added to 30 mg. of cerium, and the elution was made with ammonium lactate made by adjusting 1M lactic acid to p H 2.97. The elution curve is shown in Figure 2. In the course of the work, experiments were made with resins of lower cross linkage to check the possibility of faster separations. In general, under the conditions of our experiments, the results were unsatisfactory. Figure 3 shows a comparison between experiments made with Dowex 50W X12 and
Dowex 50W X8, both 100- to 200-mesh, with pH 3.10 ammonium lactate. Interference of any diverse ions, except phosphate, was not checked because the prior extraction of the cerium into diethylhexyl phosphoric acid had eliminated them all. Phosphate does not interfere. ACKNOWLEDGMENT
LITERATURE CITED
(l).Campbell, M. H., ANAL.CHEM.36, 2065 (1964).
(2bi"(i$;,w.
E.,
J.
Phys.
59*
(3) peppard, D. F., hfason, G , w,, Moline, S. W., J . Inorg. Nucl. Chem. 59 141 (1957). ( 4 ) Stevenson, P. C., Nervik, W. E., Nut. Acad. Sci.-Nat. Res. Council, Nucl. Sci. Ser. NAS-NS-3020, 1961.
for review February 19, 1965. The thank p, C, stevenson RECEIVED Accepted June 9, 1965. This work was and W. E. Nervik for their continued performed under the auspices of the interest and advice. U. S. Atomic Energy Commission.
Determination of Strontium in Environmental Media Using Neutron Activation PAUL J. MAGNO and FORREST E. KNOWLES, JR. U. S. Department of Health, Education, and Welfare, Northeastern Radiological Health laboratory, Winchester, Mass.
b A neutron activation procedure for the determination of strontium in environmental media is described. The method presented simplifies the handling and flux monitoring problems associated with activation analyses. Prior to irradiation, the strontium is separated from the sample by oxalate and nitrate precipitations using the calcium present in the sample as a carrier. Copper is then added to the purified strontium as in internal monitor and the sample is irradiated in a thermal neutron flux of 1012neutrons per square centimeter per second. After irradiation, strontium carrier is added and the strontium further purified by nitrate and chromate precipitations. Copper is separated by dithizone extraction and the strontium is then calculated from the induced activities of strontium-87m and copper-64. Strontium-85 is used to measure the strontium recovery. This method has been applied to the determination of strontium in food, milk, bone, hair, and blood.
S
occurs in low concentrations in foods and in the human body. Considerable interest has been shown in the concentrations of this element in these media because of the presence of its radioisotopes in the environment due to nuclear weapons testing and development of atomic energy programs. Several studies are being carried on a t this laboratory to develop a better understanding of the behavior of strontium in man. Associated with these programs was a need for a method of analysis of trace TRONTIUM
1 1 12
ANALYTICAL CHEMISTRY
quantities of stable strontium in environmental and biological media. Trace quantities of stable strontium in environmental media have been measured by emission spectrometry ( I , I 2 ) , x-ray spectrometry (3, 6, 8 ) , flame photometry (4, 7, f S), absorption spectrometry (IO), and by neutron activation (2, 5 , 9, f I ) . Although neutron activation is a reliable and extremely sensitive method for the analysis of strontium, it has not been routinely applied to the analysis of environmental or biological samples. This has probably been due to the lack of availability of a source of neutrons; but also contributing have been problems associated with handling the large amounts of induced activities produced in these samples and the care required to assure proper flux monitoring. With neutron generators now commercially available and nuclear reactors more readily accessible, neutron activation for the determination of strontium should find wider application. A method is presented which simplifies the handling procedures and flux monitoring problems associated with this technique and allows it to be applied on a routine basis. In previous applications of neutron activation for the determination of strontium in environmental media, direct irradiation of the sample was made so that large quantities of induced activities were produced. Because of the resulting high dose rates, the handling of these samples required considerable care. To avoid this problem, an extension of Harrison's (6) technique of concentrating the strontium in blood and urine prior to irradiation was used. The strontium
was separated by oxalate and nitrate precipitations using the calcium naturally present in the sample as a carrier. Strontium-85 tracer, added to the original sample and measured simultaneously with the induced activity of strontium-87m, was used to measure strontium recoveries during these separations. This pretreatment reduces the induced activity of the irradiated sample such that the radiation level is
