适合低PH范围测量的新型中性载体膜PH电极的研究

本文设计合成了一种在低ＰＨ范围对氢离子有很好Ｎｅｒｎｓｔ响应的新型中性载体－Ｎ，Ｎ－二辛基菸酰胺，并把它制成ＰＶＣ膜ＰＨ电极，测试了该电极的线性范围、选择性、稳定、重现性和内阻等各项性能参数，并试验了电极抗氢氟酸腐蚀的能力，该该电极用于氢氟酸的电离常数测定时获得了满意的结果。     

Solid-contact ionophore-based electrode for determination of pH in acidic media

Solid-contact electrode for pH measurements in acidic media is described. The sensor membrane is made of polyvinyl chloride plasticized with bis(2-ethylhexyl)phthalate and contains neutral pH-selective ionophore hexabutyltriamidophosphate and potassium tetrakis-p-Cl-phenylborate cation exchanger. The transducer layer of the solid-contact electrode contains the same membrane composition and also carbon black and electron–ion-exchanger resin EI-21(a cation exchange resin containing fine dispersion of metal copper) for stabilization of the electrode potential. The electrode is suitable for measurements of pH in the range 0–6 and works also in hydrofluoric acid (HF) solutions up to 0.1 M HF. Chronopotentiometric measurements show diffusion-limited polarization at the interface between sensor membrane and transducer layer. The slope of the linearized polarization curve correlates with the long-term stability of the electrode potentials providing a tool for prediction of the long-term stability of solid-contact potentiometric sensors.     

Ion-selective electrode for the determination of dimethylbenzylammonium ions

A sensor is proposed for the direct potentiometric determination of dimethylbenzylammonium in acid and neutral aqueous solutions. The sensor membrane is made of a polymeric composition on the basis of polyvinylchloride containing an ion associate and a solvent as a plasticizer. Salts of the tetraphenylborate anion and its derivatives served as ionophores. Basic electroanalytical parameters of the developed potentiometric sensors are studied and the pH range of their possible application is determined. The developed sensor is used as a reference electrode in the potentiometric titration of dimethylbenzylammonium with tetraphenylborate anions.     

Hydrogen ion-selective poly(vinyl chloride) membrane electrode based on a calix[4]arene.

A hydrogen ion-selective poly(vinyl chloride) membrane electrode was constructed using 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetracyanomethoxycalix[4]arene as a neutral carrier. The electrode showed an apparent Nernstian response in the 2-11.5 pH range with a slope of 54.0 +/- 0.2 mV/pH at 20 +/- degrees C. This electrode showed a rapid response of the emf to changes in the pH, high ion selectivity with respect to lithium, sodium and potassium, and characteristics similar to those reported for the conventional pH glass membrane electrode. It can be used as a potentiometric indicator electrode in hydrofluoric acid solutions. The effects of iodide, thiocyanate, perchlorate and bromide on the characteristics of the electrode were also considered.     

Comparison of a single-use pH test strip and a glass electrode for potentiometric titration

The potentiometric titration of a carbonate mixture or an acetate solution is a common experiment in analytical laboratories. Typically, a glass electrode combined with a calomel or Ag/AgCl reference electrode is used to locate the equivalence points in neutralization titrations. The dissociation constants of weak acids and bases can be calculated from the pH at the half-neutralization point. Recently, a new commercial product for measuring pH has been developed. This novel acid–base detection strip is a single-use sensor that requires neither storage in a preservation liquid nor calibration prior to use. This study examined its suitability for the continuous monitoring of pH changes in potentiometric titrations of carbonate mixtures, acetate solutions, or ammonia solutions. There were no significant differences in the concentrations of solutions tested using a glass electrode and a pH test strip. The pK_a, pK_b, and pH values determined using the two systems differed by less than 5%. The results confirmed that the pH strips are suitable for continuously monitoring pH changes during neutralization titrations. However, the strips can only be used once.     

