Table I. Precision of CVDT Measurements Average Rel. drop Std std time,a dev, dev, sec sec 6 h0.48 8.0 11 10.73 6.6 40 14.2 10.5 51 zk5.1 10.0 198 +21 10.6 287 +27 9.4 1 28 9.3 300 1080 &113 10.5 Mean = 9.4 Based on 10 drop time determinations on each sample.
z
RESULTS AND DISCUSSION Figure 6 illustrates the effect of surfactant concentration on interfacial tension and on drop detachment time. Since surfactants in levels as low as 1 ppm have a very deleterious effect on fuel quality, it is readily apparent from this plot that
the interfacial tension method lacks the sensitivity for differentiation between high quality and unsatisfactory turbine fuel. The drop time data, on the other hand, demonstrate that the CVDT method fulfills this requirement. Precision data for CVDT measurements are presented in Table I. These results are based on 10 successive measurements of drop time made on each of a series of turbine fuel samples into which dodecyl benzene sulfonic acid had been incorporated over a concentration range of 0-10 parts per million. Relative standard deviations average 9.4 over the range of 10-1100 seconds. Aviation turbine fuel samples to which naphthenic acids were added yielded precision data which were in very close agreement with these results. ACKNOWLEDGMENT The authors acknowledge the assistance of D. W. Williams of this laboratory who constructed the conductivity detector cell. RECEIVED for review July 27, 1970. Accepted November 30, 1970.
Rapid Separation of Berkelium from Rare Earth Fission Products and Trivalent Actinides R. F. Overman Sacannah River Laboratory, E . I . du Pont de Nemours and Company, Aiken, S. C. 29801
NUMEROUS METHODS for the analytical separation of berkelium from other actinides and lanthanides have been given in the literature. The adaptation by Farrar, Cooper, and Moore ( I ) of the classic isobutyrate cation exchange method of Choppin, Harvey, and Thompson (2) is rapid and gives good separations, but requires rather elaborate equipment and very close control to achieve good separation of berkelium from californium and curium. Moore and Jurriaanse (3) have published a procedure that can be used for separating berkelium from curium by liquid-liquid column extraction with di(2ethylhexy1)orthophosphoric acid (HDEHP) coated on Teflon (Du Pont) powder as the stationary phase. This method does not give good separation of berkelium from californium and europium, because the distribution coefficients are similar. Additional data on H D E H P distribution coefficients have been provided by Horwitz and coworkers ( 4 ) . Peppard (5) has reported an extraction of Bk(1V) into HDEHP. A method for the separation of berkelium and cerium by anion exchange was published by Moore (6). The method described here combines the anion exchange NaBrOa from separation of Bk(1V) in 8M "O3-0.2M (1) L. G. Farrar, J. H. Cooper, and F. L. Moore, ANAL.CHEM., 40,
1602 (1968). (2) G. R. Choppin, B. G. Harvey, and S. G. Thompson, J. Znorg. Nucl. Chem. 2,66 (1956). (3) F. L. Moore and A. Jurriaanse, ANAL.CHEM., 39,733 (1967). (4) E. P. Horwitz, C. A. A. Bloomquist, D. J. Henderson, and D. E. Nelson, J. Itzorg. Nucl. Chem., 31, 3255 (1969). (5) D. F. Peppard, S. W. Moline, and G . W. Mason, ibid., 4, 344 (1957). (6) F. L. Moore, ANAL.CHEM.,39, 1874 (1967). 600
ANALYTICAL CHEMISTRY, VOL. 43, NO. 4, APRIL 1971
Ce(1V) with the extraction of Bk(1V) on an HDEHP column. After all of the nuclides with a I11 valence are eluted from the H D E H P column, the Bk(1V) is reduced and eluted with 4 M H N 0 3 . The berkelium is sufficiently decontaminated from other actinides to permit radioassay of Z49Bk by beta counting. The method has been successfully applied to solutions originally containing activities of lO8(244Cm), 107(144Ce),and 105(lj4Eu)times that of 249Bkactivity, and is readily performed in contained facilities with relatively simple equipment and reagents. EXPERIMENTAL Equipment. A glass tube, 5 mm inside diameter and 90 mm long, was drawn to a tip at one end and was fastened to a glass reservoir, 10 mm in diameter and 80 mm long, at the other end. Glass wool was placed in the bottom of the tube. The appropriate filler was added to the tube with a medicine dropper in the form of a slurry in 8 M H N 0 3 . Anion Exchange. REAGENTS.The 8M "O3-0.2M NaB r 0 3 solution was made fresh daily from analytical grade reagents. Dowex 1-X4 (100-200 mesh) was obtained as analytical grade. PROCEDURE. After the glass tube was filled with resin, about 5 ml of a solution of 8M HN03-0.2M NaBr03 was passed through the column immediately prior to adding the sample solution. To prepare the sample solution, the sample was added to about 10 ml of 8M "O3-0.2M NaBr03, and allowed to stand for 20-30 minutes to ensure complete oxidation of the Ce(II1) and Bk(II1). The sample was introduced into the column and eluted with 3 t o 5 ml of 8M "Os0.2M NaBr03 solution. The nitrate-complexed Ce(1V) remained on the column, and the Bk(IV), Eu, Cm, Cf, and
