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Flgure 1. Optical
Anal. Chem. 1983, 55. 2460-2461
detectable quantity denotes the partial pressure of the gas at which a signal-to-noise ratio of 5 is obtained. To measure smaller partial pressures, a straight nipple section could he added between the body of the cell and the window flange to increase the path length. The long path length design was not tried in this study, but a collimator might he necessary to obtain sufficient light throughput and the effects of the additional path length on dead volume in the flowing system need to he evaluated. In a kinetics experiment, the transmission of the cell is monitored as a function of time and subsequently processed to obtain the reaction rate. Besides the kinetics experiments, the in-line absorption cells were found to he generally useful in monitoring photolysis experiments, passivation of the experimental equipment, and decomposition rate experiments.
monitor conslruction.
of the 253.7- and 365.0-nm lines is much greater than unity, hut after transmission and absorption by the 2-m fiber optic, this ratio is reduced to near unity. For the current analysis situation, the fiber absorption simplified the operation of the optical monitoring cell since the monitoring wavelength could he changed without adjusting the detector gain. However, the fiber absorption limits the maximum cable length that can be used to transmit the 253.7-nm radiation. The performance of the in-line monitor cell is shown in Table I for several gases. The column labeled minimum
Neodymium Fluoride Mounting for and Americium
01
Registry No. UF,, 7783-81-5; F,, 7782-41-4; CIF,, 7790-91-2; PuF,, 13693-06-6.
RECEIVEDfor review February 16,1983. Accepted August 11, 1983. This paper waa prepared in connection with work done under Contract No. DE-AC09-76SR00001 with the US. Department of Energy.
Spectrometric Determination of Uranium, Plutonium,
Forest D. Hindman Radiological and Enuironmental Sciences Laboratory, Department of Energy, 550 Second Street, Idaho Falls, Idaho 83401 This procedure was developed to take the place of electrodeposition ( I ) and is an extension of the Lieberman and Moghissi procedure (2). When applied to 10 g of soil or 500-mL water samples, the nuclides to he determined were separated from the sample matrix by a barium sulfate precipitation technique (3). The nuclides were separated from each other hy solvent extraction (3,4). And then americium was separated from the rare earths by column chromatography (5). T h e pure nuclides were mounted on HT-100 filters by this procedure, omitting the separations descrihed herein. Some samples had to he scoped to get an estimation of the sample size needed for analysis. Others had to be analyzed qualitatively to determine what nuclides were present. Both objectives were achieved with aliquanta of the original sample small enough to keep the total mass of calcium, thorium, uranium, and rare earths below 200 rg. Under these conditions there was no need to make prior separations of the nuclides from the sample matrix, and tracers were not necessary, hut could he used if desired. Unlike electrodeposition or precipitation with cerium hydroxide (61,this method accommodates substantial quantities of common interferences such as iron, aluminum, titanium, and zirconium since they form strong fluoro complexes. In addition, uranium cannot he carried quantitatively on cerium hydroxide. Most problems are with poor resolution, not poor yields, and the samples can he recovered easily for further purification. With experience, visual examination of samples prior to filtration suffices to identify the occasional sample which requires further purification. Usable resolution has heen obtained with 50 g of neodymium plus 50 pg of uranium-236. This
anide not subject 10
U S
Copyright.
The decontamination of one nuclide from another is around lo3 and the yields are 95-98%.
