of aluminum, the per cent aluminum is obtained directly. The per cent barium nitrate can be determined either by difference or by titration. Analytical results are listed in Table 11. The procedure which uses two samples is both faster and more accurate than the procedure using a single sample. The results for barium nitrate determined by difference, using single samples are poor because of the cumulative errors inherent in the successive procedures involved. However, by direct titration these results are shoivn to be comparable in accuracy to those obtained for aluminum and potassium perchlorate using this procedure. Analyses of this type yielding accuracies to within =tO.5yG are often sufficient for analytical specifications where speed and simplicity are of primary importance.
I
I
I
KC104 Transition 300’C
I
I
I
I
I
A r e a of Endotherm
I
d
% KC104
Figure 4. Semiquantitative analysis for potassium perchlorate from areas on differential thermograms. Endothermal transition a l 300’ C.
ACKNO WLEDGMENl
The authors are indebted to E. D. Crane, who prepared all the mixtures used in this work. LITERATURE CITED
Asociacion de productores de Yodo de Chile, French Patent 680,116 (Aug. 9, 1929). Carthew, A. R., Am. Mineralogist 40, 107-17 (1955).
Deal, S. B., ANAL. CHEM.27, 109 (1955).
Duval, C., “Inorganic Thermogravimetric Analysis,” Elsevier Publishing Co., Amsterdam, 1953. Glasner, A., Weidenfeld, L., J. Am. Chem. SOC.74, 2467 (1952). Gordon, S., Campbell, C., ANAL. CHEM.27, 1102 (1955).
( 7 ) Zbid., 28, 124 (1956). (8) Gordon, S., Cam bell, C., Fifth
Symposium on d’ombustion (Proceedings), pp. 277-84, Reinhold, New York, 1955. (9) Grim, R. E., Ann. N . Y . Acad. Sci. 53, 1031-3 (1951). (10) Grim, R. E., Machin, J. S., Bradley, W. F., “Amenability of Various
Types of Clay Minerals to Alumina Extraction by the Lime Sinter and Lime Soda Sinter Processes,” Illinois State Geol. Survey, Bull. 69, 41-4, 71-3 (1945). (11) Ishikawa, F., Murooka, T., Hagisawa. H.. Sci. Reds. TGhoku Imv. Univ: First Se;. 22, 1207-28 (1933). (12) Joint A4rmy-?javy Specification, JanA-289 (Jan. 30, 1946), aluminum
powder, flaked, grained, and atomized.
Joint Army-Navy Specification, JanP-217 (May 29, 1945), potassium perchlorate. Morita, Hirokazu, ANAL.CHEM.28, 64 (1956).
Moser, L., Marion, S., Ber. 59B, 1335-44 (1926).
Smoth?;s, W. J., Chiang, Y., Wilson, A,, Bibliography of Differential Thermal Analysis,” Univ. Arkansas Inst. Sci. and Technol. Research Ser. KO. 21 (November 1951).
Speil, S., Berkelhamer, L. H., Pask, J., Davies, B., “Differential Thermal Analyses,” U. S. Bur. Mines, Tech. Paper 664, 5-8 (1945). RECEIVED for review June 15, 1956. Accepted Xovember 2, 1956. First Delaware Valley Regional Meeting, ACS, Philadelphia, Pa., February 16, 1956.
Chromatographic Separation of Fluoride and Phosphate SIR: The determination of fluoride in biological materials requires its separation from interfering ions, chief among which is phosphate. This may be accomplished by the Willard and Winter distillation (9) or by the diffusion technique of Singer and Armstrong (8).
Recent advances in ion exchange and partition chromatography suggest that these procedures may also be feasible for the separation of fluoride and phos310
ANALYTICAL CHEMISTRY
phate, as the relative affinities of these ions for a n anion exchange resin differ greatly. Funasaka, Kawane, and Kojima (5)have reported the separation of fluoride from phosphate (1 to 60), using Amberlite IRA 410 in the hydroxyl form. I n the present studies, as little as 25 y of fluoride have been separated quantitatively from 500 times as much phosphorus on Dowex-1 (OH-), using phosphorus-32 as tracer indicator. I n
addition, fluoride has been separated‘ semiquantitatively from phosphate by a simple paper partition chromatographic technique.
EXPERIMENTAL A N D RESULTS
Ion Exchange Chromatography. Dowex 1-X10, 100-200 mesh, chloride form was cycled three times, using 100 ml. of 3 N sodium hydroxide and
3N hydrochloric acid for each cycle, and then was left in the hydroxyl form. Resin bed dimensions were
containing fluoride. These data are presentedin Figure 1.
tubes mounted on a Packard fraction collector and the volumes were calculated. Two hundred micrograms of fluoride as sodium fluoride in 0.5 ml., 100 y of phosphorus as potassium dihydrogen phosphate in 0.5 ml., and
phate. The same apparatus was used, except that no gradient was employed. Samples mere collected as previously describedthat is, 120 drops per tube a t a flow
20.0 y of phosphate as potassium phosphate in 0.01 ml. Based on six runs, a n Rf value of 0.65 was obtained for fluoride whether chromatographed alone or with phosphate. Under identical conditions, phosphate had an Rf value of 0.34, which was unaffected by the presence of fluoride. Phosphate alone appeared as an immediate yellow spot on a colorless background when sprayed with the ammonium molybdate reagent (4). When fluoride and phosphate were superimposed on the same strip and chromatographed, the zirconiumalizarin spray reagent (4) mas found applicable for both, but the phosphate spot required 1 to 2 hours for full attainment of the yellow color.
