Nitrate-selective membrane electrode based on bis(2-hydroxyanil)acetylacetone lead(II) neutral carrier.

A nitrate-selective electrode based on a recently synthesized bis(2-hydroxyanil)acetylacetone lead(II) complex [(haacac)Pb] has been developed. Among different compositions studied, a membrane containing 30.7% poly(vinyl chloride) (PVC), 61.3% dibutyl phthalate (DBP) as a plasticizer, 3% methyltrioctylammonium chloride (MTOAC) as a cationic additive and 5% ionophore (all w/w) exhibited the best potentiometric response toward nitrate ion in aqueous solutions. The potentiometric response of the electrode was linear with a Nernstian slope of -58.8 mV decade(-1) within the NO3- concentration range of 2 x 10(-5)-1 x 10(-1) mol dm(-3). The response time of the electrode was < or =10 s over the entire linear concentration range of the calibration plot. The electrode is suitable for use within the pH range of 5.3-11. The selectivity coefficients for the proposed electrode were improved for some interferences, when compared with those of commercially available nitrate-selective electrodes.     

A tetra-coordinate nickel(II) complex as neutral carrier for nitrate-selective PVC membrane electrode

The potentiometric response properties and applications of a tetra-coordinate nickel(II) complex with relatively high selectivity toward nitrate ion are described. The nickel(II) complex of 5,7,12,14-tetramethyl-1,4,8,11-tetraazacyclotetradeca-4,6,11,13-tetraene was used as a neutral carrier into plasticized poly(vinyl chloride) (PVC) membrane. The influence of several variables was investigated in order to optimize the potentiometric response and selectivity of the electrode. The resulting membrane electrode incorporating 31.0% PVC, 61.0% dioctyl phthalate (DOP) as plasticizer, 3% methyltrioctylammonium chloride (MTOAC) as a cationic additive and 5% carrier (all w/w) demonstrates a Nernstian response slope of −59.6 mV per decade over the concentration range of 5×10⁻⁶-1×10⁻¹ M NO₃⁻. The electrode exhibits a fast response time (≤10 s), a detection limit of 2.5×10⁻⁶ M, and can be used over a wide pH range of 4-12. The electrode shows improved selectivity in comparison to most of the previously reported nitrate-selective electrodes. It was successfully applied to the determination of nitrate ion in natural water samples.     

Bis (trans-cinnamaldehyde) ethylene diimine dibromonickel (II) complex as a neutral carrier for salicylate-selective liquid membrane and coated graphite sensors

A salicylate PVC-based membrane (SPME) and a coated graphite membrane (SCGE) electrodes by using a new tetracoordinate organonickel complex as ion carrier were prepared. Both sensors show a Nernstian response to salicylate ions over a very wide concentration ranges (1.0×10⁻⁵-1.0×10⁻¹ M for SPME and 1.0×10⁻⁶-1.0×10⁻² M for SCGE) in the pH of 7.0. The best selectivities were obtained for the membrane incorporating 30% PVC, 63% plasticizer, 2% cationic additive and 5% ionophore. The electrodes possess satisfactory reproducibility, very short response time (∼10 s) in the whole concentration ranges, and excellent discriminating ability for salicylate ions with respect to the most common organic and inorganic anions. The detection limits of proposed sensors are 5.0×10⁻⁶ and 7.0×10⁻⁷ M for SPME and SCGE, respectively. The electrodes were successfully used for determination of salicylate in biological samples.     

Copper(II)-selective electrode using 2,2'-dithiodianiline as neutral carrier

Poly(vinyl chloride) membrane electrode, that is highly selective and sensitive to Cu(II) ions, was developed by using 2,2'-dithiodianiline and dibutyl phthalate as carrier and plasticizer, respectively. The electrode exhibits good potentiometric response for Cu(II) over a wide concentration range (5.0x10(-2)-7.0x10(-7) mol l(-1)) with Nernstian slope of 30+/-1 mV per decade. The response time of the electrode is 10 s and it has been used for a period of one month and exhibits good selectivity towards Cu(2+) in comparison to alkali, alkaline earth, transition and heavy metal ions, with no interference caused by Pb(2+), Cd(2+) and Fe(+2) which are known to interfere with many other copper electrodes.     

