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.     

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.     

Iodide‐Selective Electrodes Based on Bis[N(2‐methyl‐phenyl) 4‐Nitro‐thiobenzamidato]mercury(II) and Bis[N‐phenyl 3,5‐Dinitro‐thiobenzamidato]mercury(II) Carriers

Highly selective poly(vinyl chloride) (PVC) membrane electrodes based on recently synthesized mercury complexes including Hg(Nmpntb)₂ and Hg(Npdntb)₂ as new carriers for iodide‐selective electrodes by incorporating the membrane ingredients on the surface of graphite electrodes are reported. The effect of various parameters including the membrane composition, pH and possible interfering anions were investigated on the response properties of the electrodes. Both sensors exhibited Nernstian responses toward iodide over a wide concentration range of 7×10^?7 to 0.1 M and 1×10^?6 to 0.1 M, with slopes of 59.6±0.8 and 58.9±0.9 mV per decade of iodide concentration and detection limit of 3×10^?7 M and 7×10^?7 for Hg(Npdntb)₂ and Hg(Nmpntb)₂, respectively, over a wide pH range of 3–11. The sensors have response times of ≤5 s and can be used for at least 2 months without any considerable divergence in their potential response. The proposed electrodes show good ability to discriminate iodide over several inorganic and organic anions. The electrodes were successfully applied to direct determination of iodide in synthetic mixture, waste water and drinking water and as indicator electrodes in precipitation titrations.     

New Macrocyclic Diamides as Neutral Ionophores for Highly Selective and Sensitive PVC‐Membrane Electrodes for Be2+ Ion

Five recently synthesized macrocyclic diamides were investigated to characterize their ability as beryllium ion carriers in potentiometric PVC‐membrane electrodes. The electrodes based on 1,15‐diaza‐3,4;12,13‐dibenzo‐5,8,11‐trioxabicyclo[13,2,2] heptadecane‐2,14‐dione exhibited a Nernstian response for Be²⁺ ion over wide concentration ranges (from 3.0×10^?6 to 3.0×10^?2 M for polymeric membrane electrode, PME, and from 5.0×10^?7 to 2.0×10^?2 M for coated glassy carbon electrode, CGCE) and very low detection limits (2.0 ×10^?6 M for PME and 4.0×10^?7 M for (CGCE). The electrodes possess low resistances, fast responses, satisfactory reproducibilities and, most importantly, good selectivities relative to a variety of other common cations. The potentiometric response of the electrodes is independent of pH of test solution in the pH range of 4.0–7.5. The proposed sensors were used to determine beryllium ion in water samples.     

Highly Selective and Sensitive Perchlorate Sensors Based on Some Recently Synthesized Ni(II)‐Hexaazacyclotetradecane Complexes

Three nickel(II)‐hexaazacyclotetradecane complexes were studied to characterize their abilities as perchlorate ion carrier in PVC membrane electrodes. The electrodes based on these complexes exhibit Nernstian responses for ClO over very wide concentration ranges (1.0×10^?1 ?5.0×10^?7 M) with detection limits of 2.0×10^?7 ?5.0×10^?7 M (20–50 ng/mL). The sensors show very good selectivity for ClO ion in comparison with the most common organic and inorganic anions. The responses of the proposed electrodes are independent of pH in the range of 3.5–11.0. The perchlorate selective membranes show fast response time (<10 s) and can be used for 4–12 weeks without any major deviation. The sensors were successfully used to determine the perchlorate ion in water, wastewater and human urine samples.     

Poly (Vinyl Chloride) Matrix Membrane Electrodes Responsive to Thiocyanate,Perchlorate and Periodate

Abstract

Three types of PVC matrix membrane ion-selective electrodes (ISEs) are described. These are based on membranes containing nitron thiocyanate with 2-nitro-phenyl phenyl ether, 2-nitrophenyl phenyl ether alone and tetraphenylarsonium thiocyanate with 2-nitrophenyl octyl ether. Each type is conditioned and stored in 0.1M sodium thiocyanate. The first two electrodes have been evaluated for thiocyanate and perchlorate response and the best linear long range (linear range down to 2.5×10^?5M) response was obtained for perchlorate. The third electrode is suitable as a periodate ISE with linear calibration range down to 2×10^?4M. The plasticized (2-nitrophenyl phenyl ether) PVC electrode for thiocyanate and perchlorate had a much longer pH interference free range (1.5–12.5) than either of the other electrodes.     

