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Cesium ion selective electrode based on calix[4]crown ether–ester
Talanta 58 (2002) 445 /450 www.elsevier.com/locate/talanta
Cesium ion selective electrode based on calix[4]crown ether ester /
R.K. Mahajan *, Manov Kumar, V. Sharma (nee Bhalla), Inderpreet Kaur Department of Chemistry, Guru Nanak Dev University, Amritsar 143005, India Received 26 November 2001; received in revised form 15 April 2002; accepted 25 April 2002
Abstract The potentiometric response characteristics of cesium ion selective PVC membrane electrode employing calix[4]crown ether /ester as an ionophore were investigated. The electrode exhibit a good response for cesium ion over wide concentration range of 5.0 /10 6 /1.0 /10 1 M with a Nernstian slope of 59 mV per decade. The detection limit of electrode is 5.0 /10 6 M. The electrode was found to have selectivity for cesium ion over alkali, alkaline and transition metals. The response time of the electrode is less than 20 s and can be used for more than 4 months without observing any divergence in potentiometric response. The electrode response was stable over wide pH range. # 2002 Elsevier Science B.V. All rights reserved. Keywords: Cesium ion; Sensor; Calix[4]crown ether /ester
1. Introduction Macrocyclic compounds, due to their selective receptor properties and ease of structural modification, have been employed as ionophores in ion selective electrodes for the determination of alkali, alkaline and many transition metal ions [1 /6]. Calix-crown compounds show strong affinities for complexation of alkali and alkaline earth metals. The analytical chemistry of cesium is complicated by the similarity of its physical properties to other group I metals [7 /9]. It has been shown that crown ethers and the derivatives of 1,3-alternate calix[4]crown-6 extract Cs ion efficiently from * Corresponding author. Fax: /91-183-258-820 E-mail address: [email protected] (R.K. Mahajan).
nuclear waste solutions by solvent extraction [10 /16]. The major sources of cesium involves nuclear waste materials and therefore the selective removal of 137Cs from medium level radioactive waste is an important environmental and technological problem [11,17].The toxicity of cesium and its ability to displace potassium from muscles and red cells,demand more attention from analytical chemists to develop such techniques which can determine Cs ions concentration in the nuclear waste solutions. The present paper deals with an ion selective electrode based on calix[4]crown ether-ester for the determination of cesium ions, as it has been observed that ionophore (I) extracts cesium more efficiently compared with other metal ions tested. The cesium ion selective electrode exhibits a good response for cesium ion over
0039-9140/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved. PII: S 0 0 3 9 - 9 1 4 0 ( 0 2 ) 0 0 3 1 0 - 7
446
R.K. Mahajan et al. / Talanta 58 (2002) 445 /450
wide concentration range of 5.0 /10 6 /1.0 / 10 1 M with a Nernstian slope of 59 mV per decade. The proposed ion selective electrode incorporates PVC as supporting material to give a pseudo-solid sensing membrane and bis(2-ethylhexyl)sebacate as plasticizing agent. The performance of this electrode which involves linear range, detection limit, response time, slope etc, is in agreement and in many respects better than those reported in literature [18,19].
2. Experimental
Fig. 1. Calibration of ionophore electrodes for various alkali metal ions.
2.1. Reagents Calix[4]crown ether ester was prepared as reported earlier [20]. High molcular weight poly(vinyl chloride), PVC and bis(2-ethylhexyl)sebacate were obtained from Fluka. All other reagents used were of AnalyticalReagent grade. Doubly distilled deionised water (DDW) was used throughout.
Fig. 2. Plot showing the variation of membrane potential with pH at 1.0 /10 1 M Cs ions.
