[Cu(L)](NO3)2 (L=4,7‐Bis(3‐aminopropyl)‐1‐thia‐4,7‐diazacyclononane) as a Suitable Ionophore for Construction of Thiocyanate‐Selective Electrodes and Their Use in Determination of Urinary and Salivary Thiocyanate Concentration

The construction, performance characteristics, and application of polymeric membrane (PME) and coated graphite (CGE) thiocyanate‐selective electrodes are reported. The electrodes were prepared by incorporating the complex [Cu(L)](NO₃)₂ (L=4,7‐bis(3‐aminopropyl)‐1‐thia‐4,7‐diazacyclononane) into a plasiticized poly(vinyl chloride) membrane. The influence of membrane composition, pH of test solution, and foreign ions were investigated. The electrodes reveal Nernstian behavior over a wide SCN^? ion concentration range (1.0×10^?6–1.0×10^?1 M for PME and 5.0×10^?7–1.0×10^?2 M for CGE) and show fast dynamic response times of 15 s and lower. The proposed sensors show high selectivity towards thiocyanate over several common organic and inorganic anions. They were successfully applied to the direct determination of thiocyanate in urine and saliva of smokers and nonsmokers, and as an indicator electrode in titration of Ag⁺ ions with thiocyanate.     

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.     

Polymeric membrane and coated graphite samarium(III)-selective electrodes based on isopropyl 2-[(isopropoxycarbothioyl)disulfanyl]ethanethioate

New polymeric membrane (PME) and coated graphite (CGE) samarium(III)-selective electrodes were prepared based on isopropyl 2-[(isopropoxycarbothioyl) disulfanyl]ethanethioate as a suitable neutral ionophore. The electrodes exhibit Nernstian slopes for Sm³⁺ ions over wide concentration ranges (1.0×10⁻⁵ to 1.0×10⁻¹ M for PME and 1.0×10⁻⁶ to 1.0×10⁻¹ M for CGE). The PME and CGE have limits of detection of 3.1×10⁻⁶ and 5.0×10⁻⁷ M, respectively, and response times of about 20 s. The potentiometric responses are independent of the pH of the test solution in the pH range 4.0-7.0. The proposed electrodes revealed good selectivities over a wide variety of other cations including alkali, alkaline earth, transition and heavy metal ions. The electrodes were successfully applied to the recovery of Sm³⁺ ion from tap water samples and also, as an indicator electrode, in potentiometric titration of samarium(III) ions.     

Electroanalytical Studies on Cobalt(II) Ion‐Selective Sensor of Polymeric Membrane Electrode and Coated Graphite Electrode Based on N2O2 Salen Ligands

Poly(vinyl chloride)‐based membranes of salen ligands, 2‐((E)‐((1R,2S)‐2‐((E)‐5‐tert‐butyl‐2‐hydroxybenzylideneamino)cyclohexylimino)methyl)‐4‐tert‐butyl phenol (S₁) and 2‐((E)‐((1R,2S)‐2‐((E)‐3,5‐di‐tert‐butyl‐2‐hydroxybenzylideneamino)cyclohexylimino)methyl)‐4,6‐di‐tert‐butylphenol (S₂) were fabricated and explored as cobalt(II) selective electrodes. The performance of the polymeric membrane electrode (PME) and coated graphite electrode (CGE) were compared and it was observed that CGE showed a wide working concentration range of 1.1×10^?8 to 1.0×10^?1 mol L^?1 with a limit of detection of 7.0×10^?9 mol L^?1 exhibiting the Nernstian slope 29.6 mV/decade of activity in the pH range 3.0–9.0. It was used for the determination of cobalt(II) ions in water, soil, beer, pharmaceutical samples and medicinal plants and would be used as an indicator electrode in potentiometric titration with EDTA.     

