Table I. Average Transmittance of Boric Acid Standards Samples containing Boron, pg Tissue-free samples animal tissue 0.00 100 100 1.OO 85.4 f 3.5 86.0 f 5.6 2.00 70.3 f 4.7 75.9 f 3.4 3.00 58.1 i 4.3 65.4 f 2.0 4.00 50.0 f 3.8 56.2 f 0.8 ~
~~
RESULTS AND DISCUSSION When the results of 20 standard experimental runs are plotted as boron content us. the log of transmittance, a nice straight line results. The transmittance readings and per cent deviations are tabulated in Table I. It is obvious that even a t the higher temperature of this procedure, very little boron escapes by volatilization or spattering, otherwise the points would not have fallen on a straight line nor would they have deviations comparable to those reported in the regular method (4). The boron content of the tissue is determined from the standard curve and the transmittance of the unknown sample. Tissues containing less than 1p g or more than 5 pg of boron, are subject to great inaccuracy by this method. Also, more than 500 mg of tissue cannot be handled satisfactorily, since solution and decolorization of the tissue take a n inordinately long time, requiring large amounts of hydrogen peroxide. Standards treated in this manner d o not give as linear or reproducible plots. Provided not more than 500 mg of tissue
are used, there does not appear t o be a need for using a comparable amount of tissue in the standard series as in the unknown samples since standard series without tissue are comparable in all respects to those with tissue. This is shown in Table I where standard samples containing tissue are compared with normal tissue-free standards. Water from the small amounts of tissue yields a small upward displacement in the plot of boron concentration us. the log of transmission. The displacement is the same for brain, muscle, and blood, and is primarily dependent on the weight of tissue. Boron concentrations in representative mouse and human tissues, following intravenous injection of a polyhedral borane derivative, were determined by the regular ( 4 ) and rapid methods, and the results are given below in micrograms of boron per gram of tissue. Rat muscle yielded 14.4 and 14.4, respectively. Human brain yielded 0.73 and 1.04, while human blood yielded 2.76 and 2.70, respectively. The technique lends itself to routine use. ACKNOWLEDGMENT The authors thank Dr. William H. Sweet, Chief of the Neurosurgical Service of the Massachusetts General Hospital, for his interest and encouragement.
RECEIVED for review August 6, 1970. Accepted October 22, 1970. Work supported by grants from the Atomic Energy Commission (NO. AT-(30-1)-3267) and the National Institutes of Health (NO. CA-07368) to the Massachusetts General Hospital.
Separation of Gallium from Group 111 Elements, Germanium, Copper, Arsenic, and Iron R. Rafaeloff Soreq Nuclear Research Centre, Yavne, Israel THEEXTRACTION OF GALLIUM, with different organic solvents has been reviewed by Sheka et al. ( I ) . The solvents studied included ethers (2, 3), ketones (4-6), esters (7, 8), higher alcohols (9), primary, secondary, and tertiary amines (10). In most cases, it was assumed that the extracted species was tetrachlorogallic acid, and that an ion-pair was formed in the (1) I. A. Sheka, I. S . Cham, and T. T . Mityureva, “The Chemistry
of Gallium,’’ Elsevier, Amsterdam, 1966. (2) E. H. Swift, J . Amer. Chem. Soc., 46, 2375 (1924). (3) W. Fisher and S. Lauter, German Patent 801,986 (1951). (4) G. W. C. Milner, A. J. Wood, and J. L. Woodhead, Analyst (London), 79, 272 (1954). (5) S . S. Korovin, A. P. Mironenko, A. P. Reznik, and L. N. Konissarova, I m . Vyssh. Ucheb. Zaoed., Khim. Khim. Tekhnol., 5 , 533 (1962). (6) M. Zangen and R. Rafaeloff, J . Inorg. Nucl. Chem., 32, 2753 (1970). (7) P. A. Akishin, V. A. Naumov, and V. M. Tatevskii, Nauch. Dokl. Vyssh. Shk., Khim. Khim. Tekhnol., 2, 229 (1959). (8) S. S. Korovin, R . V. Ivanova, 0. V. Saakova, and K. A. Bol’shakov, Zh. Prikl. Khim., (Leningrad), 34, 1007 (1961). (9) V. I. Kuznetsov, Zh. Obshch. Khim.,17, 175 (1947). (10) B. N. Laskorin and V. I. Yuzhin, Tseaet. Metal., 34 (ll), 44 (1961). 272
0
process, the hydrogen ion being solvated by the organic oxygen or nitrogen (11). Recently Finston et al. reported the synergic extraction of gallium with thenoyltrifluoroacetone and tetraphenylarsonium chloride (12) and the extraction of gallium with tetraphenylarsonium chloride (13). In the first (12) case, an anionic species [Ga(T)2(0Ac)(C1)1- was formed, which combines with one mole of tetraphenylarsonium cation to form a neutral ion association complex which is extractable in the organic solvent. In the second (13) case, the extractable species is GaCI4- (CsH&As+. These extractive reactions are not specific, however, as several other elements are also extractable under these conditions (1). The aim of the present work was to carry out a systematic study of the quantitative and selective separation of gallium (111) from: Al, In, TI(III), Sc, Y , La, Eu(III), Tm, Dy, Ge(IV), ~~
~
(11) A. Yu. Zolotov, I. V. Seryakova, A. V. Karyakin, L. A. Gribov, and M. E. Zubrilina, Dokl. Acad. Nauk SSSR, 145, 100 (1962). (12) M. S. Rahaman and H. L. Finston, ANAL.CHEM., 40, 1709 (1968). (13) H. L. Finston and M. S . Rahaman, Microchim. Acta (Wien) 78 (1969).