A highly sensitive PVC membrane iodide electrode based on complexes of mercury(II) as neutral carrier

A novel solvent polymeric membrane electrode based on bis(1,3,4-thiadiazole) complexes of Hg(II) is described which has excellent selectivity and sensitivity toward iodide ion. The electrode, containing 1,4-bis(5-methyl-1,3,4-thiadiazole-2-yl-thio)butanemercury(II) [Hg(II)BMTB(NO₃)₄], has a Nernstian potentiometric response from 2.0×10^–8 to 2.0×10^–2 mol L^–1 with a detection limit of 8.0×10^–9 mol L^–1 and a slope of –59.0±0.5 mV/decade in 0.01 mol L^–1 phosphate buffer solution (pH 3.0, 20°C). The selectivity sequence observed is iodide>bromide>thiocyanate>nitrite>nitrate>chloride>perchlorate>acetate>sulfate. The selectivity behavior is discussed in terms of the UV–Vis spectrum, and the process of transfer of iodide across the membrane interface is investigated by use of the AC impedance technique. The electrode was successfully applied to the determination of iodide in Jialing River and Spring in Jinyun Mountains, with satisfactory results.     

Bis-dimethylaminobenzaldehyde Schiff-base cobalt(II) complex as a neutral carrier for a highly selective iodide electrode.

A new solvent polymeric membrane electrode based on N,N'-bis-(dimethylaminobenzaldehyde)-glycine cobalt(II) [Co(II)-BDMABG] as a neutral carrier is described, which displays a preferential potentiometric response to iodide ion and an anti-Hofmeister selectivity sequence in the following order: I- > ClO4- > Sal- > SCN- > NO2- > Br- > NO3- > Cl- > SO3(2-) > SO4(2-). The electrode exhibits a near-Nernstian potential linear range of 9.0 x 10(-7)-1.0 x 10(-1) M with a detection limit of 6.8 x 10(-7) M and a slope of -53.0 mV/decade in pH 2.0 of a phosphate buffer solution at 20 degrees C. The response mechanism is discussed in view of the A.C. impedance technique and the UV spectroscopy technique. The electrode was successfully applied to the determination of iodide in Jialing River and Spring in Jinyun Mountains with satisfactory results.     

Lead selective membrane electrode using cryptand(222) neutral carrier

The construction, performance characteristics and applications of a polymeric membrance electrode for lead(II) ion are reported. The electrode was prepared by incorporating cryptand(222) as the neutral carrier into a plasticized poly(vinyl chloride) membrane. The influence of membrane composition, pH and concentration of internal reference solution were investigated. The electrode exhibits a potentiometric response for Pb²⁺ ion over the concentration range 10^–1–10^–5 M with a detection limit of 5 × 10^–6 M Pb²⁺. It shows a relatively fast response time of about 30 s and can be used for about two months without any considerable divergence in potential. The proposed sensor revealed good selectivities for Pb²⁺ in the presence of several metal ions and could be used in the pH range of 2.5 to 7.5. It was used as an indicator electrode in the potentiometric titration of Pb²⁺ with EDTA. Received: 20 November 1998 / Revised: 26 March 1999 / Accepted: 31 March 1999     

Lead selective membrane electrode using cryptand(222) neutral carrier

The construction, performance characteristics and applications of a polymeric membrance electrode for lead(II) ion are reported. The electrode was prepared by incorporating cryptand(222) as the neutral carrier into a plasticized poly(vinyl chloride) membrane. The influence of membrane composition, pH and concentration of internal reference solution were investigated. The electrode exhibits a potentiometric response for Pb²⁺ ion over the concentration range 10^–1–10^–5 M with a detection limit of 5 × 10^–6 M Pb²⁺. It shows a relatively fast response time of about 30 s and can be used for about two months without any considerable divergence in potential. The proposed sensor revealed good selectivities for Pb²⁺ in the presence of several metal ions and could be used in the pH range of 2.5 to 7.5. It was used as an indicator electrode in the potentiometric titration of Pb²⁺ with EDTA. Received: 20 November 1998 / Revised: 26 March 1999 / Accepted: 31 March 1999     

A mercury(II) ion-selective electrode based on N,N-dimethylformamide-salicylacylhydrazone as a neutral carrier.

