Perchlorate-selective polymeric membrane electrode based on bis(dibenzoylmethanato)cobalt(II) complex as a neutral carrier

A synthesized bis(dibenzoylmethanato)Co(II) complex (Co(DBM)(2)), has been used as a ionophore for the preparation of a new perchlorate ion-selective electrode. The electrode exhibits a Nernstian response over the perchlorate concentration range of 8.0x10(-7)-1.0x10(-1)M with a slope of 60.3+/-0.5 mV per decade of concentration. The limit of detection as determined from the intersection of the extrapolated linear segments of the calibration plot is 5.6x10(-7)M. The electrode shows good selectivity towards perchlorate with respect to many common anions. The response time of the sensor is very fast (< or = 5s), and can be used for at least 2 months in the pH range of 2.0-9.0. The electrode was used to determine perchlorate in water and human urine. The interaction of the ionophore with perchlorate ions was demonstrated by UV-vis spectroscopy.     

A fast response cadmium-selective polymeric membrane electrode based on N,N'-(4-methyl-1,2-phenylene)diquinoline-2-carboxamide as a new neutral carrier

A new polyvinylchloride membrane sensor for Cd(2+) ions based on N,N'-(4-methyl-1,2-phenylene)diquinoline-2-carboxamide (Mebqb) as a new and excellent neutral ionophore has been prepared. The sensor shows a Nernestian response for cadmium ions over a wide concentration range (1.0 x 10(-6) to 1.0 x 10(-1) M) with the determination coefficient of 0.9964 and slope of 29.9 +/- 0.5 mV decade(-1). The limit of detection is 8 x 10(-7) M. It has a fast response time of 3-8s and can be used for at least 8 weeks without any divergence in potential. The electrode can be used in the pH range from 4.0 to 9.0. The proposed sensor shows a very good discriminating ability towards Cd(2+) ion in comparison to some alkali, alkaline earth, transition and heavy metal ions. It was successfully applied for the direct determination of Cd(2+) in standard and real sample solutions.     

A fast response hafnium selective polymeric membrane electrode based on N,N'-bis(alpha-methyl-salicylidene)-dipropylenetriamine as a neutral carrier

In this study a new hafnium selective sensor was fabricated from polyvinylchloride (PVC) matrix membrane containing neutral carrier N,N'-bis(alpha-methyl-salicylidene)-dipropylenetriamine (Mesaldpt) as a new ionophore, sodium tetraphenyl borate (NaTPB) as anionic discriminator and dioctyl phthalate (DOP) as plasticizing solvent mediator in tetrahydrofuran solvent. The electrode exhibits Nernstian response for Hf(4+) (Hafnium(IV)) over a wide concentration range (2.0 x 10(-7) to 1.0 x 10(-1)M) with the determination coefficient of 0.9966 and slope of 15.1+/-0.1 mVdecades(-1). The limit of detection is 1.9 x 10(-7)M. The electrode has a fast response time of 18s and a working pH range of 4-8. The proposed membrane shows excellent discriminating ability towards Hf(4+) ion with regard to several alkali, alkaline earth transition and heavy metal ions. It can be used over a period of 1.5 months with good reproducibility. It is successfully applied for direct determination of Hf(4+) in solutions by standard addition method for real sample analysis.     

New membrane for copper-selective electrode incorporating a new thiophosphoril-containing macrocycle as neutral carrier

The new macrocycles 4-phenyl-11-(1-oxodecyl)-1,7-dithia-11-aza-4-phosphacyclotetradecane (III) and 4-phenyl-4-sulfide-11-(1-oxodecyl)-1,7-dithia-11-aza-4-phosphacyclotetradecane (IV) have been synthesised and characterised. Through their use as ionophore in an all-solid state poly(vinylchloride) matrix membrane electrode, the ability of IV as cation receptor has been studied. The electrode exhibits a Nernstian response towards copper (II) ions with a cationic slope of 30.7 ± 1.7 mV per decade, over the concentration range 3.0 × 10^− 6 to 1.0 × 10^− 2 M and the potential response remains almost unchanged over the pH range 3.9–6.4. The electrode can be used for at least seven months without a considerable alteration in its potential.     