ANALYTICAL CHEMISTRY, VOL. 43, NO. 2, FEBRUARY 1971
1.0
t-i
-9
-
/-t 0
-I
I
2 3 H2S04 M
0
4
I
2 HCL M
3
4
Figure 2. Per cent gallium extracted with methyl ethyl ketone in the presence of ammonium chloride as a function of hydrochloric acid concentration at a constant ionic strength of 5
Figure 1. Per cent gallium extracted with methyl ethyl ketone in the presence of ammonium sulfate as a function of sulfuric acid concentration at a constant ionic strength of 5 Cu(II), As(III), and Fe(II1). Gallium has been extracted from acidic aqueous chloride-sulfate solutions by methyl ethyl ketone. The extractability of the various elements was checked by labelling the solution with the appropriate radioactive element and counting the aqueous and organic phases before and after extraction. EXPERIMENTAL
l 99
o
0
l
- L
8
98
F
971
+ X
a
Reagent. Gallium solutions were prepared by dissolving weighed quantities of A.R. gallium metal in a minimum amount of nitric acid, then addition of concentrated sulfuric acid, evaporation to dryness which completely removes the nitric acid, and dissolution of the residue in triply distilled water. Stock solutions of the other reagents were prepared, using chemicals, of Analar grade, and the desired concentrations were obtained by dilution with triply distilled water. The radioisotopes used for labelling were prepared by irradiation at the IRR-I reactor at Soreq either in the pneumatic tube system at a flux of 5.101*n,cm-* or inside the reactor core at a flux up to 2.1013n.cm-2sec-1. The following isotopes were used: *8A1, l141n, 20*Tl,46Sc, '"La, 1 5 2 E ~170Tr1-1, , lS9Dy,77Ge, 64Cu,76As, and 59Fe. Procedure. The organic phase consisted of methyl ethyl ketone. The aqueous phase consisted of mixtures of hydrochloric acid, ammonium chloride, sulfuric acid, and ammonium sulfate in different ratios, maintaining constant total ionic strength of 5. The aqueous and organic phases were equilibrated for 2 minutes after preliminary experiments had shown this to be sufficient. The extractions were carried out in 50-1111 separatory funnels, the phases (10 mi each) were hand-mixed for 2-3 minutes. When the phases had separated, 2 ml of each phase was withdrawn and the gallium content was determined by counting. In some cases the gallium content was determined by activation analysis (14). The per cent gallium extracted was calculated from the concentration of gallium before and after extraction. Gallium-72 was measured using a NaI crystal in conjunction with a multichannel analyzer. The amount of the foreign element extracted was also determined by counting the labelled solution before and after extraction, and sometimes by standard analytical methods. (14) R. Rafaeloff and E. Yellin, Isr. J . Chem., 7, 173 (1969).
