Sorption Characteristics and Chromatographic Separation of 90Y3+ from 90Sr2+ from Aqueous Media by Chelex-100 (Anion Ion Exchange) Packed Column

There is growing demand for separation of 90Y carrier free from 90Sr coexisting to produce high purity 90Y essential for radiopharmaceutical uses. Thus, in this context the sorption profiles of Y3+ and Sr2+ from aqueous solutions containing diethylenetriaminepenta acetic acid (DTPA), ethylenediaminetetra-acetic acid (EDTA), acetic acid, citric acid, or NaCl onto Chelex-100 (anion ion exchange) solid sorbent were critically studied for developing an efficient and low-cost methodology for selective separation of Y3+ from Sr2+ ions (1.0 × 10−5 M). Batch experiments displayed relative chemical extraction percentage (98 ± 5.4%) of Y3+ from aqueous acetic acid solution onto Chelex-100 (anion ion exchanger), whereas Sr2+ species showed no sorption. Hence, a selective separation of Y3+ from its parent 90Sr2+ has been established based upon percolation of the aqueous solution of Y3+ and Sr2+ ions containing acetic acid at pH 1-2 through Chelex-100 sorbent packed column at a 2 mL min−1 flow rate. Y3+ species were retained quantitatively while Sr2+ ions were not sorbed and passed through the sorbent packed column without extraction. The sorbed Y3+ species were then recovered from the sorbent packed column with HNO3 (1.0 M) at a 1.0 mL min−1 flow rate. A dual extraction mechanism comprising absorption associated to “weak-base anion exchanger” and “solvent extraction” of Y3+ as (YCl6)3− and an extra part for “surface adsorption” of Y3+ by the sorbent is proposed. The established method was validated by measuring the radiochemical (99.2 ± 2 1%), radionuclide purity and retardation factor (Rf = 10.0 ± 0.1 cm) of 90Y3+ recovered in the eluate. Ultimately, the sorbent packed column also presented high stability for reusing 2-3 cycles without drop in its efficiency (±5%) towards Y3+ uptake and relative chemical recovery. A proposed flow sheet describing the analytical procedures for the separation of 90Y3+ from 90Sr2+ using chelating Chelex 100 (anion exchange) packed column is also included.


Introduction
In nuclear medicine, 90 Y is an important radioisotope due to its satisfactory physical characteristics that include β − emissions that allow tissue difusion to a moderately extensive range, a suitable half-life (t 1/2 = 64.4h) and a nonradioactive daughter [1][2][3][4][5][6].Te United States-food and drug administration (US-FDA) has accepted Zevalin drug that incorporates 90 Y [7,8].So, it is essential to the 90 Sr impurity in 90 Y samples owing to the radiotoxicity of 90 Sr [9,10]. 90Y decays to the stable 90 Zr daughter, thus it is used as a pure β-emitter.High complex formation constants of Y 3+ with complexing ligands make 90 Y 3+ valued in preparing radiopharmaceutical reagents [11,12].In light of the perceived need to abolish the radiotoxicity risk poses by 90 Sr, accurate separation, accurate, and reliable removal of 90 Sr impurities from Y samples is of great importance.Terefore, great attention has been oriented towards establishing selective and low cost methods for chromatographic separation of 90 Sr 2+ from 90 Y 3+ samples with good radiochemical and radionuclide purity.
With this background in mind, taking into account the importance of highly pure 90 Y 3+ , the characteristics of the chelating group iminodiacetate moieties of the Chelex-100 anion ion exchanger and some of the synthesized inorganic sorbents as ideal and ecofriendly solid sorbents and in continuation to our previous study [10,[38][39][40][41][42][43], the current study is aimed to (i) revising the sorption profles of Y 3+ and Sr 2+ onto the anion ion exchanger as a new candidate solid sorbent, (ii) establishing a simple and low cost and selective chromatographic separation of 90 Y from its parent 90 Sr by chelating Chelex-100 (anion ion exchanger) sorbent packed column and fnally, and (iii) testing the reusability of the established chelating Chelex-100 sorbent packed column towards separation of Y 3+ from its parent Sr 2+ species in aqueous solutions.Tese results are supportive to recognize the analytical utility of the Chelex-100 in nuclear medicine, waste management and to properly assign the physicochemical behavior of radionuclide 90 Y 3+ and 90 Sr 2+ .

