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.     

New polymeric membrane cadmium(II)-selective electrodes using tripodal amine based ionophores

Fabrication of PVC membrane electrodes incorporating selective neutral carriers for Cd(2+) was reported. The ionophores were designed to have different topologies, donor atoms and lipophilicity by attaching tripodal amine (TPA) units to the lipophilic anthracene (ionophore I) and p-tert-butylcalix[4]arene (ionophores II, III and IV). The synthesized ionophores were incorporated to the plasticized PVC membranes to prepare Cd(II) ion selective electrodes (ISEs). The membrane electrodes were optimized by changing types and amounts of ionic sites and plasticizers. The selectivity of the membranes fabricated from the synthesized ionophores was evaluated, the relationship between structures of ionophores and membrane characteristics were explored. The ionophore IV which composed of two opposites TPA units on the calix[4]arene compartment showed the best selectivity toward Cd(2+). The best membrane electrode was fabricated from ionophore IV (10.2 mmol kg(-1)) with KTpClPB (50.1 mol% related to the ionophore) as an ion exchanger incorporated in the DOS plasticized PVC membrane (1:2; PVC:DOS). The Cd-ISE fabricated from ionophore IV exhibited good properties with a Nernstian response of 29.4±0.6 mV decade(-1) of activity for Cd(2+) ions and a working concentration range of 1.6×10(-6)-1.0×10(-2)M. The sensor has a fast response time of 10s and can be used for at least 1 week without any divergence in potential. The electrode can be used in the pH range of 6.0-9.0. The proposed electrodes using ionophores III and IV were employed as a probe for determining Cd(2+) from the oxidation of CdS QDs solution and the real treatment waste water sample with excellent results.     

Cs+ -selective membrane electrodes based on ethylene glycol-functionalized polymeric microspheres

A new strategy for improving the robustness of membrane-based ion-selective electrodes (ISEs) is introduced based on the incorporation of microsphere-immobilized ionophores into plasticized polymer membranes. As a model system, a Cs⁺-selective electrode was developed by doping ethylene glycol-functionalized cross-linked polystyrene microspheres (P-EG) into a plasticized poly(vinyl chloride) (PVC) matrix containing sodium tetrakis-[3,5-bis(trifluoromethyl)phenyl] borate (TFPB) as the ion exchanger. Electrodes were evaluated with respect to Cs⁺ in terms of sensitivity, selectivity, and dynamic response. ISEs containing P-EG and TFPB that were plasticized with 2-nitrophenyl octyl ether (NPOE) yielded a linear range from 10⁻¹ to 10⁻⁵ M Cs⁺, a slope of 55.4 mV/decade, and a lower detection limit (log a_Cs) of −5.3. In addition, these membranes also demonstrated superior selectivity over Li⁺, Na⁺, and alkaline earth metal ion interferents when compared to analogous membranes plasticized with bis(2-ethylhexyl) sebacate (DOS) or membranes containing a lipophilic, mobile ethylene glycol derivative (ethylene glycol monooctadecyl ether (U-EG)) as ionophore.     

离子缔合型离子选择电极的研究 I: PVC膜铬(VI)离子选择电极的研制的和应用

A new Cr(VI)-selective electrode of PVC membrane based on triheptyl dodecyl ammonium iodide is described. The response of the electrode is Nernstian for Cr(VI) concentration down to 2X10-6M in 0.03-0.13N HF solution. Limit of detection is 5X10-7M. The plot of logarithms of selectivity coefficients vs. z/γ of various anions is essentially linear with a correlation coefficient of -- 0.88. Applications of the electrode in determination of total Cr in steels and copper alloys, and Cr(VI) in waste-water from chromium electroplating are reported.     

Silver(I)-selective coated-wire electrode based on an octahydroxycalix[4]arene derivative.

The performance of octahydroxycalix[4]arene derivative used as a neutral carrier for silver polymeric membrane electrode was studied. The sensor gave a good Nernstian response of 58 +/- 1 mV per decade for silver ion in the activity range 3.3 x 10(-6) to 3.3 x 10(-2) M Ag+. The limit of detection reached 2.1 x 10(-6) M Ag+ and exhibited high selectivity for silver ion against the alkali, alkaline earth and transition metal ions. The sensor can be used in wide pH range from 1.5 to 6.5. The response time of the sensor is less than 20 s. The potentiometric sensor was used as the indicator electrode in the titration of Ag+ ions by sodium chloride solution.     

