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Ion exchange separation of carrier-free 140Ba and 140La from their equilibrium mixture using nitrilotriacetic acid and ascorbic acid as eluents
I”,. J A,,,,,. ~oJur. lsor Prmted tn Great Bntam
OO20-708X/82/030171-03$03.00/0 CopyrIght 0 1982 Pergamon Press Lfd
Vol. 33. pp 171 to 173. 1982 All rights reserved
Ion Exchange Separation of Carrier-free 14’Ba and 14’La from their Equilibrium Mixture using Nitrilotriacetic Acid and Ascorbic Acid as Eluents N. R. DAS and S. .N. BHATTACHARYYA Nuclear Chemistry Division, Saha Institute of Nuclear Physics, 92, Acharya Prafulla Chandra Road, Calcutta-700 009, India (Received 6 June 1981; in revisedform 31 July 1981) A simple cation exchange procedure for separation of ““‘Ba-i4”La using Dowex 5OW-X8 and nitrilotriacetic acid or ascorbic acid as the eluent has been described. The optimal separation of the daughter from the parent has been achieved using a 4% Na-nitrilotriacetate or Na-ascorbate solution at pH 7. The parent, i40Ba, left in the column can be eluted with dilute hydrochloric acid or it can be retained in the column for milking off the daughter, i40La , when needed. The radiochemical purity of the separated isotopes, r40Ba and 14’La, were verified by y-ray spectrometry.
Introduction ION EXCHANGE chromatography, because of its simplicity and rapidity, has efficiently been employed by various workerst1-5i for the separation of the motherdaughter pair, 140Ba- i4’La, in an equilibrium mixture. Recently, the potentiality of eluting reagents like nitrilotriacetic acid and ascorbic acid for use in the separation of rare earths (6*7)has been examined in our laboratory. Investigations were made whether such simple reagents could be effectively used for the separation of the pair, 140Ba-‘40La, in the carrier-free state as well as for quick milking of the daughter, 14’La, from the parent, 14*Ba.
Experimental Reagents
All reagents used were of analytical grade. The cation exchanger, Dowex SOW-X8 (2&50 mesh, H+form) was converted to Na+-form, prior to use, by passing 1 M sodium chloride solution through the column containing the resin. The column was later washed with water to remove excess Na-salt. The glass column has a resin bed of 100 mm in length and 5mm in diameter supported on a glass wool plug at the bottom. Sodium salt of nitrilotriacetic acid and ascorbic acid of desired concentrations, e.g. 1, 2, 3, 4 and 5% at pHs 7 and 10 were prepared by adding requisite amounts of dilute sodium hydroxide solution to the freshly prepared reagent solutions.
Radioactive solution of ‘40Ba-‘40La in equilibrium supplied by BARC, Trombay, in hydrochloric acid medium was diluted as required. Procedure
After proper conditioning of the resin column, a few drops of the equilibrium mixture of i40Ba-‘“OLa in hydrochloric acid medium (- 2 N) was transferred to the top of the column, which was later washed with water to remove the acid. Elution of i4’La was carried out by slowly percolating Na-nitrilotriacetate or Na-ascorbate solutions of specific concentrations through the column. Drops of effluents at a flow rate of 10 drops per min were collected successively at different intervals during the course of elution. The activity in each effluent fraction was measured with an end-window G.M. counter. After complete elution of the daughter, “‘La, the column was washed with water and the parent tracer, i4’Ba, retained in the column was later eluted with dilute hydrochloric acid (-2N).
Results and Discussion Elution of 14’La by Na-nitrilotriacetate
The difference in the relative stabilities of the metal complexes formed by an eluent with the metal ions adsorbed on a column determines, in general, their degree of separation in any ion exchange separation method.@’ Thus nitrilotriacetic acid has been found to be very effective in the separation of 171
N. R. Das and S. N. Bhattacharyya
172
300
200’
,” ._
L
.? : 1001
,
100
1
I
I
I
200
300
400
500
Drop
I
I 700
600
(8)
number
FIG. 1. Elution of ““La from an equilibrium mixture of “‘“Ba-‘40La with 43; Na-nitrilotriacetate solution at pH 7 from a column of Dowex 5OW-X8 resin in Na’-form.
