Table I.
Recovery and Decontamination of Lanthanide Fission Products from Transuranium Elements
s o . of
extracmt ions 2
Transuranium Q radioactivity added, d.p.m. 1.6 x 107
x 107
3
1.6
4
1 . 1 x 109
RESULTS A N D DISCUSSION
The preferential extraction of transuranium elements by tertiary amines is highly dependent on the concentration of hydrochloric acid, lithium chloride, and amine ( 1 , 5 ) . Removal of these heavy elements must necessarily be a compromise with rare earth yield. Preliminary studies indicated best results were possible using the system 11.6.U lithium chloride-0.2M hydrochloric a ~ i d - 3 0 7.Ilamine ~ 336-S-xylene. The amine is pretreated with 1M hydrochloric acid solution to form the amine hydrochloride. Typical data (Table I) obtained using the procedure described above show that a high degree of decontamination of lanthanide fission products from transuranium elements may be achieved in a rapid and simple manner. T o
Total lanthanide fission roduct yiel , 70 83 1 81.6 71.8
a
Transuranium a radioactivity found in lanthanide product, % 1 46 1.69 0.17
50.0
0.007
61.3 73.7
0.01 0.02
determine the lanthanide yields the mixed lanthanide hydroxide was first precipitated to eliminate the lithium which interferes in the final lanthanide oxalate precipitation. The transuranium alpha emitters used for testing consisted of 239Pu (39.473, 241Am (19.9%),244Cm (39.3'27,), and 242Cm (1.4%). High levels of Bk, Cf, and heavier elements were not available for testing, but it is known that they extract considerably better than curium. The number of extractions necessary depends on the amount of alpha radioactivity which can be tolerated in the subsequent analysis. -4t this installation, transuranium alpha radioactivity in the approximate range 106 to lo7 d.p.m. may be used in a conventional chemical hood. Two extractions are often adequate. An incidental advantage in the method is
that the anionic chloride complexes of many fission products and associated elements ( 1 , 4 extract essentially quantitatively with the transuranium elements. Among these are zirconium, niobium, ruthenium, silver, molybdenum, technetium, zinc, iron, cobalt, copper, mercury, nickel, lead, titanium, manganese, palladium, cadmium, tin, antimony, thorium, protactinium, and uranium. Subsequent lanthanide chemistry may thus be simplified. The method is readily adaptable to glove box or hot cell techniques. LITERATURE CITED
(1) Baybarz,
R. D., Weaver, B. S., Kinser. H. B., Nucl. Sci. Ena. 17, 457 (1963): (2) Hume. L). K..Ballou. N . E.. Glend~,~ enin, L.' E., U.'S. At. 'Energy' Comm. Rept. CN-2815 (1945). (3) McCown, J. J., Larsen, R. P., ANAL. CHEM.32, 597 (1960). ( 4 ) Moore, F. L., U. S. At. Energy Comm. Rept. NAS-NS-3101 (1960). ( 5 ) Moore. F. L.. ANAL. CHEM.33, 748 (1961).
(6j-Stevenson, P. C., Kervik, W. E., U. S.At. Energy Comm. Rept. NAS-NS3020 (1961). FLETCHER L. MOORE W. THOMAS MULLINS Analytical Chemistry Division Oak Ridge National Laboratory Oak Ridge, Tenn. RESEARCH sponsored by the U.S. Atomic Energy Commission under contract with the Union Carbide Corp.
Voltammetric Determination of the Monomethylether of Hydroquinone with a Carbon-Ceresine W a x Paste Electrode SIR: The carbon paste electrode was developed by Adams and Olson to find a new electrode material better suited for anodic voltammetry than solid electrodes (3, 4). Other authors have used this electrode to determine trace quantities of metals in water ( I ) , and to study the electrochemical behavior of organic compounds in water (2). Attempts to use the paste electrode in nonaqueous media have been unsuccessful. Organic solvents dissolve enough of the pasting liquid to cause the paste to flake which continuously changes the effective electrode area. I t occurred to us that a paste preparation with melted Ceresine wax might produce an electrode with characteristics of the paste electrode of Adams and Olson, but usable in nonaqueous media. This report describes a specific application of a carbon-Ceresine wax paste electrode to the determination of the monomethylether of hydroquinone 420
*
ANALYTICAL CHEMISTRY
(MEHQ) in methyl monomer (MMA).
methacrylate
EXPERIMENTAL
The carbon-wax electrode (CWE) was prepared by mixing powdered graphite (Acheson Grade No. 38) with melted Ceresine wax in a beaker. This was done by weighing a given quantity of graphite on a . trip balance in a small beaker. Ceresine wax was weighed into a 2-ounce glass jar, and melted on a hot plate with a minimum of heat. The graphite was slowly poured into the melted wax and the mixture was stirred for about 10 to 15 minutes with a glass rod. The hot paste was tamped into a 2- to 3-inch tube (Du Pont Teflon) of about 1/4-inch i.d. to an approximate depth of 'I4inch. Excess paste was removed from the tip of the tube with a Kimwipe and the paste was allowed to cool and solidify. Electrical contact mas made to the paste by filling the tube with mercury. The
electrode was connected to a conventional polarograph through a platinum wire placed into the mercury. All experiments were done in 80% alcohol with 0.lN lithium chloride and 0.05M potassium acid phthalate as the supporting electrolyte. The reference electrode was 1N calomel (NCE). The cell was thermostated a t 25' f 0.1' C. Either a Leeds & Northrup Electro-chemograph Type E or a Sargent Model X X I was used to record all voltammograms. All scans were started from 0 volt. RESULTS A N D DISCUSSION
The CWE was fabricated with different weight ratios of carbon to wax. This was done to determine the effect of electrode composition on the peak current intensity. The methyl ether of hydroquinone (MEHQ) was used as the electroactive species. The data in Table I show that both the peak cur-
POTENTIAL ( V O L T S ) 41.0V 4l.OV
+ osv +OSV
0
,*-
+o.Bv +O.Bv
+Osv +OSv
t06V v
+O.lV +O.lV
+0.4v
- ------
*0.3v *0.3V
+02V
I
I
iO.1v +O.lV
0.0
Table 111.
