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.     

A highly selective thallium(I) electrode based on a thia substituted macrocyclic ionophore

A new highly Tl(I)-selective PVC membrane electrode based on tetrathia macrocycle 6,7: 14,15-dibenzo-5,8,13,16-tetraoxo-1,4,9,12-tetrathiacyclohexadecane [Bz₂O₄(16)aneS₄] (I) as membrane carrier, o-nitrophenyloctyl ether (o-NPOE) as solvent mediator and potassium tetrakis(p-chlorophenyl)borate (KTpClPB) as lipophilic additive has been developed. The best performance was given by the membrane of macrocycle (I) with composition 3:120:1.5:50 (I:o-NPOE:KTpClPB:PVC). This electrode exhibits a Nernstian response to Tl(I) ions in the concentration range 1.0 × 10⁻¹-2.23 × 10⁻⁶ M with a slope of 58.2 mV/decade of concentration and a detection limit of 1.58 × 10⁻⁶ M. The response time of the sensor is 12 s and can be used over a period of 4 months with good reproducibility. The proposed electrode revealed good selectivity over a wide variety of other cations including alkali, alkaline earth, heavy and transition metals. The electrode works well over a pH range of 3.2-11.5 and in partially non-aqueous medium with up to 30% organic content. The sensor was also used as an indicator electrode in potentiometric titration of Tl(I) ions with KI solution.     

Strontium(II)-selective electrode based on a macrocyclic tetraamide

A new PVC membrane electrode based on 5,7,12,14-dibenzo-2,3,9,10-tetraoxa-1,4,8,11-tetraazacyclotetradecane (I) as an ion carrier, o-nitrophenyloctyl ether (o-NPOE) as solvent mediator and sodium tetraphenylborate (NaTPB) as lipophilic additive was fabricated and investigated as Sr²⁺-selective electrode. The best performance was exhibited by the membrane having composition 8:200:4:120 (I:o-NPOE:NaTPB:PVC). The electrode exhibited a Nernstian response for strontium ion over a wide concentration range 3.98 × 10⁻⁶ to 1.0 × 10⁻¹ M with a slope of 29.0 ± 0.1 mV/decade of concentration and a detection limit of 2.82 × 10⁻⁶ M. It showed a response time of less than 10 s and could be used for at least 3 months without any divergence in potential. The proposed electrode showed a good discriminating ability towards strontium(II) ion over a wide variety of other metal ions including alkali, alkaline earth, transition, and heavy metal ions. The electrode can be used in the pH range of 2.5-10.5 and in mixtures containing up to 35% (v/v) non-aqueous content. It was used as an indicator electrode in potentiometric titration of strontium ion against EDTA.     

A calixarene-based ion-selective electrode for thallium(I) detection

Three new calixarene Tl⁺ ionophores have been utilized in Tl⁺ ion-selective electrodes (ISEs) yielding Nernstian response in the concentration range of 10⁻²–10⁻⁶ M TlNO₃ with a non-optimized filling solution in a conventional liquid contact ISE configuration. The complex formation constants (log β_IL) for two of the calixarene derivatives with thallium(I) (i.e. 6.44 and 5.85) were measured using the sandwich membrane technique, with the other ionophore immeasurable due to eventual precipitation of the ionophore during these long-term experiments. Furthermore, the unbiased selectivity coefficients for these ionophores displayed excellent selectivity against Zn²⁺, Ca²⁺, Ba²⁺, Cu²⁺, Cd²⁺ and Al³⁺ with moderate selectivity against Pb²⁺, Li⁺, Na⁺, H⁺, K⁺, NH₄⁺ and Cs⁺, noting that silver was the only significant interferent with these calixarene-based ionophores. When optimizing the filling solution in a liquid contact ISE, it was possible to achieve a lower limit of detection of approximately 8 nM according to the IUPAC definition. Last, the new ionophores were also evaluated in four solid-contact (SC) designs leading to Nernstian response, with the best response noted with a SC electrode utilizing a gold substrate, a poly(3-octylthiophene) (POT) ion-to-electron transducer and a poly(methyl methacrylate)–poly(decyl methacrylate) (PMMA–PDMA) co-polymer membrane. This electrode exhibited a slope of 58.4 mV decade⁻¹ and a lower detection limit of 30.2 nM. Due to the presence of an undesirable water layer and/or leaching of redox mediator from the graphite redox buffered SC, a coated wire electrode on gold and graphite redox buffered SC yielded grossly inferior detection limits against the polypyrrole/PVC SC and POT/PMMA–PDMA SC ISEs that did not display signs of a water layer or leaching of SC ingredients into the membrane.     

