Determination of cerium ion by polymeric membrane and coated graphite electrode based on novel pendant armed macrocycle

Plasticized membranes using 2,3,4:12,13,14-dipyridine-1,3,5,8,11,13,15,18-octaazacycloicosa-2,12-diene (L₁) and 2,3,4:12,13,14-dipyridine-1,5,8,11,15,18-hexamethylacrylate-1,3,5,8,11,13,15,18-octaazacycloicosa-2,12-diene (L₂) have been prepared and explored as Ce(III) selective sensors. Effect of various plasticizers viz. dibutylphthalate (DBP), tri-n-butylphthalate (TBP), o-nitrophenyloctylether (o-NPOE), dioctylphthalate (DOP), benzylacetate (BA) and anion excluders, sodium tetraphenylborate (NaTPB) and potassium tetrakis p-(chlorophenyl) borate was studied in detail and improved performance was observed. Optimum performance was observed for the membrane sensor having a composition of L₂:PVC:o-NPOE:KTpClPB in the ratio of 6:34:58:2 (w/w, mg). The performance of the membrane based on L₂ was compared with polymeric membrane electrode (PME) as well as with coated graphite electrode (CGE). The electrodes exhibit Nernstian slope for Ce(III) ions with limits of detection of 8.3 × 10⁻⁸ mol L⁻¹ for PME and 7.7 × 10⁻⁹ mol L⁻¹ for CGE. The response time for PME and CGE was found to be 12 s and 10 s respectively. The potentiometric responses are independent of the pH of the test solution in the pH range 3.5-7.5 for PME and 2.5-8.5 for CGE. The CGE could be used for a period of 5 months. The practical utility of the CGE has been demonstrated by its usage as an indicator electrode in potentiometric titration of oxalate and fluoride ions with Ce(III) solution. The proposed electrode was also successfully applied to the determination of fluoride ions in mouthwash solution and oxalate ions in real samples.     

Development of electrochemical sensors for nano scale Tb(III) ion determination based on pendant macrocyclic ligands

The two macrocyclic pendant ligands 3,4,5:12,13,14-dipyridine-2,6,11,15-tetramethyl-1,7,10,16-tetramethylacrylate-1,4,7,10,13,16-hexaazacyclooctadeca-3,13-di ene (L₁) and 3,4,5:12,13,14-dipyridine-2,6,11,15-tetramethyl-1,7,10,16-tetra(2-cyano ethane)-1,4,7,10,13,16-hexaazacyclooctadeca-3,13-diene (L₂) have been synthesized and explored as neutral ionophores for preparing poly(vinylchloride) (PVC) based membrane sensors selective to Tb(III) ions. Effects of various plasticizers and anion excluders were studied in detail and improved performance was observed. The best performance was obtained for the membrane sensor having a composition of L₁: PVC:1-CN:NaTPB in the ratio of 6: 32: 58: 4 (w/w; mg). The performance of the membrane based on L₁ was compared with polymeric membrane electrode (PME) as well as with coated graphite electrode (CGE). The electrodes exhibit Nernstian slope for Tb³⁺ ions with limits of detection of 3.4 × 10⁻⁸ mol L⁻¹ for PME and 5.7 × 10⁻⁹ mol L⁻¹ for CGE. The response time for PME and CGE was found to be 10 s and 8 s, respectively. The potentiometric responses are independent of the pH of the test solution in the pH range 3.0-7.5 for PME and 2.0-8.5 for CGE. The CGE has found to work satisfactorily in partially non-aqueous media upto 30% (v/v) content of methanol, ethanol and 20% (v/v) content of acetonitrile and could be used for a period of 5 months. The CGE was used as indicator electrode in the potentiometric titration of Tb³⁺ ions with EDTA and in determination of fluoride ions in various samples. It can also be used in direct determination of Tb³⁺ ions in tap water and various binary mixtures with quantitative results.     