A Ho(III) potentiometric polymeric membrane sensor based on a new four dentate neutral ion carrier

In this research, we report a new Ho^3 +-PVC membrane electrode based on N-(4,5-dimethyl-2-(picolinamido)phenyl)picolinamide (H₂Me₂bpb) as a suitable ion carrier. Poly vinylchloride (PVC)-based membrane composed of H₂Me₂bpb with oleic acid (OA) as anionic additives, and o-nitrophenyloctyl ether (NPOE) as plasticized solvent mediator. The sensor exhibits a Nernstian slope of 20.1 ± 0.2 mV decade^? 1 over the concentration range of 1.0 × 10^? 6 to 1.0 × 1^? 2 mol L^? 1, and a detection limit of 5.0 × 10^? 7 mol L^? 1 of Ho^3 + ions. The potentiometric response of the sensor is independent of the solution pH in the range of 3.5–9.4. It has a very short response time, in the whole concentration range (< 10 s), and can be used for at least eight weeks. The proposed electrode shows a good selectivity towards Ho^3 + ions over a wide variety of cations, including alkali, alkaline earth, transition and heavy metal ions. To assess its analytical applicability the proposed Ho^3 + sensor was successfully applied as an indicator electrode in the titration of Ho^3 + ion solutions in certified reference materials, alloy samples and for the determination of the fluoride ion in two mouthwash preparations.     

Potentiometric detection of silver (I) ion based on carbon paste electrode modified with diazo-thiophenol-functionalized nanoporous silica gel

For the first time, triazene compound functionalized silica gel was incorporated into carbon paste electrode for the potentiometric detection of silver (I) ion. A novel diazo-thiophenol-functionalized silica gel (DTPSG) was synthesized, and the presence of DTPSG acted as not only a paste binder, but also a reactive material. The electrode with optimum composition, exhibited an excellent Nernstian response to Ag⁺ ion ranging from 1.0 × 10^? 6 to 1.0 × 10^? 1 M with a detection limit of 9.5 × 10^? 7 M and a slope of 60.4 ± 0.2 mV dec^? 1 over a wide pH range (4.0–9.0) with a fast response time (50 s) at 25 °C. The electrode also showed a long-time stability, high selectivity and reproducibility. The response mechanism of the proposed electrode was investigated by using AC impedance. Moreover, the electrode was successfully applied for the determination of silver ions in radiology films, and for potentiometric titration of the mixture solution of Cl^? and Br^? ions.     

Designing and synthesis of bis(2,4-dihydroxybenzylidene)-1,6-diaminohexane and its efficient application as neutral carrier for preparation of new copper selective electrode

A new copper carbon paste electrode (CPE) based on incorporation bis(2, 4-dihydroxybenzyliden)-1,6-diaminohexane (DHBDAH) in graphite powder matrix has been described. The influence of variables including an amount of graphite, sodium tetraphenylborate (NaTPB), DHBDAH and nujol on the Cu²⁺ carbon paste electrode response was studied and optimized. The optimum carbon paste composition was set as follows, graphite powder: NaTPB: Nujol: DHBDAH with amount of 150:2.3:30:4 mg, respectively. At the optimum conditions, the potential response is linear over the concentration range of 5.0 × 10^? 8 to 1.0 × 10^? 1 mol L^? 1 with a Nernstian slope of 29.5 ± 1.1 mV per decade of Cu²⁺ ion concentration. The good performance of electrode such as low detection limit of (LOD) (4 × 10^? 8 mol L^? 1), wide applicable pH range (2.5–5.5), fast response time (?10 s) and adequate shelf life (69 days) indicate the utility of the proposed electrode for evaluation of Cu²⁺ ion content in various analysis. Due to moderate potentiometric selectivity coefficients of proposed electrode obtained by fixed interference method (FIM) and separate solution method (SSM), the proposed electrode successfully can be applied for the determination of Cu²⁺ ions content in some real samples.     