Copper(II)-selective electrode based on dithioacetal

A PVC membrane electrode for copper ion based on 1,3-dithiane,2-(4-methoxy phenyl) as ionophore and o-nitrophenyl octyl ether as a plasticizer is demonstrated. The electrode exhibits a Nernstian slope of 29.5±1 mV per decade in a linear range of 3.0×10⁻⁶ to 5.0×10⁻² M for Cu²⁺ ion. The detection limit of this electrode is 1.0×10⁻⁶ mol/l. This sensor has a very short response time of about 5 s and could be used in a pH range of 4.0-7.0. High selectivity was obtained over a wide variety of metal ions. The proposed electrode was successfully applied as an indicator electrode for the potentiometric titration of copper ion with EDTA and for the direct determination of copper in river water.     

Studies on the potentiometric thallium(III)-selective carbon paste electrode and its possible applications

Construction, performance characteristics and applications of a carbon paste thallium(III) ion-selective electrode are described. The electrode, which is based on ion-associate compounds formed between cetylpyridinium and chlorothallate(III) complexes dissolved in tricresyl phosphate as pasting liquid, showed near-Nernstian response over the concentration range of 5.8 x 10(-6) - 2.9 x 10(-3) mol/L. Potentiometric titrations of thallium(III) with cetylpyridinium chloride were affected by higher concentrations of excess halides, probably due to the formation of higher halogenothallates.     

Studies on the potentiometric thallium(III)-selective carbon paste electrode and its possible applications

Construction, performance characteristics and applications of a carbon paste thallium(III) ion-selective electrode are described. The electrode, which is based on ion-associate compounds formed between cetylpyridinium and chlorothallate(III) complexes dissolved in tricresyl phosphate as pasting liquid, showed near-Nernstian response over the concentration range of 5.8 × 10^–6– 2.9 × 10^–3 mol/L. Potentiometric titrations of thallium(III) with cetylpyridinium chloride were affected by higher concentrations of excess halides, probably due to the formation of higher halogenothallates.     

Lead(II)-selective electrode based on phenyl disulfide.

A PVC membrane electrode for lead ions based on phenyl disulfide as the membrane carrier was developed. The electrode exhibits a good Nernstian slope of 29.3 +/- 0.7 mV/decade and a linear range of 2.0 x 10(-6)-1.0 x 10(-2) M for Pb(NO3)2. The limit of detection is 1.2 x 10(-6) M. It has a response time of 45 s and can be used for at least fifty days without any divergence in potential. The proposed membrane sensor revealed high selectivity for Pb2+ over a wide variety of other metal ions and could be used in the pH range of 3.5-6.3. The electrode was used as an indicator electrode in potentiometric titration of lead ions.     

Aluminium(III)-selective electrode based on a newly synthesized tetradentate Schiff base

A PVC membrane electrode for aluminium ion based on bis(5-phenyl azo salicylaldehyde) 2,3-naphthalene diimine (5PHAZOSALNPHN) as an ion carrier was developed. The electrode exhibits a Nernstian slope of 19.3+/-0.8 mV per decade and a linear range of 5.0x10(-6)-1.0x10(-2) M for Al(NO(3))(3). The limit of detection is 2.5x10(-6) M. It has a fast response time of about 10 s and can be used for at least 10 weeks without observing any deviation. The proposed membrane sensor revealed good selectivity for Al(3+) over a wide variety of other metal ions and could be used in pH range of 2.9-5.0. It was used as an indicator electrode in potentiometric titration of aluminium ion.     

New cadmium(II)-selective electrode based on a tetraazacyclohexadeca macrocyclic ionophore.

A poly(vinyl chloride)-based membrane of 3,4:11,12-dibenzo-1,6,9,14-tetraazacyclohexadecane with sodium tetraphenyl borate (NaTPB) as an anion excluder and dibutylphthalate (DBP), dibutyl(butyl)phosphonate (DBBP), tris(2-ethylhexyl)phosphate (TEHP) and tributyl phosphate (TBP) as a plasticizing solvent mediator was prepared and investigated as a Cd2+-selective electrode. The best performance was observed with the membrane having a ligand-PVC-DBP-NaTPB composition of 2:25:60:1, which worked well over a wide concentration range (1.6 x 10(-6) - 1.0 x 10(-1) M) with a Nernstian slope of 29.5 mV per decade of activity between pH 2.0 - 6.0. This electrode showed a fast response time of 13 s and was used over a period of 4 months with good reproducibility (S = 0.4 mV). The selectivity coefficient for mono-, di- and trivalent cations indicated excellent selectivity for Cd2+ ions over a large number of cations. Anions such as NO3- and SO4(2-) , did not interfere. The membrane sensor has been successfully used to determine Cd2+ in real samples.     