Silver selective benzimidazol-2(1H)-one based,sulphur-containing podands

Podands based on benzimidazol-2(1H)-one, containing S and terminal NH₂ groups, selectively transport and extract silver picrate over Mg²⁺, Ca²⁺, Sr²⁺, Ph²⁺ and Tl⁺ picrates.     

Silver(I) ion selective PVC membrane based on bis-pyridine tetramide macrocycle

A PVC membrane based on bis-pyridine tetramide macrocycle exhibits a good response for silver ion over a wide concentration range (1.0x10(-1)-4.0x10(-5) mol l(-1)). The electrode has a relatively fast response time and can be used for more than 5 months without observing any divergence. High selectivity for Ag(+) ions over that of Na(+), K(+), Ca(2+), Sr(2+), Pb(2+) and Hg(2+) have been observed.     

Silver(I)-selective electrode based on [Bz2Oxo4(18)dieneS4] tetrathia macrocyclic carrier

A polystyrene-based membrane of 7,8:16,17-dibenzo-6,9,15,18-tetraoxo-1,5,10,14-tetrathiacyclooctadeca-7,16-diene [Bz₂Oxo₄(18)dieneS₄] was fabricated using sodium tetraphenylborate (NaTPB) and dioctyl phthalate (DOP) as anion excluder and plasticizing agent. The best performance was obtained from the membrane with the composition ionophore [Bz₂Oxo₄(18)dieneS₄]:polystyrene:DOP:NaTPB, 5:100:150:10 (w/w). The response of the electrode was linear over a wide range of concentration, 1.26×10^–6–1.00×10^–1 mol L⁻¹ for silver ion with a Nernstian slope of 58.4±0.1 mV per decade and a detection limit of 1.0×10⁻⁶ mol L⁻¹. The electrode was found to be chemically inert and of adequate stability with a response time of 10 s and could be used for a period of 3 months without change of potential. It worked satisfactorily in mixtures containing up to 35% (v/v) non-aqueous content. The proposed membrane sensor had good selectivity for Ag⁺ over a wide variety of metal ions in the pH range 2.2–8.5. It was successfully used as an indicator electrode in potentiometric titration of silver ion. The electrode was also useful for determination of Ag⁺ in waste from photographic films.     

Silver(I) ion-selective membrane based on Schiff base-p-tert-butylcalix[4]arene

A PVC membrane electrode for silver(I) ion based on Schiff base-p-tert-butylcalix[4]arene is reported. The electrode works well over a wide range of concentration (1.0 x 10(-5)-1.0 x 10(-1) mol dm-3) with a Nernstian slope of 59.7 mV per decade. The electrode shows a fast response time of 20 s and operates in the pH range 1.0-5.6. The sensor can be used for more than 6 months without any divergence in the potential. The selectivity of the electrode was studied and it was found that the electrode exhibits good selectivity for silver ion over some alkali, alkaline earth and transition metal ions. The silver ion-selective electrode was used as an indicator electrode for the potentiometric titration of silver ion in solution using a standard solution of sodium chloride; a sharp potential change occurs at the end-point. The applicability of the sensor to silver(I) ion measurement in water samples spiked with silver nitrate is illustrated.     

Copper(II)-selective membrane electrodes based on some recently synthesized mixed aza-thioether crowns containing a 1,10-phenanthroline sub-unit

Three different mixed aza-thioether crowns containing a 1,10-phenanthroline sub-unit were investigated to characterize their abilities as copper(II) ion carriers in PVC-membrane electrodes. The electrode based on L1 exhibited a Nernstian response for Cu²⁺ ions over a wide concentration range (2×10⁻¹ to 1×10⁻⁵ M) with a limit of detection of 8.0×10⁻⁶ M (0.5 p.p.m.). The response time of sensor is 15 s, and the membrane can be used for more than 3 months without observing any deviation. The electrode revealed comparatively good selectivities with respect to many alkali, alkaline earth, transition and heavy metal ions, and could be used in a pH range of 2.5–5.5. It was applied to the direct determination and potentiometric titration of the copper(II) ion.     