Novel Ag ion-selective electrodes based on two new mixed azathioether crowns containing a 1,10-phenanthroline sub-unit

Novel polymeric membrane (PME) and coated graphite (CGE) silver-selective electrodes based on two recently synthesized mixed azathioether crowns containing a 1,10-phenanthroline sub-unit were prepared. The electrodes reveal a Nernstian behavior over quite wide Ag⁺ ion concentration ranges with a very low limits of detection (LOD) (i.e. down to 1.0×10⁻⁸ M for CGEs and 8.0×10⁻⁷ M for PMEs). The potentiometric responses are independent of the pH of the test solution in the pH range 3.0-7.0. The electrodes possess advantages of low resistance, very fast response time, relatively long lifetimes and, especially, good selectivities relative to a wide variety of other cations. The electrodes were used, as indicator electrodes, in the potentiometric titration of silver ion and in the determination of Ag⁺ in waste water, photographic emulsion and radiographic and photographic films.     

Determination of cobalt ions at nano-level based on newly synthesized pendant armed macrocycle by polymeric membrane and coated graphite electrode

Poly(vinylchloride) (PVC) based membranes of macrocycles 2,3,4:9,10,11-dipyridine-1,3,5,8,10,12-hexaazacyclotetradeca-2,9-diene (L₁) and 2,3,4:9,10,11-dipyridine-1,5,8,12-tetramethylacrylate-1,3,5,8,10,12-hexaazacyclotetradeca-2,9-diene (L₂) with NaTPB and KTpClPB as anion excluders and dibutylphthalate (DBP), benzyl acetate (BA), dioctylphthalate (DOP), o-nitrophenyloctyl ether (o-NPOE) and tri-n-butylphosphate (TBP) as plasticizing solvent mediators were prepared and investigated as Co²⁺ selective electrodes. The best performance was observed with the membranes having the composition L₂:PVC:TBP:NaTPB in the ratio of 6:39:53:2 (w/w; mg). The performance of the membrane based on L₂ was compared with polymeric membrane electrode (PME) and coated graphite electrode (CGE). The PME exhibits detection limit of 4.7 × 10⁻⁸ M with a Nernstian slope of 29.7 mV decade⁻¹ of activity between pH 2.5 and 8.5 whereas CGE exhibits the detection limit of 6.8 × 10⁻⁹ M with a Nernstian slope of 29.5 mV decade⁻¹ of activity between pH 2.0 and 9.0. The response time for PME and CGE was found to be 11 and 8 s, respectively. The CGE has been found to work satisfactorily in partially non-aqueous media up to 35% (v/v) content of methanol, ethanol and 25% (v/v) content of acetonitrile and could be used for a period of 4 months. The CGE was successfully applied for the determination of Co²⁺ in real and pharmaceutical samples and as an indicator electrode in potentiometric titration of cobalt ion.     

Ion imprinted polymer based ion-selective electrode for the trace determination of dysprosium(III) ions

Ion-selective electrode (ISE) was designed by dispersing the dysprosium(III) IIP particles in 2-nitrophenyloctyl ether plasticizer and then embedded in polyvinyl chloride matrix. The ISE shows a Nernstian response for dysprosium(III) over a wide concentration range (8.0 × 10⁻⁶ to 1.0 × 10⁻¹ M) with a slope of 21.7 mV per decade. The limit of detection was 2 × 10⁻⁶ M. This sensor has a very fast response time (∼10 s) and offers high selectivity compared to conventional chemical sensors towards dysprosium(III) with respect to several alkali, alkaline earth and transition metal ions as the selectivity is 10-100-fold better. The sensor was used for determination of dysprosium(III) ions by potentiometric (EDTA) titration and has been successfully demonstrated for the determination of fluoride in mouth wash solution.     

