Because of the easy availability t o this laboratory of blood from sheep containing dieldrin in uiuo, a large pooled sample of this blood was obtained. Repetitive analyses of this blood were made. The level of dieldrin was shown to be 0.32 ppm with a standard deviation of 3.0z with two operators (twelve samples were analyzed). Freezing the blood did not affect the recovery of pesticides.
Table 111. Effect of Method of Evaporation on Recovery Efficiency.
z
Block, Nz, Pesticide recovery recovery 70 99 Y-BHC Heptachlor 72 100 70 99 Aldrin o,p’-DDE 70 97 70 95 Dieldrin o,p’-DDD 73 93 o,p’-DDT 78 97 Data cited are from the evaporation of solvent spiked with the same amount of pesticides used in the blood.
SUMMARY
A rapid and accurate method for the analysis of pesticides in blood has been developed. Recoveries have been shown t o be >90% with a relative standard deviation of A 3 Z . Twelve samples can easily be extracted in two and one-half hours. Comparison of this method with other methods indicates this to be a n improvement in accuracy, precision, and time for analysis.
Several other factors have been shown t o be important to the extraction. Decomposition of the pesticides, especially dieldrin, occurred when they were allowed to be in contact with the blood-acid mixture for a n excessive length of time. Three to four hours did not appear t o be critical, but if all three extractions were not completed and the solution was left overnight, recoveries were considerably lower. Recovery data indicated that evaporation using a heating block (Kontes) resulted in erratic loss of pesticides (Table 111). Subsequently, all evaporation has been carried out by blowing a very gentle stream of clean, dry nitrogen over the surface of the solvent at room temperature.
ACKNOWLEDGMENT The authors thank W. B. Buck, G. A. Van Gelder, and J. J. O’Toole for helpful discussions and for providing research samples for this work. RECEIVED for review March 11, 1970. Accepted November 23, 1970. This work was supported in part by the Iowa Community Pesticides Study, Public Health Service Subcontract N o . PH 86-66-NEG-26, William B. Buck, Principal Investigator.
Quantitative Cation Exchange Separation of Zirconium and Hafnium in Formic Acid Media Mohsin Qureshi and Khadim Husain Chemistry Department, Aligarh Muslim Uniaersity, Aligarh, India
SEPARATION OF ZIRCONIUM from hafnium has become very important in recent years because of the increasing use of zirconium metal as construction material in nuclear reactors, where even a slight impurity of hafnium plays a dominant role in retarding the nuclear chain reaction t o a considerable extent. Many workers have reported the separation of these two elements by ion-exchange chromatography using different media-particularly hydrofluoric acid, hydrochloric acid, sulfuric acid and citric acid (1-7). However, n o effort has been made t o separate these elements by ion exchange in formic acid media. The present communication briefly describes the adsorption behavior of these two elements in dilute as well as concentrated formic acid solutions and quantitative separation of zirconium from hafnium in varying ratio. (1) K. Street, Jr., and G. T. Seaborg, J. Amer. Chem. SOC.,70,
4268 (1948). (2) K. A. Kraus and G. E. Moore, ibid., 71, 3263 (1949). (3) E. H. Huffman and R. C . Lilly, ibid., p 4147. (4) B. A. J. Lister, J . Chenz. SOC.,1951, 3123. (5) Joseph T. Benedict, Walter C . Schumb, and C . D. Coryell, J . Amer. Chem. SOC.,16,2036 (1954). (6) F. W. E. Strelow and C . J. C . Bothma, ANAL.CHEM., 39,595 (1967). (7) C . L. Luke, Anal. Cliim. Acta, 41, 453-8 (1968).