LED-compatible copper(II)-selective optrode membrane based on lipophilized Zincon

An optical single shot test for copper(II) ion is presented. The membrane consists of a polyester support and an active layer composed of hydrogel, a hydroxylic plasticizer, and Zincon. The latter has been made lipophilic by ion-pairing with tetraoctyl-ammonium bromide. The membrane responds to copper ions in giving a color change from pink to blue. Because the layer irreversibly extracts copper from the solution, a kinetic approach has been used for quantitation, in that the membrane has been exposed to the sample for 2 min and the initial slope of the response curve has been determined. A linear calibration graph has been obtained for the 1 to 100 mol/l (63.5 g/kg to 6.35 mg/kg) copper concentration range. The complexed form of the dye exhibits an absorption maximum of 620 nm which matches the emission band of the orange light-emitting diode (LED). Measurements have been performed at pH 6, because no complexation of zinc occurs in this range. The long term stability of the membrane exceeds 6 months when stored dry and in the dark. The strong binding of copper ions along with the fairly high selectivity of the membrane also suggests its use as a preconcentration phase.Dedicated to Professor Dr. Dieter Klockow on the occasion of his 60th birthday     

Tetrachloroferrate(III)-selective liquid membrane electrode based on crystal violet

An extract of crystal violet-tetrachloroferrate(III) in nitrobenzene was used to prepare a tetrachloroferrate(III)-selective liquid membrane electrode with a poly(vinyl chloride) support. The optimal conditions to determine 2.5 × 10^–5 – 5.0 × 10^–2 M iron(III) as tetrachloroferrate(III) (anionic slope 56 mV/decade, detection limit 7.9 × 10^–6 M) were found to be 4.0–5.5.M total chloride in 0.75–1.5M hydrochloric acid. The electrode was reliably applied to determine iron in human blood, haematite and mineralized vitamin syrup by direct potentiometry, standard and sample additions as well as standard subtraction techniques.     

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.     

Zn(II)-selective membrane electrode based on tetra(2-aminophenyl) porphyrin

A new PVC membrane electrode for Zn²⁺ ions based on tetra(2-aminophenyl) porphyrin (TAPP) as membrane carrier is prepared. The sensor exhibits a linear stable response over a wide concentration range (5.0×10⁻⁵ to 1.0×10⁻¹ M) with a slope of 26.5 mV/decade and a limit of detection 3.0×10⁻⁵ M (1.96 ppm). It has a response time of about l0 s and can be used for at least 8 months without any divergence in potential. The propose membrane sensor revealed good selectivities for Zn²⁺ over a wide variety of other metal ions and can be used in pH range of 3.0–6.0. It was successfully applied to the direct determination of zinc in a pharmaceutical sample and also as an indicator electrode in potentiometric titration of Zn²⁺ ions.     

Ion-selective electrodes for determination of phenylalanine based on uranyl complexes of phosphoryl-containing podands

The possibility of phenylalanine determination using membrane ion-selective electrodes based on uranyl complexes with phosphoryl-containing podands was shown. The variation of the procedure of membrane preparation (either entrapping the preliminarily synthesized uranyl-podand complex in the membrane phase or conditioning of the podand-containing membrane in the uranyl solution) was found to have practically no effect on the electrode properties. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1729–1732, October, 2000.     

New BF(-)(4) and ClO(-)(4)-selective membrane electrodes and their pharmaceutical applications

The construction and general performance characteristics of ion-selective membrane electrodes sensitive to BF(-)(4) and ClO(-)(4) anions, respectively, are described. All electrodes show near-Nernstian responses in the range 10(-2) -10(-5)M. The selectivity of the electrodes to a number of organic and inorganic anions are reported. The electrodes are useful in the potentiometric determination of a few pharmaceutical preparations. The method is simple, rapid and does not require prior sample pre-treatment.     

An evaluation of some commercial lead(II)-selective electrodes

Two types of commercial lead(II)-selective electrode, the Orion 94-82 and the R??i?ka lead Selectrode, are compared. Calibration curves were determined in both buffered and unbuffered lead-ion solutions repeatedly for several weeks. Selectivities with respect to copper(II), silver(I), mercury(II), iron(III), zinc and cadmium were examined as well as the pH response by the mixed solution method. The response times of the electrodes were also studied.     

Liquid membrane electrodes based on quaternary ammonium tetrakis(m-trifluoromethylphenyl)borates

Electrodes based on the appropriate salts give linear responses for 10^-1–10^-4 M tetramethylammonium and tetraethylammonium ions, with some selectivity against alkali metal ions. Use as indicator electrodes in titrations with tetraphenylborate solutions is outlined.