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Use of ascorbic acid as an eluent for cation exchange separation of rare earth tracers
Inwrrwrionsl Journul of Applied Rudiurion & Isotop~~n Vol. 0 Pergnmon Press Ltd 1980. Printed in Great Brilain W~0-708Xi~0!0901-0575S02.00/0
However, the applicability of the reagent as an eluent for separation of individual rare earth from their mixtures has not yet been verified. It is expected that the lanthanides which form weak anionic complexes with ascorbic acid will also follow the same general trend of elution as is observed with other eluting agents. The aim of the present study is to see whether ascorbic acid can be used as an effective eluting agent for the separation of rare earths in a mixture through cation exchange chromatography or not. The work described is specifically applied to the separation of some radioactive rare earth nuclei without resorting to carrier materials.
31. pp. 575 to 576
A f
Use of Ascorbic Acid as an Eluent for Cation Exchange Separation of Rare Earth Tracers 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
22 Junuary
1980;
in wised
form
11 March
Experimental
1980)
Chemical reagents used were all of analytical grade. Dowex-50W-X8 (20-50 U.S. Mesh, H+-form) was used as cation exchanger. For conversion of the resin (H+-form) into Na+-form, an excess of 1M NaCl solution was run through the column and was washed with water to remove the excess salt solution. The glass column had a resin bed of 90 mm in length and 5 mm in dia. supported at the bottom by a small glass wool plug. Sodium ascorbate solutions used for the elution were prepared by adding required amount of dilute sodium hydroxide solution to freshly prepared ascorbic acid solutions of specific concentrations, e.g. 0.25%, OSOo/,, LO%, l.S”/, 2.0% and 5.0% at pHs 6.5-7.0 and 10.0 respectively. The radioactive isotopes, “‘Ce (32.5 days), ‘53Sm(47 h) 16”Tb (71 days) and i’@Tm (127 days) of high specific activities supplied by BARC, Trombay, India, in hydrochloric acid medium were used as the representative rare earth elements after proper dilution according to the requirements.
A simple cation exchange procedure for effective separation of rare earths in a mixture using ascorbic acid as a complexing agent has been demonstrated. Sodium ascorbate solution of OS%, concentration at pH 6.5-7.0 was found to be most effective in separating the radioactive species, namely, “‘Tm, i6’Tb, “‘Sm and 14’Ce from their mixture under the experimental conditions. The method described was specifically applied to the separation of tracers, without resorting to carrier materials.
Introduction EFFECTIVE separation of rare earth elements through ion exchange chromatography utilizing various hydroxyorganic acids. specially x-hydroxy isobutyric acid, as eluents is well established.“-” Recently, a report on the use of ascorbic acid as a complexing eluent involving anion exchange separation of a group of rare earth elements from scandium and some other metal ions has been published.“’
Procedure
After conditioning the resin column, a desired amount of
400
f!
d
‘D nE
I 16’Tb
r
4
“jSrn
30
.
1
“‘Tm I
.
.
I
D
0
0
’
’
40
’
I
.
14'Ce
,.
1
:.,t. .I;)(
. .
’
I
’
’
l
II.
’
60
’
‘t
120 Volume
“x,
’ ‘t(
160
,
0
lml)
FIG. 1. Elution curve of ““Tm, i6’Tb, ‘s3Sm and 14iCe with O.!$, sodium ascorbate solution at pH 6.5-7.0 using Na+-form of Dowex 5OW-X8 resin.
40
60
120 Volume
200
160
200
(ml)
FIG. 2. Elution curve of “0Trn, 16@Tb,‘s3Sm and i4iCe with sodium ascorbate solution of 0.5% concentration using (A) Na+- and (B) H+-forms of Dowex 5OW-X8 at pH 6.5-7.0. 575
mixed tracers solution in dilute hydrochloric acid medium was transferred to the top of the resin bed where the tracers were adsorbed and then washed with water. Elution of the tracers from the column was carried out by slowly percolating sodium ascorbate solution of specific strength and pH through the column. Fractions (0.5 ml) of effluents (flow rate - 10 drops min-‘) were collected successively during the entire course of elution directly on plastic trays for subsequent measurement of activity with an endwindow G. M. counter.