Materials and Methods
2.1.Chemicals.Analytical reagents chemicals were used as received.High-density polyethylene (HDPE) bottles and all glassware's were immersed in hot detergent for 24 h and soaked in the acid mixture of HCl (50% v/v)-conc.HNO 3 (3.0M) at 1 : 1 v/v ratio, washed with double distilled water and fnally dried in oven at 80-90 °C.Stock solutions (1.0 M) of Sigma-Aldrich diethylenetriaminepenta acetic acid (DTPA), ethylenediaminetetra acetic acid (EDTA), HCl, HNO 3 , acetic acid, citric acid, and NaCl were prepared in deionized water.Te chelating Chelex-100 (anion exchanger) (100-200 mesh) was purchased from BDH (Poole, England) and was used after washing 3-4 times with deionized water before use. 89Sr tracer was used as a substitute for 90 Sr and the radio tracers 90 Y 3+ and 90 Sr 2+ were acquired by exposing the target Y 2 O 3 and SrCO 3 (99.9%purity) in Al container at an average thermal neutron fux density of 1.3 × 10 13 neutrons/cm 2 /s at the ERR-1 research reactor (Atomic Energy Authority, Inshas, Egypt).Beta counting (liquid scintillation) was used to check 90 Sr 2+ effciency.Millipore water (resistivity 18.2 MΩcm) was used in all experiments.Te test solutions were prepared by spiking 100 mL of the water sample with a certain amount of YCl 3 (1.771× 10 −2 M) and SrCl 2 (1.323 × 10 −2 M) individually.

Apparatus.
A Geiger-Muller (β − Counter) and window detector and a Scaler Ratementer SR7 (c-Scintillation Counter) were used for ordinary gamma ray counter and it is fxed with well NaI (Tl) crystal.A high purity germanium (HPGe) coupled to a calibrated multichannel gamma analyzer (Silena, Milan, Italy) was employed to test impurities in the irradiated Y 2 O 3 and SrCO 3 as reported earlier [10].Te activity of 90 Sr activity was monitored as reported [10].Standard radionuclides were prepared from a mixed source of the radioisotopes 155 Eu (86.5 and 105.3 keV), 57 Co (122.1 and 136.5 keV), and 137 Cs (661.6 keV).A mechanical shaker (Corporation Precision Scientifc, Chicago, USA) with a shaking rate of 10-250 rpm was used for performing batch experiments.A centrifuge Chermle Z 230 A of 5500 rpm speed was also used.A close-ftting glass Jar chromatography (40 cm L and 5 cm id) of Whatmann paper No 1 (3 cm × 30 cm), Milli-Q Plus water system (Millipore, Bedford, MA, USA), and glass columns of 10.0 cm length (8, 15, and 20.0 mm internal diameter) were used in fow experiments.A digital micropipette (5.0-100 µL) and a Jenway pH meter (model 3510) were used for the preparation and measuring the pH of more diluted working solutions, respectively.(1.771 × 10 −2 M), respectively.In the irradiated product, the impurities were then checked as reported earlier [10].Te specifc activity (S) was then computed as reported earlier [40][41][42].Te purity of irradiated 90 YCl 3 was also confrmed from the decay shape over 3 half-lives (t 1/2 ) period at neutron fux density of 1.3 × 10 13 neutrons/cm 2 /s as reported [44,45].