Table 1 The selectivity coefficients of diverse ions
2.2. Electrode preparation The procedure adopted to prepare the PVC membrane was to mix thoroughly 100.1 mg of powdered PVC, 200.1 mg of plasticizer bis(2ethylhexyl)sebacate and 7.0 mg of ionophore in 5
Diverse ions
KPot Cs,M
Log KPot Cs,M
Li K Na NH4 Mg2 Ca2 Ba2 Ni2 Co2 Cu2 Pb2 Hg2 Zn2 Cd2
1.35 /10 2 1.0 /10 2 5.0 /10 2 3.16 /10 2 1.2 /10 3 2.95 /10 4 7.94 /10 4 6.31 /10 4 3.31 /10 4 1.41 /10 4 3.98 /10 4 3.16 /10 3 1.78 /10 4 1.66 /10 2
/1.87 /2.00 /1.30 /1.50 /2.92 /3.53 /3.10 /3.20 /3.48 /3.85 /3.40 /2.50 /3.75 /1.78
R.K. Mahajan et al. / Talanta 58 (2002) 445 /450
447
2.3. Measurement of electrode potentials All the measurements of the electrode potentials were made with Elico LI-model-120 pH meter. The electrochemical system was as follows: Internal reference electrode Ag /AgCl
Internal reference solution 1.0 /10 2 M Cs
PVC membrane
Test solution
External reference electrode Ag /AgCl
The standard cesium chloride solutions used for calibration were obtained by the dilution of 1.0 / 10 1 M CsCl solutions and pH of these solutions lies between the functional pH range of the ion selective electrode, hence do not need any pH adjustment. Fig. 3. Plots showing E vs. Log[Cs ] in the presence of Na ions at varying level of interference (m) 1.0 /10 2, (j) 1.0 / 10 3, (') 5.0 /10 4 and ( /) 0.0 M Na .
3. Results and discussion 3.1. Response characteristics of the electrode
Fig. 4. Plots showing E vs. Log[Cs ] in the presence of Cd2 ions at varying level of interference (m) 1.0 /10 2, (j) 1.0 / 10 4, (') 1.0 /10 5 and ( /) 0.0 M Cd2 .
ml of tetrahydrofuran. After complete dissolution of all the components and thorough mixing, the resulting solution was transferred to a petridish of 2 cm in diameter. Solvent was made to evaporate at room temperature. After 24 h, a transparent membrane of 0.4 mm thickness was obtained. The membrane was cut to size, attached to the PVC tube with the help of PVC glue and conditioned for 48 h by soaking in 1.0 /10 2 M cesium chloride solution.
Calix[4]crown ether /ester contains oxygen atoms as donor atoms which can effectively coordinate with alkali metal ions. In the preliminary experiments, it was used to prepare PVC membrane ion selective electrodes based on calix[4]crown ether /ester for sodium, potassium and cesium ions. The potential responses of the electrodes for Na , K and Cs ions are shown in Fig. 1. The non-Nernstian slopes for sodium and potassium ion selective electrodes were found to be 48.2 and 20.2 mV per decade, respectively. The electrode response order for these alkali metal ions was found to be Cs /Na /K . The PVC membrane electrode based on calix[4]crown ether /ester demonstrated a linear potentiometric response for Cs ions in the concentration range 5.0 /10 6 /1.0 /10 1 M with a Nernstian slope of 59 mV decade 1. The detection limit of electrode is 5.0 /10 6 M. The response time of the sensor was measured at various concentrations of test solution and it was found to be less than 20 s and no change was observed upto 5 min. Potentials were monitored periodically at fixed concentration and standard deviation of ten identical measurements was 9/2 mV.
448
Ionophore
Response time(s)
Linearity (M)
Detection limit (M)
Slope (mV)
log KPot Cs,M Li
15-Crown-5 phosphotungstic acid precipitate [18] 2,3-Benzoquino-crown-5 [19] Calix[4]crown ether-ester
B/60 B/30 B/20
1.0 /10 1 /1.0 /10 4 1.0 /10 1 /1.0 /10 4 1.0 /10 1 /5.0 /10 6
1.0 /10 5 1.0 /10 5 5.0 /10 6
60 51.9 59
Na
K
NH4
/0.89 /0.46 /0.31 / /3.00 /2.38 /0.99 /1.40 /1.87 /1.30 /2.0 /1.50
R.K. Mahajan et al. / Talanta 58 (2002) 445 /450
Table 2 Comparison studies of Cs -ion selective electrode based on calix[4]crown ether /ester and previously reported in literature
R.K. Mahajan et al. / Talanta 58 (2002) 445 /450
Table 3 Analysis of water sample spiked with cesium(I) Sample no.