00 W
m
CONCLUSIONS
3
+ ‘2.
60
2
40
x
I-
O t-
20
- 20
n
30
40
50
60
70
00
TUBE NO.
Figure 1.
200
y
Twenty-five micrograms of fluoride have been quantitatively eeparated from 12.5 mg. of phosphorus (F/P = 1/500) on Dowex-1 (OH-) using 0.5N sodium hydroxide. Fluoride and phosphate may be easily separated qualitatively by paper partition chromatography on Whatman No. 3MM strips, using a n ammoniacal methanol solvent. Both ions are identified by the zirconium-alizarin spray reagent.
Gradient elution curve for fluoride and phosphate
of F as NaF, 100 y of P as KHzPO,, and 25 pc. of P32placed on column
1.0 nil. of a phosphorus-32 solution (Catalog No. P-32-P-1, Oak Ridge Xational Laboratory, Oak Ridge, Tenn.) containing approximately 25 pc. per ml. were mixed and placed on the column. The gradient elution technique (3) was used to find the minimal concentration of alkali sufficient to separate fluoride quantitatively from phosphate. Gradients were established by introducing a 1 N sodium hydroxide solution from a Mariotte-tube-controlled separatory funnel into a constant-volume mixing chamber containing 250 ml. of water. Mixing was provided by a magnetic stirrer, and the eluting fluid was transferred to the resin bed by a narrow-bore rubber tubing to minimize lag. A11 samples were carefully neutralized to p-nitrophenol end point with hydrochloric acid and made up to 10.0 ml.; and 3.0 ml. or less was taken for direct analysis for fluoride-Le., without distillation-according to the authors’ modification of the IckenBlank procedure (7). Aliquots of 0.1 ml. from each tube were plated in shallow stainless steel planchets and counted, using a conventional endwindow Geiger-Muller tube. When corrected for the blank, 99.3% of the added fluoride mas recovered in tubes 26 to 29. Of the original phosphorus-32 activity 99.5%, corrected for background and decay, was recovered, and none was found in any of the tubes
rate of 8 to 9 drops per minute. A new column mas prepared, and 25 y of fluoride in 0.5 ml. as sodium fluoride, 12.5 mg. of phosphorus in 0.5 ml. as potassium dihydrogen phosphate (F/P = 1/500), and 1.0 ml. of phosphorus-32 as tracer indicator mere mixed, placed on the column, and eluted with 0.5N sodium hydroxide as previously described. Of the fluoride, 99.2%, corrected for the blank, appeared in tubes 7 t o 9 (10.0, 12.3, and 2.5 y, respectively), and the first etidence of radioactivity appeared in tube 29. Hence, 25 y of fluoride have been quantitatively separated from 500 times as much phosphorus present as phosphate. Paper Partition Chromatography. For paper partition chromatography, the ammoniacal methanol solvent of Burrows, Grylls, and Harrison (a) was used (70 volumes of absolute methanol and 30 volumes of 2N ammonium hydroxide). Whatman No. 3MM filter paper strips (Chicago Apparatus Co., Chicago, Ill., Cat. KO. 24503R) prepared according to Armstrong and Carr (1) were used in the simplified milk bottle technique of Gage, Douglass, and Wender (6). Ten micrograms of fluoride as sodium fluoride in 0.01 ml. was separated from
LITERATURE CITED
Armstrong, W. D., Carr, C. JJ7., “Physiological Chemistry,” Burgess Publishing Co., Minneapolis, Xinn., 1951. Burrows, S., Grylls, S. S. X., Harrison, J. s.,Nature 170, 800 (1952). Cherkin, A., Martinez, F. E., Dunn, b4. S., J . Am. Chem. SOC.75, 1244 (1953). (4) Feigl, F., “Qualitative Analysis by Spot Tests,” 3rd ed., Elsevier, New York, 1946. (5) Funasaka, W.,Kamane, &I.,Kojima, T., Mem. Fac. Eng., Kyoto Univ. 18, 44 (1956). Gage, T. G., Douglass, C. D., Kender, S. H., J. Chem. Educ. 27, 159 (1950). Icken, J. ?*I.,Blank, B. hl., ANAL. CHEM.25, 1741 (1953). Singer, L., Armstrong, W. D., Ibid., 26,904 (1954). JJ7illard, H. H., Winter, 0. B., IND. ENG.CHEhI., L h A L . ED.5, 7 (1933). ISADORE ZlPKlN National lnstilute of Dental Research, National lnstitutesof Health, Public Health Service, U. S. Department of Health, Education, and Welfare, Bethesda 14, Md. WALLACE D. ARMSTRONG LEON SINGER Department of Physiological Chemistry, University of Minnesota, Minneapolis 14, Minn.
RECEIVEDfor review August 4, 1956. Accepted November 30,1956. Work done at the University of Minnesota, Minneapolis, Minn. VOL. 2 9 , NO. 2, FEBRUARY 1957
31 1