Preparation of the
2.4.General Batch Extraction Procedures.In a series of precleaned penicillin bottle, accurate masses (0.100 ± 0.002 g) of the precleaned Chelex-100 (Anion ion exchanger) were transferred and equilibrated with 20.0 mL solutions containing known concentrations (1.0 × 10 −5 M) of YCl 3 or SrCl 2 in acetic acid, DTPA, EDTA, citric acid, or NaCl (1.0 × 10 −3 M).Te test solutions were then shaken for 60 min at various pH at 25 °C.Te solid phase extractor in each solution was allowed to settle down and an accurate volume (1.0 mL) of the aqueous phase of each solution was separated out.Te radioactivity of 90 Y and 90 Sr, the relative extraction percentage (%E) and the amount (q e ) of Y 3+ and/or Sr 2+ between the sorbent phase and the aqueous solution were then computed from their activities before and after extraction as reported [38,39].Te distribution ratio (D, mL/g) of Y 3+ and/or Sr 2+ were also calculated using the following equation [43]: where V is the volume of solution (mL) and W is the mass of the dry ion exchanger (g).Te quantity (q e ) of Y 3+ extracted per unit mass of the sorbent (mol g −1 ) was then calculated as reported earlier [39].

Separation of Y 3+ from Sr 2+ by Chelex-100 (Anion Exchanger) Packed
Column.An accurate mass (1.0 ± 0.002 g) of the Chelex-100 (anion exchanger) sorbent was homogeneously packed in glass column (10.0 cm length × 0.8 cm i.d).An aqueous solution of acetic acid (1.0 × 10 −3 M) of pH 1-2 was introduced into the sorbent packed column and quartz wool was then placed at the top of the resin after the sorbent had established down.Tis step helps in avoiding the disturbance of the resin particles during percolation of the test solution.Column was then washed with water 2-3 times at a 2.0 mL/min fow rate.Te test solution (25 mL) containing Y 3+ and Sr 2+ and DTPA (1.0 × 10 −3 M) was permeated to pass through the column at a 2.0 mL min −1 fow rate.Y 3+ was only sorbed quantitatively, whereas Sr 2+ species were passed through the column without sorption as specifed from the radioactivity measurement of 90 Y 3+ and 90 Sr 2+ in the efuent.Te sorbed Y 3+ species were then recovered from the sorbent packed column with HNO 3 (10 mL, 1.0 × 10 −1 M) at a 2.0 mL min −1 fow rate.Te recovered Y 3+ solutions were heated to dryness, redissolved in ultra-pure water, and the Y 3+ purity was fnally determined via computation of the half life (t 1/2 ) as reported [39,44].Moreover, the infuence of other parameter such as fow rates (1.0-5 mL min −1 ) and the internal diameter (0.8, 1.5, and 2.0 cm) on the analytical performance of Chelex-100 packed column for separation of 90 Y 3+ from 90 Sr 2+ was also examined.

Determination of Radiochemical and Radionuclidic Purity
of 90 Y. 90 Y purity was critically checked as follows: On a strip of Whatmann No. 1 paper, a drop of 5.0 µL was put on the lower end of the chromatographic paper.After the spot has dried, the strip was immersed at its lower end in TRIS bufer (0.1 M) of pH 7 as a developer using ascending chromatograph technique without reaching the spot.Te paper was left for 5-6 min to develop; the solution was then reserved out and the paper was allowed to dry.Te paper was divided into equal parts (1.0 cm sections) and GM was used for counting β activity and the sorption factor (R f ) was then computed.Te radionuclidic purity of 90 Y 3+ in the eluate was determined from the purifcation factor (P f ) � A/A o , where A and A o are the activity of 89 Sr in the eluate and solution, respectively.Te radionuclidic purity was also computed from the decay curve over a period of at least 3 half-lives.Te decay curve of 90 Y 3+ was planned by detecting β − activity at one day intervals for 10 days after elution [46,47].

Preliminary Study on the Sorption Profle of Y 3+ and 89 Sr 2+
onto Chelex-100.Te majority of ion exchangers using organic resin and chelator/complexing agent are simple and fast for separation of elements.However, they do not ofer a ready-to-use eluate [3,5].Introductory study on Y 3+ and Sr 2+ uptake from the aqueous solution by chelating Chelex-100 (anionic form) displayed signifcant Y 3+ sorption in a short time.Tus, a detailed study on the sorption profle of Y 3+ and Sr 2+ from the aqueous solution onto the established Chelex-100 sorbent was critically studied.3).At pH 1-3, Sr 2+ species did not retained except in NaCl, where K d � 66654.6 ± 5.7 (Table 1).