Y 3
3.0
Conc.Of Formic Acid ( M ) Figure 1. Log Kd cs. concentration of formic acid (dilute) EXPERIMENTAL Dowex 50 W-X8 (20-50 mesh) in hydrogen form was used for distribution studies and column operations. Cationic solutions of zirconium and hafnium of appropriate concentration were prepared using zirconium oxychloride “pro analysi” grade and hafnium oxide (99.5 supplied ANALYTICAL CHEMISTRY, VOL. 43, NO. 3, M A R C H 1971
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i
4.0 -
ch 22.0
0
2.0 4 0 6 0
15.0
10.0
Conc.Of Foi-rnic Acid
26.0
20.0 (MI
Figure 2. Log Kd cs. concentration of formic acid (concentrated) The columii was then saturated with 1.OM formic acid. The mixture of zirconium and hafnium in 1.OM formic acid was loaded on the column and an elution curve was plotted by collecting several fractions of ef3uer.t and titrating with 0.01M EDTA solution (See Figure 3). Then mixtures containing varying amounts of hafnium were tried. Zirconium was eluted with 1.OM formic acid. About 100-120 ml of the effluent was collected at a flow rate of 5.0 ml/min. and the amount of zirconium was determined. Then the column was washed with water, Hafnium was eluted with 4.OM nitric acid at a flow rate of 1.0 ml/min, and the total effluent collected was 100-150 ml. Excess of nitric acid was removed
by National Bureau of Standards, U.S.A.). Distribution coefficients were determined in dilute as well as concentrated formic acid solution by batch process and the estimation of the cations before and after equilibration was made chelometrically using xylenol orange as indicator after destroying formic acid. The results thus obtained are plotted as log Kd cs. concentration of formic acid (See Figures 1 and 2). For separation of zirconium from hafnium, a column of 0.28-cm internal diameter made of borosilicate glass with a plug of glass wool to support 1.0-gram resin heads was used. After thoroughly washing the column, the resin was washed with 3.OM HCI and, subsequently, with demineralized water.
Wash in9
tOM Formic acid
4.OM
vifh w a t e r c
I 1.00
-E I-
0.80
t-
Nitric a c i d
I
. 0*90
0
1
2
3
4
5
6
7
Number
6 Of
9
10
11
12
13
14
15
16
17
Fraction Of Eluant
Figure 3. Separation of zirconium and hafnium over Dowex 50 W-X8 column in 1.OM formic acid (I) Amount of Zr = 0.5 ml = 1.0 ml0.01M EDTA (11) Amount of Hf = 0.5 ml = 1.32 ml 0.01M EDTA (111) One fraction = 5.0 ml of eluant 448
ANALYTICAL CHEMISTRY, VOL. 43, NO. 3, MARCH 1971
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Table I. Quantitative Separation of Zirconium from Hafnium Amount of Zr and Hf taken in the mixture, mg Hf Zr Hf Zr found, found, error error Zr Hf mg mg 2.34 0.91 2.32 0.91 0.0 +o. 02 4.60 0.0 1.82 -0.04 1.82 4.64 2.32 -0.04 0.00 3.60 3.64 2.32 0.464 $0.02 0.00 0.93 0.91 0.464 0.92 1.81 -0.01 -0.01 1.82 0.93 1.78 1.82 1.39 -0.04 +0.04 1.43 2.70 1.82 1.82 2.78 0.0 +0.02 3.70 1.82 3.75 1.81 -0.05 -0.01 0.26 1.82 0.24 1.83 $0.01 +o. 02 1.81 2.43 -0.01 1.82 2.43 0.00
The plot of log Kd us. Concentration of formic acid given in Figure 1 is very interesting. It appears that hafnium forms a positively charged stable complex with formic acid at concentrations from 0.25-1.75M and, therefore, in these concentrations the Kd values are very high and almost constant. However, in case of Zr it appears that two complexes are formed with formic acid in this range. First a positively charged complex is formed at 0.75M, and there is a n increase in Kd value up to 1.OM. When the concentration of formic acid is increased further, an uncharged complex is formed and, hence, the Kd value falls abruptly. The reactions involved may tentatively be postulated as follows:
+ HCOOH ZrO(HC00)+ + H + ZrO(HC00)+ + HCOOH ZrO(HC00)2 + H + Zr02+
+
+
by evaporation and hafnium content was determined chelometrically. It was ascertained by loading the column with halfnium solution and eluting with formic acid that hafnium was completely retained in the column. The results are given in Table I.