The first use of a Rh(III) complex as a novel ionophore for thiocyanate-selective polymeric membrane electrodes

The feasibility of a newly synthesized Rh(III) complex, Rh[(trpy)(bpy)Cl](PF₆)₂, as a novel ionophore for the preparation of anion-selective polymeric membrane electrodes was tested. The ionophore exhibited anti-Hofmeister behavior with enhanced potentiometric selectivity toward thiocyanate ion compared to other anions. The influence of some experimental parameters such as membrane composition, nature and amount of plasticizer and additive and concentration of internal solution on the potential response of the SCN⁻ sensor were investigated. The electrode exhibits a Nernstian response for SCN⁻ over a wide concentration range (1.0 × 10⁻⁵ to 1.0 × 10⁻¹ M) with a slope −58.7 ± 0.5 mV per decade and a detection limit of 4.0 × 10⁻⁶ M (0.23 ppm). It could be used in a pH range of 3.0-8.0 and has a fast response time of about 15 s. The proposed sensor was used for the determination of thiocyanate ions in real samples such as urine and saliva of smokers and nonsmokers and, as an indicator electrode, in potentiometric titrations of SCN⁻ ion.     

Fabrication of novel coated pyrolytic graphite electrodes for the selective nano-level monitoring of Cd ions in biological and environmental samples using polymeric membrane of newly synthesized macrocycle

Novel 5-amino-1,3,4-thiadiazole-2-thiol unit based macrocyclic ionophore 5,11,17-trithia-1,3,7,9,13,15,19,20,21-nonaazatetracyclo[14.2.1.1^4,7.1^10,13]henicosa-4(20),10(21),16(19)-triene-6,12,18-trithione (M₁), was synthesized and characterized. Preliminary studies on M₁ have showed that it has more the affinity toward Cd²⁺ ion. Thus, the macrocyclic ionophore (M₁) was used as electroactive material in the fabrication of PVC-membrane electrodes such as polymeric membrane electrode (PME), coated graphite electrode (CGE) and coated pyrolytic graphite electrode (CPGE) were prepared and its performance characteristic were compared with. The electroanalytical studies performed on PME, CGE and CPGE revealed that CPGE having membrane composition M₁:PVC:1-CN:NaTPB in the ratio of 7:37:54:2 exhibits the best potentiometric characteristics in terms of detection limit of 7.58 × 10⁻⁹ mol L⁻¹, Nernstian slope of 29.6 mV decade⁻¹ of activity. The sensor was found to be independent of pH in the range 2.5–8.5. The sensor showed a fast response time of 10 s and could be used over a period of 4 months without any significant divergence in its potentiometric characteristics. The sensor has been employed for monitoring of the Cd²⁺ ion in real samples and also used as an indicator electrode in the potentiometric titration of Cd²⁺ ion with EDTA.     

Comparative studies of mercapto thiadiazoles self-assembled on gold nanoparticle as ionophores for Cu(II) carbon paste sensors

Comparative studies of the potentiometric behavior of three mercapto compounds [2-((5-mercapto-1,3,4-thiadiazol-2-ylimino)methyl)phenol] (MTMP), [5-(2-methoxy benzylidene amino)-1,3,4-thiadiazole-2-thiol] (MBYT) and [5-(pyridin-2-ylmethyleneamino)-1,3,4-thiadiazole-2-thiol] (PYTT) self-assembled on gold nanoparticles (GNPs) as ionophores in carbon paste electrodes (CPEs) have been made. These mercapto thiadiazole compounds were self-assembled onto gold nanoparticles and then incorporated within carbon paste electrode. The self-assembled ionophores exhibit a high selectivity for copper ion (Cu²⁺), in which the sulfur and nitrogen atoms in their structure play a role as the effective coordination donor site for the copper ion. These carbon paste electrodes were applied as indicator electrodes for potentiometric determination of copper ions. The sensor based on PYTT exhibits the working concentration range of 4.0 × 10⁻⁹ to 7.0 × 10⁻² M and a Nernstian slope of 28.7 ± 0.3 mV decade⁻¹ of copper activity. The detection limit of electrode was 1.0 × 10⁻⁹ M and potential response was pH independent across the range of 3.0-6.5. It exhibited a quick response time of <5 s and could be used for a period of 45 days. The ion selectivity of this electrode for Cu²⁺ was over 10⁴ times that for other metal cations. The application of prepared sensors has been demonstrated for the determination of copper ions in spiked water and natural water samples.     