[Cs ]AAS (ppm)/S.D. (n /4)
[Cs ]ISE (ppm)/S.D. (n /4)
1 2 3 4
50/0.3 29/0.4 19.5/0.3 8.5/0.3
49.5/0.2 29.1/0.3 19.3/0.3 8.4/0.2
3.2. Effect of pH on response characteristics of the electrode The pH dependence of PVC membrane Cs ion selective electrode based on calix[4]crown ether / ester was examined over the pH range 1/11 (Fig. 2) at cesium ion concentration 1.0 /10 1 M and the electrode shows no significant change in potentiometric response in the wide pH range of 4 /9.Therefore, all the potentiometric measurements were made at pH 6.1 which is the pH of the cesium chloride solution. 3.3. Selectivity Selectivity is one of the most important characteristic of a sensor, as it helps to determine whether a reliable measurement in the target sample is possible. This is measured in terms of potentiometric selectivity coefficients (log KPot Cs,M) which has been evaluated using fixed interference method at 1.0 /10 2 M concentration of interfering ions. The fixed interference method is based on semi emperical Nikolsky /Eisenman equation. Under ideal conditions, the electrode response function follows Nernst equation Pot EISE E 09RT =ZA F ln[aA SKA;B (aB )ZA =ZB ]
where, EISE is measured potential, E0 is standard cell potential aA and aB are the activities of primary and interfering ions. KPot A,B can be calculated using expression Pot KA;B aA =(aB )ZA =ZB
The potentiometric selectivity coefficients (log KPot Cs,M) measures the response of the electrode
449
for the primary ion in the presence of foreign ions. The selectivity coefficients data indicate that 2 for KPot Cs,M values are of the order of 10 4 for the divalent metal ions monovalent and 10 (except for the cadmium ions). Therefore, the electrode can be used for the determination of cesium ions in the presence of interfering ions (Table 1). As the selectivity coefficients values for Na and Cd2 are quite high they are expected to cause interference. They do not cause any disturbance to the performance of electrode when present in small concentration, as KPot Cs,M values dependent on the relative concentration of primary ion as well as interfering ions. In order to establish the limiting concentration of Na and Cd2 ions that can be tolerated in the determination of cesium ions, various experiments were carried out at different concentrations of these interfering ions which are shown in the plots of Figs. 3 and 4, respectively. It is evident from these plots that Na and Cd2 when present at concentration less than 5.0 /10 4 and 1.0 /10 5 M respectively caused no divergence in the potentiometric response of the electrode. Fig. 3 shows that Na ions when at high concentration caused significant divergence from the original E versus log[Cs ] plot and therefore cannot be tolerated over whole concentration range. The cesium ion selective electrode based on calix[4]crown ether /ester is comparable and superior in many respects than those reported in literature (Table 2). As shown in Table 2, the proposed Cs ion selective electrode posses better linear range (5.0 /10 6 /1.0 /10 1 M) and detection limit 5.0 /10 6 M than previously reported ISEs for cesium. The Cs-ion selective electrode based on calix[4]crown ether /ester shows good selectivity for Cs ion over other alkali metal ions. The applicability of the sensor is illustrated by measuring the cesium(I) ion potentiometrically in doubly distilled deionised water (DDW) spiked with 50, 30, 20 and 10 ppm cesium (I). The results obtained were compared with those obtained from atomic absorption spectrometric analysis (Table 3) and were found in good agreement.
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R.K. Mahajan et al. / Talanta 58 (2002) 445 /450
4. Conclusion It can be concluded that the Cs-ion selective electrode based on calix[4]crown ether /ester exhibit good sensitivity, detection limit, reproducibilities, selectivities and better life time.
Acknowledgements We are thankful to Council of Scientific and Industrial Research, New Delhi,India for financial assistance. One of us (I.K) is thankful to Guru Nanak Dev University, Amritsar, India for providing Junior Research Fellowship.
References [1] R.J. Foster, A. Cadogan, M.T. Diaz, D. Diamond, Sens. Actuators B 4 (1991) 325. [2] J.S. Kim, I.Y. Yu, J.H. Pang, J.K. Kim, Y-III. Lee, Y.Z. Oh, Microchem. J. 58 (1998) 225. [3] J.S. Kim, I.H. Suh, J.K. Kim, M.H. Cho, J. Chem. Soc., Perkin Trans. 1 (1998) 307. [4] R.K. Mahajan, O. Parkash, Talanta 52 (2000) 691. [5] R.K. Mahajan, M. Kumar, V. Sharma, I. Kaur, Analyst 126 (2001) 505.