Effect of Monomer on Peak Current of MEHQ
Scan rate, v
I:I
/
I
/
in cell
in,. pa.
0 6.3 11.7 21.0 34.8
4.25 4.18 4.26 4.42 5.95
b
0.262 m M MEHQ
rent intensity (i,) and residual current (i7) increase as the ratio of carbon to wax increases. This would be expected on the basis that a n increase in carbon content should increase the effective electrode area. We chose a carbon to wax ratio of 1.3 for the remainder of the experiments because this electrode is easier to fabricate. The peak current-concentration relation was studied by adding aliquots of a
Table
1. Effect of Carbon-to-Wax Ratio on Current Intensity
0.161 mmole MEHQ/liter; scan rate, v = 1.3 mv./second; E, = $0.75 volt us. NCE
Weight ratio, carbonto-wax 0.8 1. 0 .
1.3 1.7 2.0 a
ips, pa. 1.34 1.98 .. 2.40 2.42 2.40
i,, pa. 0.34 0.44 0.40 0.96 0.80
~
Corrected for residual current.
solution of M E H Q to a solution of MMA4 in 80% alcohol containing the supporting electrolyte. Voltammograms of the solution were obtained after each addition of M E H Q and the peak current (i,) was plotted as a function of M E H Q concentration. The data in Table I1 show that a linear relation is obtained between i, and M E H Q concentration, and that the peak potential (E,) is independent of M E H Q concentration. Some compounds interact with solid electrode surfaces. T o determine if the carbon-wax electrode would be affected by monomers such as the acrylics, the peak current of M E H Q was measured in the presence of varying concentrations of uninhibited MMA. The data in Table 111 show that i, increases with increasing monomer concentration. However, the residual current or “background current” also increases with increasing monomer concentration. The net effect of the increases in both currents causes them to merge so that the peak current is less distinctly resolved from the background (Figure 1).
3.3 mv./second; MEHQ, 0.262 m M
yo MMA
5
Figure 1. Effect of monomer concentration on voltammogram of MEHQ
=
Cell E, (volts) resistance, us. NCEb Q +0.73 +0.70
+0.70 f0.68 +0.57
3,180 3,400 3,400 3,700 4,350
Corrected for residual current. Corrected for cell resistance.
We chose a range of monomer concentrations in the cell of 1 to 21% for the analyses because in this range i, is distinctly separated from the residual current. One major disadvantage of solid electrodes is that they usually must be reproducibly treated before and/or after each analysis. Platinum electrodes are sometimes dipped into nitric acid to remove oxides, and the tips of waximpregnated graphite rods are sandpapered or cut off after each analysis. Improper or nonreproducible treatments may cause serious errors to arise in the analyses of organic compounds. The time involved in treating these electrodes can vary from 1 to 30 minutes or longer; however, in the hands of experienced analysts reproducible results are obtained. The carbon-wax electrode can be used repeatedly without a n y pretreatment for the oxidation of MEHQ. A new electrode surface can be prepared by simply wiping the tip of the electrode with a Kimwipe, and new electrodes can be fabricated in a matter of minutes. The reproducibility of the carbon-wax electrode used without a n y pretreatment in the oxidation of 0.306 mmole MEHQ/liter (five determinations) is about 2 to 3% (2u). Similar results are obtained when new electrodes are made for each analysis. ACKNOWLEDGMENT
II. Peak Current-Concentration Relation Scan rate, v = 3.3 mv./second; 11.7% MMA in cell; cell resistance, 4020 t o 4050 ohms MEHQ, mM i P ,pa. ~ E , (volts) us. NCE* iP/C Table
0 0.081 0.161 0.242 0.323 0.484 0.645 0.807
n
(0.15) 1.24 2.54 3.84 5.26 7.76 10.70 12.20
Corrected for residual current
* Corrected for cell resistance.
+0.74 +O. 75 +0.74 + O . 75
+0.74 +0.74 +0.74 +0.74
... 15.3 15.8 15.9 16.3 16.0 16.6 15.1 Av. = 1 5 . 9 0 = *5%
Alfred Langnas assisted in some of the experimental work. LITERATURE CITED
( I ) Jacobs, E. S., ANAL.CHEM.35, 2113 (1963). (2) Kuwana, T., French, W. G:, Ibid., 1 - - - - 1
36, 241 (1964).
(3) Olson, C. L., Diss. Abstr. 23, N o . 3098 (1963). (4) Olson, C. L., Adarns, R . N., Anal. Chim. Acta 22, 582 (1960).
JOHN R. COVINGTON REKEJ. LACOSTE
Rohm & Haas Co. 5000 Richmond St. Philadelphia, Pa. VOL. 37, NO. 3, MARCH 1965
421