14’La from 14’Ba because the reagent is known to form a with lanthanum, compoundrgP’ r) CWNCH2C00hIJ3, whose stability constant in neutral or alkali medium(r2’ is much larger than the corresponding compound with barium.(r3) For separation of r40La from r4’Ba, the tracers were initially adsorbed on the column and the elution of 14’La from the column was later carried out with Na-nitrilotriacetate solutions in varying concentrations at pHs 7 and 10. Of these, 4% Na-nitrilotriacetate solution at pH 7, as shown in Fig. 1, was found
3000
-
(0)
,” ._ > ._
2000
-
: 1000
-
A
0
200
300 Drop
400
500
600
I 70C
number
FIG. 2. Elution of ‘-“‘La from an equilibrium mixture of ‘40Ba-‘40La with 4% Na-ascorbate solution at pH 7 from a column of Dowex 5OW-X8 resin in Na’-form.
FIG. 3. Gamma spectra of an equilibrium mixture of 140Ba-140La (A), the fractions eluted separately by Nanitrilotriacetate (B) and Na-ascorbate (C) and the fraction eluted by HCI (D) after separation of 14’La by Na-ascorbate.
Ion exchange separation of “‘Ba to
be most suitable for the elution of the daughter isotope, 140La, completely free of 14’Ba. With Nanitrilotriacetate solutions of lower concentrations, longer tailing of the elution curve occurs and for solution of higher concentrations either at pH 7 or at 10, possibility of contamination due to partial elution of 140Ba increases. Elution of
’ 40La with Na-ascorbate
Similarly, ascorbic acid, which forms an anionic complex with lanthanides,‘15) although comparatively weaker than the nitrilotriacetic acid complexes, does not form any complex with alkaline earth elements at pH 7, which in fact, provides the clue to its effective utilisation in separation of lanthanum from barium. However, very little is known about the relevant properties of the complexes of ascorbic acid with either rare earths or alkaline earth elements. Figure 2 shows that in case of elution with ascorbic acid, isolation of 14’La, completely free from ‘“‘Ba, can be achieved when a 3-5% Na-ascorbate solution at pH 7 is used as the eluent. Eluent solutions at other concentrations under the experimental conditions were not, however, found to be so effective. The radiochemical purity of 14’La separated by either nitrilotriacetic acid or ascorbic acid was, in fact, further verified by y-ray spectrometry and half-life determination. Figure 3 shows the y-ray spectra of the fractions eluted by means of Na-nitrilotriacetate (curve B) and Na-ascorbate (curve C) where the photopeaks due to 14’La are only evident whereas the mixture contains photopeaks due to both 14’La and 14’Ba in equilibrium (curve A). The half-life of the radioactive product in the eluted fractions of each of the eluents was found to be about 40 h which agrees well with that of 14’La as reported in the literature.““) Of the two eluents, nitrilotriacetic acid and ascorbic acid, described here, the latter appears to be more effective than the former, because the separation peak, as is evident from Figs 1 and 2, is sharp and tailing is less in case of ascorbic acid (Fig. 2) than that in case of nitrilotiracetic acid (Fig. 1). This increased eficiency of ascorbic acid in affecting a clean separation of 140La from 14’Ba is probably due to the fact that ascorbic acid, unlike nitrilotriacetic acid does not form any complex with barium.‘15)
173
and “‘La
The parent isotope, 14’Ba, left behind in the column after separation of the daughter, 140La, was also quantitatively extracted with -2 N HCl, the radiochemical purity of which was again ascertained by y-ray spectrometry (Fig. 3, curve D). 14’Ba may be eluted in this way from the column or it may be left over so that a radioactive equilibrium with the daughter is attained after its /Idecay, and this may later be used for milking off the daughter when desired. The reagents used in the method are cheap and moreover the method is simple, quick, effective and reproducible. The simplicity of this separation procedure using either nitrilotriacetic acid or ascorbic acid as the eluent for obtaining lanthanum of high radiochemical purity makes the method potentially useful for the construction of a generator system yielding the nuclide mentioned in high quality.