Investigation of Silver(I) Ion Sensing Property of Ruthenium(II) Thiosemicarbazone Complex Using Coated Graphite and Polymeric Membrane Electrodes

A ruthenium(II) complex [Ru(PPh₃)₂(pytsc)₂] {Hpytsc = pyridine‐2‐carbaldehydethiosemicarbazone, (C₅H₅N)C²(H)=N³‐N²(H)‐C¹(=S)N¹H} has been used as an ion carrier for the selective determination of silver(I) ions in solution. Silver(I) ion‐selective coated graphite based (CGE) and PVC polymeric membrane based (PME) electrodes exhibit Nernstian slope for silver(I) ions over a wide concentration range from 1.0 × 10⁻¹ M to 5.0 × 10⁻⁶ M (with CGE) and 1.0 × 10⁻¹ M to 2.0 × 10⁻⁵ M (with PME). The working pH range of these electrodes has been found to be from 1.2 to 7.2 for CGE and 2.2 to 6.5 for PME. The proposed CGE sensor exhibits better analytical features like sensitivity and selectivity towards different secondary ions in comparison to the corresponding PME with no interference from mercury(II) ions . These electrodes also act as indicator electrodes in potentiometric titration and have been successfully used for the determination of silver content in solution of real samples (1 gm dissolved in 100 mL of dilute nitric acid) such as silver ornaments and thin silver foils. Silver content determined by the use of ion selective electrode was found to vary in the concentration range from 1.20 x 10⁻² M to 7.45 x 10⁻² M and results were found to be comparable with those obtained from the traditional volumetric method of analysis. It is the first report of a metal‐ligand complex used as an ion carrier in ion selective electrode, which is selective for a metal ion other than the one used in the complex.     

Al(III)-selective electrode based on newly synthesized xanthone derivative as neutral ionophore

The suitability of a xanthone derivative, 1-hydroxy-3-methyl-9H-xanthen-9-one (HMX) as a neutral ionophore for the preparation of a polyvinylchloride (PVC) membrane electrode for aluminum(III) ions was investigated. The prepared electrode exhibits a Nernstian response for Al³⁺ ions over a wide concentration range (1.0 × 10⁻⁶ to 1.6 × 10⁻¹ M) with a limit of detection 6.0 × 10⁻⁷ M. It has a relatively fast response time and can be used for at least three months without any considerable divergence in potentials. The proposed membrane electrode revealed very good selectivity for Al³⁺ ions over a wide variety of other cations and could be used at a working pH range of 3.0-8.5. It was used as an indicator electrode in potentiometric titration of aluminum ions with EDTA and in the determination of Al³⁺ in different real samples.     

A cerium(III) selective polyvinyl chloride membrane sensor based on a Schiff base complex of N,N'-bis[2-(salicylideneamino)ethyl]ethane-1,2-diamine

A polyvinyl chloride (PVC) based membrane sensor for cerium ions was prepared by employing N,N′-bis[2-(salicylideneamino)ethyl]ethane-1,2-diamine as an ionophore, oleic acid (OA) as anion excluder and o-nitrophenyloctyl ether (o-NPOE) as plasticizer. The plasticized membrane sensor exhibits a Nernstian response for Ce(III) ions over a wide concentration range (1.41 × 10⁻⁷ to 1.0 × 10⁻² M) with a limit of detection as low as 8.91 × 10⁻⁸ M. It has a fast response time (<10 s) and can be used for 4 months. The sensor revealed a very good selectivity with respect to common alkali, alkaline earth and heavy metal ions. The response of the proposed sensor is independent of pH between 3.0 and 8.0. It was used as an indicator electrode in potentiometric titration of fluoride, carbonate and oxalate anions and determination of cerium in simulated mixtures.     