[6] R.K. Mahajan, M. Kumar, V. Sharma, I. Kaur, H. Singh, R. Kumar, Tetrahedron Lett. 42 (2001) 5315. [7] C.D. Gutsche, Calixarenes, RSC. MonoGraphs in Supramolecular Chemistry No.1, Royal Society of Chemistry, Cambridge, UK, 1989. [8] C. Asfieri, E. Dradi, A. Pochina, R. Ungaro, C.D. Andreeti, J. Chem. Soc., Chem. Commun. (1983) 1075. [9] D.N. Reinhoudt, J.F. Engbersen, Z. Brozozka, H.H. Van den Viekkert, G.W. Honig, A.J. Holterman, U.H. Verkerk, Anal. Chem. 66 (1994) 3618. [10] Z. Asfari, C. Bressot, J.F. Rozol, H. Rouquette, S. Eymard, V. Lamare, B. Tourmois, Anal. Chem. 67 (1995) 3133. [11] W.J. McDowell, G.N. Case, J.A. McDonough, R.A. Bartsh, Anal. Chem. 64 (1992) 3013. [12] I.H. Gerow, M.V. Davis, Sep. Sci. Technol. 14 (1979) 395. [13] I.H. Gerow, J.E. Smith, M.V. Davis, Sep. Sci. Technol. 16 (1981) 519. [14] E. Blausius, K.-H. Nilles, Radiochim. Acta 359 (1984) 173. [15] W.W. Schultz, L.A. Bray, Sep. Sci. Technol. 22 (1987) 191. [16] J.-F. Dozol, in: L. Cecille, M. Casarci, L. Pietrelli (Eds.), New Separation Chemistry Techniques for Radioactive Waste and other Applications, Elsevier, Amsterdam, 1991, p. 163. [17] L.Cecille (Ed.), Radioactive waste Management and Disposal, Elsevier, London, 1991. [18] D. Wang, S.J. Shih, Analyst 110 (1985) 635. [19] G.F. Michael, M. David, S.M. William, D.G. Jermy, Analyst 121 (1996) 127. [20] M. Kumar, G. Hundal, V. Bhalla Madhu, M. Singh, J. Inclu. Phenom. Macrocyclic Chemistry (2000) 461.
Cesium ion selective electrode based on calix[4]crown ether ester /
R.K. Mahajan *, Manov Kumar, V. Sharma (nee Bhalla), Inderpreet Kaur Department of Chemistry, Guru Nanak Dev University, Amritsar 143005, India Received 26 November 2001; received in revised form 15 April 2002; accepted 25 April 2002
Abstract The potentiometric response characteristics of cesium ion selective PVC membrane electrode employing calix[4]crown ether /ester as an ionophore were investigated. The electrode exhibit a good response for cesium ion over wide concentration range of 5.0 /10 6 /1.0 /10 1 M with a Nernstian slope of 59 mV per decade. The detection limit of electrode is 5.0 /10 6 M. The electrode was found to have selectivity for cesium ion over alkali, alkaline and transition metals. The response time of the electrode is less than 20 s and can be used for more than 4 months without observing any divergence in potentiometric response. The electrode response was stable over wide pH range. # 2002 Elsevier Science B.V. All rights reserved. Keywords: Cesium ion; Sensor; Calix[4]crown ether /ester
1. Introduction Macrocyclic compounds, due to their selective receptor properties and ease of structural modification, have been employed as ionophores in ion selective electrodes for the determination of alkali, alkaline and many transition metal ions [1 /6]. Calix-crown compounds show strong affinities for complexation of alkali and alkaline earth metals. The analytical chemistry of cesium is complicated by the similarity of its physical properties to other group I metals [7 /9]. It has been shown that crown ethers and the derivatives of 1,3-alternate calix[4]crown-6 extract Cs ion efficiently from * Corresponding author. Fax: /91-183-258-820 E-mail address: [email protected] (R.K. Mahajan).