Programming of the
In DTPA or acetic acid media of pH ranging from pH 1 to pH 4, Y 3+ species were retained quantitatively onto the chelating Chelex-100 ion exchanger sorbent and the values of K d were reproducible compared to EDTA, citric acid, or NaCl.Representative plot of K d versus of pH of Y 3+ and Sr 2+ sorption onto Chelex-100 (anion ion exchanger) from aqueous DTPA solution (1.0 × 10 −3 M) after 60 min shaking time at 25 ± 0.1 °C is shown in Figure 2. Te observed behavior in Figure 2 is most likely attributed to the possible formation of nonpolar complex species of Y 3+ species (YCl 6 ) 3− with the available iminodiacetate moieties of the chelating Chelex 100 sorbent at pH ≤ 3 (pK a1 � 3.2) [40,42,43].At low pH (pH ≤ 3), the possible interaction between the formed complex anion of yttrium (YCl 6 ) 3− and the protonated iminodiacteate moieties of the chelating Chelex−100 anion ion exchanger by forming ternary complex ion associate may also contributed in the observed trend at low pH ≤ 3 [42,43].On the other hand, at pH above pH 3, one of the two carboxylic acids of the iminodiacetate moiety is deprotonated carrying a negative charge which attracts other positive cation present in extraction media, e.g., Na + (introduced from pH adjustment by diluted NaOH which compete efectively with Y 3+ because of their considerably higher concentration in solution [42].Te fact that, in acidic solutions, the N atom of the iminodiactic group retaining free electron pair is protonated, hence the resin is most likely can acts as weakly basic anion exchanger [43].In addition, deprotonation of the second carboxylic group of the iminodiacetic moieties could also be proceeded at pH > 7, resulting in destabilization of the "guest-host" complexes between Y 3+ and aminocarboxylic moieties [43].Tis exchanger is also commonly regarded as an amphoteric ion exchanger and its ion exchange function depends on the solution pH that in contact with the resin as presented in Scheme 1. In DTPA, EDTA, acetic acid, citric acid, or NaCl medium at pH > 7, Chelex-100 sorbent displayed good retention towards Sr 2+ and the extraction profle of Sr 2+ followed the order: NaCl (K d � 12276.9± 5.7> citric acid (K d � 9759.6 ± 5.7) > acetic acid (K d � 7212.2 ± 5.8) > EDTA (K d � 3623.4 ± 3.7) > DTPA (K d � 1614.5 ± 5.2) was achieved.On the other hand, at pH > 7, the chelating Chelex-100 sorbent displayed no afnity towards Y 3+ from citric acid, EDTA or DTPA.Te fact that the chelating agents EDTA and DTPA act as competitors having similar groups with the Chelex-100 sorbent and both are able to form complexes in solution with Y 3+ and Sr 2+ preventing their adsorption while acetic acid is the weakest medium [42,48].Tis behavior is most likely attributed to the strong and weak ion-association interaction of the accessible specifc active sites of the Chelex-100 solid extractor towards Sr 2+ and Y 3+ , respectively, as reported the authors in [42,48].On the other hand, it may be thought that for smaller molecules a more pronounced difference between the adsorption sites on the surface of Chelex-100 and inside the sorbent pores as reported [48].In acetic acid, EDTA or NaCl at pH > 7, separation of Y 3+ from Sr 2+ was not complete.Tus, in Y 3+ separation from Sr 2+ , acetic acid, or DTPA (1.0 × 10 −3 M) was implemented as a preferred extraction medium at lower pH in the subsequent study.).Tus, the rate-controlling step for Y 3+ sorption by the sorbent is not only gel difusion control as in the ion exchangers [49,50].At the initial stage of shaking time, the plot of %E of Y 3+ versus log time was fast and linear approving the occurrence of intraparticle difusion [10,50].Tus, a 60 min shaking time was adopted in the following study.  1 where in acetic acid media at pH ≤ 5, Y 3+ species were retained quantitatively while Sr 2+ ions did not get sorbed.However, in the subsequent study, HNO 3 (1.0 × 10 −1 M) was nominated as a prober reagent for Y 3+ recovery from Chelex-100 sorbent packed column since it is easily evaporated by gentle heating.