Fluoride determination in some mouth wash preparations by a novel La(III) graphite coated membrane sensor based on amitraz

Solution studies on the binding properties of N-2,4-dimethylphenyl-N′-ethylformamidine (amitraz) toward nine lanthanide ions including lanthanum, cerium, neodium, samarium, europium, gadolinium, terbium, dysprosium, ytterbium and some other transition and heavy metal ions such as copper, lead, cobalt, nickel ions, showed a selective 1:1 complexation between amitraz and lanthanum ions. Consequently, amitraz was applied as an ion carrier in construction of a novel poly(vinyl chloride) membrane sensor for La(III). The sensor has a linear dynamic range of 1.0 × 10⁻¹ to 1.0 × 10⁻⁷ M with a Nernstian slope of 19.8 ± 0.2 mV per decade and a detection limit of 8.0 × 10⁻⁸ M. The proposed sensor displays a fast response time (<8 s), and can be used for at least 2 months without any considerable divergences in the potentials. The La(III) membrane sensor revealed comparatively good selectivity with respect to most of cations including alkaline, alkaline earth, and some transition and heavy metal ions. It could be used in a pH range of 3.0-9.0. The proposed membrane electrode was used as an indicator electrode in the potentiometric titration of La(III) ions with an EDTA solution, and also in the determination of fluoride concentration in some mouth wash preparations.     

Highly Selective and Sensitive Membrane Sensors for Copper(II) Ion Based on a New Benzo‐Substituted Macrocyclic Diamide 6,7,8,9,10‐Hexahydro‐2H‐1,13,4,7,10‐benzodioxatriazacyclopentadecine‐3,11(4H,12H)‐dione

Novel PVC membrane (PME) and coated graphite (CGE) Cu²⁺‐selective electrodes based on 5,6,7,8,9,10‐hexahydro‐2H‐1,13,4,7,10‐benzodioxatriazacyclopentadecine‐3,11(4H,12H)‐dione are prepared. The electrodes reveal a Nernstian behavior over wide Cu²⁺ ion concentration ranges (1.0×10^?7–1.0×10^?1 M for PME and 1.0×10^?8–1.0×10^?1 M for CGE) with very low limits of detection (7.8×10^?8 M for PME and 9.1×10^?9 M for CGE). The potentiometric responses are independent of the pH of the test solutions in the pH range 2.7–6.2. The proposed electrodes possess very good selectivities for Cu²⁺ over a wide variety of the cations including alkali, alkaline earth, transitions and heavy metal ions. The practical utility of the proposed electrodes have been demonstrated by their use in the study of interactions between copper ions and human growth hormone (hGH) in biological systems, potentiometric titration of copper with EDTA and determination of copper content of a sheep blood serum sample and some other real samples.     

Lanthanum-selective sensors based on 3-amino-2-mercapto-3H-quinazolin-4-one in PVC matrix

A new solvent polymeric membrane (PME) and coated graphite (CGE) electrodes based on 3-amino-2-mercapto-3H-quinazolin-4-one as a suitable carrier for La(III) ion are described. The sensors exhibited a Nernstian response for La(III) ion over a wide concentration range (3.0 × 10^?7 to 1.0 × 10^?1 M for PME and 1.0 × 10^?7 to 1.0 × 10^?1 M for CGE) with a slope of 20.1 ± 0.3 (PME) and 23.4 ± 0.4 (CGE) mV decade^?1. The lower detection limits by PME and CGE were 2.0 × 10^?7 and 7.1 × 10^?8 M, respectively. The potentiometric response of the proposed electrodes was independent of the pH of the test solution in the pH range 3.0–9.0 with a fast response time (<10 s). The applications of prepared sensors were demonstrated in the determination of lanthanum ions in spiked water sample and also utilized for indirect determination of fluoride content of two mouth wash preparation samples.     