Batch and flow measurement of hydrogen ions in highly acidic media using 2-(4-methoxy phenyl) 6-(4-nitrophenyl)-4-phenyl-1,3-diazabicyclo [3.1.0] hex-3-ene as an H-selective ionophore

A hydrogen ion-selective poly(vinyl chloride) (PVC) membrane electrode was developed using 2-(4-methoxy phenyl) 6-(4-nitrophenyl)-4-phenyl-1,3-diazabicyclo [3.1.0] hex-3-ene as ionophore. Effects of experimental parameters such as membrane composition, nature and amount of plasticizer, and the amount of additive on the potential response of pH sensor were investigated. This H⁺-selective membrane electrode gave a linear response over the pH range 0-4 (10⁻⁴ to 1 mol L⁻¹ HCl) with slope of 57.4 ± 0.3 mV pH⁻¹ and limit of detection 6.3 × 10⁻⁵ mol L⁻¹ at 20 °C. Also, hydrofluoric acid did not influence the surface of this electrode and thus it was maintained without showing any changes in potentials after being used in a hydrofluoric acid solution. The equilibrium water content of the electrode was determined in the presence of two different plasticizers as membrane solvent. The alkaline cation binding affinity of ionophore was very low that prove these cations do not have specific interaction with this ionophore. The electrode had fairly low electrical resistance, good potential stability and reproducibility. It has a rapid potential response to changes of pH (10 s), easily used in a single channel wall-jet flow injection system with good reproducibility (RSD% = 1.67%) and high reversibility. It was used as indicator electrode in potentiometric determination of pH in real samples.     

A novel membrane sensor for histamine H1-receptor antagonist "fexofenadine".

The construction and general performance of thirteen new polymeric membrane sensors for the determination of fexofenadine hydrochloride based on its ion exchange with reineckate, tetraphenylborate and tetraiodomercurate have been studied. The effects of membrane composition, type of plasticizer, pH value of sample solution and concentration of the analyte in the sensor internal solution have been thoroughly investigated. The novel sensor based on reineckate exchanger shows a stable, potentiometric response for fexofenadine in the concentration range of 1 x 10(-2) - 2.5 x 10(-6) M at 25 degrees C that is independent of pH in the range of 2.0 - 4.5. The sensor possesses a Nernstian cationic slope of 62.3+/-0.7 mV/concentration decade and a lower detection limit of 1.3 x 10(-6) M with a fast response time of 20 - 40 s. Selectivity coefficients for a number of interfering ions and excipients relative to fexofenadine were investigated. There is negligible interference from almost all studied cations, anions, and pharmaceutical excipients, however, citrizine that has a structure homologous to that of fexofenadine was found to interfere. The determination of fexofenadine in aqueous solution shows an average recovery of 99.83% with a mean relative standard deviation (RSD) of 0.5%. Direct potentiometric determination of fexofenadine in tablets gave results that compare favorably with those obtained by standard spectrophotometric methods. Potentiometric titration of fexofenadine with phosphomolybdic acid as a titrant has been monitored with the proposed sensor as an end point indicator electrode.     

Hybrid Nanocomposite Based Graphene Sensor for Ultrasensitive Clomipramine HCl Detection

A potentiometric sensor modified with a nanocomposite of montmorillonite sheets decorated with polyaniline nanofibers (MT-PANI-NFs) as an efficient electroactive material and tricresyl phosphate (TCP) as a solvent mediator has been developed for the estimation of clomipramine HCl (CLP.HCl). The optimum potentiometric performance of the sensor was achieved by mixing of MT-PANI-NFs : TCP : graphene with a ratio of 2.69 : 30.11 : 67.20 (% wt/wt). The sensor exhibited a Nernstian slope of 59.0±0.1 mV decade⁻¹ over the concentration range of 1.0×10⁻⁵−1.0×10⁻² mol L⁻¹ with a theoretically calculated detection limit of 5.0×10⁻⁶ mol L⁻¹. The sensor performance was scrutinized in terms of several factors including thermal stability, pH effect, response time and selectivity. As, it displayed a high thermal stability at various temperature degrees (10–60 °C) with pH independency in the range of 3.5–8.5. Additionally, the developed sensor exhibited a very rapid performance for CLP.HCl detection with a fast response time of 4 s and reflecting a superior selectivity towards CLP.HCl over the other interfering species. SEM (scanning electron microscope) was used as a characteristic tool for the investigation of the proposed graphene sensor surface. Furthermore, the graphene sensor has been efficiently used for CLP.HCl estimation in its pharmaceutical formulations.     