(-2N)
Discussion Study on the separation of the mixture of rare earth radioisotopes, namely, “‘Ice, ‘%m. “‘Tb and ““Tm using ascorbic acid as an eluent reveals that the anionic ascorbic acid complexes of the lanthanides also follow the general sequence of elution i.e. elements of higher atomic number come out first then the lower one. It is evident from Fig. 1 that sodium ascorbate solution of 0.5% concentration at pH 6.5-7.0 is found to be most effective in separating the nuclei from the mixtures where sharp peaks corresponding to each of the nuclides were obtained. Changes in the concentrations of the complexing agent have noticeable effect on the rate of elution of the tracers. At the other eluant concentrations investigated the separations were not so good. However, for separation of a smaller number of rare earths with larger differences in atomic numbers or for lanthanides in a group from other elements such as alkali or alkaline earth metals which do not form any negatively charged complex with the reagent”’ eluents at higher concentrations can be used whereby the separation will be comparatively quicker.
Further. the ionic form of resin used also plays an important role (6) in the separation of the rare earth elements. In the present investigation, of the two ionic forms used namely, H+- and Na’-forms, the later form was found to be more suitable for the purpose than the former one under the experimental conditions as shown in Fig. 2. Thus, the preliminary study made on the use of ascorbic acid as an eluting agent in the separation of the rare earth species indicates that the reagent may find its fruitful application in the separation chemistry of lantha ides. However, detailed studies on the relevant propertt *fs of the reagent e.g. dissociation constants, solubility of sodium ascorbate in water, complex formation constants etc. with rare earth elements, yet to be determined, are necessary before establishing the reagent as an effective eluent for the purpose.
References I. HULETE. K. and BODE D. D. In Lanrharlides and Acti-
2. 3. 4. 5. 6.
nides (Edited by BAGNALLK. W.) Inorganic Chemistry, Series I, Vol. 7. MTP International Review of Sciences, London (1972). CHOPPING. R. and SILVAR. J. J. inorg. nucl. Cheln. 3, 153 (1956). SMITHH. L. and HOFFMANND. C. J. inorg. nucl. Chenl. 3, 243 (1956). VOBECKYM. and MASTALKAA. Co/l. Czech. chenl. Co,nmun. 28. 709 (1963). CHAKRABORTY M. and KHOPKARS. M. Chrotnarograpllia 10, 100 (1977). DAS N. R. and BHATTA~HARYYA S. N. Int. J. appl. Radiat. Isoropcs 28, 733 (1977).
However, the applicability of the reagent as an eluent for separation of individual rare earth from their mixtures has not yet been verified. It is expected that the lanthanides which form weak anionic complexes with ascorbic acid will also follow the same general trend of elution as is observed with other eluting agents. The aim of the present study is to see whether ascorbic acid can be used as an effective eluting agent for the separation of rare earths in a mixture through cation exchange chromatography or not. The work described is specifically applied to the separation of some radioactive rare earth nuclei without resorting to carrier materials.
31. pp. 575 to 576
A f
Use of Ascorbic Acid as an Eluent for Cation Exchange Separation of Rare Earth Tracers 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
22 Junuary
1980;
in wised
form
11 March
Experimental
1980)
Chemical reagents used were all of analytical grade. Dowex-50W-X8 (20-50 U.S. Mesh, H+-form) was used as cation exchanger. For conversion of the resin (H+-form) into Na+-form, an excess of 1M NaCl solution was run through the column and was washed with water to remove the excess salt solution. The glass column had a resin bed of 90 mm in length and 5 mm in dia. supported at the bottom by a small glass wool plug. Sodium ascorbate solutions used for the elution were prepared by adding required amount of dilute sodium hydroxide solution to freshly prepared ascorbic acid solutions of specific concentrations, e.g. 0.25%, OSOo/,, LO%, l.S”/, 2.0% and 5.0% at pHs 6.5-7.0 and 10.0 respectively. The radioactive isotopes, “‘Ce (32.5 days), ‘53Sm(47 h) 16”Tb (71 days) and i’@Tm (127 days) of high specific activities supplied by BARC, Trombay, India, in hydrochloric acid medium were used as the representative rare earth elements after proper dilution according to the requirements.
A simple cation exchange procedure for effective separation of rare earths in a mixture using ascorbic acid as a complexing agent has been demonstrated. Sodium ascorbate solution of OS%, concentration at pH 6.5-7.0 was found to be most effective in separating the radioactive species, namely, “‘Tm, i6’Tb, “‘Sm and 14’Ce from their mixture under the experimental conditions. The method described was specifically applied to the separation of tracers, without resorting to carrier materials.