Thermal Studies of New Lead(II) Coated‐Wire Membrane Electrodes

Five plastic membrane Pb²⁺‐selective electrodes were prepared based on 1,4‐bis(N‐tosyl‐o‐aminophenoxy)butane I , 1,4‐bis(N‐allyl‐N‐tosyl‐o‐aminophenoxy)butane II , 1,4‐bis(N‐benzyl‐N‐tosyl‐o‐aminophenoxy)butane III , 1,4‐bis[N‐(o‐allyloxybenzyl)‐N‐tosyl‐o‐aminophenoxy]butane IV , and 1,4‐bis(N‐octyl‐N‐tosyl‐o‐aminophenoxy)butane V as neutral carriers. The electrodes exhibited nearly Nernstian responses over the concentration ranges, 2.5×10^?4–4.0×10^?2, 2.5×10^?5–4.0×10^?2, 7.9×10^?5–4.0×10^?2, 2.2×10^?5–4.0×10^?2, and 1.9×10^?4–4.0×10^?2 M for electrodes composed with the ionophores I–V , respectively. All electrodes showed pH range of about 4.0 to 11.5 and working temperature range of 22 to 70 °C with isothermal temperature coefficients of 1.19×10^?3, 1.16×10^?3, 1.16×10^?3, 1.00×10^?3 , and 1.32×10^?3 V/°C for electrodes I–V respectively.     

On-selective electrodes for some β-adrenergic and calcium blockers

Potentiometric sensors based on dinonylnaphthalene sulfonic acid (DNNS) were prepared for several recently developed drugs used in the treatment of cardiovascular disorders. Thus, incorporation of DNNS along with the β-adrenergic blocker Acebutalol, or calcium-channel blockers Verapamil, Diltiazem, Nicardipine, or Lidoflazine into a plasticized poly(vinyl chloride) membrane resulted in coated-wire ion-selective electrodes which displayed nearly Nernstian response in the concentration range 10^?3–10^?5 M and quantitatively useful responses down to 10^?6 M. Selectivity behavior for each set of electrodes was accurately predicted from calculated distribution constants for the respective drugs. Application of these electrodes to pharmaceutical preparations is discussed, as is their utility in pharmacokinetic studies.     

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.     

Design of a Vitamin B1‐Selective Electrode Based on an Ion‐Pair and Its Application to Pharmaceutical Analysis

Vitamin B₁‐selective electrodes with PVC membrane were developed that contain ion associates of vitamin B₁ with an inorganic anion, BiI₄^?, and an organic anion, brilliant yellow, as electrode‐active substances. The linearity ranges of the electrode function are 1.0×10^?5–1.0×10^?2 and 1.0×10^?4–1.0×10^?2 M, the electrode function slopes are 33.0±1.0 and 33.1±1.1 mV decade^?1, the detection limits are 5.5×10^?6 and 8.3×10^?5 M for BiI₄^? and brilliant yellow respectively. The working range of pH is 5–12. The efficiency of the use of electrodes for the vitamin B₁ content control in multivitamin pharmaceutical preparations was shown by direct potentiometry and potentiometric titration methods.     

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.     

Potentiometric Anion Selectivity and Analytical Applications of Polymer Membrane Electrodes Based on Novel Mn(III)‐ and Mn(IV)‐Salophen Complexes

New Mn(III)‐L and Mn(IV)‐L complexes were prepared from the highly lipophilic salophen ligand (L): phenol 2,2′‐[(4,5‐dimethyl‐1,2‐phenylene)bis[(E)‐nitrilomethylidyne]]bis[4,6‐bis(1,1‐dimethylethyl). The prepared complexes were fully characterized and used for the construction of thiocyanate membrane electrodes. Optimized membrane electrodes contained 33.0 mg PVC, 66.0 mg o‐nitrophenyloctylether, 50 or 5 (mole %) tetrakis(trifluoromethyl)phenyl borate and 1 mg Mn(III)‐L (sensor 2) or Mn‐(IV)‐L (sensor 12), respectively. Such electrodes exhibited linear responses toward thiocynate in a concentration range of 10^?1–10^?5 M and detection limits of 8.3×10^?6, 8.9×10^?6 M for sensor 2 and 12, respectively. Optimized membrane electrodes exhbited high selectivty toward thiocayante compared to more lipophilic anions. The observed thiocyanate selectivity of the optimized membranes was confirmed by formation constant calculations for Mn(III)‐L and Mn(IV)‐L with SCN^?, β=10^14.1 and 10^12.5, which was measured potentiometrically using the sandwich membrane method. Furthermore, computational study using DFT calculations was performed to at DFT/B3LYP level of theory to confirm the observed selectivity data. The response times were 3 and 0.5 min for low and high concentrations. The lifetimes of the optimized electrodes were ～4–6 weeks. The analytical utility of the optimized membrane electrodes was demonstrated by the analysis of thiocyanate level in different saliva samples.     