Silver(I)-selective membrane potentiometric sensor based on two recently synthesized ionophores containing calix[4]arene

Two new PVC membrane electrodes that are highly selective to Ag(I) ions were prepared using (L₁) calyx[4]arene (L₂) as two suitable neutral carriers. The silver(I) ion selective electrodes exhibit a good response for silver ion over a wide concentration range of 1.0 × 10⁻¹ to 4.2 × 10⁻⁶ M (L₁) and 1.0 × 10⁻¹ to 6.5 × 10⁻⁶ M (L₂) with a Nernstian slope of 60 mV per decade (L₁) and 58 mV per decade (L₂) at 25°C, and was found to be very selective, precise, and usable within the pH range 4.0–8.0. They have a response time of <15 s and can be used for at least 3 months without any measurable divergence in potential. The proposed sensors show a fairly good discriminating ability towards Ag⁺ ion in comparison to some hard and soft metal ions. The electrodes were used as indicator electrodes in the potentiometric titration of silver ion and in the determination of Ag⁺ in photographic emulsion and radiographic and photographic films. Published in Russian in Elektrokhimiya, 2009, Vol. 45, No. 7, pp. 862–868. The article is published in the original.     

Asymmetrical Schiff Bases as Carriers in PVC Membrane Electrodes for Cadmium (II) Ions

5‐[((4‐Methyl phenyl) azo)‐N‐(6‐amino‐2‐pyridin) salicylaldimine] (S₁), and 5‐[((4‐methyl phenyl) azo)‐N‐(2‐diamino‐2‐cyano‐1‐ethyl cyanide) salicylaldehyde] (S₂) with N and O donor atoms are effective ionophores to make Cd²⁺‐selective membrane electrodes. The electrodes based on S₁ and S₂ exhibits a Nernstian or near‐Nernstian response for cadmium ion over a wide concentration range 1.5×10^?1–7.5×10^?7 with a slope of 28 and 2.0×10^?1–4.0×10^?7 with a slope of 22, respectively. They have quick response and can be used for three or four months without any divergence in potential. The proposed sensors show fairly good selectivity over some alkali, alkaline earth, transition and heavy metal ions. The electrodes based on S₁ and S₂ can be used in the pH range 3.5–9. These electrodes were used as an indicator electrode in potentiometric titration of cadmium ion with EDTA and in the direct determination of cadmium ion in aqueous solutions.     

Polymeric membrane and coated graphite electrode based on newly synthesized tetraazamacrocyclic ligand for trace level determination of nickel ion in fruit juices and wine samples

Novel polymeric membrane electrode (PME) and coated graphite electrode (CGE) for nickel ion were prepared based on 2,9-(2-methoxyaniline)₂-4,11-Me₂-[14]-1,4,8,11-tetraene-1,5,8,12-N₄ as a suitable neutral ionophore. The addition of lipophilic anion excluder (NaTPB) and various plasticizers viz o-nitrophenyloctylether (o-NPOE), dioctylphthalate (DOP), dibutylphthalate (DBP), 1-chloronaphthalene (CN) and tri-n-butylphosphate (TBP) have found to improve the performance of the sensors. The best performance was obtained for the membrane sensor having a composition of I:NaTPB:TBP:PVC in the ratio 6:4:100:90 (w/w; mg). The electrodes exhibit Nernstian slopes for Ni²⁺ ions over wide concentration ranges of 4.6 × 10^?7–1.0 × 10^?1 M for PME and 7.7 × 10^?8–1.0 × 10^?1 M for CGE with limits of detection of 2.7 × 10^?7 M for PME and 3.7 × 10^?8 M for CGE. The response time for PME and CGE was found to be 10 and 8 s respectively. The potentiometric responses are independent of the pH of the test solution in the pH range 3.0–8.0. The proposed electrodes revealed good selectivities over a wide variety of other cations including alkali, alkaline earth, transition and heavy metal ions. The coated graphite electrode was used as an indicator electrode in the potentiometric titration of nickel ion with EDTA and in direct determination in different fruit juices and wine 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.     

1,3,4-Trisubstituted-2-azetidinone Derivatives as Novel Receptors for Bismuth(III) Ion-Selective Electrodes: Application in Pharmaceutical and Glass Samples

Abstract

Polymeric membrane electrodes (PMEs) and coated graphite electrodes (CGEs) containing 1,3,4-trisubstituted-2-azetidinone derivatives as ion carriers are reported here for bismuth(III) ion selectivity. These electrodes exhibited Nernstian response for Bi³⁺ ions over a wide concentration range (5.0 × 10^?7 M to 1.0 × 10^?1 M for CGE) with a lower detection limit of 3.98 × 10^?7 M (for CGE) and wide pH range (1.3–5.0). Compared to polymeric membrane electrode, the coated graphite electrode has shown better selectivity for Bi³⁺ ions with respect to common metal ions. Proposed electrodes have been used for the estimation of Bi³⁺ ions in pharmaceutical and glass samples.     

