infrared values by more than the probable error of the infrared method. When a straight line is passed through the origin and the upper points, the deviation in the lower Fercentage range is less than twice the probable error Of the infrared data. I t is not known
whether this deviation is due to the limits of the infrared procedure or linearity deviation in the GLC method. LITERATURE CITED
(1) Anderson, W. M., Carter, G. B., Landua, A. J., ANAL.CHEM.31, 1214
(1959).
( 2 ) Challa, G., Hermans, P. H., Zbid., 32, 778 ( l g 6 0 ) . ( 3 ) Kanne, F., Stange, K., Z. ANAL.CHEM. 189,261-5(1962). ( 4 ) Torninaga, Sachiyuki, Bunseki Kagaku 12 ( 3 ) , 137-43 (1963).
RECEIVEDfor review October 4, 1963. Accepted February 19, 1964.
Selective Liquid-Liquid Extraction of Radiotin with 2-Thenoyltrifluoroacetone JAMES R. STOKELEY' and FLETCHER L. MOORE Analytical Chemistry Division, Oak Ridge National laboratory, Oak Ridge, Tenn.
b A new, rapid, highly selective liquid-liquid extraction method for radiotin is based on the extraction of radiotin from a sulfuri'c acid-chloride aqueous medium with 0.5M Z-thenoyltrifluoroacetone-methyl isobutyl ketone. Tartaric acid or sulfuriic acid readily strips the tin from the organic phase. The method has been employed successfully in the radicichemical purification and isolation of radiotin from both old and new fission product mixtures. A redetermination of the half life and gamma spectral characteristics of tin-1 28 is reported.
T
lack of completely satisfactory separation methods for radiotin has been discussed in a recent review (9). Precipitation and distillation procedures are not completely selective and are tedious, time-consuming, and cumbersome. Liquid-liquid extraction is often a desirable separation method, because of its speed and adaptability for use with both tracer and macro levels of ions. However, a highly selective solvent extraction method for radiotin has not been previously reported, with the possible exception of .,he method of Pappas (10) which is based on the extraction of tin(I1) clithionate with little regard for high yield. Because of the successful use of the versatile chelating agent, thenoyltrifluoroacetone (TTA), by many radiochemists (8, I I ) , the writers investigated its possible application in the selective liquid-liquid extraction of radiotin. TTA has previously proved t o be a highly selective extractant for other quadrivalent metal ions from solutions of relatively high acidity (8). HE
EXPERIMENTAL
Apparatus. Vortex test tube mixer, Model K-500-4, supplied b y Scientific Industries, Inc., Springfield, Mass.
NBI(T1) well-type gamma scintillation counter, 13/4X 2 inches. Gamma scintillation pulse height analyses were performed with a 256channel pulse-height analyzer coupled to a 3 X 3 inch NaI(T1) detector. Samples were counted on a 1.23-gram per sq. cm. beryllium beta absorber. Beta counting was done with a methaneflow proportional counter. Reagents. Analytical grade reagents were used without further purification. T h e 2-thenoyltrifluoroacetone (TTA, M . W . 222) was supplied bv the Columbia Organic Chemicals C'o., Columbia, S. C . The 0.5M TT.4-methvl isobutvl ketone (hexone) was pre-kquilibratid with an equal-volume portion of I N hydrochloric acid solution. Procedure. If the sample is a uranyl salt, dissolve in a minimal a m o u n t of concentrated hydrochloric acid which contains sufficient tin(1V) chloride so t h a t t h e final aliquot preferably does not contain more t h a n 0.2 mg. of tin per ml. H e a t just below boiling for a few seconds to ensure exchange. Adjust the aqueous solution t o a concentration of 1 to 2N hydrochloric acid, 1 to 2 N sulfuric acid, and approximately 1 volume % hydrogen peroxide. Extract for 2 minutes with a n equal-volume portion of O.jlk' TTA-methyl isobutyl ketone, using a Vortex mixer or other suitable extraction technique. Centrifuge for 1 minute in a clinical centrifuge. Draw off and discard the aqueous phase. Carefully wash the sides of the extraction vessel with several milliliters of a 1.2N sulfuric acid-2M ammonium chloride solution, Draw off and discard the aqueous phase. Scrub the organic phase by mixing for 1 minute with a n equal-volume portion of a solution made up of 1.2N sulfuric acid-2M ammonium chloride and 1 volume % hydrogen peroxide. Centrifuge and discard the aqueous phase. Repeat the scrub step once. Strip the tin from the organic phase by extracting with a n equal-volume portion of 1Jf tartaric acid for 10 minutes. Centrifuge for 1 minute, and use a n aliquot of the aqueous strippant for radioactivity measurements. If a yield
determination for tin is desired, the spectrophotometric method of Luke (4,5 ) i i useful. RESULTS A N D DlSCUSSlON
Two stock solutions of tin-113 tracer were prepared for the evaluation of pertinent variables. One solution contained 15 pg. of inactive tin per ml. in 5 N hydrochloric acid; the other contained 20 pg. of inactive tin per ml. in 6 N sulfuric acid. All counting was done a t least 18 hours after the final separatbn in order to allow the tin-113 daughter, 1.73-hour indium-] 13m, to grow into equilibrium.
Extraction Characteristics. Preliminary experiments indicated t h a t reasonable amounts of tin-1 13 tracer could be extracted only from chloride media; moreover, a polar solvent was necessary for the TT.4. An almost direct correlation was found between increased extraction and solvent polarity. Less than 1% of the tin113 tracer was extracted by 0.5M T T I in xylene, while more polar solvents, such as nitrobenzene, raised the extraction to approximately 60%. Hexone, when used as the solvent for TTA, extracted tin essentially quantitatively from an aqueous phase which was greater than 0.5N in hydrochloric acid. Diisobutyl ketone, a likely substitute for hexone, extracted approximately 50% of the tin-113 tracer under identical conditions. Figure 1 shows the extraction of tin113 tracer into 0.5M TTA-hexone as a function of hydrochloric acid concentration. Aqueous solutions of varying hydrochloric acid content, containing 1% hydrogen peroxide and tin-1 13 tracer (2.5 X lo4 gamma c.p.m.), were extracted for 2 minutes at room temperature with equal-volume portions of 0.5M TTA-hexone. Vortex test tube mixers were employed. After centrifuPresent address, Chemistry Ile artment, Clemson College, Clemson, S.
8.
VOL. 36, NO. 7, JUNE 1964
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gation, each phase was analyzed for - o tin-113 using a well-type gamma scintillation counter. These data indicate that radiotin extracts essentially quantitatively from aqueous solutions of 0.5-11 to 5M hydrochloric acid. A hydrochloric acid concentration of 1 to 2N is recommended. At lower concentrations hydrolytic tendencies of tin become pronounced, while a t higher concentrations phases separation is slower. The extraction of tin-113 tracer with hexone in the absence of TTA is also shown in Figure 1 for comparison. These data closely reproduce the wellknown work of Goto and coworkers (3). To effect a respectable yield of tin in the latter case, aqueous hydrochloric acid concentrations in the range 5 to 6 N must be used. Under such conditions the selectivity is lost, because many metals extract into hexone as chloro ion association-type complexes. Thus, it is clear that in the hexone system, tin(1V) tracer may be extracted essentially quantitatively as a TTA complex from dilute hydrochloric acid solution (0.5 to 2N). This avoids the undesirable coextraction of many other metal ions.
Table I. Extraction of Tin-1 13, Zirconium-95, and Iron-59 Tracers from Aqueous Sulfate-Chloride Media
1.2 1 2
1 2
..
0.1