EXPERIMENTAL SECTION Instrumentation. The a spectrometry system has heen described previously (3). Reagents. All solutions were stored in polypropylene bottles. Neodymium Nitrate. A solution containing 0.5 mg/mL of neodymium in 0.2 M nitric acid was prepared from neodymium nitrate. Carbon Suspension. A 47-mm GA-6 Metricel filter (Gelman Instrument Co., Ann Arbor, MI) was fumed in 5 mL of sulfuric acid. The suspension was cooled and diluted to 50 mL with water. Substrate Suspension. Ten milligrams of neodymium as a nitrate solution and 20 mL of hydrochloric acid were diluted to 400 mL with water. Ten milliliters of 48% hydrofluoric acid was added and the solution was diluted ta 500 mL. Then 2-3 mL of carhon suspension was added. Tracer Solutions. The uranium, plutonium, and americium tracer solutionswere purified (7) and standardized (3)as descrihed previously. Procedure. The sample, such as water, a smear, or air dust, was wet ashed with hydrofluoric, nitric, and perchloric acids in a Teflon beaker and transferred to a 250-mL Erlenmeyer flask, The solution was fused in sulfuric acid and enough sodium and potassium sulfate to dissolve the sample in 200 mg each of sodium acid sulfate and potassium acid sulfate melt. The melt was cooled and dissolved with heat in 10 mL of 3 M hydrochloric acid, The solution was held a t the boiling temperature for 5 min and then transferred to a clear, 50-mL, round-hottomed, polycarbonate centrifuge tube (Nalge Co., Rochester, NY) and then 0.1 mL of neodymium nitrate solution and 5 mL of 30 M hydrofluoric acid were added with swirling after each addition. The sample was allowed to stand for 30 min. A 25-mm DM-450, filter was mounted on the stainless steel support in a polysulfone twist-lock funnel
Published 1983 by the American Chemlcal Societ)
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Anal. Chem. 1983, 55,2461-2464
(Gelman Instrument Co., Ann Arbor, MI). The filtering apparatus was attached to a vacuum system. The transfer and rinse of the sample were made with a minimum of 4% hydrofluoric acid wash solution. The uranium filtrate was caught in a 50-mL roundbottomed polycarbonate centriguge tube and saved for the uranium determination. The filter containing the precipitated plutonium, americium, thorium, and curium was placed in a 50-mL glass beaker. c Four milliliters of 12 M perchloric acid and 10 drops of 1% potassium dichromate solution were added to the filter and precipitate containing plutonium, americium, thorium, and curium. The contents were heated until the filter was charred and then treated with (1:l)16 M nitric acid-12 M perchloric acid to completely oxidize the filter paper. The sample was fumed for 15 min. The final volume was 2-3 mL and the solution was dichromate yellow throughout the 15 min. The solution was cooled in a cold water bath, diluted with 10 mL of 1% perchloric acid0.01 % potassium dichromate wash solution, and transferred to a polycarbonate centrifuge tube containing 5 mL of 30 M hydrofluoricacid and 10 drops of 1% potassium dichromate solution. The transfer was made with a minimum of 1% perchloric acid0.01% potassium dichromate wash solution. The sample was allowed to stand for 30 min. A 25-mm, HT-100, filter was mounted as previously described for the 25-mm DM-450. With vacuum applied, 1-2 mL of 8 2 95% ethanol: water was drawn through the filter. As the filter went dry the following solutions were added, in order, to the center of the filter: 5 mL of substrate suspension (6) (after vigorous shaking), the sample (after vigorous swirling), a 2-3 mL 4% hydrofluoric acid4.01% potassium dichromate rinse of the centrifuge tube, and 1-2 mL of the 8:2 95% ethanokwater rinse of the filter. The ethanokwater rinse of the filter was not added to the filtrate containing plutonium. Only the plutonium filtrate and the rinse of the centrifuge tube which followed was caught in a 50-mL polycarbonate centrifuge tube and saved for the determination of plutonium. The filter was dried for 5 min under a heat lamp at a distance of 12-16 in. and sumitted to a spectrometry for the determination of americium. Thorium and curium would be here also if present in the sample. To the uranium filtrate 1drop of 0.1% safranine 0 , l drop of 20% titanium trichloride, and 0.1 mL of neodymium nitrate solution were added, with swirling. To the plutonium filtrate solid stannous chloride was added, with swirling, until the yellow chromium(V1) was completely reduced to green chromium(III), then 0.1 mL of neodymium nitrate solution was added with swirling. The uranium and plutonium filtrates were allowed to stand for 30 min and filtered onto 25-mm HT-100, filters as described for americium. However, the sample solutions were rinsed from the centrifuge tubes with 4% hydrofluoric acid wash solution in
place of the 4% hydrofluoric acid wash solution containing 0.01% potassium dichromate. The filters were dried and submitted to a spectrometry for uranium and plutonium determination.