A new PVC membrane mercury(II) ion electrode based on N,N-dimethylformamide-salicylacylhydrazone (DMFAS) as an ionophore is described, which shows excellent potentiometric response characteristics and displays a linear log[Hg(2+)] versus EMF response over a wide concentration range between 6.2 x 10(-7) and 8.0 x 10(-2) M with a Nerstian slope of 29.6 mV per decade and a detection limit of 5.0 x 10(-7) M. The response time for the electrode is less than 30 s and the electrode can be used for more than 2 months with less than a 2 mV observed divergence in a potentials. The proposed electrode exhibits very good selectivity for mercury(II) ions over many cations in a wide pH range (pH 1 - 4). The electrode was also applied to the determination of a mercury(II) ion in vegetables and in Azolla filiculoides.     

Response mechanism of a neutral carrier Hg(II) polymeric membrane ion-selective electrode. SEM and EDAX study

Scanning electron microscopy (SEM) and energy dispersive atomic X-ray spectrometry (EDAX) were used to study the response mechanism of a previously reported new Hg membrane ion-selective electrode (ISE) based on 1,3-diphenylthiourea. These techniques allowed the study of the membrane surface characteristics, such as the morphological homogeneity and chemical composition. A 'twice Nernstian' response at pH > or = 7 was explained by the detection of the Hg(OH)+ cation. A normal Nernstian response was found at acidic pH values. Using these techniques, both coordination compounds, [Ligand-Hg-OH] at pH 7 and [Ligand-Hg-Ligand] at pH 4.5, were confirmed on the electrode membrane surface activated with Hg(NO3)2 solution at both pH values. These methods provide results which are independent of the potential measurement data and in agreement with them. A successful response model has explained both independent and unbiased sets of results. These conclusions confirm the proposed response mechanisms for this new Hg membrane sensor.     

A PVC membrane pH-sensitive electrode based on methyldioctadecylamine as neutral carrier

A pH-sensitive PVC membrane electrode based on methyldioctadecylamine as neutral carrier has been prepared. It gives linear response over the pH-range 3.0-11.0 and a slope of - 58.4 +/- 0.3 mV/pH (at 20 degrees). The electrode has fairly low resistance and good potential reproducibility. The selectivity and other characteristics of the electrode have been studied.     

Highly selective thiocyanate electrode based on bis-bebzoin-semitriethylenetetraamine binuclear copper(II) complex as neutral carrier

A novel selective thiocyanate PVC membrane electrode based on bis-bebzoin-semitriethylenetetraamine binuclear copper(II) [Cu(II)₂–BBSTA] as neutral carrier is reported, which displays an anti-Hofmeister selectivity sequence in following order: SCN⁻ > ClO₄⁻ > I⁻ >Sal⁻ >SO₃²⁻ >NO₃⁻ > H₂PO₄⁻ > Cl⁻ >NO₂⁻ > SO₄²⁻. The electrode exhibits Nernstian potential linear range to thiocyanate from 1.0 × 10⁻¹ to 9.0 × 10⁻⁷ mol/l with a detection limit 7.0 × 10⁻⁷ mol/l and a slope of −57.0 mV/decade in pH 5.0 of phosphorate buffer solution at 25 °C. The response mechanism is discussed in view of the AC impedance technique and the UV spectroscopy technique. From comparison of potentiometric response characteristics between the binuclear metallic complex copper(II) [Cu(II)₂–BBSTA] and mononuclear copper(II) metallic complex [Cu(II)–BBSDA], an enhanced response towards thiocyanate from the electrode based on binuclear metallic complex copper (II) [Cu(II)₂–BBSTA] was observed. The electrode based on binuclear copper(II) compound was used to determine the thiocyanate content in waste water with satisfactory results.     

Nickel(II) selective membrane potentiometric sensor using a recently synthesized mercapto compound as neutral carrier

A PVC membrane electrode for Ni²⁺ ions based on a recently synthesized mercapto compound, as an ionophore was prepared. The electrode exhibits a Nernstian slope of 28-30 mV per concentration decade at wide concentration range of (1.0×10⁻²-1.0×10⁻⁷ M). It has a fast response time of <15 s and can be used for at least 4 weeks. The potentiometric response is independent of the pH of the test solution in the pH range 5-8.5. The proposed electrode revealed good selectivities over a wide variety of other cations including alkali, alkaline earth, transition and heavy metal ions. It was successfully applied to the direct determination and potentiometric titration of nickel ion with EDTA.     