Possible sorption Mechanism for Y 3+
Retention.Te affnity of the sorbent towards Y 3+ played an important role on its uptake.Te nature and number of the specifc sorbent 6 International Journal of Analytical Chemistry sites are involved instantaneously in Y 3+ uptake from the solution [16].Te chelating Chelex-100 sorbent acts as an active "weak anion-exchanger" towards complex species of Y 3+ such as (YCl 6 ) 3− in HCl media [53] and "liquid-liquid extraction" with the salt performing as salting-out reagent in Y 3+ uptake.Te salt added decreases the water molecules available to solvate Y 3+ ions which would be required out of the solvent onto the sorbent phase.Tus, water structure enforced ion pairing is somewhat the driving force for Y 3+ uptake and "surface adsorption" efectively take part in the Y 3+ extraction [53,54].Based on the obtainable results and the data reported earlier [54,55], a dual sorption mechanism involving absorption related to "weak-base anion exchange" and "solvent extraction" in addition to "surface adsorption" of Y 3+ is proposed.Tus, retention mechanism of Y 3+ can be stated by the following equation [54,55]: where C r and C aq are the equilibrium concentrations of Y 3+ ions onto the sorbent and in solution, respectively.C abs and C ads are the equilibrium concentrations of Y 3+ absorbed and adsorbed onto the sorbent while S and K L are the parameters of the Langmuir adsorption model [54,55].).Y 3+ species were retained quantitatively whereas Sr 2+ ions were passed without uptake as revealed from ICP-OES determination of 90 Y 3+ and 90 Sr 2+ ions in the efuent versus reagent blank.Selection of proper eluting agent prior to use of 90 Y 3+ for labeling and radiolysis of organic support materials is crucial and is identifed as the main limitations of current 90Sr/90Y [35,56].Tus, the established methodology ofered a facile, better selectivity and simple approach compared to the published work [12][13][14][15][16][17][18][19][20][21]57].Numerous eluting agents such as HNO 3 , HClO 4 , H 2 SO 4 , and acetic acid (1.0 × 10 −1 M) were checked for recovery of Y 3+ from chelated Chelex-1000 packed column.Among these reagents, good percentage recovery (99.5 ± 2.9%) of 90 Y 3+ was only achieved with HNO 3 (10 mL, 1.0 × 10 −1 M) as a prober agent for Y 3+ recovery at a 1.0 mL/ min fow rate using Chelex-100 sorbent packed glass column of 8 mm internal diameter.On the other hand, HNO 3 can easily remove from the recovered 90 Y 3+ solution by gentle evaporation.Te solid residue was redissolved in deionized water and analyzed as reported [56].Moreover, the impact of the internal column diameter (0.8, 1.5, and 2.0 cm) on the performance of chelated Chelex-100 packed column on the separation of Y 3+ from Sr 2+ ions was examined at a 1.0 mL min −1 fow rate.Acceptable separation and relative chemical recovery of Y 3+ from Sr 2+ was only achieved at 8 mm internal diameter of the column, whereas at internal diameter greater than 8 mm, Y 3+ recovery was not complete (<90%) Te infuence of the fow rate (1.0-5 mL min −1 ) on Y 3+ separation from 9 Sr 2+ ions was critically tested.Good separation with acceptable relative chemical recovery (over 99%) of Y 3+ from Sr 2+ ions was achieved at a fow rate of 1.0 mL min −1 .Tus, in the subsequent study, the fow rate and the internal diameter of the Chelex −100 sorbent packed column were adopted at a 1.0 mL min −1 fow rate and 8 mm internal diameter.90 Y 3+ .Validation of Chelex-100 (anion form)-packed column for chromatographic separation of 90 Y from 90 Sr was critically tested by calculating the retardation factor (R f ) from the radio chromatogram of 90 Y on the original spot constructed by plotting radioactivity (cpm) versus travelled distance, cm.Te data are presented in Figure 4 and the R f value was 10.0 ± 0.1 cm of total activity on the original spot in agreement with the data published earlier [31][32][33][34][35][36].Tese data also signify that over 99.2 ± 2.1% of 90 Y 3+ species are present in the eluate as 90 YCl 3 as reported by the authors in [46,56].