RESULTS AND DISCUSSION A precipitation of all of the nuclides in the sample had been made by reducing uranium with titanium trichloride before the precipitation with hydrofluoric acid and before the filtration on to an HT-100 filter. After the sample was examined by a spectrometry, the separations of uranium and plutonium from the rest were made when desired. Samples have been mounted for a spectrometry with this procedure in place of electrodeposition routinely for the past 4 years, with excellent results. Furthermore, uranium and plutonium can now be separated, one from the other, after, rather than before the extraction (3). Thus, the extraction time can be decreased by half because only one extraction separation is needed for both nuclides rather than an extraction separation for each. Hundreds of routine bioassay samples have been analyzed this way over the past 4 years with little if any trouble. Future studies will show where the fractions of protactinium, neptunium, and radium actually remain. A more rigorous paper is contemplated to evaluate the remaining unknowns.
ACKNOWLEDGMENT The author wishes to thank K. W. Puphal for useful suggestions in the development of this procedure. The author also thanks R. L. Williams for the many a spectrometry measurements needed to complete this work. Registry No. Neodymium fluoride, 13709-42-7;uranium, 7440-61-1;plutonium, 7440-07-5; americium, 7440-35-9.
LITERATURE CITED (1) Puphai, K. W.; Oisen, D. R. Anal. Chem. 1972, 4 4 , 284-289. (2) Lieberman, R.; Moghissi, A. A. Health Phys. 1968, 75,359-362. (3) Sill, C. W.; Puphal, K. W.; Hindman, F. D. Anal. Chem. 1974, 46, 1725-1737. ~. . (4) Bernabee, R. P.; Percival, D. R.; Hindman, F. D. Anal. Chem. 1980, 52. 2351-2353. . ~_.. , (5) Filer, T. D. Anal. Chem. 1974, 46, 608-610. (6) Stili, C. W.; Williams, R. L. Anal. Chem. 1981, 53, 412-415. (7) Sill, C. W. Anal. Cbem. 1974, 46, 1426-1431.
RECEIVEDfor review July 11,1983. Accepted August 18,1983. Use of commercial product names is for accuracy in technical reporting and does not constitute endorsement of the product by the United States Government.
Comparison of Sample Injection Systems for Flow Injection Analysis Jeffrey J. Harrow and Jiti Janata* Department of Bioengineering, University of Utah, Salt Lake City, Utah 84112 In low-pressure analytical systems such as flow injection analysis, the traditional method of sample injection has been some sort of a commutating valve, either rotary or sliding, actuated manually or mechanically. Such valves are usually the "weakest link in flow injection analysis technology" ( l ) , as they require expensive precision manufacturing and, in our hands and others (2),usually wear and leak. Efforts to improve the method of injection have resulted in several alternative solutions; these have been recently reviewed (3). The commercially available FIAtron SHS-200 system (FIAtron,
Milwaukee, WI) uses four three-way magnetic solenoid valves. The commercially available FIA 5020 (Tecator, Sweden) in its "hydrodynamic mode" uses two precision two-channel peristaltic pumps, which are alternately pumped (I). A British group uses a precision pump for controlled aspiration, followed by subsequent return of the sample aspirating probe to a carrier reservoir (21,calling this method "controlled dispersion analysis". The purpose of this paper is to show a new method for injection that is extremely inexpensive and reliable. Appli-
0003-2700/83/0355-2461$01.50/00 1983 American Chemical Society
