occupied a-orbital (high electron density over the chain of four carbon atoms) one of the vibrations excited is almost certainly v 3 (27), and it seems reasonable to assign this to the highest frequency vibration observed in each case. The frequencies of the vibrational progressions observed in the second bands of the spectra are summarized in Table VI. Comparison with Other Spectroscopic Methods (Figures 15 and 16). The mass spectra and infrared spectra of 2-bromo- and 3-bromothiophene are shown for comparison (28, 29). The former does not allow ready differentiation between the two compounds; the latter, over the range scanned, does not directly reflect the presence of bromine in the molecules. Both, of course, convey information that is not contained in the photoelectron spectra; thus all the techniques are complementary. It is not possible to say what information might ultimately be gleaned a priori from the photoelectron spectra by an expert because so far there has been no systematic attempt to (27) Notation of G. Herzberg, “Molecular Spectra and Molecular Structure, Part 111,” Van Nostrand, New York, N. Y., 1966. (28) B. Akesson and S . Gronowitz, Ark. Kemi, 28, 155 (1967). (29) S. Gronowitz, Ark. Kemi. Mineral. Geol., 7,267 (1954).
correlate the a-bonding region from 13-21 eV, and so few spectra have been measured. However, even at the present time it would be possible at the very least to deduce the presence of a halogen substituent adjacent to a a-system, to identify the individual halogen, to infer that the a-system was associated with an aromatic system other than benzene and, with the aid of correlation diagrams and comparative spectra, to identify the compound. Insofar as the basic ionization process is similar to that in the argon-ionization detector used in gas chromatography, it is reasonable to assume that great improvement in sensitivity is possible and that photoelectron spectrometry should become a useful tool of the analyst.
ACKNOWLEDGMENT We are grateful to the Agricultural Research Council for providing the photoelectron spectrometer. RECEIVED for review February 2, 1970. Accepted March 23, 1970. A research fellowship to A.D.B. from the Agricultural Research Council and a maintenance grant to N.R.K. from the Science Research Council are gratefully acknowledged.
Determination of Actinides in Biological Samples with Bidentate Organophosphorus Extractant F. E. Butler’ and R. M. Hall E . I . du Pont de Nemours & Company, Savannah River Laboratory, Aiken, S. C. 29801 A procedure for the determination of actinides was developed using the bidentate extractant dibutyl N,Ndiethylcarbamylphosphonate. Nine actinides were extracted from 12N “Os, back-extracted to 2N “Os, and counted in a low-background alpha counter. A procedure was developed for sequential extraction of plutonium, neptunium, and uranium with tri-isooctylamine (TIOA), followed by extraction of thorium, americium, curium, berkelium, californium, and einsteinium with bidentate. Compared with previous methods, the new procedure is simpler, requires less analysis time, and gives better recovery. The recovery of Am-Cm-Cf from 250 ml of urine or 20 grams of feces was 90%. Sensitivity of analysis is 0.02 f 0.01 d/min/sample. An alternative method of exchange of trivalent actinides as oxalate anion complexes with TIOA is also described.
PRODUCTION OF TRANSPLUTONIUM elements has increased in the past five years, thus increasing the risk of personnel exposure ( I ) . Programs for the large-scale production of 244cm (2) and 252Cf(3, 4) have been reported. A dependable, simple bioassay method was needed therefore to determine the 24aAm,244cm, and 262Cf produced in these programs. Present address, Southeastern Radiological Health Laboratory, Montgomery, Ala. 36101
The previous method for determining the trivalent actinides in this laboratory employed the liquid ion exchanger di-2ethylhexylphosphoric acid (HDEHP) (5). Although americium, curium, and californium exchanged to HDEHP from acid solution adjusted to pH 4 to 5, calcium also exchanged in sufficient amount to interfere with the determination. An additional extraction step was required to extract the actinides to thenoyl trifluoroacetone. This extraction was also from a solution adjusted to pH 4 to 5. These extractions are time consuming and tedious. The method was used for analysis of urine and blood, but it was not suitable for analyzing feces. Siddall reported on bidentate chelating compounds with the unique property of extracting trivalent lanthanide and actinide elements from highly acidic waste concentrates from the reprocessing of nuclear fuels (6). These compounds contain two C==O or P = O complexing groups. Dibutyl N,N-diethylcarbamylphosphonate (DDCP), the most promising of the bidentates, was used in development of the procedure reported here. However, because this bidentate was not initially available in sufficient quantity for routine analyses, another procedure for oxalate anion complexing of trivalent actinides with tri-isooctylamine (TIOA) was developed. This procedure is also reported. EXPERIMENTAL
(1) D. H. Denham, HealthPhys., 16,475 (1969). (2) H. J. Groh, R. T. Huntoon, C . S. Schlea, J. A. Smith, and F. H. Springer, Nucl. Appl., 1, 327-36 (1965). (3) W. C. Reinig, ibid., 5, 24 (1968). (4) D. E. Ferguson and J. E. Bigelow, Actinides R e a , 1, 213 (1969).