nuclear waste solutions by solvent extraction [10 /16]. The major sources of cesium involves nuclear waste materials and therefore the selective removal of 137Cs from medium level radioactive waste is an important environmental and technological problem [11,17].The toxicity of cesium and its ability to displace potassium from muscles and red cells,demand more attention from analytical chemists to develop such techniques which can determine Cs ions concentration in the nuclear waste solutions. The present paper deals with an ion selective electrode based on calix[4]crown ether-ester for the determination of cesium ions, as it has been observed that ionophore (I) extracts cesium more efficiently compared with other metal ions tested. The cesium ion selective electrode exhibits a good response for cesium ion over
0039-9140/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved. PII: S 0 0 3 9 - 9 1 4 0 ( 0 2 ) 0 0 3 1 0 - 7
446
R.K. Mahajan et al. / Talanta 58 (2002) 445 /450
wide concentration range of 5.0 /10 6 /1.0 / 10 1 M with a Nernstian slope of 59 mV per decade. The proposed ion selective electrode incorporates PVC as supporting material to give a pseudo-solid sensing membrane and bis(2-ethylhexyl)sebacate as plasticizing agent. The performance of this electrode which involves linear range, detection limit, response time, slope etc, is in agreement and in many respects better than those reported in literature [18,19].
2. Experimental
Fig. 1. Calibration of ionophore electrodes for various alkali metal ions.
2.1. Reagents Calix[4]crown ether ester was prepared as reported earlier [20]. High molcular weight poly(vinyl chloride), PVC and bis(2-ethylhexyl)sebacate were obtained from Fluka. All other reagents used were of AnalyticalReagent grade. Doubly distilled deionised water (DDW) was used throughout.
Fig. 2. Plot showing the variation of membrane potential with pH at 1.0 /10 1 M Cs ions.
Table 1 The selectivity coefficients of diverse ions
2.2. Electrode preparation The procedure adopted to prepare the PVC membrane was to mix thoroughly 100.1 mg of powdered PVC, 200.1 mg of plasticizer bis(2ethylhexyl)sebacate and 7.0 mg of ionophore in 5
Diverse ions
KPot Cs,M
Log KPot Cs,M
Li K Na NH4 Mg2 Ca2 Ba2 Ni2 Co2 Cu2 Pb2 Hg2 Zn2 Cd2
1.35 /10 2 1.0 /10 2 5.0 /10 2 3.16 /10 2 1.2 /10 3 2.95 /10 4 7.94 /10 4 6.31 /10 4 3.31 /10 4 1.41 /10 4 3.98 /10 4 3.16 /10 3 1.78 /10 4 1.66 /10 2
/1.87 /2.00 /1.30 /1.50 /2.92 /3.53 /3.10 /3.20 /3.48 /3.85 /3.40 /2.50 /3.75 /1.78
R.K. Mahajan et al. / Talanta 58 (2002) 445 /450
447
2.3. Measurement of electrode potentials All the measurements of the electrode potentials were made with Elico LI-model-120 pH meter. The electrochemical system was as follows: Internal reference electrode Ag /AgCl
Internal reference solution 1.0 /10 2 M Cs
PVC membrane
Test solution
External reference electrode Ag /AgCl
The standard cesium chloride solutions used for calibration were obtained by the dilution of 1.0 / 10 1 M CsCl solutions and pH of these solutions lies between the functional pH range of the ion selective electrode, hence do not need any pH adjustment. Fig. 3. Plots showing E vs. Log[Cs ] in the presence of Na ions at varying level of interference (m) 1.0 /10 2, (j) 1.0 / 10 3, (') 5.0 /10 4 and ( /) 0.0 M Na .
3. Results and discussion 3.1. Response characteristics of the electrode
Fig. 4. Plots showing E vs. Log[Cs ] in the presence of Cd2 ions at varying level of interference (m) 1.0 /10 2, (j) 1.0 / 10 4, (') 1.0 /10 5 and ( /) 0.0 M Cd2 .
ml of tetrahydrofuran. After complete dissolution of all the components and thorough mixing, the resulting solution was transferred to a petridish of 2 cm in diameter. Solvent was made to evaporate at room temperature. After 24 h, a transparent membrane of 0.4 mm thickness was obtained. The membrane was cut to size, attached to the PVC tube with the help of PVC glue and conditioned for 48 h by soaking in 1.0 /10 2 M cesium chloride solution.