3.6.
Radionuclides Purity of 90 Y 3+ .Te proposed protocol was tested by measuring the radionuclidic purity using the purifcation factor (P f � A/A o ), where A and A o are the 90 Sr 2+ activity in the recovered and loaded solution, respectively.Te P f value was lower than 1.1 × 10 −6 , demonstrating negligible impurity of 90 Sr 2+ in 90 Y 3+ solution [45,46].Te radionuclidic purity of 90 Y 3+ was also computed from radioactivity (cpm) plot of 90 Y 3+ in solution versus time (day) (Figure 5).Te value of half life (t 1/2 ) of 90 Y as computed from the decay curve (Figure 5) was found equal 64.4 h in good agreement with the data reported earlier [38,39], revealing high purity of 90 Y 3+ with good performance of Chelex-100-packed column International Journal of Analytical Chemistry towards 90 Y 3+ separation from 90 Sr 2+ .Te whole analytical procedures for 90 Y 3+ separation from 90 Sr 2+ by Chelex−100 sorbent is presented in the proposed fowsheet (Figure 6).

Conclusion, Drawbacks, and Future Outlooks
In summary, the current study presented an optimized protocol for selective separation of 90 Y 3+ from 90 Sr 2+ with good purity using chelating Chelex-100 (anion exchanger) packed column.Te membrane-like structures and the available active sites of the Chelex-100 solid extractor permit good separation of Y 3+ from Sr 2+ compared to other sorbents [12][13][14][15][16][17][18][19][20][21][22]57].Compared to previous methods for separation of 90 Y 3+ from 90 Sr, Chelex-100 requires slight sample operation to reduce the analysis time, and it does not require solvent evaporations and reconstruction step.Tis method displays high selectivity for separation of 90 Y 3+ from 90 Sr 2+ at the low level.Te purity of 90 Y can be tested by quality control procedures.Te established extractor looks low cost and valuable alternative sorbent over the common rigid or granular solid extractors.A dual sorption mechanism of Y 3+ comprising both "surface adsorption" and an added component of "ion exchanger and/or solvent extraction" is anticipated.In addition, the results revealed the possible use of Chelex-100 sorbent packed column for complete enrichment and recovery of Y 3+ for 2-3 times without signifcant decrease in its performance.Work is ongoing for studying the impact of memory efect, various organic materials in water samples and online enrichment of ultratrace levels of Y 3+ from great volume of water samples followed by subsequent determination. Testudy also shows that the established extractor can be used as cheap, efcient and ecofriendly solid sorbent for Y 3+ separation from Sr 2+ , whereas other methodologies have high operational costs and sometimes yield undesirable byproducts when linked to physical and chemical methods. Tefact that the use of one factor at a time has many drawbacks and shortcomings and the cooperating results of numerous features might advance the signal and the utility of the proposed methodology.Terefore, design experiment for separation of Y 3+ from Sr 2+ is suggested in the forthcoming study.Te developed strategy provides new sorbents for establishing a method for radiochemical separation.

Data Availability
Te data used to support the fndings of this study are included within the manuscript and supplementary materials and also from corresponding author upon request.Y 3+ was sorbed quantitatively Sr 2+ was passed without sorption retained Y 3+ was then eluted with HNO 3 (10 mL, 1.0×10 -1 M) Sr 2+ radioactivity was then measured recovered Y 3+ was dried and redissolved in ultra-pure water Y 3+ was determined via calculation of the half-life (t 1/2 ) 25 mL of Y 3+ and Sr 2+ solution containing DTPA (1.0×10 -3 M) was passed through Chelex-100 column @ 2.0 mL min -1 fow rate.