other nuclides (with I, 11, or 111valence states) passed through the column. The eluate was collected and was allowed to stand 15-30 minutes for the Bk(II1) to reoxidize. [Apparently a partial reduction of the Bk(1V) occurs during the elution because of its reaction with radiation products or with chemically degraded resin, and this much time is needed to assure complete reoxidation.] The column was discarded after one use, because the anion resin was rapidly attacked by the radiation and by the reagents. Liquid-Liquid Chromatography. REAGENTS.A flux-calcined diatomaceous earth (100-110 mesh), which had been washed with acid and base and treated with silicone to make it hydrophobic, was obtained from Analabs, Inc., Hamden, Conn. Di(2-ethylhexyl)orthophosphoric acid (HDEHP) was purified by mixing with ethylene glycol, according to the procedure given by Moore (6). To ensure absorption of the HDEHP by the diatomaceous earth, the surface tension of the HDEHP was reduced by adding 8 volumes of chloroform. Then, 2.4 ml of HDEHP-chloroform solution was added to 3 grams of diatomaceous earth. The mixture was heated and stirred until most of the chloroform had evaporated. Ten milliliters of H 2 0 was added, and the mixture was boiled to remove all of the chloroform. The floating hydrophobic particles were removed. PROCEDURE.After the tube was filled with HDEHPcoated diatomaceous earth, the earth was conditioned with 3 to 5 ml of 8M "03-0.2M NaBrOs immediately prior to adding the sample solution. The sample solution containing the Bk(1V) was passed through the column. The column was eluted with about 10 ml of the 8M HN03-0.2M NaBrO, solution to remove all of the trivalent elements. The bromate was washed out of the column with 5 to 10 mi of 0.15M "03. Failure to remove all of the bromate causes undesirable gassing in the column when HnOs is added. Any Ce(1V) on the column was reduced to Ce(II1) and removed from the column with 10-15 ml of 0.15M HNO3--l0z HzOz Bk(1V) is also refollowed by 5-10 ml of 0.15M "03. duced by H202, but remains on the column. The Bk(JI1) was removed from the column with 4M "03 and collected in a 10-ml volumetric flask. Aliquots of the 10-ml solution were prepared for beta, alpha, and gamma counting. The column was not reused. If the trivalent ion content is greater than 1 mg, the volumes of the wash solutions should be doubled. If the alpha or beta activity contamination is too high for direct beta counting of the 24QBk, the 4M"03 eluate and 0.2M NaBrO,, and the solution is adjusted to 8M " 0 3 is recycled through a new HDEHP column.
dpm 1 5 4 E ~and , 2 X lo6 dpm 249Bk. After the first dualcolumn separation, these quantities were reduced to 3.4 X IO6 dpm 244Cmand less than 6 X l o 4dpm 144Ceor 1 5 4 E ~ How, ever, alpha activity from the 24Tm was too high to allow counting of the beta activity from 249Bk. Therefore, the berkelium was reoxidized to Bk(IV), and the sample was run through a second HDEHP column to remove the remaining 244Cm. The "tailing" of the 244Cminto the berkelium fraction from the HDEHP column might be explained by the radiolytic decomposition of the HDEHP from the high flux of alpha particles being emitted. When less than 1O1O dpm curium is put on the column, decontamination factors of lo7 relative to 249Bk were obtained with lS4Eu, 2j2Cf, 14Ce, and 244Cm. Only a column loading of >1O1O dpm 244Cmshowed radioactive impurity in the final berkelium product sufficient to distort the beta spectrum of the 0.125 MeV 24gBkbetas, as measured with a lithium-drifted silicon beta spectrometer. The radiolytic decomposition products of HDEHP have not been determined; however, some of the products may be better extractants than HDEHP. Peppard (7) has shown that mono(2-ethylhexyl)orthophosphoric acid (H2MEHP) in concentration less than one mole increases the extraction of rare earths and decreases the separation factors. The presence of H2MEHP would cause a tailing of curium under these conditions. Peppard has also shown that the presence of pyro esters increases the extractive powers of HDEHP. Berkelium yields of 90 + 5 % were obtained from analysis of 12 synthetic samples which contained known amounts of 249Bk, Alpha-hydroxyisobutyric acid and diethylenetriaminepentaacetic acid, complexing agents used in actinide processing, did not interfere. The method of analysis has been used in glove boxes and in shielded cells. No special adaptations are required for remote operation of the equipment. The final beta count may be performed by any standard technique, such as internal proportional counting or liquid scintillation,
RECEIVED for review July 10, 1970. Accepted December 8, 1970. The information contained in this article was developed during the course of work under Contract AT (07-2)-l with the U S . Atomic Energy Commission.
RESULTS AND DISCUSSION
The procedure was tested by analyzing a sample which contained 8.1 X 10I1 dpm 244Cm,2.4 X 10I1dpm I44Ce,1 x 109
(7) D. F. Peppard, G. W. Mason, J. L. Maier, and W. J. Driscoll, J. Itiorg. Nucl. Chern., 4, 334 (1957).
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