References 1. MARCUS Y. and NELSON
F. J. Phys. Chem. 63, 77 (1959). 2. FARABEEL. B. Report ORNL-192, p. 12 (1955). 3. FRITZ J. S. and GARRARLDA B. B. Talanta 10, 91 (1963). N. D., MARTYNENKOL. I. and PEROVAI. 4. MITROFANOVA N. Russ. J. Phys. Chem. (Eng. Trans.) 47, 187 (1973). 5. DUYCKAERTSG. and LEJEUNER. J. Chromatogr. 3, 58 (1960). 6. DAS N. R. and BHATTACHARYYAS. N. Int. J. Appl. Radiat. Isor. 28, 731 (1977). 7. DAS N. R. and BHATTACHARYYAS. N. Int. J. Appl. Radiat. Isot. 31, 575 (1980). 8. POWELLJ. E. and SPEDDINGF. H. Trans. AIME 215. ~I 457 (1959). 9. BECK G. and GAFFERA. Anal. Chim. Acta 3, 41 (1949). 10. FITCH F. T. and RUSSEL D. S. Can. J. Chem. 29, 363 (1951). 11. VICKERYR. C. J. Chem. Sot. 245 (1955). 12. IRVING H. M. N. H. and MILES M. G. J. Chem. Sot. (A), 727 (1966). 13. NODDAK W. and OERTEL G. Z. Electrochem. 61, 1216 (1957). 14. CROUTHAMELC. E., ADAMS F. and DAMS R. Applied Gamma-ray Spectromecry. (Pergamon Press, Oxford, 1960). 15. CHAKRABORTYM. and KHOPKAR S. M. Chromatographia 10, 100 (1977).
OO20-708X/82/030171-03$03.00/0 CopyrIght 0 1982 Pergamon Press Lfd
Vol. 33. pp 171 to 173. 1982 All rights reserved
Ion Exchange Separation of Carrier-free 14’Ba and 14’La from their Equilibrium Mixture using Nitrilotriacetic Acid and Ascorbic Acid as Eluents N. R. DAS and S. .N. BHATTACHARYYA Nuclear Chemistry Division, Saha Institute of Nuclear Physics, 92, Acharya Prafulla Chandra Road, Calcutta-700 009, India (Received 6 June 1981; in revisedform 31 July 1981) A simple cation exchange procedure for separation of ““‘Ba-i4”La using Dowex 5OW-X8 and nitrilotriacetic acid or ascorbic acid as the eluent has been described. The optimal separation of the daughter from the parent has been achieved using a 4% Na-nitrilotriacetate or Na-ascorbate solution at pH 7. The parent, i40Ba, left in the column can be eluted with dilute hydrochloric acid or it can be retained in the column for milking off the daughter, i40La , when needed. The radiochemical purity of the separated isotopes, r40Ba and 14’La, were verified by y-ray spectrometry.
Introduction ION EXCHANGE chromatography, because of its simplicity and rapidity, has efficiently been employed by various workerst1-5i for the separation of the motherdaughter pair, 140Ba- i4’La, in an equilibrium mixture. Recently, the potentiality of eluting reagents like nitrilotriacetic acid and ascorbic acid for use in the separation of rare earths (6*7)has been examined in our laboratory. Investigations were made whether such simple reagents could be effectively used for the separation of the pair, 140Ba-‘40La, in the carrier-free state as well as for quick milking of the daughter, 14’La, from the parent, 14*Ba.