Intracellular magnesium ion selective microelectrode based on a neutral carrier

A magnesium ion selective microelectrode based on a synthetic neutral carrier is presented. The selectivity of Mg2+ over Na+, K+, H+, and Ca2+ is sufficient for assays of intracellular magnesium ion activities. The microelectrodes with an optimized membrane composition have a resistance of about 5 x 10(10) omega and a 90% response time of less than or equal to 3 s for a tip diameter around 1 microns. The lifetime of the microelectrode cell assembly is longer than 1 week and the emf drift after equilibration is less than or equal to 0.3 mV/h.     

A new monopole mass-analyzer based on a hyperboloid electrode system

A new version of the monopole mass spectrometer with improved characteristics, which advances the idea of the quadrupole analyzer, is described.     

A new immobilized glucose oxidase using SiO2 nanoparticles as carrier

Using SiO₂ nanoparticles as a carrier, a novel immobilized glucose oxidase (GOD) (EC1.1.3.4) was prepared via crosslinking with glutaraldehyde (GA). The optimal immobilization condition was achieved with 1% (v/v) GA, 2% (v/v) 3-aminopropiltrietoxysilane (APTS), 2.5 mg GOD (in 34 mg carrier) and solution pH of 6.5. The immobilized GOD showed maximal catalytic activity at pH 7.0 and 60 °C, and more than 85% of initial activity at the temperature from 20 °C to 80 °C. After immobilization, the enzyme exhibited improved thermal, storage and operation stability. The immobilized GOD still maintained 85% of its initial activity after the incubation at 45 °C for 360 min, whereas free enzyme had only 23% of initial activity after the same incubation. After kept at 4 °C for 30 days, the immobilized and free enzyme retained 84% and 60% of initial activity, respectively. The immobilized GOD also preserved 87% of its initial activity after six consecutive operations.     

Preparation of PbO nanoparticles by microwave irradiation and their application to Pb(II)-selective electrode based on cellulose acetate

Nanosized lead oxide particles were prepared by thermal decomposition of lead hydroxycarbonate synthesized under microwave irradiation. Urea and lead nitrate were used as the starting materials. Microstructure and morphology of the products were investigated by means of XRD, AFM, TEM, and IR absorption spectra. The results indicated that well crystallized, finely dispersed and spherical -PbO nanoparticles with a size of ca. 30 nm were obtained. Meanwhile, an orthogonal phase β-PbO with a size of ca. 38 nm was also obtained when the calcinations temperature was up to 600 °C. In addition, a Pb(II)-selective electrode based on cellulose acetate was prepared using nanosized -PbO powders synthesized. The electrode exhibited a Nernstian slope of 29±1 mV per decade in a linear range of 2.5×10⁻⁵ mol L⁻¹ to 1.0×10⁻¹ mol L⁻¹ for Pb²⁺ ion. The detection limit of this electrode is down to 8.0×10⁻⁶ mol L⁻¹. This sensor has a short response time of about 10 s and could be used in a pH range of 2.0–8.0. High selectivity was obtained over a wide variety of metal ions.     

A Schiff base complex of Zn(II) as a neutral carrier for highly selective PVC membrane sensors for the sulfate ion

Novel polymeric membrane (PME) and coated graphite (CGE) sulfate-selective electrodes based on a recently synthesized Schiff base complex of Zn(II) were prepared. The electrodes reveal a Nernstian behavior over wide SO4(2-) ion concentration ranges (5.0 x 10(-5)-1.0 x 10(-1) M for PME and 1.0 x 10(-7)-1.0 x 10(-1) M for CGE) and very low detection limits (2.8 x 10(-5) M for PME and 8.5 x 10(-8) M for CGE). The potentiometric response is independent of the pH of the solution in the pH range 3.0-7.0. The electrodes manifest advantages of low resistance, very fast response, and, most importantly, good selectivities relative to a wide variety of other anions. In fact, the selectivity behavior of the proposed SO4(2) ion-selective electrodes shows a great improvement compared to the previously reported electrodes for sulfate ion. The electrodes can be used for at least 3 months without any appreciable divergence in potentials. The electrodes were used as an indicator electrode in the potentiometric titration of sulfate and barium ions and in the determination of iron in ferrous sulfate tablets.     