Bidentate Method. REAGENT. Dibutyl N,N-diethylcarbamylphosphonate (DDCP), was shown by Siddall (6) to be ( 5 ) F. E. Butler, ANAL.CHEM., 37, 340 (1965). (6) T. H. Siddall 111, U. S. Patent 3,243,254 (1966).
ANALYTICAL CHEMISTRY, VOL. 42, NO. 9, AUGUST 1970
1073
CH CH CH CH e,0'2
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Figure 1. Dibutyl N,N-diethylcarbamylphosphonate 1-
10 Second Mixing 60 Min. Separation
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NITRIC ACID NORMALITY Figure 2. z41Am exchanged to 1 ml DDCP from 50 ml of " 0 3
.IO0 I
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the best extractant for trivalent lanthanides and actinides. The structure of this molecule is shown in Figure 1. Siddall described two methods for its synthesis. One liter of DDCP was obtained from Columbia Organic Chemicals Company, Inc., Columbia, S. C., and was used without further treatment. Preliminary experiments showed that the DDCP was not effective when diluted more than 25% with toluene or xylene; therefore, all tests described below are with undiluted reagent. BIDENTATE-HNO~ TESTS. Experiments with Z4lAm as a model trivalent actinide demonstrated the direct extraction of the trivalent actinides from 12N H N 0 3solution into DDCP. Figure 2 shows 241Am is nearly quantitatively extracted from 50 ml of 12N H N 0 3 to 1 ml of DDCP. At least 30 minutes settling time was required for adequate separation of the small volume of DDCP from the large volume of acid. Figure 2 also indicates that 2N HNOI can be used to back-extract the trivalent actinides. BIDENTATE-HC1 TBTS. In a previous study, plutonium, neptunium, and uranium extracted from 8N HCl to 10% tri-isooctylamine-xylene (7). No trivalent actinides were extracted under these conditions. The plutonium, neptunium, and uranium may be stripped sequentially from the TIOA for quantitative determinations of each. Extraction from hydrochloric acid was investigated since the trivalent actinides will be in an 8N HCI solution following the plutonium, neptunium, and uranium decontamination step. However, Figure 3 shows no appreciable extraction of 241Amfrom 2 to 12N HCl to 1 ml of DDCP. When either 5 ml of 16N H N 0 3 or 5 ml of saturated NH4N03 are added to 50 ml of these acid solutions, the extraction is increased as the HCl concentration increases. Figure 4 shows the exchange of z41Am from 12N HCl to 15 ml of DDCP. Fifteen milliliters of DDCP extracted 88 of z41Am. Addition of 5 ml of 16N HNOI increased the extraction to 99%. However, this technique of adding HNO, was not practical in general, because of the large volume of acid and DDCP required. (7) F. E.Butler, Health Phys., 15, 19-24 (1968). 1074
75
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Figure 4.
