t o be high. This waa confirmed by the large amount of scatter of the points and the large variations in absorbance values of the blank which ranged from 0.05 to 0.30. A steroid mixture consisting of 5c~-androstan-3,17dioneand 5p-androstan-aJ17-dione could not be resolved. The fractionation of two mixtures with sample sizes of 33 and 57 mg. resulted in single broad peaks, stretching over tubes No. 10 t o 25 and No. 10 to 29, respectively. Gradient elution from alumina also failed to separate this mixture (11). Knights and Thomas (IO) list relative retention times of r = 4.31 for the cis-isomer and r = 4.72 for the trans-isomer. The presence of the carbonyl group in position C-3 introduces a certain amount of strain into the cyclohexane ring, which will also affect the relative position of the hydrogen atom in position C-5 and its interactions with neighboring atoms and bonds. One would expect that the difference in these
interactions between the cis- and trans-isomers, on which basis they ca.n only be separated, to be diminished. Apparently, this difference has become so small that the isomers cannot be separated by fractional precipitation under the conditions employed. LITERATURE CITED
(1) Baker, C. A. ,Williams, R. J.,J. Chem. SOC.1956, 2352. (2) Clayton, R. B., Nature 190, 1071 (1961). (3) Fieser, I,. F., Fieser, M., “Organic Chemistry,” 3rd ed., Heath, Boston, 1956. (4) Haahti, E. O., VandenHeuvel, W. J., Horning, C. E., Anal. Biochem. 2, 182 (1961). (5) Ibid., p. 344. (6) Heftmann, E., Chem. Revs. 55, 679 (1955). (7) Hellmann, M., Alexander, R. L., Jr.. Covle. C. F.. ANAL. CHEM.30. 1206 (1958). (8) Kellie, A. E., Smith, E. R., Wade, A. P., Biochem. J. 53, 578 (1953). (9) Kellie, A. E., Wade, A. P., Analyst 82,722 (1957). \----I
(10) Knights, A. B., Thomas, G. H., ANAL.CHEM.34,1046 (1962). (11) Lakshmanan, T. K., Lieberman, S., Arch. Biochem. Bwphys. 53, 258 (1954). (12) Migeon, C. J., Plager, J. E., J. Biol. Chem. 209, 767 (1954). (13) Schneider, J. J., Lewbart, M. L., Recent Progr. Hormone Res. 15, 201 (1959). (14) Schulz, W. W., Purdy, W. C., ANAL. CHEM.35,2222 (1963). (15) .Seli Eon, D., “Stydard Methods of Chnica! Chemistry, Vol. 11, p. 80, Academic Press, New York, 1958. (16) VandenHeuvel, W. J., Haahti, E. O., Horning, E. C., J . Am. Chem. SOC.83, 1513 (1961). (17) VandenHeuvel, W. J., Horning, E. C., Bwchem. Biophys. Res. Commun. 3,356 (1960).
RECEIVEDfor review April 19, 1963. Accepted August 29, 1963. Division of Analytical Chemistry, 144th Meeting, ACS, Los Angeles, Calif., April 1963. Taken in part from the Ph.D. dissertation of Wolfgang W. Schulz, University of Maryland, College Park, Md. , 1963. The authors are indebted to the United States Air Force [Contract AF33(616)50631 and to the National Science Foundation for support of this work.
Radiochemical Determination of Cerium by Solvent Extraction Method M. A. AWWALl Radiochemistry Division, Atomic Energy Centre, P.O. Box No. 658, Lahore, Pakistan
b An efficient radiochemical method for the determination of cerium(ll1) has been developed based on the principle of the synergic effect in solvent extraction with 2-thenoyltrifluoroacetone and tri-n-butyl phosphate. The mixed solvents enhanced the extraction by 103-fold over either of the components alone. The extraction procedure provides a clean and efficient separation of radiocerium from other fission products. This method is particularly suitable for the separation of cerium from solutions of fission product mixtures a year or more out of the reactor.