Voltammetric determination of 4-nitrophenol using a modified carbon paste electrode based on a new synthetic crown ether/silver nanoparticles

A novel modified carbon-paste electrode (CPE) with a new synthetic ligand: 6,7,9,10,17,18,19, 20,21, 22-decahydrodibenzo[h,r][1,4,7,11,15]trioxadiazacyclonanodecine-16,23dione(DTD)/Ag nanoparticles (AgNP) was employed for 4-nitrophenol measurement in natural water. Various parameters such as pH, modifier, accumulation time and scan rate were optimized. The proposed electrode showed a good response towards 4-nitrophenol determination. Under the optimized conditions the reduction peak current, showed a good linear relationship with the nitrophenol concentration in the range comprised between 1 × 10^− 6 mol L^− 1 and 1 × 10^− 4 mol L^− 1. The developed electrode was successfully applied for the determination of 4-nitrophenol in water samples.     

Mercury(II) selective membrane electrode based on 1,3-bis(2-methoxybenzene)triazene

A plasticized poly (vinyl chloride) membrane electrode based on 1,3-bis(2-methoxybenzene)triazene (MBT) for highly selective determination of mercury(II) has been developed. The electrode showed a good Nernstian response (30.2 ± 0.3 mV decade^− 1) over a wide concentration range (1.0 × 10^− 7−1.0 × 10^− 2 mol L^− 1). The limit of detection was 5.0 × 10^− 8 mol L^− 1. The electrode has a response time about 15 s and can be used for at least 1 month without observing any deviation from Nernstain response. The proposed electrode revealed an excellent selectivity toward mercury(II) ion over a wide variety of alkali, alkaline earth, transition, and heavy metal ions and could be used in the pH range 2.6–4.2. The electrode was used in the determination of Hg²⁺ in aqueous samples and as an indicator electrode in potentiometric titration of Hg(II) ions.     

A nasicon-type phase as intercalation electrode: NaTi2(PO4)3

Reversible intercalation of sodium in NaTi₂(PO₄)₃ at room temperature can be achieved either chemically or electrochemically. Na₃Ti₂(PO₄)₃ is obtained as final product via a two phase mechanism. The non-existence between both extreme compounds of a Na_1+xTi₂(PO₄)₃ solid solution seems to result from a topotactic demixtion reaction which requires only Na⁺ and e⁻ transfers without skeleton bond breaking and recombination.     

基于碳纤维的新型自支撑电极制备方法

借鉴自支撑电极的制备原理,利用电化学沉积结合(NH₄)₂S₂O₈和NaOH沉积液进行表面处理等手段制备了基于碳纤维表面Cu(OH)₂纳米结构的自支撑电极,分析测试了碳纤维表面的微观形貌、表面元素组成及其分布和表面物质的晶型以及利用水热反应在其表面附着电化学物质MnO₂后的电化学性能。结果发现,当(NH₄)₂S₂O₈的浓度为0.43 g/L、NaOH浓度为30.48 g/L、处理时间为12 min时,由SEM观察发现碳纤维表面的Cu(OH)₂纳米纤维的直径、长度、数量都较适宜;XPS、XRD和EDS的测试结果,沉积液处理后碳纤维表面部分单质铜转化为Cu(OH)₂,此结构非常有利于电化学物质的负载而由此构成开放、具有核壳结构的高性能电极材料;恒电流充放电(GCD)测试结果表明此电极材料具有极快的充放电速度。因此本文首次成功地在碳纤维表面的铜层表面原位生长出Cu(OH)₂纳米纤维,为未来以超级电容器为代表的能源设备的性能提升和商业化应用开拓了一种新的电极制备方法。      

Poly(vinyl) chloride membrane copper-selective electrode based on 1-phenyl-2-(2-hydroxyphenylhydrazo)butane-1,3-dione

1-Phenyl-2-(2-hydroxyphenylhydrazo)butane-1,3-dione (H(2)L) was used as an effective ionophore for copper-selective poly(vinyl) chloride (PVC) membrane electrodes. Optimization of the composition of the membrane and of the conditions of the analysis was performed, and under the optimized conditions the electrode has a detection limit of 6.30×10(-7) M Cu(II) at pH 4.0 with response time 10s and displays a linear EMF versus log[Cu(2+)] response over the concentration range 2.0×10(-6) to 5.0×10(-3) M Cu(II) with a Nernstian slope of 28.80±0.11 mV/decade over the pH range of 3.0-8.0. The sensor is stable for 9 weeks and exhibits good selectivity with respect to alkali, alkali earth and transition metal ions (e.g. Na(+), K(+), Ba(2+), Ca(2+), Zn(2+), Cd(2+), Co(2+), Mn(2+), Ni(2+), Fe(2+), Al(3+)) in the 3.0-8.0 pH range. It was successfully applied for the direct determination of copper(II) in zinc, aluminum and nickel based alloys, in soils polluted by oil, and as an indicator electrode for potentiometric titration of copper ions with EDTA.     