Organically nanoporous silica gel based on carbon paste electrode for potentiometric detection of trace Cr(III)

A new ion-selective electrode (ISE) for the detection of trace chromium(III) was designed by using 2-acetylpyridine and nanoporous silica gel (APNSG)-functionalized carbon paste electrode (CPE). The presence of APNSG acted as not only a paste binder, but also a reactive material. With 7.5 wt% APNSG proportions, the developed electrode exhibited wide dynamic range of 1.0 × 10⁻⁸ to 1.0 × 10⁻³ M toward Cr(III) with a detection limit of 8.0 × 10⁻⁹ M and a Nernstian slope of 19.8 ± 0.2 mV decade⁻¹. The as-prepared electrode displayed rapid response (∼55 s), long-time stability, and high sensitivity. Moreover, the potentiometric responses could be carried out with wide pH range of 1.5-5.0. In addition, the content of Cr(III) in food samples, e.g. coffee and tea leaves, has been assayed by the developed electrode, atomic absorption spectrophotometer (AAS) and atomic emission spectrometer (ICP-AES), respectively, and consistent results were obtained. Importantly, the response mechanism of the proposed electrode was investigated by using AC impedance and UV-vis spectroscopy.     

A selective and sensitive carbon composite coated platinum electrode for aluminium determination in pharmaceutical and mineral water samples

A novel coated wire electrode (CWE) for Al(III) ions is described based on 2-(1H-benzo[d]imidazole-1-yl)-1-phenylethanoneoxime as a new ionophore in carbon-PVC composite. The sensor exhibits significantly enhanced selectivity toward Al³⁺ ions over the concentration range 4.3 × 10⁻⁷ to 5.0 × 10⁻² M with a lower detection limit of 2.5 × 10⁻⁷ M and a Nernstian slope of 19.41 ± 0.52 mV decade⁻¹ of aluminium activity. This sensor has a short response time of about 10 s and is reproducible and stable for at least forty-five days. This proposed CWE which is designed for the first time revealed good selectivity for Al(III) over a wide variety of other cations. The performance of the sensor is best in the pH range of 3.1-5.5 and it also works well in partially non-aqueous medium. Moreover, the assembly has been successfully used as an indicator electrode in the potentiometric titration of aluminium (III) against EDTA and also in determining Al(III) quantitatively in pharmaceutical and mineral water samples.     

Coated wire linear alkylbenzenesulfonate sensor based on polypyrrole and improvement of the selectivity behavior

The potentiometric behavior of coated wire electrodes based on dodecylbenzenesulfonate-doped polypyrrole (PPy-DBS) and hyamine as ion exchanger was investigated. The PPy-DBS was prepared electrochemically by anodic polymerization of pyrrole in the presence of DBS⁻ ions in aqueous solution and used as ionophore for construction of the sensor. Two types of coated wire electrodes made of PVC-PPy-DBS and PVC-Hyamine-DBS, plasticized with ortho-nitrophenyloctylether (o-NPOE) showed the Nernstian behavior (with respective calibration slopes of about 58 and 60 mV per decade) over the DBS⁻ concentration range of 3.0×10⁻⁶ to 1.1×10⁻³ M and 5.0×10⁻⁶ to 1.3×10⁻³ M, respectively. The influence of membrane composition, type of plasticizer, and pH of test solution on the potentiometric responses of the two electrodes was investigated. The potentiometric response was independent of the pH of test solution in the range 3-10. The response time of electrodes was fast (10 s for both types of electrode), and they can be used for at least 3 months without any significant change in potential. The proposed electrodes revealed very good selectivity for DBS⁻ ion over diverse inorganic and organic anions. The potentiometric selectivity coefficients for the PPy-DBS based electrode revealed a significant improvement as compared to the electrode made by conventional Hyamine-DBS (Hya-DBS) anion exchanger. The proposed electrode was used for determination of DBS⁻ ion in some commercial detergents. The results of the potentiometric determinations were in satisfactory agreement with those obtained by a standard method (two-phase titration).     