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Z41Am exchanged to DDCP from 50 ml of 12N HCl
Procedure. Sequential extiactions with TIOA and DDCP provide a simple, accurate method for quantitative determination of actinides in biological and environmental samples. Figure 5 shows the procedure for analysis of the actinides schematically, Plutonium, neptunium, and uranium are exchanged from 8N HCl to TIOA by a procedure reported previously (7). The residual 8N HCl containing the Z43Am, 244Cm,and 252Cf and an 8N HC1 rinse of the TIOA is evaporated. The DDCP procedure is as follows. Add 40 ml of 8N H N 0 3 to residues and evaporate the solution to dryness. Allow the beaker to cool and add 20 ml of distilled water and swirl to dissolve the salts. The salts dissolve endothermically, Most salts go into solution at room temperature. This step and subsequent steps are designed to completely dissolve the salts in 11 to 12N HNO1. Add 10 ml of 16N "03 to the solution and heat to near
ANALYTICAL CHEMISTRY, VOL. 42, NO. 9,AUGUST 1970
URINE SALTS
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STRIP
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Table I. Extraction Tests with DDCP Aqueous: 50 ml Of 12 HNOa
TIOA Exchange
DCCP: 1 ml Mixing time: 10 seconds
EVAPORATE AQUEOUS. DISSOLVE IN 12 N HN03 I
A
Exchange to I m l DDCP
DISCARD AQUEOUS
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Figure 5. TIOA-DDCP actinide procedure boiling. Remove the solution from the hot-plate and add 20 ml of 16N "0,. Pour the solution into a 125-ml separatory funnel and rinse the beaker with two 10-ml volumes of 16N H N 0 3 . Transfer rinses to the funnel. Allow the solution to cool to ambient temperature, add 1 ml of DDCP, and mix the solutions vigorously for 10 seconds. Allow the layers to separate for at least 30 minutes. Drain and discard the aqueous (lower) phase. Pour 10 ml of 12N H N 0 3 into the funnel and shake for 1 second. After the layers separate, drain and discard the rinse solution. Add 5 ml of toluene to the DDCP. The inert solvent decreases the affinity of the actinides for DDCP, decreases the density of the organic phase allowing rapid separation, and reduces the possibility of inclusion of the nonoxidizable phosphate in the strip solution. Add 20 ml of 2N HNOI to the funnel and shake vigorously for 10 seconds. Drain the 2N HNO, to a 100-ml beaker. Repeat with a second 20-ml of 2N H N 0 3 strip solution. Evaporate the 2N HNO,, mount residue on planchet, and count in a low background solid state counter described previously (7). OXALATE ANIONCOMPLEX METHOD. In a beryllium analysis method, several elements including americium extracted into TIOA as oxalate anion complexes (8). Calcium, sodium, and phosphorous (the bulk of salts in biological samples) do not extract as oxalates. Americium, curium, and californium were extracted at greater than 90 % recovery by the following procedure. One hundred milliliters of urine was wet ashed and dissolved in 150 ml of 0.25N HCl. Five milliliters of 1M oxalic acid was added and the solution was extracted for 10 seconds with 50 ml of 50% TIOA-xylene. The aqueous phase was discarded. The TIOA was rinsed with 50 ml of 0.1N HCI solution, which was also discarded. The trivalent actinides Approximately 10 were stripped into 25 ml of 4N "0,. mg of nonoxidizable residue remained after evaporation of the strip solution. Emission spectrographic analysis indicated the bulk of the residue was borosilicates. The solids were eliminated by either of two methods. In one method, the residue was dissolved in 50 ml of 0.05N "03, and the actinides were extracted into 25 ml of 50% HDEHP-toluene and stripped to 4N HN03. In the second method, HDEHP was absorbed on diatomaceous earth or Teflon (Du Pont) powder to form an ion exchange column (9, IO). The actinides were absorbed from dilute acid and stripped with 4N HN03. RESULTS AND DISCUSSION
Selected radioisotopes were extracted from 50 ml of 12N "03 to 1 ml of DDCP (Table I). Extraction efficiency for (8) F. E. Butler, Amer. J. Znd. Hygiene, 30, 559-563 (1969). (9) F. L. Moore and A. Jurriaanse, ANAL.CHEM. 39, 733 (1967). (10) E. P. Horwitz, C. A. A. Bloomquist, D. J. Henderson, and D. E. Nelson, J. Inorg. Nuci. Chem., 31, 3255-3271 (1969).
Element Ca cs Fe Pm Ce Th U
NP Pu Am Cm Bk Cf Es
Principal valence 2
1 3 3 3 4 6 5
4 3 3 3 3 3
Extracted,