Effects of two-phase reactions on composition and potential response of zirconium(IV)-tetraphenylporphyrin complexes as carrier for citrate-selective electrode

The reactions between zirconium(IV)-tetraphenylporphyrin(tpp)-hydroxide complexes ([ZrIV2(OH)4(tpp)2] and [ZrIV(OH)2(tpp)]) in chlorobenzene and various acids (HX: HClO4, HCl, HNO3, CH3COOH) in water were studied. Three species [ZrIV2(OH)3(tpp)2],X, [ZrIV(OH)X(tpp)], and [ZrIVX2(tpp)] were identified, and their stability constants were determined. The extent of formation of each species depends on the coordination ability and lipophilicity of X-. The performance of these complexes was evaluated as a carrier of an anion-selective electrode. The cationic complex [ZrIV2(OH)3(tpp)2],X exhibited selectivity following the Hofmeister series to weakly coordinating anions, while showing a super-Nernstian response to strongly coordinating citrates. The latter suggests the cleavage of the dimeric structure. The dichloro complex [ZrIVCl2(tpp)] was prone to hydrolyze in contact with an aqueous solution and gave drifting potentials. The monochloro complex [ZrIV(OH)Cl(tpp)] was more stable and strongly responded to acetates, which may be ascribed to substitution of a weakly bound chloride. A slow hydrolysis giving [ZrIV(OH)2(tpp)], however, caused gradual deterioration of this strong response to acetates. Conditioning of the membrane in 1 M HCl regenerated the once-deteriorated carrier [ZrIV(OH)Cl(tpp)], while continuous conditioning extended its operating life. This carrier was effectively used to continuously monitor the acetate in a flow system. The dihydroxo complex [ZrIV(OH)2(tpp)] showed lower responses to common anions due to strong Zr-OH bonding and was thus successfully used for selective potentiometry of citrates.     

Salicylate-selective membrane electrode based on tin(IV) tetraphenylporphyrin

The response properties of a new solvent/polymeric membrane electrode with unique selectivity toward anionic salicylate are reported. The electrode is prepared by incorporating 5, 10, 15, 20-tetraphenyl(porphyrinato)tin(IV) dichloride (Sn[TPP]Cl2) into a plasticized poly(vinyl chloride) membrane. The resulting sensor exhibits an anti-Hofmeister selectivity pattern, with high specificity for salicylate over lipophilic inorganic anions (perchlorate, periodate, thiocyanate, iodide, etc.) and biological organic anions (citrate, lactate, acetate). Moderate selectivity over structural analogues of salicylate (3- and 4-hydroxybenzoate, benzoate) is also observed. Radiotracer uptake experiments using [14C]salicylate clearly show that the metal center of the metalloporphyrin is critical for selective salicylate transport in the membrane phase. Minimal response to chloride ions makes the new electrode potentially useful for estimating salicylate levels in biological samples.     

The use of silver(I)-2-[2-(2-methoxyethoxy)ethoxy]acetate as precursor in the deposition of thin silver layers on float glass by the atmospheric pressure combustion chemical vapor deposition process

The innovative use of silver(I)-2-[2-(2-methoxyethoxy)ethoxy]acetate ([AgO₂C(CH₂OCH₂)₃H], 3) as precursor for the deposition of silver on float glass by applying the atmospheric pressure combustion chemical vapor deposition process is described. As nucleation layer tungsten oxide was utilized, conformal, closed and dense silver layers of ca. 70 nm thickness were obtained. They are adhesive and high reflective with a resistivity of 5 ? 10⁻⁸ Ωm.