Electrochemical characterization and application of Ni-RuO2 as a pH sensor for determination of petroleum oil acid number

Electrochemical characterization and application of nickel ruthenium dioxide (Ni-RuO₂) as a pH sensor for the determination of petroleum oil acid number is described. The sensor consists of RuCl₃ thermally decomposed onto the upper side of a polycrystalline nickel electrode at 400 °C in an open furnace. The advantages of the sensor are: (i) easy preparation, (ii) fast response in a large pH range, (iii) high physical and chemical stability, and (iv) excellent reproducibility as determined by the reproducible linear variation of charge transfer resistance (R_ct) as a function of overpotential (η) obtained by electrochemical impedance spectroscopy (EIS), and the Nernstian slope of the electrode potential in a wide range of pH (1.5–12.5) obtained by potentiometric measurements. The potentiometric selectivity coefficients of the sensor toward some anions and cations were evaluated in aqueous solution. The characterized Ni-RuO₂ pH sensor was successfully tested for the determination of petroleum oil acid number.     

Potentiometric carbon paste sensors for lead(II) based on dithiodibenzoic and mercaptobenzoic acids.

Dithiodibenzoic (DTB) acid and mercaptobenzoic (MB) acid were studied to characterize their abilities as modifier agents for lead(II) sensors. For both sensors, the best results were obtained with modified carbon paste electrodes with 24.1% of ligand. The pH influence on the potentiometric response was studied. The selectivity coefficients for both modified electrodes were tabulated. A potentiometric sensor based on DTB acid exhibited a more sensitive and selective response to lead ions than an MB electrode. The limits of detection for the DTB and MB electrodes were very similar, 5.01 x 10(-8) M and 3.98 x 10(-8) M, respectively, for lead(II) activity. The DTB sensor was applied to lead(II) ion determination in real samples and as an indicator electrode in potentiometric titrations. Natural and commercial humic acids were titrated using the DTB electrode to estimate the stability constant between these organic compounds and the lead(II) ions with successful results.     

Copper(II) Ion‐Selective Electrodes Based on Dithiosalicylic and Thiosalicylic Acids

Potentiometric carbon paste electrodes for copper(II) based on dithiosalicylic and thiosalicylic acids are described. The sensor based on dithiosalicylic acid (DTS) exhibits a linear response with a nearly Nernstian slope of 27.7 mV per decade, whereas the electrode based on thiosalicylic acid (TS) shows a super‐Nernstian slope. The limits of detection for the DTS sensor and the TS sensor are 10^?7.9and 10^?6.3 M for copper(II) activity, respectively. Selectivity coefficients are tabulated, and the influence of the pH on the response of these ISEs is studied. The DTS electrode is successfully used for potentiometric titration of humic acids with copper in order to get more information about complexing properties of these acids.     

Chromium(III) ion-selective electrode based on 4-dimethylaminoazobenzene

A PVC-based membrane of 4-dimethylaminoazobenzene reveals a Nernstian potentiometric response (with slope of 19.5+/-0.6 mV/decade and a correlation coefficient of 0.999) for Cr(III) over a wide concentration range (1.66 x 10(-6)-1.0 x10(-2) mol dm(-3)). The potential of this electrode is independent of pH in the range of 3.0-5.5. It has a fast response time of about 10 s and was used for a period of 3 months with good reproducibility. The detection limits of this membrane electrode was 8 x 10(-7) M. the proposed electrode has been used as an indicator electrode in the potentiometric titration of Cr(III) with EDTA. This sensor exhibits a very good selectivities for Cr(III) over a wide variety of metal ions.     

Cobalt(II)-selective membrane electrode based on a recently synthesized benzo-substituted macrocyclic diamide.