Calix[4]crown ether /ester contains oxygen atoms as donor atoms which can effectively coordinate with alkali metal ions. In the preliminary experiments, it was used to prepare PVC membrane ion selective electrodes based on calix[4]crown ether /ester for sodium, potassium and cesium ions. The potential responses of the electrodes for Na , K and Cs ions are shown in Fig. 1. The non-Nernstian slopes for sodium and potassium ion selective electrodes were found to be 48.2 and 20.2 mV per decade, respectively. The electrode response order for these alkali metal ions was found to be Cs /Na /K . The PVC membrane electrode based on calix[4]crown ether /ester demonstrated a linear potentiometric response for Cs ions in the concentration range 5.0 /10 6 /1.0 /10 1 M with a Nernstian slope of 59 mV decade 1. The detection limit of electrode is 5.0 /10 6 M. The response time of the sensor was measured at various concentrations of test solution and it was found to be less than 20 s and no change was observed upto 5 min. Potentials were monitored periodically at fixed concentration and standard deviation of ten identical measurements was 9/2 mV.
448
Ionophore
Response time(s)
Linearity (M)
Detection limit (M)
Slope (mV)
log KPot Cs,M Li
15-Crown-5 phosphotungstic acid precipitate [18] 2,3-Benzoquino-crown-5 [19] Calix[4]crown ether-ester
B/60 B/30 B/20
1.0 /10 1 /1.0 /10 4 1.0 /10 1 /1.0 /10 4 1.0 /10 1 /5.0 /10 6
1.0 /10 5 1.0 /10 5 5.0 /10 6
60 51.9 59
Na
K
NH4
/0.89 /0.46 /0.31 / /3.00 /2.38 /0.99 /1.40 /1.87 /1.30 /2.0 /1.50
R.K. Mahajan et al. / Talanta 58 (2002) 445 /450
Table 2 Comparison studies of Cs -ion selective electrode based on calix[4]crown ether /ester and previously reported in literature
R.K. Mahajan et al. / Talanta 58 (2002) 445 /450
Table 3 Analysis of water sample spiked with cesium(I) Sample no.
[Cs ]AAS (ppm)/S.D. (n /4)
[Cs ]ISE (ppm)/S.D. (n /4)
1 2 3 4
50/0.3 29/0.4 19.5/0.3 8.5/0.3
49.5/0.2 29.1/0.3 19.3/0.3 8.4/0.2
3.2. Effect of pH on response characteristics of the electrode The pH dependence of PVC membrane Cs ion selective electrode based on calix[4]crown ether / ester was examined over the pH range 1/11 (Fig. 2) at cesium ion concentration 1.0 /10 1 M and the electrode shows no significant change in potentiometric response in the wide pH range of 4 /9.Therefore, all the potentiometric measurements were made at pH 6.1 which is the pH of the cesium chloride solution. 3.3. Selectivity Selectivity is one of the most important characteristic of a sensor, as it helps to determine whether a reliable measurement in the target sample is possible. This is measured in terms of potentiometric selectivity coefficients (log KPot Cs,M) which has been evaluated using fixed interference method at 1.0 /10 2 M concentration of interfering ions. The fixed interference method is based on semi emperical Nikolsky /Eisenman equation. Under ideal conditions, the electrode response function follows Nernst equation Pot EISE E 09RT =ZA F ln[aA SKA;B (aB )ZA =ZB ]
where, EISE is measured potential, E0 is standard cell potential aA and aB are the activities of primary and interfering ions. KPot A,B can be calculated using expression Pot KA;B aA =(aB )ZA =ZB
The potentiometric selectivity coefficients (log KPot Cs,M) measures the response of the electrode
449
for the primary ion in the presence of foreign ions. The selectivity coefficients data indicate that 2 for KPot Cs,M values are of the order of 10 4 for the divalent metal ions monovalent and 10 (except for the cadmium ions). Therefore, the electrode can be used for the determination of cesium ions in the presence of interfering ions (Table 1). As the selectivity coefficients values for Na and Cd2 are quite high they are expected to cause interference. They do not cause any disturbance to the performance of electrode when present in small concentration, as KPot Cs,M values dependent on the relative concentration of primary ion as well as interfering ions. In order to establish the limiting concentration of Na and Cd2 ions that can be tolerated in the determination of cesium ions, various experiments were carried out at different concentrations of these interfering ions which are shown in the plots of Figs. 3 and 4, respectively. It is evident from these plots that Na and Cd2 when present at concentration less than 5.0 /10 4 and 1.0 /10 5 M respectively caused no divergence in the potentiometric response of the electrode. Fig. 3 shows that Na ions when at high concentration caused significant divergence from the original E versus log[Cs ] plot and therefore cannot be tolerated over whole concentration range. The cesium ion selective electrode based on calix[4]crown ether /ester is comparable and superior in many respects than those reported in literature (Table 2). As shown in Table 2, the proposed Cs ion selective electrode posses better linear range (5.0 /10 6 /1.0 /10 1 M) and detection limit 5.0 /10 6 M than previously reported ISEs for cesium. The Cs-ion selective electrode based on calix[4]crown ether /ester shows good selectivity for Cs ion over other alkali metal ions. The applicability of the sensor is illustrated by measuring the cesium(I) ion potentiometrically in doubly distilled deionised water (DDW) spiked with 50, 30, 20 and 10 ppm cesium (I). The results obtained were compared with those obtained from atomic absorption spectrometric analysis (Table 3) and were found in good agreement.