0.5
1.5
1.0
2.0
HCL M
Figure 3. Per cent gallium extracted with methyl ethyl ketone as a function of hydrochloric acid concentration in the presence of sulfuric acid and ammonium sulfate at a constant ionic strength of 5, obtained by addition of ammonium chloride 0 0.5M HzSOaand 0.5M ("&SO1 0 1M H S O , and 1M ("$304
RESULTS AND DISCUSSION Effect of Acidity. The extraction and separation of Ga(II1) from the different elements was investigated at varying relative concentrations of hydrochloric and sulfuric acid at constant ionic strength of 5, which was maintained by adding ammonium chloride in the case of hydrochloric acid, and ammonium sulfate in the case of sulfuric acid. Figure 1 shows that the gallium extracted from sulfuric acid was less than 1%. This very low extraction has been attributed to the considerable hydration of the sulfate ion (1). Figure 2 shows the extraction of gallium from varying concentrations of hydrochloric acid. In this case, a maximum gallium extraction of 92.1% was found. Figure 3 and Table I show the extraction of gallium from mixtures of hydrochloric acid,
ANALYTICAL CHEMISTRY, VOL. 43, NO. 2, FEBRUARY 1971
273
Table I. Extraction of Gallium from Aqueous Chloride Sulfate Solutions HCl, M
NHaC1, M
0.5 1 .o 1.25 1.5 1.75 2.0 0.5 1.o 1.25 1.5 1.75 2.0
3.5 3.0 2.75 2.5 2.25 2.0 2.5 2.0 1.75 1.5 1.25 1.0
Ga (NH4)*SOc, extracted, HtSO4, M M % 0.5 0.5 0.5 0.5 0.5 0.5 1.o 1 .o 1 .o 1.o 1.o 1.o
0.5 0.5 0.5 0.5 0.5 0.5 1 .o 1.0 1 .o 1 .o 1.o 1.0
84.3 93.7 96.9 97.3 97.7 98.0 99.4 99.7 99.7 99.8 99.9 99.9
Table 11. Per Cent Foreign Elements Coextracted with Gallium Per cent foreign Foreign element element extracted A1 In
Tl(II1) sc Y
La Eu(II1)
Tm DY
Ge(1V) Cu(I1) As(II1) Fe(II1)
0.04 93.6 88.9 0.01 0.002 0.004 0.002 0.02 0.02 0.08 0.1 36.0 0.03
ammonium chloride, sulfuric acid, and ammonium sulfate at different concentrations, but at a constant total ionic strength of 5. The optimum conditions of extraction were found to be a solution containing 2MHC1, 1MNH4Cl,lMHzS04, and 1M (NH4)2S04. In this case 99.9% of the gallium was extracted in the organic phase and exhibited no inhibition due to the presence of foreign elements. Effect of Foreign Elements. The extractions were performed under optimum conditions, Le., solution was 2 M HCl, 1M NH4C1, 1M HzSO4 and 1 M (NH4)zS04,to determine the
274
interferences from Al, In, Tl(III), Sc, Y,La, Eu(III), Tm, Dy, Ge(IV), Cu(II), As(II1) and Fe(III), usually associated with gallium (I). It was found (Table 11) that only In (93.6%), As (36.0%), and T1 (88.9%) were markedly coextracted with gallium. The amount of copper coextracted was about 0.1 % and less than 0.01 % of all other elements was coextracted. Effect of Metal Ion Concentration. The concentration of gallium was varied from 1 pg/ml to 10 mg/ml in order to study the effect of concentration. It was found that under the optimum conditions, the degree of extraction and separation is independent of gallium concentration. Back Extraction of Gallium from the Organic Phase. The gallium can be stripped from the organic phase by washing with small quantities of water; under most conditions tested, two washings were sufficient to reextract at least 99% of the gallium. Large Scale Extraction and Separation of Gallium from Foreign Elements. The proposed method for extraction and separation of gallium from the above tested metal impurities was confirmed in a large scale extraction, using solution volumes of up to 3 liters. The extractions each with 200 ml of methyl ethyl ketone extracted more than 97% of the gallium present. More than 98% of gallium in the organic phase was reextracted by washing the organic phase twice with water (50 ml each). APPLICATION The proposed method of extraction and separation of gallium can be used for quantitative extraction and separation of gallium on a small laboratory scale. Since there is only one patent ( I , 15) which proposes the direct extraction of gallium from its ores by chlorination it seems that this method may have some industrial application for the separation of gallium from its ores. ACKNOWLEDGMENT Thanks are due to Mr. Y . Weiss for technical assistance.
RECEIVED for review March 13, 1970. Accepted August 21, 1970.
(15) E. Papp and K. Solymar, Acta Chim. Acad. Sei. Hung,, 24, 451 (1960).
ANALYTICAL CHEMISTRY, VOL. 43, NO. 2, FEBRUARY 1971