Chelex-100
Figure 6: A proposed fow sheet of the analytical procedures for the separation of 90 Y 3+ from 90 Sr 2+ using Chelex 100 (anion exchange) packed column.

7 † 3 M. 4 International
Te concentration of acetic acid, citric acid, DTPA, EDTA, or NaCl is equal to 1.0 × 10 −Journal of Analytical Chemistry increasing the solution pH and reached minimum value (K d close to zero negligible value) at pH11 as shown in Figure 1.On the other hand, Sr 2+ uptake was insignifcant in the pH range pH 1-5 (K d � 0.0) and it gradually increased on growing the pH and reached maximum value at pH 9 (K d � 9910.6 ± 10.6) and levelled of at higher pH up to pH 11 (K d � 6000.7 ± 9.3) as shown in Figure 1.Te sorption selectivity of Y 3+ at pH 1-3 onto chelating Chelex-100 sorbent in the various extraction media followed the order: NaCl (K d �12278.5 ± 13.8 > acetic acid (K d � 9930.6 ± 12.4) > EDTA (K d � 9905.3 ± 5.4) > citric acid (K d � 9886.4 ± 5.8) > DTPA (K d � 7004.7 ± 3.
Polarity.Te extraction medium in solid phase extraction procedures has a pronounced efect on the performance of Y 3+ separation.Tus, Y 3+ and Sr 2+ ions uptake from the test aqueous solutions (20.0 mL) containing various known concentrations (1 × 10 −5 -1.0 M) of HCl or HNO 3 at standard concentration of Y 3+ and Sr 2+ (1.0 × 10 −5 M) was studied over a shaking time of 60 min at room temperature.At equilibrium, the remained Y 3+ and Sr 2+ ions in the aqueous phase was measured and the extraction percentage (E, %) and the D were then computed as reported[10].In HCl media, the data are presented in Figure3, where the E% and D of Y 3+ and Sr 2+ by the sorbent decreased on rising HCl concentration from 1.0 × 10 −5 to 1.0 M. At HCl concentration ≥1.0 × 10 −1 M, Sr 2+ species were not retained, while 75.0 ± 2.1% of Y 3+ was retained.Te strong interaction of the active sites of the sorbent with Y 3+ may account for this trend[51,52].Te strong binding of Y 3+ to form [YCl 6 ] 3− complex species[53] compared to Sr 2+ in HCl media may also account for the observed trend.In HNO 3 (1.0 × 10 −5 -1.0 M), Y 3+ species did not sorbed onto chelating Chelex-100 sorbent whereas signifcant sorption of Sr 2+ (K d = 650.4± 3.64 mL g −1 ) was noticed at 1.0 × 10 −5 M and decreased on rising HNO 3 concentration up to 1.0 M (K d = 210.2± 3.64 mL g −1 ).Te average chemical extraction percentage of 89 Sr and 90 Y from acetic acid (1.0 × 10 −3 M) at diferent solution pH onto Chelex-100 was also studied.Te results are illustrated in Figure

Figure 3 :
Scheme 1: A scheme describing the possible interactions between Y 3+ ions and the iminodiacetate moieties of Chelex -100 at various solution pH forming diferent complex species of Y 3+ with Chelex-100 (anion ion exchanger).

Figure 4 :Figure 5 :
Figure 4: Plot of radioactivity of 90 Y 3+ species in the eluate versus travelled distance.

Table 1 :
Infuence of the extraction media (acetic acid, citric acid, DTPA, EDTA and NaCl), and the solution pH on the distribution ratio (K 3+and Sr2+from the various extraction media into Chelex-100 (anionic form) are summarized in Table1.In acetic acid and DTPA media, the sorption profles of Y 3+ and Sr 2+ are also illustrated in Figures1 and 2, respectively.In acetic acid media, the K d of Y 3+ sorption onto Chelex-100 sorbent reached a maximum value at pH 1-6 (K d � 9930.6 ± 12.4), whereas the K d gradually decreased on International Journal of Analytical Chemistry