450
R.K. Mahajan et al. / Talanta 58 (2002) 445 /450
4. Conclusion It can be concluded that the Cs-ion selective electrode based on calix[4]crown ether /ester exhibit good sensitivity, detection limit, reproducibilities, selectivities and better life time.
Acknowledgements We are thankful to Council of Scientific and Industrial Research, New Delhi,India for financial assistance. One of us (I.K) is thankful to Guru Nanak Dev University, Amritsar, India for providing Junior Research Fellowship.
References [1] R.J. Foster, A. Cadogan, M.T. Diaz, D. Diamond, Sens. Actuators B 4 (1991) 325. [2] J.S. Kim, I.Y. Yu, J.H. Pang, J.K. Kim, Y-III. Lee, Y.Z. Oh, Microchem. J. 58 (1998) 225. [3] J.S. Kim, I.H. Suh, J.K. Kim, M.H. Cho, J. Chem. Soc., Perkin Trans. 1 (1998) 307. [4] R.K. Mahajan, O. Parkash, Talanta 52 (2000) 691. [5] R.K. Mahajan, M. Kumar, V. Sharma, I. Kaur, Analyst 126 (2001) 505.
[6] R.K. Mahajan, M. Kumar, V. Sharma, I. Kaur, H. Singh, R. Kumar, Tetrahedron Lett. 42 (2001) 5315. [7] C.D. Gutsche, Calixarenes, RSC. MonoGraphs in Supramolecular Chemistry No.1, Royal Society of Chemistry, Cambridge, UK, 1989. [8] C. Asfieri, E. Dradi, A. Pochina, R. Ungaro, C.D. Andreeti, J. Chem. Soc., Chem. Commun. (1983) 1075. [9] D.N. Reinhoudt, J.F. Engbersen, Z. Brozozka, H.H. Van den Viekkert, G.W. Honig, A.J. Holterman, U.H. Verkerk, Anal. Chem. 66 (1994) 3618. [10] Z. Asfari, C. Bressot, J.F. Rozol, H. Rouquette, S. Eymard, V. Lamare, B. Tourmois, Anal. Chem. 67 (1995) 3133. [11] W.J. McDowell, G.N. Case, J.A. McDonough, R.A. Bartsh, Anal. Chem. 64 (1992) 3013. [12] I.H. Gerow, M.V. Davis, Sep. Sci. Technol. 14 (1979) 395. [13] I.H. Gerow, J.E. Smith, M.V. Davis, Sep. Sci. Technol. 16 (1981) 519. [14] E. Blausius, K.-H. Nilles, Radiochim. Acta 359 (1984) 173. [15] W.W. Schultz, L.A. Bray, Sep. Sci. Technol. 22 (1987) 191. [16] J.-F. Dozol, in: L. Cecille, M. Casarci, L. Pietrelli (Eds.), New Separation Chemistry Techniques for Radioactive Waste and other Applications, Elsevier, Amsterdam, 1991, p. 163. [17] L.Cecille (Ed.), Radioactive waste Management and Disposal, Elsevier, London, 1991. [18] D. Wang, S.J. Shih, Analyst 110 (1985) 635. [19] G.F. Michael, M. David, S.M. William, D.G. Jermy, Analyst 121 (1996) 127. [20] M. Kumar, G. Hundal, V. Bhalla Madhu, M. Singh, J. Inclu. Phenom. Macrocyclic Chemistry (2000) 461.