ic systems, it is possible to determine the acid and anhydride concentrations via the potentiometric titration curve. The same is true for the phthalic system. It should be clear that for all systems, it is possible to do a potentiometric titration instead of an indicator titration. It is worth mentioning that as part of the effort to determine the purity of maleic acid samples, it was found that fumaric acid is titrated as a diprotic acid in the TBAH-Thymol Blue method (8). It also was found that fumaric acid is not titrated in the straight TPA method of Siggia and Floramo (10). [As stated earlier, fumaric acid is a diprotic acid in the presence of the Ba(OC14)Z acidity enhancement salt (3) whereas maleic is a monoprotic acid under these conditions.] These properties provide the
basis for determining the maleic and fumaric acid contents of binary mixtures of the two. For example, one maleic acid sample which gave an apparent maleic acid content of 110.0% by the TBAH method was calculated to have 90.0 maleic and 9.96% fumaric via simultaneous equations with the assumption that the sample was a binary mixture of the two acids. Titration of the same sample with TPA without Ba(OC14)Z gave a maleic content of 90.17% and, by difference, a fumaric content of 9.83%. Received for review December 31, 1973. Accepted March 1, 1974. The authors wish to acknowledge the support of the National Science Foundation Undergraduate Student Program.
Simple Recovery of Plutonium, Americium, Uranium, and Polonium from Large Volumes of Ocean Water V. F. Hodge, F. L. Hoffman, R. L. Foreman, andT. R . Folsom Scripps institution of Oceanography, La d o h , Calif. 92037
Fallout plutonium concentrations in the world's oceans are extremely low-so low that if we are to understand the present distributions of this man-made element in order to predict the impact of future inputs, assays of many large volumes of sea water will have to be made. Moreover, as an increasing number of nuclear reactors locate on exposed sea coasts, and as plutonium makes its debut as a commercial nuclear fuel, many assays of coastal waters also will have to be made. Unfortunately, the two most widely used methods for extracting the small amounts of plutonium from large volumes of sea water, coprecipitation with ferric hydroxide or bismuth phosphate, are characterized by low and erratic recoveries of tracer plutonium and thus, presumably, environmental plutonium (1-4). However, we have found that plutonium can be consistently recovered from 50- and 200-liter volumes of coastal water in high yields simply by the partial precipitation of magnesium hydroxide and calcium carbonate by the addition of small amounts of sodium hydroxide. Morever, americium, uranium, and polonium can be concentrated likewise from sea water and easily purified for alpha spectrometric determination.
EXPERIMENTAL Exploratory tests demonstrated that large fractions of plutonium, americium, uranium, and polonium were removed from sea water by the partial precipitation of calcium and magnesium on the addition of as little as 2.5 mmol NaOH/liter of sea water (Table I). However, from 3 to 4 mmol NaOH/liter of sea water gave volumes of precipitate that were convenient to transfer from the 50- and 200-liter sea water containers and subsequently re-
v. T. Bowen, K. M . Wong, and v. E. Noshkin. J. Mar. Res.. 29, 1 (1971). (21 T. lmai and M. Sakanoue. J. Oceanographical SOC. Jap., 29, 76 (1973) (3) H. D. Livingston, D. R Mann, and V. T. Bowen. in "Reference Methods for Marine Radioactivity Studies-Determination of Transuranic Elements, Radioruthenium and Other Radionuclides in Marine Environmental Samples," International Atomic Energy Agency, Vienna (1972) in press. (4) K . C . Pillai, ib/d. (1)
1334
sulted in relatively small volumes of 9M HCI, desirable for ion exchange. In general, unfiltered sea water was collected at the end of Scripps Pier, poured into polyethylene containers, and spiked with the appropriate tracers-approximately equal to the suspected environmental activities (see Table 11). However, somewhat larger spikes, 0.5 pCi, were used during the initial recovery tests of plutonium and americium from 1- and 50-liter samples. In subsequent assays of 50 and 200 liters of sea water, 0.05 pCi to 0.10 pCi of plutonium and americium tracers were added. Two to three hours were allowed for the tracer to mix thoroughly into the rapidly stirred solution. Then, 3.5 ml 1N NaOH/liter of sea water were added to 1- and 7-liter volumes, 10.5 ml of 50% NaOH (Mallinckrodt) to 50-liter volumes and 34 ml 50% NaOH to 200-liter volumes. The resulting milky mixture of hydroxides and carbonates was stirred for 1 to 2 hours and the fine precipitate allowed to settle overnight. The clear water was aspirated from above the precipitate leaving only enough for transfer of the precipitate to liter centrifuge tubes (cut off liter poly bottles). After centrifuging for 20 minutes a t 2500 rpm, precipitates from 50 liters of sea water occupied a volume of only about 100 ml (-10 gram dry salt). They are free of the large amounts of iron or bismuth that usually are employed. Isolation of Plutonium and Uranium. Precipitates were dissolved in the liter centrifuge bottles with concentrated hydrochloric acid and transferred to appropriate sized beakers. A volume of 12M hydrochloric acid, three times that of the dissolved material, was added to bring the acid strength to 9M; the final volume was adjusted to about 100 ml for 1-liter samples, 400 ml for 50-liter samples, and 750 ml for 200-liter samples. One drop of 30% H202 was added for each 10 ml of solution, and the solution was then heated just below boiling for 1 hour (5). After the solution had cooled, plutonium and uranium were isolated by the anion exchange techniques described by Talvitie (5) using the fact that plutonium-IV, uranium-VI, iron-111 and many other ions are strongly absorbed from 9M HC1 by Dowex 1-X2 (Bio-Rad AG 1-X2) ( 6 ) , while americium is not. The 9M HC1 effluent was saved for the americium assay. After the sample had drained and the column had been washed with 50 ml 9M HC1, iron ( a distinct yellow band) was eluted with 50 ml of 7.2M "08. Uranium was collected in the next 100 ml of ( 5 ) N. A. Talvitie. Anal. Chern., 43, 1827 (1971). (6) G. H. Coleman, "The Radiochemistry of Plutonium," Nat. Acad. Sci.-Nat. Res. Counc. Pub/.. NAS-NS 3058, 1965, p 92.
A N A L Y T I C A L C H E M I S T R Y , V O L . 46, NO. 9, A U G U S T 1974
Table I. P r e l i m i n a r y T e s t of the Recovery of 2"6Pu,Z43Am, WJ, a n d z a s Pf r~o m One-Liter Volumes of Sea Water Recovery, .-
NaOH, mmol
2.5 3.8 5.0 10.0 20.0
69 70 75 70 65
:t 1 standard error.
a
+
5 3: 5 316 315 rk 4
yoa
Precipitate
X3An,
2 3 2 u
2ospo
Volume, mlb
Dry weight, gC
75 i 3 80 i 4 76 -L 3 85 I 4 84 c 4
64 I 3 6 3 =k 3 69 =t 4 77 i 5 68 & 4
...
0.8 2.0 4.0 9.3 20
0.20 0.28 0.39 0.69 1.25
:36pu
After centrifuging for 15 min a t 2500 rpm.
65 i 4 60 i 4 62 i 4 ...
Dried a t 110 'C.
~~
Table 11. E n v i r o n m e n t a l ?39Pu, sc1Am, * 3 4 , 2 3 5 , 2 3 5 U , and zlOPoin Unfiltered Scripps Pier Sea Water, Collected October 1-December 20, 1973 pCi/l. Nuclide
Volume, 1.
No. of runs
1
10
7 50 50 200 200
12 20 5 4 1
2"Uj 21 O P0
239Pu 2"Am ?:!9pU
Z41Am a
Standard counting errors
