. of 1 N sodium hydroxide were pipetted into each
reaction bubbler, B and B'. One hundred milliliters of 5 sodium hydrox-
ide were added to the final scrubber C, and two milliliters of chloroform
were placed in flask D. A vacuum line was attached to the exit side of the
system, and the flow rate was roughly adjusted to 1 liter/minute by drawing
argon through the system. The exact flow rate is unimportant since the sys-
tem shows no deviation at flow rates from as 100 ml./minute to * 4 1./minute.
The sample to be analyzed was attached to the entrance side of the sys-
tem and was allowed to flush out through the bubblers for a time suitable to
the sample size (2-5 minutes). After flushing, the solutions in B and B!
were drained and rinsed into flask D with water. Three milliliters of 10 N
sulfuric acid were added to flask D and the liberated iodine was extracted
into the chloroform. The phases were allowed to separate, and the lower
layer was drained into a tube suitable for use in the well counter. A 86 :
ond and third extraction with two milliliter portions of chloroform served
..
...
.
..
...
..
O
i.....
-3-.
to quantitatively remove the lodine from the aqueous phase. The sample was
counted and tae sulfur dioxide concentration determined.
3.2.1 Blank Determinations. Using the above procedure, the response
of the system was determined using air, free of sulfur dioxide. The results
of these experiments are shown in Table I. The sulfur dioxide equivalent
found in the blank determinstion can be attributed to (1) traces of reducing
substances in the reagents and (2) mechanical carry-over in the extraction. ...
It is dificult to estimate the effect of the above variables separately.
However, it is doubtful that further purification of the reagents will reduce
the blank significantly.
2.2.2 Response of the System to Sulfur dioxide. Duplicate standard
samples of sulfur dioxide were analyzed, again using the standard procedure,
The results of this series are sbowa in F8. 2. A 0.07 ug blank was subtrac- .
ted from each run. The results shown are essentially linear relationships
from 0.1 to 25 ws. of sulfur dioxide. Higher concentrations of sulfur dioxide
were not studied since it was assumed that samples could be reduced to this
size without difficulty.
Eight samples containing 1.0 mg of sample were checked to test the repro.
ducibility of the system. The results are reported to the nearest 0.01 ms.
(w 1% counting error) in Table II. Note that one standard deviation amounts
to about 5% of the sample size,
2.2.3 Interferences. Interference studies were made with materials
that could be present in the atmosphere during a sulfur dioxide analysis.
Slace interference can occur in both the positive and negative directions,
these tests were run in a 5.0 MB. sample of sulfur dioxide. The interference
materials were obtained as compressed gases or as reagent grade liquids. The
results of these studies are shown in Table III.
.........
.
....
...
.........
.-.
.
.
.
.
..
.
.
3. Discussion and Conculsions
A radio-reagent method is presented for the sensitive determination of
sulfur dioxide in the atmosphere. The system exhibits a number of advan-
tages when compared with existing methods. Foremost of these advantages 18
the extreme sensitivity and dynamic range of the method. Witbout changing
any operational step or reagent, sulfur dioxide can be determined from
8 x 1024 to 0.2 ppm. in a 200 liter gas sample. This range is not fixed,
however, since the specific activity of the reagent can be varied over wide :
...........
..
..
..
..
limits both up and down, flow rates can be suited to the particular applica-
tion; no error was observed at any flow rate up to 4 1./minute. The method
does not require the judgment of a skilled operator making possible e como
pletely automatic rigute monitoring station. Although the radio-reagent was
synthesized with I+54, which requires a day-to-day decay correction, the:
reagent can also be made with longer ball-ur. Is to extend the worul
11fe.
There are essentially no important variables in the method, and the
only significant interference 16 hydrogen sulfide. However, this is not a
real problem since hydrogen sulfide levels are typically lower than those of
sulfur dioxide by more than two orders of magnitude <").
The method should be generally adaptable to any gas system without modi.
fication of the basic system. .
.
:
4. Bibliographical References
(1) Altshuller, A. P., Anal. Chem. 35, SR (1963).
[2] Chem. Eng. News, July 13, 58 (1964).
Gillespie, A. s. and Richter, H. G., Trans. Am. Nucl. Soc. 5, 273
(1962).
Jacobs, M. B., The Chemical Analysis of Air Pollutants, Interscience,
New York, 1960.
[5] Richter, . G. and Gillespie, A. s., Anal. Chem. 34, 1116 (1962).
Stephens, B. G. and Lindstrom, F., Anal. Chem. 36, 1308 (1964).
-
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· TABLE I
BLANK DETERMINATIONS
80, Equivalent
Pound (x 10-2 8)
Sample
6.8
6.7
7.1
7.0
7.3
7.1
5
7.0
6.8
Average
• 7.0 +
Standard Deviation - 0.25 ·
TABLE II
REPRODUCDBILMY OF SULFUR DIOXIDE DETERMINATIONS
Samples
302 Found ()
1.02
0.96
1.04
0.92
0.89
0.94
0.98
1.00
0.97
0.05
Standard Deviation
41.00 4 0.02 Mg. 802/sample.
°0.07 ug. blank subtracted and resulting value
rounded off to nearest 0.01 ug.
.
TABLE III
INTERFERENCES
802 Found (us)
802 AddedAg2
1.00
1.00
Sample
Benzone
Carbon Dioxide
Carbon Disulfide
Carbon Monoxide
Formaldehyde
1.00€
1.00
1.06€
1.00
1.446
Hydrogen Chloride
Hydrogen sulfide
Methanol
Nitrogen Dioxide
1.00
0.96€
45.0 Mg sample + 5.0 ug sulfur dioxide.
Washed with 0.5 N NaOH.
CTWO ox more runs.
.8

.
ORNL-DWG. 64-7841
I.
Fig. 1. Cas absorption train and reaction apparatus.
A
.
A
-
-
.
-
-
-
.
UNCLASSIFIED
OR NL-DWG. 64-7841
-> OUT

ORNI-DWO. 64-7842
Fig. 2. Response of radio-release system to sulfur dioxide.
.
V
i
mani
UNCLASSIFIED
ORNL-DWG. 64- 7842
.
ACTIVITY (C.P.M. $ 103)
10
20
30 - 2 4 6 8
SULFUR DIOXIDE (ug)
-
0.5
1.0
1.5



END


DATE FILMED
9 / 15/65







MI