LITERATURE CITED
(1) Brandt, W. W., Duswalt, A. A,, ANAL.CHEM.30,1120 (1958). (2) Fischer, R. B., Yates, M. L,, Batts,
M.~ Acta * O , 501 (3) Goddu, R. B., Hume, D. S., ANAL. CHEM.26,1740 (1954). (4) Hulst, H. C. van de, “Light Scatter-
ing by Small Particles,” wiley, sew York, 1957. (5) Jirgensons, B., Makromol. Chem. 6, 30 (1951).
(6) Karrman, K. J., Bladh, E., Gedda, P. O., Mikrochim. Acta 5, 779 (1959). (7) Meehan, E. J., Beattie, W. H., ANAL. CHEM.33,632 (1961). (8) Meehan, E. J., Beattie, w. H., J. Opt. SOC.Am. 49,735 (1959). (9) Meehan, E. J., Beattie, W. H., J. Phys. Chem. 64, 1006 (1960). (10) Meehan, E. J., Beattie, W. H., Ibid., 65,1522(1961)* (11) Meehan, E. J., Hugus, Z. Z.9 J. Opt. SOC.Am. 51, 260 (1961). (12) Nieuwenberg, C. T. van, Bevervoode, B. F. van, Anal. Chim. Acta 19, 32 (1958).
(13) Pangonis, W. J., Heller, W., Jacobson, A., “Tables of Light Scattering Functions for Spherical Particles,”
Wayne State Univ. Press, Detroit,
1957. (14) Penndorf, R. B., J . Opt. SOC.Am. 47, 1010 (1957). (15) Ringbom, A., Z . Anal. Chem. 122, 263 (1941).
RECEIVEDfor review June 17, 1963. Accepted November 15, 1963. Taken from the Ph. D. thesis of Grace Chiu, January 1962, University of Minnesota.
Flame Photometric Determination of Stable Strontium in Environmental Media LAWRENCE A. ELFERS, PAUL F. HALLBACH, and RICHARD J. VELTEN Robert A. Taft Sanitary Engineering Center, U . S. Department of Health, Education, and Welfare, Cincinnati 26, Ohio
b An analytical procedure for the determinarion of strontium in environmental media by flame photometry at 461 mp is described. Strontium and other alkaline earths ore separated from interfering ions such as phosphate by oxalate and nitrate precipitations. Calcium is removed by ion exchange chromatography after preferential chelation with Versene at pH 5.0. Monovalent ions are washed from the ion exchange resin with 0.5N HCI prior to eluting strontium and barium with 3N HCI. Strontium-85 tracer is used to monitor strontium losses during purification. As liitle as 0.05 mg. of strontium may be measured with 5% error. Strontium has been determined in food, water, excreta, and bone by this method.
C
interest has been directed toward the radionuclides of strontium. These are present in the environment from fallout, waste disposal operations, and the beneficial use of radioactive materials. Associated with this interest is a need for an accurate method for the determination of stable strontium in a wide variety of environmental media. For the measurement of trace quantities of strontium, instrumental methods involving the use of emission spectrometry ( I ) , flame photometry ( l a ) , absorptiometry (9), x-ray spectrometry (8), and neutron activation (7) have been reported. Because of its relatively low cost, the flame photometric technique is desirable. However, the accurate flame photometric determination of trace quantities of strontium in environmental media is complicated by the presence of calcium (Sr :Ca ratios are generally between
540
ONSIDERABLE
ANALYTICAL CHEMISTRY
1 : l O O and 1:3000) and other interferences. A number of methods have overcome these interferences by addition of foreign or similar ions to standards (3, 11) or by use of the radiation buffer technique ( I O ) . h technique (IS) for separating calcium from strontium by ion exchange chromatography through preferential chelation with EDTA at p H 5.0 and for determining strontium flame photometrically was unsuccessful in the analysis of feces-diaper ash, in that low recoveries of strontium were obtained. These flame photometric methods have been devised for application to specific samples, and when they are applied to a wide variety of environmental media, difficulties are encountered in obtaining accurate values. To circumvent this difficulty, strontium is separated in this procedure from calcium and other interferences prior to the flame measurement. Samples of mixed food ash and of beef bone ash were analyzed by several
Table
Laboratory A
A B
C D E F F
G H
SEC
I.
laboratories by various methods. The comparative data summarized in Table I are sufficiently conflicting to indicate the need for a reliable method. In the method described herein, interfering anions and cations are separated from alkaline earths by oxalate and nitrate precipitations. Calcium is removed from strontium by ion exchange chromatography (4), and stable strontium is then determined flame photometrically in the absence of major interferences. Since the analytical separations employed are semiquantitative, strontium-85 tracer is used to correct radiometrically for stable strontium losses. EXPERIMENTAL
Apparatus. A line-operated Beckman Model DU spectrophotometer, equipped with flame attachments, spectral energy recording attachment, and Sargent SR recorder, was used.
Comparative Strontium Analyses
Strontium, p.p.m. Mixed food ash Beef bone ash 9 2 b 2 45 109 71 ‘2 P 80 108 98 63 * 70 104 i sc
Range of two determinations. Single value re orted. 1 u deviation o f 19 determinations.
208 =!= lon 221 2 ’ 7 ” 220 f 10” 1 3 4 * f 13c 165 190b 180* 145 * 130* 236 f 14c
Method Emission spectrometry Flame photometric Flame photometric Neutron activation Neutron activation Flame photometric Arc-quantometer Flame hotometric X-ray luorescence X-ray fluorescence Flame photometric tracer
+
I n place of the nongraduated 100% adjust knob, a ten-tuim helipot graduated from 0 to 1000 was installed. Instrument settings were: Fuel-hydrogen Photomultiplier Selector switch 1 0 0 ~ adjust o Phototube Gas-oxygen Zero suppression Wavelength Phototube load resistor Slit width
Table II. Analyses of SrClz Standards for Strontium Strontium concn., mg./l. 2 .oo 6.00 FI- on _. 13.0 17.0
5 p.s.i.
Full 0.1 0.0
Blue (RCA 1P28) 10 p.s.i. 1 461 mp 2 0.01 mm.
The 0.01-mm. slit width was the narrowest that yielded reproducible results. A specially desigied fume hood was mounted over the 3urner housing to remove all of the aspirated gases. The concentration of the strontium-85 in the solution aspirated is approximately 5000 picocuries per ml. and can be expelled t o the a t r osphere without creating a radiation hrizard. For measuring the strontium-85, a single-channel diffei entia1 analyzer equipped with linear amplifier, decade scaler, precision power supply, and shielded 2-inch NaI crystal was used. The single channel was operated to count the 0.51-L1.e.~. -pray of the tracer. Beds of 50- to LOO-mesh Dowex 50-X8(Na+) resin were DreDared in borosilicate glass columns (i5-cm. length with 2 sq. cm. area cross section). Rubber stoppers fitted to the base of the columns were ccvered with glass wool to hold the rwin beds. Glass tubing inch in diameter was inserted into the rubber stoppers and curved so that the outlet was above the level of the resin. Separatory funnels (300-ml.) were attached to the column with rubber stoppers and used as reservoirs for feed and wash solutions. It was expedient to use small amounts of resin (20-ml. wet volume) to minimize elutriant solution volumes. The resin was washed with 250 ml. of 3N HCl, rinsed with 200 ml. of HzO, converted to the sodium form with 150 ml. of 2N NaC1, and finally buffered with 150 ml. of 4%