Experimental Reagents
All reagents used were of analytical grade. The cation exchanger, Dowex SOW-X8 (2&50 mesh, H+form) was converted to Na+-form, prior to use, by passing 1 M sodium chloride solution through the column containing the resin. The column was later washed with water to remove excess Na-salt. The glass column has a resin bed of 100 mm in length and 5mm in diameter supported on a glass wool plug at the bottom. Sodium salt of nitrilotriacetic acid and ascorbic acid of desired concentrations, e.g. 1, 2, 3, 4 and 5% at pHs 7 and 10 were prepared by adding requisite amounts of dilute sodium hydroxide solution to the freshly prepared reagent solutions.
Radioactive solution of ‘40Ba-‘40La in equilibrium supplied by BARC, Trombay, in hydrochloric acid medium was diluted as required. Procedure
After proper conditioning of the resin column, a few drops of the equilibrium mixture of i40Ba-‘“OLa in hydrochloric acid medium (- 2 N) was transferred to the top of the column, which was later washed with water to remove the acid. Elution of i4’La was carried out by slowly percolating Na-nitrilotriacetate or Na-ascorbate solutions of specific concentrations through the column. Drops of effluents at a flow rate of 10 drops per min were collected successively at different intervals during the course of elution. The activity in each effluent fraction was measured with an end-window G.M. counter. After complete elution of the daughter, “‘La, the column was washed with water and the parent tracer, i4’Ba, retained in the column was later eluted with dilute hydrochloric acid (-2N).
Results and Discussion Elution of 14’La by Na-nitrilotriacetate
The difference in the relative stabilities of the metal complexes formed by an eluent with the metal ions adsorbed on a column determines, in general, their degree of separation in any ion exchange separation method.@’ Thus nitrilotriacetic acid has been found to be very effective in the separation of 171
N. R. Das and S. N. Bhattacharyya
172
300
200’
,” ._
L
.? : 1001
,
100
1
I
I
I
200
300
400
500
Drop
I
I 700
600
(8)
number
FIG. 1. Elution of ““La from an equilibrium mixture of “‘“Ba-‘40La with 43; Na-nitrilotriacetate solution at pH 7 from a column of Dowex 5OW-X8 resin in Na’-form.
14’La from 14’Ba because the reagent is known to form a with lanthanum, compoundrgP’ r) CWNCH2C00hIJ3, whose stability constant in neutral or alkali medium(r2’ is much larger than the corresponding compound with barium.(r3) For separation of r40La from r4’Ba, the tracers were initially adsorbed on the column and the elution of 14’La from the column was later carried out with Na-nitrilotriacetate solutions in varying concentrations at pHs 7 and 10. Of these, 4% Na-nitrilotriacetate solution at pH 7, as shown in Fig. 1, was found
3000
-
(0)
,” ._ > ._
2000
-
: 1000
-
A
0
200
300 Drop
400
500
600
I 70C
number
FIG. 2. Elution of ‘-“‘La from an equilibrium mixture of ‘40Ba-‘40La with 4% Na-ascorbate solution at pH 7 from a column of Dowex 5OW-X8 resin in Na’-form.
FIG. 3. Gamma spectra of an equilibrium mixture of 140Ba-140La (A), the fractions eluted separately by Nanitrilotriacetate (B) and Na-ascorbate (C) and the fraction eluted by HCI (D) after separation of 14’La by Na-ascorbate.