A PVC-membrane electrode based on a recently synthesized 18-membered macrocyclic diamide is presented. The electrode reveals a Nernstian potentiometric response for Co2+ over a wide concentration range (2.0 x 10(-6)-1.0 x 10(-2) M). The electrode has a response time of about 10 s and can be used for at least 2 months without any divergence. The proposed sensor revealed very good selectivities for Co2+ over a wide variety of other metal ions, and could be used over a wide pH range (3.0-8.0). The detection limit of the sensor is 6.0 x 10(-7) M. It was successfully applied to the direct determination and potentiometric titration of cobalt ion.     

Clotrimazole-triiodide ion association as an ion exchanger for a triiodide ion-selective electrode.

A novel triiodide ion-selective electrode based on a clotrimazole-triiodide ion pair as a membrane carrier was prepared. It has a linear response to triiodide from 8 x 10(-6) to 5 x 10(-3) M with a slope of -68.9 mV per decade and a detection limit of 5 x 10(-6) M. The electrode response is independent of the pH of the solution in the pH range 2-9. It has a very short response time and can be used for at least 3 months without any considerable divergence in the potentials. The proposed sensor revealed very good selectivities for I3- over a variety of other anions. It was used as an indicator electrode in the potentiometric titration of triiodide ions and in an indirect potentiometric determination of clotrimazole in pharmaceutical preparations.     

Novel potentiometric membrane sensor for the determination of trace amounts of chromium(III) ions.

A plasticized Cr3+ ion sensor by incorporating 2,3,8,9-tetraphenyl-1,4,7,10-tetraazacyclododeca-1,3,7,9-tetraene (TTCT) ionophore exhibits a good potentiometric response for Cr3+ over a wide concentration range (1.0 x 10(-6)-1.0 x 10(-1) M) with a slope of 19.5 mV per decade. The sensor response is stable for at least three months. Good selectivity for Cr3+ in comparison with alkali, alkaline earth, transition and heavy metal ions, and minimal interference are caused by Li+, Na+, K+, Co2+, Hg2+, Ca2+, Pb2+ and Zn2+ ions, which are known to interfere with other chromium membrane sensors. The TTCT-based electrode shows a fast response time (15 s), and can be used in aqueous solutions of pH 3-5.5. The proposed sensor was used for the potentiometric titration of Cr3+ with EDTA and for a direct potentiometric determination of Cr3+ content in environmental samples.     

Facile Synthesis and Characterization of 5-[(3-Methylthiophene-2-yl-methyleneamino)]-2-mercaptobenzimidazole and Its Potentiometric Sensor Application in a Polyvinyl Chloride Membrane for the Determination of Copper(II)

A novel Schiff base designated as 5-[(3-methylthiophene-2-yl-methyleneamino)]-2-mercaptobenzimidazole was synthesized and characterized. A polyvinyl chloride-membrane potentiometric copper(II)-selective sensor was prepared by using the synthesized 5-[(3-methylthiophene-2-yl-methyleneamino)]-2-mercaptobenzimidazole compound. The prepared polyvinyl chloride-membrane copper(II)-selective sensor exhibited very good selectivity and sensitive potentiometric response towards copper(II) ions compared to a wide variety of other cations. The sensor had a fast response time of <5?s, and showed a linear Nerstian behavior to copper(II) ions over a wide concentration range from 1.0?×?10^?5 to 1.0?×?10^?1 mol L^?1 with a slope of 29.2?±?0.7 and correlation coefficient of 0.9998. The prepared polyvinyl chloride-membrane copper(II)-selective sensor was used for 14 weeks without any significant change in its potentiometric response. The potentiometric response of the developed sensor was highly repeatable. Additionally, the developed sensor was used as an indicator electrode for the potentiometric titration of copper(II) ion with ethylenediaminetetraacetic acid. The sensor was also successfully applied to the direct determination of copper(II) ions in tap water, river water, and dam water samples.     