Bifunctional Ion‐Selective Electrode Based on C60‐Cryptand 22 for Silver and Iodine Ions

Fullerence C60‐cryptand 22 was prepared and successfully applied as the electric carrier in the PVC electrode membrane of a bifunctional ion‐selective electrode for cations, e.g., Ag⁺ ions as well as anions, e.g., I^? ions. The bifunctional ion‐selective electrode based on C60‐cryptand 22 can be applied as a Silver (Ag⁺) ion selective electrode with an internal electrode solution of 10^?3 M AgNO₃ in water (pH = 6.3), or as an Iodide (I^?) ion selective electrode with an acidic internal electrode solution of 10^?4 M KI_(aq) (pH = 2) in which the cryptand 22 is protonated, and the C60‐cryptand 22 is changed to C60‐Cryptand22–H⁺ and becomes an anionic electro‐carrier to absorb the I^? ion. The Ag⁺ ion selective electrode based on C60‐cryptand 22 gave a linear response with a near‐Nernstian slope (59.5 mV decade^?1) within the concentration range 10^?1‐10^?3 M Ag⁺_(aq). The Ag⁺ ion electrode exhibited comparatively good selectivity for silver ions, over other transition‐metal ions, alkali and alkaline earth metal ions. The Ag⁺ ion selective electrode with good stability and reproducibility was successfully used for the titration of Ag⁺_(aq) with Cl^? ions. The Iodide (I^?) Ion selective electrode based on protonated C60–cryptand22‐H⁺ also showed a linear response with a nearly Nernstian slope (58.5 mV decade^?1) within 10^?1 ‐ 10^?3 M I^? _(aq) and exhibited good selectivity for I^? ions and had small selectivity coefficients (10^?2–10^?3) for most of other anions, e.g., F^? , OH^?, CH₃COO^?, SO₄^2?, CO₃^2?, CrO₄^2?, Cr₂O₇^2? and PO₄^3? ions.     

Highly Selective Chromium(III) PVC‐Membrane Electrodes Based on Some Recently Synthesized Schiff's Bases

Three recently synthesized Schiff's bases were studied to characterize their ability as Cr³⁺ ion carrier in PVC‐membrane electrodes. The polymeric membrane (PME) and coated glassy carbon (CGCE) electrodes based on 2‐hydroxybenzaldehyde‐O,O′‐(1,2‐dioxetane‐1,2‐diyl) oxime (L1) exhibited Nernstian responses for Cr³⁺ ion over wide concentration ranges (1.5×10^?6–8.0×10^?3 M for PME and 4.0×10^?7–3.0×10^?3 M for CGCE) and very low limits of detection (1.0×10^?6 M for PME and 2.0×10^?7 M for CGCE). The proposed potentiometric sensors manifest advantages of relatively fast response and, most importantly, good selectivities relative to a wide variety of other cations. The selectivity behavior of the proposed Cr³⁺ ion‐selective electrodes revealed a considerable improvement compared to the best previously PVC‐membrane electrodes for chromium(III) ion. The potentiometric responses of the electrodes are independent of pH of the test solution in the pH range 3.0–6.0. The electrodes were successfully applied to determine chromium(III) in water samples.     

Electrochemically Generated Recognition Sites in Self‐doped Polyaniline Modified Electrodes for Voltammetric and Potentiometric Determination of Copper(II) Ion

Chemical recognition elements for copper(II) ion have been generated in electrodes modified with poly(aniline‐co‐metanilic acid), P(An‐co‐MA), membrane and the resulting electrodes were used as selective sensors for voltammetric and potentiometric determination of this ion in an extended pH range. The P(An‐co‐MA) membrane was electrodeposited from aqueous mixed monomer solutions of An and MA, without the presence of a supporting electrolyte. For generating the recognition elements, P(An‐co‐MA) modified electrodes were subjected to several consecutive reduction/oxidation potential steps in copper(II) ion solution. It seems that during these potential steps, the receptor sites of the membrane are adjusted to the size, complexing property and hard/soft nature of copper(II) ion. This electrochemically mediated templating process, provided a selective sensor for determination of copper(II) ion. The results of preconcentration/differential pulse anodic stripping voltammetry, indicated analytical relation between the peak current and concentration of copper(II) from 1.0×10⁻⁹ to 1.0×10⁻⁴ M. The interference effect of various metal ions was explored and it was found that only mercury and silver ions show a considerable interference. The sensor exhibited selective potentiometric response for copper(II) over a wide concentration range (1.0×10⁻⁸ to 1.0×10⁻³ M) with a Nernstian slope of 27.9±0.3 mV per decade of copper(II) ion activity.     