Use of organofunctionalized nanoporous silica gel to improve the lifetime of carbon paste electrode for determination of copper(II) ions

A new functionalized nanoporous silica gel with dipyridyl group (DPNSG) was synthesized. Then, the potentiometric response of the copper(II) ion was investigated at a carbon paste electrode chemically modified with this newly designed functionalized nanoporous silica gel. The electrodes with DPNSG proportions of 15.0% (w/w) demonstrated very stable potentials. Calibration plots with Nernstian slopes for Cu²⁺ were observed, 28.4 (±1.0) mV decade⁻¹, over a wide linear concentration range (1.0 × 10⁻⁷ to 1.0 × 10⁻² M). The electrode exhibited a detection limit of 8.0 × 10⁻⁸ M. Moreover, the selectivity coefficients measured by the match potential method in acetate buffer, pH 5.5, were investigated. The electrode presented a response time of ∼50 s, high performance, high sensitivity in a wide range of cation activities and good long-term stability (more than 9 months). The method was satisfactory and was used to determine the copper ion concentration in waste waters, contaminated by this metal.     

Carbon nanotube composite coated platinum electrode for detection of Cr(III) in real samples

This paper demonstrates the application of composite multi-walled carbon nanotube (MWNT) polyvinylchloride (MWNT-PVC) based on 1,5-diphenylcarbazide as chromium ionophore in potentiometric measurement. The sensor shows a good Nernstian slope of 19.52 ± 0.40 mV/decade in a wide linear range concentration of 6.3 × 10⁻⁸ to 1.0 × 10⁻² M for Cr(NO₃)₃. The detection limit of this electrode was found to be 3.2 × 10⁻⁸ M of Cr(NO₃)₃ and is applicable in a pH range of 3.0-6.8. It has a short response time of about 10 s. This chromium electrode has a good selectivity over 16 various metal ions. The practical analytical utility of this electrode was demonstrated by measurement of Cr(III) in drinking water and mineral water samples without any serious preliminary pre-treatment and chromium in multivitamin.     

Application of 8-amino-N-(2-hydroxybenzylidene)naphthyl amine as a neutral ionophore in the construction of a lanthanum ion-selective sensor

In this work, a novel La(III) membrane sensor based on 8-amino-N-(2-hydroxybenzylidene)naphthylamine (AIP) is presented. This electrode reveals good selectivity for La³⁺ over a wide variety of lanthanides metal ions. Theoretical calculations and conductance study of AIP to lanthanum and some other metal ions were carried out and confirmed selectivity toward La(III) ions. The electrode comprises 7% AIP, 30% PVC, 61% NPOE and 2% KTpClPB. The sensor displays a linear dynamic range between 1.0 × 10⁻⁷ and 1.0 × 10⁻¹ M, with a nice Nernstian slope of 20.3 ± 0.3 mV per decade and a detection limit of 8.0 × 10⁻⁸ M. The potentiometric response is independent of pH in the range of 4.0-9.0. The proposed sensor posses the advantage of short response time, and especially, very good selectivity towards a large number of cations, such as Sm(III), Ce(III, Pr(III), Yb(III) and Hg(II), low detection limit and wide linear dynamic range in comparison with former ones. The electrode can be used for at least seven weeks without any considerable divergence in the potentials. It was used as an indicator electrode in the potentiometric titration of La(III) ions with EDTA. The sensor was applied to the determination of La(III) ions concentration in binary mixtures. It was also applied for the determination of fluoride ions in mouth wash preparations.