T
radiochemical procedures (2, 5, 6, IO, 11, 13) for determination of cerium in fission product mixtures are either based on the repeated ceric iodate precipitation method or solvent extraction methods. Separation by the precipitation method (2) is tedious and time consuming. A radiochemical method developed by Glendenin (6) using 4-methyl-2-pentanone (hexone) requires handling a mixture of an organic solvent and strong nitric acid which can be hazardous. The procedure of Smith and Moore (13) for separation HE
2048
0
ANALYTICAL CHEMISTRY
of radiocerium by extraction with 2thenoyltriiluoroacetone (TTA) in xylene from 1N sulfuric acid calls for a chemical yield determination by standard methods. Recent work by McCown and Larsen (11) showed that cerium is well extracted with di-2-ethyl hexyl phosphoric acid from 10N nitric acid solution, I n this method a small amount of ruthenium is coextracted with cerium and removed by fuming with perchloric acid. Butler and Ketchen (3) developed themmethod for the separation of multicurie amounts of cerium and yttrium from fission product mixtures which were relatively free of strontium-90, zirconium-95-niobium95, cesium-137, technetium-99 and, in particular, to ruthenium-106. The most recent work by Marsh and Maeck (10) showed that radiocerium extracts as the tetra-n-propylammonium nitratocerate ion-association complex into nitroethane from strong nitric acid solution. The formation of solid phase in the liquid-liquid extraction seems to be a disadvantageous step in this method. The present work was undertaken to develop a solvent extraction method for radiocerium based on the synergic effect in solvent extraction of mixed solvents as predicted by Irving and
Edgington (9). Healy (8) observed that di-, tri-, and tetravalent metal ions showed synergistic extraction. I n the present procedure, cerium(II1) showed extraction improved by 103-fold with mixed TTA and T B P in benzene from nitric acid solutions of pH 2.90. Cerium(1V) was reduced nith a drop of hydrogen peroxide and after adjusting the pH of the solution by the addition of 0.02N sodium hydroxide, was extracted with equal volumes of 0.2M TTA and 0.5M T B P (1:l) mixture in benzene. Cerium was back-extracted into an aqueous phase with an aqueous nitric acid solution of pH 0.80. The cerium was obtained in good yield of satisfactory radiochemical purity. EXPERIMENTAL
Reagents. Tri-n-butyl phosphate to 1.OM) ; Z-thenoyltrifluoroacetone (10-3M t o 1.OM); benzene; dilute and concentrated nitric acid; sodium hydroxide (0.02N); hydrogen peroxide; and cerium carrier 5 mg. per (lO-3N
1 Present address, Department of Nuclear and Radiation Chemistry, The University of New South Wales, P. 0. Box, 1, Kensington, Sydney, Australia.
Table I. Extraction Coefficients of Trivalent Cerium-1 44 Tracer as Function of Varying TTA Concentration at Constant 1.OM TBP and pH 2.90
._
TTA, M 0.50 0.20 0.10 0.05 0.01
I; 10-3
I/
carrier-free
0
--
Ce-i44.
j
2
3 PH HNO,
1
5
TBP, M 1 .o 0.50 0.20 0.10 0.01
6
Figure 1. Effect of pH on extraction of cerium by TTA-TBP mixtures (1 to 1 by volume)
ml., standardized by the method of Glendenin (6). Procedure. For extraction studies the reagent grade T B P was purified by distillation (1) and TTA was purified by recrystallization in benzene. The synergism in the extra1:tion of cerium (111) was investigated by extracting tracer cerium-144 with varying proportions of TTA and TBP in benzene. The optimum pH of the aqueous solution for maximum extraction coefficient both for carrier-free cerium-144 and with carrier at a concentration of 1 mg. per ml. of cerium was determined with mixed solvents of 0.2M TTA and 0.5ill T B P in benzene. The extraction coefficients were found by counting equal aliquots of organic and aqueous phase with end-window Geigcr-Muller counters using 46 mg. per sq. cm. of aluminum absorber. Recommended Procedure. Pipet a n aliquot of the sample (total activity lo5 to lo7 c.p.m. 0) into a centrifuge tube containing 5 ml. of an aqueous nitric acid solution of pH 2.7 to 3.0. Adjust the h a 1 p1-I to 2.90 by 0.02N sodium hydroxide and add 2 drops of 3oY0 hydrogen peroxide. Transfer to a 50-ml. se3aratory funnel containing 5 ml. of 0.5M T B P and 0.2M TTA in benzene in the ratio of 1:1 and shake for 15 minutes. Withdraw the aqueous phase and scrub the organic phase twice with 5-ml. portions of nitric acid solution of p:6 2.90 together with 2 drops of 3oY0 hydrogen peroxide. Discard the aqueous phase. Backextract the cerium by [;haking the organic phase with 2 ml of nitric acid solution of p H 0.80 for 2 minutes. Allow praseodymium-144 to grow for 2 hours. Take a n aliquot from the aqueous stripped solution and count for beta activity using a n absorber of 46 mg. per sq. cm. of aluminum.
Element
Separation from the Other Elements.