5,10,15-Tris(pentafluorophenyl)corrole as highly selective neutral carrier for a silver ion-sensitive electrode

A new highly selective silver(I) electrode was prepared with a PVC membrane using 5,10,15-tris(pentafluorophenyl)corrole as an electroactive material, 2-nitrophenyl octyl ether (o-NPOE) as a plasticizer and sodium tetraphenylborate (NaTPB) as an additive in the percentage ratio of 3:3:62:32 (corrole:NaTPB:o-NPOE:PVC, w:w). The electrode exhibited linear response with a near Nernstian slope of 54.8 mV/decade within the concentration range of 5.1 × 10⁻⁶ to 1.0 × 10⁻¹ M silver ions, with a working pH range from 4.0 to 8.0, and a fast response time of <30 s. Selectivity coefficients for Ag(I) relative to a number of interfering ions were investigated. The electrode is highly selective for Ag(I) ions over a large number of mono-, bi-, and tri-valent cations. Common interferents like Hg²⁺ and Cd²⁺ show very low interfering effect on the silver assay, which is valuable property of the proposed electrode. Several electroactive materials and solvent mediators have been compared and the experimental conditions were optimized. The sensor was applied to the determination of silver in real ore samples with satisfied results.     

Highly selective thiocyanate electrode based on bis-[N-(2-hydroxyethyl)salicylaldimino]copper(II) complex as a neutral carrier.

A novel selective thiocyanate electrode of a PVC membrane based on bis-[N-(2-hydroxyethyl)salicylaldimino]copper(II) [Cu(II)-BNSDM] as a neutral carrier is reported. The selectivity sequence of this electrode is as follows: SCN- > ClO4- > I- > Sal- > Br- > NO2- > Cl- > NO3- > H2PO4- > SO4(2-), which is an anti-Hofmeister selectivity sequence. The electrode exhibits a Nernstian potential linear range to thiocyanate from 1.0 x 10(-1) to 6.0 x 10(-6) mol/L with a detection limit of 2.0 x 10(-6) mol/L and a slope of (-59.0+/-0.2)mV/decade in pH 5.0 of a phosphate buffer solution at 25 degrees C. Electrochemical impedance spectroscopy (EIS) and UV spectroscopy techniques were performed to understand the response mechanism of the electrode. The electrode had the advantage of simplicity, high selectivity, fast response and low detection limit compared with the other electrode, which had been reported before. The electrode had been applied to wastewater analysis, and the obtained results were satisfactory.     

中性载体可咯化合物应用于银离子电位传感器的研究

研制了一种以5,10,15-三(五氟苯基)可咯[H_3(tpfc)]为活性组分物质、以邻硝基苯辛醚o-NPOE为增塑剂、以四苯硼钠为亲脂性大阴离子添加剂的PVC膜电极(4种物质的质量比为3:3:62:32),电极能斯特斜率为54.8 mV/decade、工作浓度范围为5.1×10~(-6)～0.1 mol/L,pH为4.0～8.0,响应时间不超过30 s,该电极对银离子能抵抗来自Hg~(2+)、Pb~(2+)等离子干扰,表现出较高的选择性.这种传感器可用于对实际矿石样品进行检测.     

A new coated-wire cobalt(II)-selective electrode based on the benzalkonium tetrathiocyanatocobaltate(II) ion pair

A cobalt-selective electrode based on the benzalkonium tetrathiocyanatocobaltate(II) ion pair is described. The response is Nemstian (slope 29.3 $\text{mV}\text{pCo}$) in the cobalt concentration range 10^-1–10^-4 M in solutions with a constant ionic strength of 3.0 M made up with KSCN at 25°C. The electrode is suitable for end-point detection in titrations of cobalt(II) with EDTA as well as for direct potentiometric determinations of cobalt(II), even in the presence of large amounts of several metal ions (Ni²⁺, Fe²⁺, Mn²⁺, Mg²⁺, Ca²⁺, Ba²⁺) and anions (HCO₃^-, Br^-, I^-, NO₃^-, SO₄^2-).