(2)
When the concentration of formic acid is increased further, Hf shows a decrease in the Kd value after 10.OMformic acid. At this concentration, there is probably a formation of uncharged Hf complex-Le., HfO (HC00)2. The bimodal behavior shown by zirconium in 4.OM-20.OM formic acid is probably due to adsorption and not to ion exchange.
DISCUSSION AND RESULTS It is clear from the results that formic acid offers an exceedingly favorable separation factor for the separation of these two elements. We have demonstrated the importance of the method by choosing the less favorable concentration of formic acid-i.e., 1.OM. At this concentration, the separation factor is about 40 and the separation is easily achieved. In more favorable cases, the separation factor is still greater-i.e. > 100 and better separations should be possible.
ACKNOWLEDGMENT The authors are thankful to Dr. S.M.F. Rahman for providing research facilities. RECEIVED for review July 6, 1970. Accepted October 8, 1970. One of us (K. H.) extends his heartfelt gratefulness to C.S.I.R. India, New Delhi, for providing financial assistance.
Plutonium Determination in Soil by Leaching and Ion-Exchange Separation Norton Y. Chu Health and Safety Laboratory, U . S. Atomic Energy Commission, New York, N . Y . 10014
DURING MAY1969 a fire occurred at the Dow Chemical Company’s Rocky Flats, Colo., facility where plutonium components for nuclear weapons are fabricated. After the accident, many soil samples were taken in the immediate and outlying vicinity of the facility to determine the extent of the radioactive contamination. This report describes the methods used at the Health and Safety Laboratory (HASL) to determine the levels of plutonium in 100 gram samples of soil. Over a number of years plutonium analyses (1-8) have been (1) Health and Safety Laboratory Manual of Standard Procedures, J. H. Harley, Ed., U. S. At. Energy Comm. NYO-4700, Rev.
1970. (2) H. Levine and A. Lamanna, Health Phys., 11, 117-125 (1965). (3) P. J. Magno, P. E. Kauffman, and B. Schleien, ibid., 13, 13251330 (1967). (4) E. E. Campbell and W . D. Moss, ibid., 11, 737-742 (1965). (5) K. Wolfsberg, W. R. Daniels, G. P. Ford, and E. T. Hitchcock, Nuel. Appl., 3, 375-377 (1967). 39, 375-377 (1967). (6) M. C. deBortoli, ANAL.CHEM., (7) K. C. Pillai, R. C. Smith, and T. R. Folsom, Nature, 203, 568-571 (1964). (8) E. L. Geiger, Health Phys., 1,405-408 (1959).
performed on different biological and environmental samples for monitoring purposes. These samples include air, food, water, excreta, fused rock, and soil. Several authors have used anion exchange systems to isolate plutonium from complex matrices (9-1 I ) . The ion-exchange separation scheme used here was suggested by the investigations of Kressin and Waterbury (IO). Plutonium has been measured in 1-10 grams of soil and while this is adequate when the plutonium concentrations are sufficiently high, such small sample sizes may prevent plutonium detection when the levels are low. Except for deBortoli (6), the analysis for plutonium has not been made routinely on 100 grams of soil although plutonium and other actinides have been measured on kilograms of fused rock (5). For the analysis of the Colorado soils, it seemed desirable to analyze a minimum 100-gram (9) D. B. James, Los Alamos Scientific Laboratory Rep., TID-4500, January 1967. 34, 1598(10) I. K. Kressin and G. R. Waterbury, ANAL. CHEM., 1601 (1962). (11) R. F. Buchanan, J. P. Farris, K. A. Orlandini, and T. P. Hughes, U.S.At. Energy Rep., TID-7560, 1958, p 179. ANALYTICAL CHEMISTRY, VOL. 43, NO. 3, MARCH 1971
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