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.     

Synthesis,metal ion complexation and first use of a thia-aza substituted macrocyclic diamide as a novel sensing material for preparation of selective and sensitive poly(vinyl chloride)-membrane potentiometric sensors for Ag+ ion

A novel thia-aza substituted macrocyclic diamide 7,10,13-triaza-1-thia-4,16-dioxa-20,24-dimethyl-2,3;17,18-dibenzo-cyclooctadecane-6,14-dione (L) was synthesized and stability of its complexes with several alkaline earth, transition and heavy metal ions were studied conductometrically in methanol solution. The resulting 1:1 Ag⁺–L complex found to be the most stable one among all cation complexes studied. The optimized structures of the ligand and its Ag⁺ complex were also investigated. Based on the preliminary results thus obtained, L was used as an excellent sensing material to prepare polymeric membrane (PME) and coated graphite (CGE) silver-selective electrodes. The electrodes revealed a Nernstian behavior over wide Ag⁺ ion concentration ranges (i.e., 2.0 × 10^?6–1.0 × 10^?2 M for PME and 5.0 × 10^?7–1.0 × 10^?2 M for CGE). The potentiometric responses were independent of pH of the test solution in the range 2.9–6.8. The electrodes possessed advantages of low resistance, relatively fast response time, long lifetimes and, especially, good selectivity 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⁺ ion in waste water, photographic emulsion, radiographic and photographic films and dental amalgams.     

Electroanalytical Studies of Chromone Based Ionophores for the Selective Determination of Arsenite Ion

Two chemosensors 4H‐1‐benzopyran‐3‐carboxaldehyde, 4‐oxo‐, 3‐(2‐phenylhydrazone), [I₁] and 4H‐1‐benzopyran‐3‐carboxaldehyde, 4‐oxo‐, 3‐[2‐(2,4‐dinitrophenyl)hydrazone], [I₂] with hydrazone‐NH group as binding site have been shown excellent selectivity for arsenite ion. It is confirmed by the UV‐vis titration that I₂ is more selective than I₁. The performance of the coated graphite electrode (CGE) was found to be better than polymeric membrane electrode (PME) in terms of linear range of 4.89×10^?7–1.0×10^?1 mol L^?1, low detection limit of 8.31×10^?8 mol L^?1 and short response time. The proposed sensors were also used to determine the arsenite ion in different water samples.     

Mixed Aza‐Thioether Crowns Containing a 1,10‐Phenanthroline Sub‐Unit as Neutral Ionophores for Silver Ion

Three different recently synthesized aza‐thioether crowns containing a 1,10‐phenanthroline sub‐unit (L1–L3) and a corresponding acyclic ligand (L4) were studied to characterize their abilities as silver ion ionophores in PVC‐membrane electrodes. Novel conventional silver‐selective electrodes with internal reference solution (CONISE) and coated graphite‐solid contact electrodes (SCISE) were prepared based on one of the 15‐membered crowns containing two donating S atoms and two phenanthroline‐N atoms (L1). The electrodes reveal a Nernstian behavior over wide Ag⁺ ion concentration ranges (1.0×10^?5?1.0×10^?1 M for CONISE and 5.0×10^?8?4.0×10^?2 M for SCISE) and very low limits of detection (8.0×10^?6 M for CONISE and 3.0×10^?8 M for SCISE). The potentiometric response is independent from pH of the solution in the pH range 3.0–8.0. The electrodes manifest advantages of low resistance, very fast response and, most importantly, good selectivities relative to a wide variety of other cations. The electrodes can be used for at least 2 months (for CONISE) and 4 months for (SCISE) without any appreciable divergence in potentials. The electrodes were used as an indicator electrode in the potentiometric titration of Ag⁺ ion and in the determination of silver in photographic emulsions and in radiographic and photographic films.     