Ion exchange separation of “‘Ba to
be most suitable for the elution of the daughter isotope, 140La, completely free of 14’Ba. With Nanitrilotriacetate solutions of lower concentrations, longer tailing of the elution curve occurs and for solution of higher concentrations either at pH 7 or at 10, possibility of contamination due to partial elution of 140Ba increases. Elution of
’ 40La with Na-ascorbate
Similarly, ascorbic acid, which forms an anionic complex with lanthanides,‘15) although comparatively weaker than the nitrilotriacetic acid complexes, does not form any complex with alkaline earth elements at pH 7, which in fact, provides the clue to its effective utilisation in separation of lanthanum from barium. However, very little is known about the relevant properties of the complexes of ascorbic acid with either rare earths or alkaline earth elements. Figure 2 shows that in case of elution with ascorbic acid, isolation of 14’La, completely free from ‘“‘Ba, can be achieved when a 3-5% Na-ascorbate solution at pH 7 is used as the eluent. Eluent solutions at other concentrations under the experimental conditions were not, however, found to be so effective. The radiochemical purity of 14’La separated by either nitrilotriacetic acid or ascorbic acid was, in fact, further verified by y-ray spectrometry and half-life determination. Figure 3 shows the y-ray spectra of the fractions eluted by means of Na-nitrilotriacetate (curve B) and Na-ascorbate (curve C) where the photopeaks due to 14’La are only evident whereas the mixture contains photopeaks due to both 14’La and 14’Ba in equilibrium (curve A). The half-life of the radioactive product in the eluted fractions of each of the eluents was found to be about 40 h which agrees well with that of 14’La as reported in the literature.““) Of the two eluents, nitrilotriacetic acid and ascorbic acid, described here, the latter appears to be more effective than the former, because the separation peak, as is evident from Figs 1 and 2, is sharp and tailing is less in case of ascorbic acid (Fig. 2) than that in case of nitrilotiracetic acid (Fig. 1). This increased eficiency of ascorbic acid in affecting a clean separation of 140La from 14’Ba is probably due to the fact that ascorbic acid, unlike nitrilotriacetic acid does not form any complex with barium.‘15)
173
and “‘La
The parent isotope, 14’Ba, left behind in the column after separation of the daughter, 140La, was also quantitatively extracted with -2 N HCl, the radiochemical purity of which was again ascertained by y-ray spectrometry (Fig. 3, curve D). 14’Ba may be eluted in this way from the column or it may be left over so that a radioactive equilibrium with the daughter is attained after its /Idecay, and this may later be used for milking off the daughter when desired. The reagents used in the method are cheap and moreover the method is simple, quick, effective and reproducible. The simplicity of this separation procedure using either nitrilotriacetic acid or ascorbic acid as the eluent for obtaining lanthanum of high radiochemical purity makes the method potentially useful for the construction of a generator system yielding the nuclide mentioned in high quality.
References 1. MARCUS Y. and NELSON
F. J. Phys. Chem. 63, 77 (1959). 2. FARABEEL. B. Report ORNL-192, p. 12 (1955). 3. FRITZ J. S. and GARRARLDA B. B. Talanta 10, 91 (1963). N. D., MARTYNENKOL. I. and PEROVAI. 4. MITROFANOVA N. Russ. J. Phys. Chem. (Eng. Trans.) 47, 187 (1973). 5. DUYCKAERTSG. and LEJEUNER. J. Chromatogr. 3, 58 (1960). 6. DAS N. R. and BHATTACHARYYAS. N. Int. J. Appl. Radiat. Isor. 28, 731 (1977). 7. DAS N. R. and BHATTACHARYYAS. N. Int. J. Appl. Radiat. Isot. 31, 575 (1980). 8. POWELLJ. E. and SPEDDINGF. H. Trans. AIME 215. ~I 457 (1959). 9. BECK G. and GAFFERA. Anal. Chim. Acta 3, 41 (1949). 10. FITCH F. T. and RUSSEL D. S. Can. J. Chem. 29, 363 (1951). 11. VICKERYR. C. J. Chem. Sot. 245 (1955). 12. IRVING H. M. N. H. and MILES M. G. J. Chem. Sot. (A), 727 (1966). 13. NODDAK W. and OERTEL G. Z. Electrochem. 61, 1216 (1957). 14. CROUTHAMELC. E., ADAMS F. and DAMS R. Applied Gamma-ray Spectromecry. (Pergamon Press, Oxford, 1960). 15. CHAKRABORTYM. and KHOPKAR S. M. Chromatographia 10, 100 (1977).