Introduction EFFECTIVE separation of rare earth elements through ion exchange chromatography utilizing various hydroxyorganic acids. specially x-hydroxy isobutyric acid, as eluents is well established.“-” Recently, a report on the use of ascorbic acid as a complexing eluent involving anion exchange separation of a group of rare earth elements from scandium and some other metal ions has been published.“’
Procedure
After conditioning the resin column, a desired amount of
400
f!
d
‘D nE
I 16’Tb
r
4
“jSrn
30
.
1
“‘Tm I
.
.
I
D
0
0
’
’
40
’
I
.
14'Ce
,.
1
:.,t. .I;)(
. .
’
I
’
’
l
II.
’
60
’
‘t
120 Volume
“x,
’ ‘t(
160
,
0
lml)
FIG. 1. Elution curve of ““Tm, i6’Tb, ‘s3Sm and 14iCe with O.!$, sodium ascorbate solution at pH 6.5-7.0 using Na+-form of Dowex 5OW-X8 resin.
40
60
120 Volume
200
160
200
(ml)
FIG. 2. Elution curve of “0Trn, 16@Tb,‘s3Sm and i4iCe with sodium ascorbate solution of 0.5% concentration using (A) Na+- and (B) H+-forms of Dowex 5OW-X8 at pH 6.5-7.0. 575
mixed tracers solution in dilute hydrochloric acid medium was transferred to the top of the resin bed where the tracers were adsorbed and then washed with water. Elution of the tracers from the column was carried out by slowly percolating sodium ascorbate solution of specific strength and pH through the column. Fractions (0.5 ml) of effluents (flow rate - 10 drops min-‘) were collected successively during the entire course of elution directly on plastic trays for subsequent measurement of activity with an endwindow G. M. counter.
(-2N)
Discussion Study on the separation of the mixture of rare earth radioisotopes, namely, “‘Ice, ‘%m. “‘Tb and ““Tm using ascorbic acid as an eluent reveals that the anionic ascorbic acid complexes of the lanthanides also follow the general sequence of elution i.e. elements of higher atomic number come out first then the lower one. It is evident from Fig. 1 that sodium ascorbate solution of 0.5% concentration at pH 6.5-7.0 is found to be most effective in separating the nuclei from the mixtures where sharp peaks corresponding to each of the nuclides were obtained. Changes in the concentrations of the complexing agent have noticeable effect on the rate of elution of the tracers. At the other eluant concentrations investigated the separations were not so good. However, for separation of a smaller number of rare earths with larger differences in atomic numbers or for lanthanides in a group from other elements such as alkali or alkaline earth metals which do not form any negatively charged complex with the reagent”’ eluents at higher concentrations can be used whereby the separation will be comparatively quicker.
Further. the ionic form of resin used also plays an important role (6) in the separation of the rare earth elements. In the present investigation, of the two ionic forms used namely, H+- and Na’-forms, the later form was found to be more suitable for the purpose than the former one under the experimental conditions as shown in Fig. 2. Thus, the preliminary study made on the use of ascorbic acid as an eluting agent in the separation of the rare earth species indicates that the reagent may find its fruitful application in the separation chemistry of lantha ides. However, detailed studies on the relevant propertt *fs of the reagent e.g. dissociation constants, solubility of sodium ascorbate in water, complex formation constants etc. with rare earth elements, yet to be determined, are necessary before establishing the reagent as an effective eluent for the purpose.
References I. HULETE. K. and BODE D. D. In Lanrharlides and Acti-
2. 3. 4. 5. 6.
nides (Edited by BAGNALLK. W.) Inorganic Chemistry, Series I, Vol. 7. MTP International Review of Sciences, London (1972). CHOPPING. R. and SILVAR. J. J. inorg. nucl. Cheln. 3, 153 (1956). SMITHH. L. and HOFFMANND. C. J. inorg. nucl. Chenl. 3, 243 (1956). VOBECKYM. and MASTALKAA. Co/l. Czech. chenl. Co,nmun. 28. 709 (1963). CHAKRABORTY M. and KHOPKARS. M. Chrotnarograpllia 10, 100 (1977). DAS N. R. and BHATTA~HARYYA S. N. Int. J. appl. Radiat. Isoropcs 28, 733 (1977).