Chromium(III) Ion Selective Electrode Based on Oxalic Acid Bis(Cyclohexylidene Hydrazide)

A poly(vinyl chloride) membrane sensor based on oxalic acid bis (cyclohexylidene hydrazide) as membrane carrier was prepared and investigated as a Cr(III)‐selective electrode. The electrode reveals a Nernstian behavior (slope 19.8±0.4 mV decade^?1) over a wide Cr(III) ion concentration range 1.0×10^?7–1.0×10^?2 mol dm^?3 with a very low limit of detection (i.e., down to 6.3×10^?8 mol dm^?3). The potentiometric response of the sensor is independent of the pH of the test solution in the pH range 1.7–6.5. The electrode possesses advantage of very fast response, relatively long lifetime and especially good selectivity to wide variety of other cations. The sensor was used as an indicator electrode, in the potentiometric titration of chromium ion and in the determination of Cr(III) in waste water and alloy samples.     

共价键合修饰壳聚糖pH传感器的研制

以共价键合的方法将壳聚糖修饰到玻碳电极上制成了pH传感器,探讨了该传感器的性能及作用机理.结果表明该传感器在pH 0.7～11.0的范围内电极电势与pH符合Nernst响应,斜率为58.3 mV/pH,可准确测定较高酸度溶液的pH,克服了玻璃pH传感器的"酸误差"的缺点.该传感器内阻小,易微型化,在一定的pH范围内对温度不敏感且具有较好的准确度和重现性,较快的响应速度.可用于雨水和饮料等实际样品溶液的pH的测定.     

The behavior of a poly(aniline) solid contact pH selective electrode based on N,N,N',N'-tetrabenzylethanediamine ionophore.

A hydrogen ion-selective solid-contact electrode based on N,N,N',N'-tetrabenzylethanediamine has shown the best Nernstian slope and selectivity and the widest response range in a Tris buffered pH sample solution. Its linear dynamic range was pH 3.50-11.94, and the Nernstian slope showed 52.1 mV/pH (at 20 +/- 0.2 degrees C). When it was directly applied to human whole blood (in pH range 6.0-8.5) we could obtain the same satisfying results. This electrode continuously contacted a Tris 7.47 buffered solution, human whole blood and a hydrofluoric acid solution for one month without any loss of performance. Also, hydrofluoric acid did not influence the surface of this electrode, and thus it was maintained without showing any changes in potentials after being used in a hydrofluoric acid solution. The standard deviation in the determined e.m.f. differences was 1.5 mV (N = 5) for Tris buffer solutions of pH 6.5 and 1.1 mV at a Tris buffer solutions of pH 8.5. The 90% response time of the electrodes obtained by injecting of hydrochloric acid into the Tris buffer sample solution was less than 10 s. Especially, in the this paper, with these potential response characteristics of hydrogen ion selective poly(aniline) solid contact electrode, we have also presented the pH response mechanism of this electrode and the role of poly(aniline) and a doped anion in a poly(aniline) layer.     

A new macrocyclic polystyrene-based sensor for chromium (III) ions

A new tetradentate dihydrogen perchlorate macrocyclic ligand (2,4,9,11-tetraphenyl-1,5,8,12-tetraazacyclotetradeca-1,4,8,11-tetraene dihydrogen perchlorate) was prepared and characterised. The macrocycle behaves as a selective chelating ion-exchanger for some metal ions. The polystyrene-based membrane electrode is found to exhibit quite promising selectivity for Cr3+ ions. It can be used to estimate chromium concentrations in the range 3.16x 10(-6)-1.00x10(-1) M with a near-Nernstian slope of 17.5 mV per decade of concentration between pH 3.0 to 6.5. The electrode is found to possess a fast response time of 15 s and was used over a period of three months with good reproducibility (s = +/- 0.3 mV). The selectivity coefficient values for mono-, di- and trivalent cations indicate excellent selectivity for Cr3+ ions over a large number of other cations. Anions such as Cl- and SO4(2-) do not interfere and the electrode also works satisfactorily in a mixed organic-water solution. The sensor has been used as an indicator electrode for the potentiometric titration of Cr3+ with EDTA. The practical utility of the membrane sensor has also been demonstrated in solutions contaminated with detergents (CTAB and SDS). Above all, the membrane sensor has been very successfully used to determine Cr3+ in some foods.