1 0 0 ~ 3 , 5 - D I N I T B O B E N Z C ~ ~OF E OCTADECANCL i
80 [ 60
1
o , , , , , , , , 48
I
40
,
, , , 24
,
32
,
,
,
,
16
,
,
,
, u
8
0
I 60
401
o , , , , , , , , , , 48
Figure 1.
40
32
,
,
,
,
, , , , , , , ,u 8 0
,
24 16 DEGREES, 2 8
X-ray diffraction patterns for 3,5-dinitrobenzoate esters of four typical alcohols
about 1% for a minor component. this procedure n’orks for mixtures of the 3,5-dinitrobenzoate esters, fractional crystallization or preferential reaction becomes a problem when the derivatives are prepared from a mixture of hydroxyl compounds. LITERATURE CITED
(1) A Z a r O f f , L. V., Buerger, M. J., “The
Powder Method,” p. 181, McGraw-Hill, New York, 1958.
(2) Cheronis, N. D., Entrikin, J. B.,
“Semimicro Qualitative Organic Anal-
ysis,” p. 368, Interscience, New York,
1957.
c., Gar&, K. J., yarborough, V. A., Development Department, Union Carbide Chemicals Co., South Charleston, W. Va., unpublished data. (4) Dunbar, R. E,, Ferrin, F. J., Mimechem. J. 3, 65 (1959). (5) McElvain, S. M., ‘‘Characterization of Organic Compounds,” P. 199, Macmillan, New York, 1953. (6) Meigh, D. F., Nature 169, 706 (1952). (3) Dout&t, R.
(7) Rice, R. G., Leller, G. J., Kirchner, J. G., ANAL.CHEM.23, 195 (1951). (8) Robinson, W. T., Jr., Cundiff, R. H., Sensabaugh, A. J., Markunas, P. C., Talanta 3,307 (1959). (9) ROSS, J. H.9 ANAL* CHEM. 25, l288
(1953). (lo) Warren, G. G., Matthew% F. IVY Ibid., 26, 1986 (1954). (11) White, J. W., Jr., Dryden, E* c*, Zbid., 20, 853 (1948). RECEIVED for review September 29, 1960. Accepted November 22, 1960. 3rd Annual Rocky Mountain Spectroscopy Conference, August 1960.
Flame Photometric Determination of Phosphorus in the Presence of Sodium, Potassium, and Other Cations D. N. BERNHART, W. 6. CHESS, and DAVID ROY Research laboratories, Victor Chemical Works, Division of Sfauffer Chemical Co., Chicago Heights, 111.
b Phosphorus content in an aqueous solution can be determined b y its interference on the flame emission of strontium at 660 mp. At this wave length there i s no interference due to sodium, potassium, or many other cations. The same interference holds whether the phosphate i s present as ortho, cyclic, or condensed. However, with lower oxidation states of phosphorus, the interference decreases and requires the use of calibration curves containing the same oxidation state of phosphorus as in the samples to be analyzed. In either case, the samples may merely be dissolved in water and determined in this manner, eliminating the lengthy hydrolysis to orthophosphate. The calibration curve may be set up differentially, using a reference
standard containing phosphorus. Thus, samples may be run very rapidly with a good degree of accuracy.
A
FLAME PHOTOMETRIC DETERMINATION of phosphorus by its inter-
ference of the emission of the calcium flame a t 422 mp was reported by Dippel et al. (2). I n 1955, a year later, Brite (1) reported the flame photometric determination of organic phosphorus compounds by their continuous emission at 540 mp. Although both of these procedures are good, neither will work in the presence of cations such as sodium or potassium. I n 1958, Moore and coworkers (3) reported the flame emission of strontium at 660 mp with little interference from cations, but with a large interference due to phosphates. This
appeared to be the basis of a modification of Dippel’s method which might work in the presence of sodium and potassium. The following experimental work was carried out and resulted in a very rapid control procedure for accurately determining the phosphorus content of sodium and potassium ortho- and polyphosphates. EXPERIMENTAL
The source of strontium was made by dissolving SrClz.6I&O in 0.7N HC1. All of the phosphate solutions were acidified in the same manner to prevent precipitation of strontium phosphate. A Beckman D U spectrophotometer with an oxygen-hydrogen burner was used with the photomultiplier set at full and a ratio of 10 pounds of oxygen to 21/2 pounds of fuel. This ratio gave optimum VOL. 33, NO. 3, MARCH 1961
395
of P occurs at the point, where the maxiTable 1.