T h e elements with long-lived radioisotopes formed in appreciable yield in fission, and likely to be extracted with cerium by the mixed solvents TTA and TBP, are yttrium-91, zirconium-95, niobium-95, ruthenium-106, promethium-147, and samarium-151. Other interfering elements present in fission product sources are thorium, uranium, neptunium, and plutonium. The described cerium procedure was tested for
Kd
10.1 10.4 7.9 5.4 0.01
Table 111. Coseparation of Heavy Elements and Other Fission Products
RESULTS AND DISCUSSION
Tracer cerium was well extracted between pH 2.60 to 3.40 with the optimum p H at 2.80 to 3.10. The results are shown in Figure 1. The extractions have been studied as a function of time. The maximum extraction was obtained after contacting for 15 minutes. Stripping was completed within 2 minutes after shaking the organic phase with aqueous nitric acid of pH 0.80. The effect of solvent concentrations on the extractability of tracer cerium was determined and the results are shown in Tables I and 11. Highest extractions were obtained with 0.5M TTA and 1 . O M T B P a t pH 2.90. I n the recommended procedure, the concentration of 0.2M TTA and 0.5M T B P was chosen since a higher concentration is likely to contaminate the product with zirconium-95 and other fission products. Carrier cerium did not extract as well as the tracer cerium. The low extractability may be due to the dimer and other species (4, 6). Butler (3) observed the similar effect with di-%ethyl hexyl phosphoric acid extraction of cerium.
9.8 .. -
4.7 0.12
Table II. Extraction Coefficients of Trivalent Cerium Tracer-1 44 as Function of TBP Concentrations at Constant 0.2M TTA and pH 2.90
I
1
Kd 10.7 10.1
Per cent extraction
US38
NP
Pu Th13‘ Rul’Je Zrg6-N bQ6
Per cent backextraction
... ... ...
99.9 99.0 99.0 98.9 0.47 12.1
32.5 0.28 0.006
Table IV. Comparison of the Solvent Extraction Method with the Ceric Iodate Precipitation Method
Counts in 1 ml. (8) fission product, X lo6 c.p.m. Precipitation Solvent method extraction method 1.74 f 0.02 1.75 f 0.04 1.75 f 0.03 1.74 f 0.03 1.75 f 0.05 1.75 f 0.04 1.75 f 0.06 1.75 f 0.04
1.73 f 0.03 1.78 f 0.05 1.76 f 0 . 0 2 1.79 f 0.04 1.78 f 0.03 1.79 f 0 . 0 4 1.75 f 0.03 1.76 f 0.06
coseparation of these elements by using the following radioactive tracer, zirconium-95-niobium-95, ruthenium-106, and thorium-234. The distribution data of uranium were taken from the work of Irving (9). Neptunium and plutonium as actinides will be extracted by the solvent. The coseparation results are shown in the Table 111. The data indicate that the separation from zirconium, niobium, and ruthenium is satisfactory. Promethium147 and samarium-151 might extract but the activities will not be detected if VOL. 35, NO. 13, DECEMBER 1963
0
2049
an absorber is used. Yttrium-91 does not coextract to any appreciable extent as is evident from the comparison of the procedure with the ceric iodate method ( 2 ) shown in Table IT’. This method ib witahle for fiqsion producxt mixtures obtained :A% waste from p r o c r . k g pI:iiit\ or irr:ttlinted sample. from which actinides have been remorcrl hr rvtractioii from nitric acid (7, 1%’). Ten aliquots of cerium-144 tracer solution containing 3.5 x 106 c.p.m. were carried through the extraction procedure. The average yield for the 10 determinations was 91.2 =t 0.iyh Samples of a one-gear-old fission product mixture were analyzed for cerium by the extraction procedure described and by the ceric iodate precipitation method ( 2 ) . The results obtained by the two methods are given in the Table IV and agree to within 2% for every sample. Radiochemical purity of the separated cerium by this procedure was checked by gamma-ray spectrometry. Less than
1% of the activities present were due to fission products other than cerium. The precision of the method was chccked by carrying out 10 replicate. allalybP5 or1 one-year-old f i 4 o n product cleiianii\tiiiw T h e ichtii htar~(l:rr~l tiori M :is & I .2%. Itesiclet spred and iinililic,ity, mi ndtlml xdv:tnt a g o~f the procctluie i, thc of rea(lilv :I! :iil:il)le solvrnt P . (A
ACKNOWLEDGMENT
The author is grateful to D. J. Carsne11 from the Department of Kuclear and Radiation Cheniiftry, University of S e w South Wales, for his many valuable suggestions and discussions on this paper. LITERATURE CITED
(1) Alcock, K., Grimley, S. S., Healy, T. V., McKav, H. A. C., Trans. Faradazi SOC.
52,
39 (iS56).
W. F.. Hume. D. Xi.. “Radiochj,mical Studies. The Fission Products, C. D. Coryell, 5 . Sugarman, eds., Vol. 9, p. 1693, hfcGrawHill, New York, 1951.
121 Boldridee. \
I
(3) Butler, T. A , , Ketchen, E. E., Ind. Eng. Chenz. 53, 651 (1961). (4) Fionaeus, Y.,Ostman, O., .lcfu. r h e i n . Scand. 10, 769 (1956). (5) Glendenin, I,. E., Flyiln, K. B’., Buchanit11, It. F., Steiuberg, E. l’., , A U A I ~ (’IIEM 27, 59; J lO55). (6) IIaitIwic~l,, I . .I., Itulm-ts~m,1 2 , ( ‘ ( i t ) .