New Ion-Selective Electrodes for Determination of Bupivacaine and Oxybuprocaine

Abstract

PVC membrane electrodes selective for hydrochlorides of the anaesthetics bupivacaine (BpC) and oxybuprocaine (ObC) are prepared. The electrodes have a near Nernstian slope (58 mV for BpC and 51 mV for ObC electrodes) over the range of 1.6 × 10^?5-10^?1M and 1.3 × 10^?1M for BpC and ObC electrodes, respectively. The change in pH of the test solution within the ranges 2.5–6.0 and 3.0–7.4 does not affect the EpC-and ObC-electrodes, respectively. The electrodes have very long life times (10 days for BpC, and 3 months for ObC) and exhibit good seletivity for the investigated compounds with respect to a large number of inorganic cations and organic substances of biological importance. The isothermal coefficients of the electrodes are calculated from the standard electrode potentials at different temperatures. BpC and ObC are determined successfully in some pharmaceutical preparations using the calibration graph technique and potentiometric titration.     

1‐Pyrrolidine Dicarbodithioate Based Electrodes for Determination of Iron(III) in Lubrication Oil

The lipophillic ammonium salt of 1‐pyrrolidine dicarbodithioic acid (PCDT) (I) was introduced as a new selective ionophore for an iron selective electrode. In addition, the effect of immobilization of 18‐crown‐6 (18CE6) (membrane type‐II), on the electrode performance was discussed. The slope of the PCDT‐based (I) electrode was (20 mV/decade). The linear concentration range was (10^?5–10^?1 M) after one day doping. The detection limit for electrode type‐(II) was (1.3×10^?6 M). For membrane with only 18CE6 (type‐III) the linear range and the detection limit were improved (10^?5–10^?1 M and 3.2×10^?6 M, respectively). The pH‐range was between 5–11 for type‐II, and III electrodes, while it was 7–11 for type‐I electrode. Most of the common cations were tested for the evaluation of the electrode selectivity with correlation to the ionic radii of the tested cations. Among them only Ag⁺ and Pb²⁺ were the real interference for type‐III electrode. Application of using the electrode for the determination of iron in lubrication oil samples was performed with RSD (1.77–2.7%) and (1.01–2.3%) for type‐II and III electrodes, respectively. The corresponding recovery ranges were (93.0–99.9%) and (96.3–100%). The obtained results were compared to those of an atomic absorption spectrophotometric method.     

Electrochemical Investigations of the Anticancer Drug Idarubicin Using Multiwalled Carbon Nanotubes Modified Glassy Carbon and Pyrolytic Graphite Electrodes

The effect of surface modifications on the electrochemical behavior of the anticancer drug idarubicin was studied at multiwalled carbon nanotubes modified glassy carbon and edge plane pyrolytic graphite electrodes. The surface morphology of the modified electrodes was characterized by scanning electron microscopy. The modified electrodes were constructed for the determination of idarubicin using adsorptive stripping differential pulse voltammetry. The experimental parameters such as supporting electrolyte, pH, accumulation time and potential, amount of carbon nanotubes for the sensitive assay of idarubicin were studied as details. Under the optimized conditions, idarubicin gave a linear response in the range 9.36×10^?8–1.87×10^?6 M for modified glassy carbon and 9.36×10^?8–9.36×10^?7 M for modified edge plane pyrolytic graphite electrodes. The detection limits were found as 1.87×10^?8 M and 3.75×10^?8 M based on modified glassy carbon and edge plane pyrolytic graphite electrodes, respectively. Interfering species such as ascorbic acid, dopamine, and aspirin showed no interference with the selective determination of idarubicin. The analyzing method was fully validated and successfully applied for the determination of idarubicin in its pharmaceutical dosage form. The possible oxidation mechanism of idarubicin was also discussed. The results revealed that the modified electrodes showed an obvious electrocatalytic activity toward the oxidation of idarubicin by a remarkable enhancement in the current response compared with bare electrodes.     