Calibration Data on Various Ratios of P 2 0 5to Sr
(1.200 grams of Sr present per liter of solution) Mg./Ml. of P2O5 % ' Emission at 660 MIL
n- . 40 -_ 0.45 0.50 0.55 0.60 0.65
-inn __
78 100 60 80 100 42 58 71 100 27 38 48 68 100 22 33 42 66 96
Table 11. Effect of Various Cations on the Reference Standard
(Ref. std. containing 1.2 mg./ml. Sr and 0.4 mg./ml. PzOsset to read 100% E ) Cation % Ea Na 99.5 K 100 "4 99.0 >I15 Ca 100 bfg AI 110 Fe 68 100 cu B 56 Identical concentrations of Sr and P206 plus 3 mg./ml. of the listed cations. ~~
5
calibration curves. Hydrochloric acid had no effect on the results. Calibration Curves of H3P04 us. SrC12. At concentrations varying
from 0.1 to 1.2 mg. per ml. of Sr in solutions acidic to HCl, a ratio of 1.5 moles of Sr to 1 mole of P obtained a maximum interference of the Sr emission. Table I shows t h a t the greatest change in emission, E, per concentration
mum interference is approached. Therefore, it is possible to obtain linear curves with as much as a 50% spread in emission between 0.5 and 0.6 mg. per ml. of P205in the presence of 1.2 mg. per ml. of Sr. Effect of Cations. The effect of various cations on the method is given in Table 11, which shows t h a t Na, K, "4, Mg, and Cu do not interfere. Ca and A1 tend to remove the phosphate interference. B and Fe increase the interference and could probably be determined by their interference in the absence of P, Ca, and Al.
calibration curve of per cent E us. milligrams per milliliter of PzOs. SAMPLE ANALYSIS.Dissolve a sample that contains 0.500 to 0.600 gram of PZO5in 100 ml. of H20 15 ml. of HC1 (concentrated) and dilute to 250 ml. Transfer a 25-ml. aliquot to a 100-ml. volumetric flask, pipet 5 ml. of SrC12 solution to the flask, dilute to volume, and mix. Read the per cent E us. the 0.50 mg. per ml. of P z O ~standard a t 100% E as in the calibration curve and calculate per cent P2OS.
+
RESULTS
The method gave good results on Effect of Various Phosphorus Comsamples of potassium, ammonium, magpounds. Ortho, pyro, tripoly, trimeta, nesium, and copper phosphates, and the tetrameta, and glassy phosphates had ortho, cyclic, and condensed sodium identical interferences. The interphosphates. On 25 determinations of a ference due to phosphite was decreased greatly, and that due to hypophossample of sodium tripolyphosphate conphite even more. taining 57.5% P205, the standard deviaGeneral Procedures. CALIBRATION tion for single readings was 0.30%. By CURVE. Prepare a stock solution of using a calibration curve made of so72 grams of SrC12 6Hz0 60 ml. of dium tripolyphosphate and taking an HC1 (concentrated) diluted to 1 liter average of three readings, the standard and another stock solution of 2.000 deviation was 0.12%. This latter revigrams of ACS grade disodium phosphate sion should be used where more precise 60 ml. HCl (concentrated) diluted to results are required. 1 liter. To three 100-ml. volumetric flakes pipet 5 ml. of the SrCln solution. Mark one flask 0.50 mg. per ml. of P2Os LITERATURE CITED and to it add 50.0 ml. of the sodium (1) Brite, D. W., ANAL. CHEM. 27, 1815 phosphate solution. Mark another 0.55 (1955'1, mg. per ml. of P20jand add 55.0 ml. of sodium phosphate solution, and likewise add 60.0 ml. to the third flask marked 0.60 mg. per ml. of PzOS. Dilute to vol. Chicago, Ill. ume and mix. With the photomultiplier set a t full and a ratio of 10 pounds of RECEIVED for review July 22, 1960. Acoxygen to 21/2 pounds of fuel, set the cepted October 27, 1960. Accepted for 0.50 mg. per ml. of P205standard to presentation by the Pittsburgh Conference read 100% emission and read the emison Analytical Chemistry and Applied sion of the other two standards. Plot a Spectroscopy, March 2, 1961.
+
+
'
X- Ray Spectrometric Determination of Strontium in Human Serum a n d Bone SAMUEL NATELSON and BERTRUM SHEID Department of Biochemistry, Roosevelf Hospital, New York, N. Y.
b A convenient and accurate technique for the estimation of strontium with the x-ray spectrometer in human serum and bone is described. For bone a Ca-Sr ratio of 1204 and 1231 is found for rib and skull, respectively, in the human. For human serum a Ca-Sr ratio of 390 is obtained. Normal human serum contains 25.6 pg. of Sr per 100 ml. with a standard deviation of h l . 0 2 for six pools. Fifteen sera, both normal and abnormal, taken a t random from the routine clinical laboratory, yielded values ranging from 16.4 to 3 1 .O pg. per 100 ml. An instrument is described for evaporating a strontium 396
0
ANALYTICAL CHEMISTRY
solution onto filter paper to obtain a relatively uniform spot for analysis by x-ray spectrometry.
B
of the current interest in strontium metabolism (1, 6, 14, 15) and in anticipation of a study of the effect of calcium and strontium intake on strontium levels in human serum, the suitability of x-ray spectrometry for this purpose was investigated. Strontium estimation of bone ash by x-ray spectrometry has been reported (2, 10). In this technique a pellet is prepared by compressing bone ash, using collodion as a binder. Because ECAUSE
this technique requires the ashing of excessively large volumes of serum, it is unsatisfactory. For this reason a study of techniques and conditions for estimating minute amounts of strontium was instituted. Strontium assay in the microgram range by x-ray spectrometry presents difficulties peculiar to the element. The K , lines have a relatively high background because they are located on the white light hump and are adjacent to a fourth-order K , line for tungsten. At 50 kv.,the tungsten line is not excited, but an unidentified line occurs a t a slightly higher wave length than for strontium K,. Because the L , !ine of