.r. m,)tz. 29, xi8 ( i
~1.
i
( 7 ) f I ( J M t d Y l G . H., IIllghPS, ‘r. ci., RIackey, G. It., Saddington, IC., l’/:W, International Conference of Penref 111 Uses of Atomic Energy, Geneva, 1 %S. ( 8 ) Heal?-, T. V., J . Inorg. ,\’ucl. Chem. 19, 314 (1961). ( 9 ) Irving, H., Edgington, D. S . , I M . , 15, 158 (1960). ( l a ) Marsh, S. F., Maeck, W.J., Booman, G. L.. Rein, J. E., ANAL. CHEK 34.
1406 (1962).’
(11) McCown, J. J., Larsen, R. P., Ibid., 3 2 . 597 (1960). \ - - - - ,
(12jkairn, J. S., Collins, D. .4.,McKay, H. A. C., Maddock, A. G., P/1458, International Conference on Peaceful Uses of Atomic Energy, Geneva, 1958. (13) Smith, G. W., Moore. F. L. ANAL. CHERI.29, 448 (1957). RECEIVEDfor review January 9, 1963. Accepted Sugust 7 , 1963.
Fast Paper Chromatography of Different Valence States of Mercury and Antimony MOHSIN QURESHI and MUKHTAR A. KHAN Prince of Wales Chemical Laboratories, Deparfmenf of Chemistry, Aligarh Muslim University, Aligarh, India
b A decrease in the separation time of metals in differing valence states is effected by use of a suitable solvent system. A number of solvent systems are studied for the separation of Hg;’-Hg’’ and Sb+3-Sb’5. The most selective separation of Hgi2Hg’a is obtained with a mixture of HN03-HCI-isopropanol; Sb’3-Sb’5 separations are efficient in a mixture of acetic acid-water-ethyl acetate. I?, values are given for ions which are likely to interfere in the procedure, and the phenomenon of double spots is discussed.
T
of separation is a particularly important factor in the paper chromatographic separation of a metal in different valence states. If the separation time is long enough, some interconversion of valence state may occur. Also, one of the valence statesSb+5 in the present case-may be sufficiently reactive to interact slowly with the paper or the solvent system. Several techniques may be utilized to decrease the separation time, including the use of a higher temperature, centrifugal chromatography, or choice of a proper solvent system. A higher temperature may inrrease the rate of HE TIME
2050 *
ANALYTICAL CHEMISTRY
interconversion, as well as decrease the separation time, and centrifngal chromatography requires specialized equipment. Therefore, the choice of a proper solvent system offers the simplest solution t o the problem. The importance of the study of such separations has been discussed previously (1-3). -4 fast solvent system (3) was reported for the separation of Fe+2 and Fe+3. This paper summarizes recent findings on the separation of different valence states of Hg and Sb. These separations were reported earlier by Bighi (1) and Pollard ( 2 ) . We could not reproduce Righi’s separation of Hg2+2and Hgf2. The separation of Sbf3 and Sb+5, as reported by Pollard, requires 1 hour, and Sbf6 tails. Neither Bighi nor Pollard mentions the selectivity of the separations. Therefore, we have made a more detailed study and developed faster and more selective solvent systems.
using reagent grade chemicals. All solvents were purified b y distillation. Mercury Test Solution. Three grams of freshly prepared mercurous nitrate (mercurous nitrate E. Merck, which contains a n appreciable quantity of mercuric nitrate, was treated with dilute nitric acid and mercury until colorless crystals of mercurous nitrate appeared) were dissolved in 50 ml. of approximately 3M Hn’03. Two grams of mercuric nitrate were boiled with 5 mi. of concd. “0,. Spotting was done with 0.1M solutions. Ammonia gas and ammonium sulfide were used as detectors. Antimony Test Solution. The Sb+8 solution, 0.2M, was prepared as reported earlier (4). The 0.2M SbC13 solution in HC1 was boiled with KClOa, cooled, and filtered. This was used as the Sb+5 solution. Ammonium sulfide and H2S gas were used as detectors. Rhodamine B was used for the detection of Sb+5 only.
EXPERIMENTAL
To develop suitable methods of separation, a number of pure solvents were examined. The results are summarized in Table I. Separation of Hgz+2 and Hgf2. The following solvent systems gave fast separations of Hgz+* and Hg+2: 0.1M €IC1 ( S I ) ; 15% aqueous am-
Apparatus. Development was performed in 20-X 5-cm. glass jars, using the ascending method. T h e diniensions of the paper strips were 15 X 4 cm. Reagents. All results were obt,ained on Whntmwn No. 1 paper
RESULTS