[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.     

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.     

Construction and Performance Characterization of Ion‐Selective Electrodes for Potentiometric Determination of Paroxetine Hydrochloride in Pharmaceutical Preparations and Biological Fluids

Three types of ion‐selective electrodes: PVC membrane, modified carbon paste (CPE), and coated graphite electrodes (CGE) have been constructed for determining paroxetine hydrochloride (Prx). The electrodes are based on the ion pair of paroxetine with sodium tetraphenylborate (NaTPB) using dibutyl phthalate as plasticizing solvent. Fast, stable and potentiometric response was obtained over the concentration range of 1.1×10^?5–1×10^?2 mol L^?1 with low detection limit of 6.9×10^?6 mol L^?1 and slope of a 56.7±0.3mV decade^?1 for PVC membrane electrode, the concentration range of 2×10^?5–1×10^?2 mol L^?1 with low detection limit of 1.2×10^?5 mol L^?1 and slope of a 57.7±0.6 mV decade^?1 for CPE, and the concentration range of 2×10^?5–1×10^?2 mol L^?1 with low detection limit of 8.9×10^?6 mol L^?1 and slope of a 56.1±0.1 mV decade^?1 for CGE. The proposed electrodes display good selectivity for paroxetine with respect to a number of common inorganic and organic species. The electrodes were successfully applied to the potentiometric determination of paroxetine hydrochloride in its pure state, its pharmaceutical preparation, human urine and plasma.     

Novel Plastic Chromium(III)‐Ion Selective Electrodes Based on Different Ionophoric Species and Plasticizing Solvent Mediators

Different ionophoric species, viz.: 18‐crown‐6 (18C6), dibenzo‐18‐crown‐6 (DB18C6) and calix[6]arene (CAX), as electroactive materials, with 2‐nitrophenyloctylether (2‐NPOE), bis(ethylhexyl)sebacate (DOS), dioctyl phthalate (DOP), and didecyl phthalate (DDP) as plasticizing solvent mediators were used to construct Cr³⁺ selective electrodes in a PVC matrix in the ratio (w/w) PVC: ionophore: plasticizer (60 : 2 : 120). Seven electrodes out of the fabricated 12 electrodes, gave best results in terms of working concentration range (1.0×10^?5?1.0×10^?1 M) with a close to Nernstian slope of 18.5 and a Nernstian slope of 20.0 mV/decade of activity. The usable pH range of the sensors is 4.0–7.0. The detection limit of the selected electrodes is ≤1.0×10^?7 M. The response time of the sensors is 8–35 s, depending on the concentration of Cr³⁺ used. The selectivity coefficient values indicate that the electrodes are highly selective for Cr³⁺ over a number of other cations except Pb²⁺ and Na⁺ (for some electrodes). The electrodes have successfully been used to determine Cr³⁺ in certified and real alloys and in effluents of electroplating shops with a precision as relative standard deviation (RSD)<3%, for each of the proposed Cr³⁺‐ion selective electrodes. The results obtained by the proposed ISEs are in good agreement with the results obtained by direct flame AAS method.     

A nafion/crown ether film electrode and its application in the anodic stripping voltammetric determination of traces of silver

Glassy carbon electrodes are modified by coating with dicyclohexyl-18-crown-6 in Nafion-117. The electrode is used for a very sensitive anodic stripping voltammetric determination of silver. High sensitivity is obtained owing to the release of crown molecules from the silver-crown complex during the deposition. The detection limit is 2×10^?12 M after electrodeposition for 30 min. The recommended supporting electrolyte is 4×10^?3–7×10^?3 M potassium chloride in 0.01 M nitric acid with a deposition potential of ?0.30 V vs. SCE and a linear potential scan. Three typical calibration graphs were linear over the range 2×10^?11–1×10^?8 M for deposition times of 30, 20 and 8 min, respectively. The silver content of reagent-grade ammonium nitrate was found to be 0.48×10^?4% with a relative standard deviation of 3.7% (n=7) for parallel determinations.