Silver Selective Electrode Based on Hybrid Mesoporous Silica (MCM‐41) Modified Material

A silver selective electrode based on TEPQA‐MCM‐41 material was developed and used for the selective determination of Ag⁺ ion in various samples. The effect of various plasticizers i. e. dimethyl phthalate (DMP), Tris(ethylhexyl)phosphate (TEP), bis‐(2‐ethylhexyl)sebacate (BEHS), bis‐(2‐ethylhexyl)adipate (BEHA) was investigated. The electrode of the composition of 2 : 1 : 77 : 12 : 8 (w/w, %) of TEPQA‐MCM‐41 : NaTPB : Graphite powder : paraffin oil : DMP respectively, works satisfactorily in a wide concentration range of 1.3×10^?9 M–1.0×10^?1 M for Ag⁺ ion with a lower detection limit (LOD) of 1.0×10^?9 M and has Nernstian slope of 63.4 1 mV/decay. The electrode can be used in a pH range of 2.3 to 6.7 for a period of 3 months without any divergence in potential response. The selectivity coefficient calculated by fixed interference method indicates the high selectivity of the electrode towards Ag⁺ ion over other tested cations.     

A Novel Molecularly Imprinted Photoelectrochemical Sensor Based on g‐C3N4‐AuNPs for the Highly Sensitive and Selective Detection of Triclosan

A novel molecularly imprinted polymer (MIP) photoelectrochemical sensor was fabricated for the highly sensitive and selective detection of triclosan. The MIP photoelectrochemical sensor was fabricated using graphite‐like carbon nitride (g‐C₃N₄) and gold nanoparticles (AuNPs) as photoelectric materials. The MIP/g‐C₃N₄‐AuNPs sensor used photocurrent as the detection signal and was triggered by ultraviolet light (UV‐Light 365 nm). g‐C₃N₄‐AuNPs was immobilized on indium tin oxide electrodes to produce the photoelectrochemically responsive electrode of the MIP/g‐C₃N₄‐AuNPs sensor. A MIP layer of poly‐o‐phenylenediamine was electropolymerized on the g‐C₃N₄‐AuNPs‐modified electrode to act as the recognition element of the MIP/g‐C₃N₄‐AuNPs sensor and to enable the selective adsorption of triclosan to the sensor through specific binding. Under optimal experimental conditions, the designed MIP/g‐C₃N₄‐AuNPs sensor presented high sensitivity for triclosan with a linear range of 2×10⁻¹² to 8×10⁻¹⁰ M and a limit of detection of 6.01×10⁻¹³ M. Moreover, the MIP/g‐C₃N₄‐AuNPs sensor showed excellent selectivity. The sensor had been successfully applied in the analysis of toothpaste samples.     

A New Silver(I) Potentiometric Sensor Based on a Calix[4]arene Substituted at the Narrow Rim by Amide/Phosphoryl Groups

A coated‐wire type silver ion‐selective electrode has been constructed using a modified p‐tert‐butyl‐calix[4]arene by amide‐phosphoryl groups, named 5, 11, 17, 23‐tetra‐tert‐butyl‐25, 27‐bis(diethylcarbamoylmethoxy)‐26,28‐bis(diphenylphosphinoylmethoxy)calix[4]arene (Calix), as neutral carrier. A plasticized PVC membrane containing 30% PVC, 60% ortho‐nitrophenyloctylether (NPOE), 2% sodium tetraphenylborate (NaTPB) and 8% “Calix” was coated on a graphite rod. The prepared electrode exhibited a linear Nernstian response over the range 1 × 10^?6 to 1 × 10^?2 M with a slope 58.4 (±0.2) mV per decade change and a detection limit of 6.3 × 10^?7 M. The working pH range of the sensor is 4‐6.7. It is found that the dynamic response time of the electrode to achieve a steady potential was very fast (～11 s). The selectivity of the sensor relative to NH₄⁺, Li⁺, Na⁺, K⁺, Ca²⁺, Sr²⁺, Ba²⁺, Mn²⁺, Pb²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Fe³⁺, La³⁺, Sm³⁺ and Th⁴⁺ was examined. The prepared electrode exhibits adequate stability with good reproducibility (57.6 ± 0.5 mV per decade change for 10 weeks). It was successfully used as an indicator electrode in potentiometric titration of silver ions with standard solution of EDTA. The sensor was also used for silver ion measurements in various synthetic samples.     

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.