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.     

A mercury-free electrochemical sensor for the determination of thallium(I) based on the rotating-disc bismuth film electrode

A bismuth film electrode was tested and proposed as an environmentally friendly sensor for the determination of trace levels of Tl(I) in non-deoxygenated solutions. Determination of thallium was made by anodic stripping voltammetry at a rotating-disc bismuth film electrode plated in situ, using acetate buffer as the supporting electrolyte. The stripping step was carried out by a square wave potential-time excitation signal. A univariate optimisation study was performed with several experimental parameters as variables. Under the selected optimised conditions, a linear calibration plot was obtained in the submicromolar concentration range, allowing the electrochemical determination of thallium in trace amounts; the calculated detection limit was 10.8 nM and the relative standard deviation for 15 measurements of 0.1 μM Tl(I) was ±0.2%, for a 120 s accumulation time. Interference of other metals on the response of Tl(I) was investigated. Application to real environmental samples was tested. The bismuth film electrode appears to be a promising tool for electroanalytical purposes, ensuring the use of clean methodology.     

Voltammetric determination of thallium(I) at a mechanically renewed Bi-graphite electrode

A composite of high-purity grade carbon powder and an epoxy resin is used to in situ obtain a bismuth-film electrode. The surface of the indicator electrode is renewed by cutting a thin surface layer before each determination. The in situ obtained Bi-film electrode is virtually no different from an Hg-film electrode in sensitivity, reproducibility, and the ability to separate signals from Tl, Cd, and Pb. The calibration graph is linear in the range of thallium concentrations from 0.01 to 1 mg/L (RSD varies from 4 to 2%). A significant excess of Pb(II), Sn(II), and Cd(II) does not interfere with the determination of thallium. A procedure for determining down to 5 × 10^?6% thallium in lithium carbonate is developed.     

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.     

A new lead(II)-selective PVC-coated graphite rod electrode based on a Schiff base complex.

A new lead(II)-selective electrode has been developed based on bis(acetylacetone)-p-phenylenediamine-lead(II) [LPb(NO3)2]H2O complex ionophore as a sensing material, dioctylphthalate (DOP) as a solvent mediator and PVC as a matrix. This electrode exhibits a linear Nernstian response over the concentration range of 1 x 10(-5)-1 x 10(-1) mol l(-1) of Pb(II) cation, with a cationic calibration slope of 30.0 +/- 0.2 mV/concentration decade and a detection limit of 2 x 10(-6) mol l(-1) (0.40 ppm). It has a fast response time and can be used for a period of 2 months without any divergence in potentials. The proposed electrode reveals a good selectivity for Pb(II) over a wide variety of other tested cations and could be used in the pH range of 4-8. It was successfully used for direct determination of Pb(II) concentration in some samples. The obtained results show a good agreement with those obtained by an atomic absorption spectrometric method. The average recovery obtained is 96.5 +/- 0.5% with standard deviation of 1.2% (n = 8).     

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.     

Graphite disk Lanthanum(III)-selective electrode based on Kryptofix-22DD

ABSTRACT

A novel ion-selective electrochemical sensor based on kryptofix-22DD (1,10-didecyl-1,10-diaza-18-crown-6) as an ionophore was constructed for determination of lanthanum(III) cation in solutions. The D-Optimal Mixture Design(D-OMD) was used as an experimental design strategy for optimal formulation of the membrane ingredients, and the actual values of the ingredients were compared with their predicted values. The amounts of the ionophore, plasticizer, PVC, and also the graphite powder which influence the performance of the fabricated electrode were analyzed using D-OMD. A non-linear relationship was observed between the slope of the electrochemical response of the electrode and these variables and the interaction between the variables as well. The experimental results showed that the amount of the ionophore has the most positive effect on the electrochemical response of the electrode. The constructed electrode exhibits a Nernstian slope (20.60 ± 0.21 mv.decade^?1) in a wide linear concentration range from 1.0 × 10^?7 to 1.0 × 10^?1 M with respect to La³⁺ cation at pH range of 4.0 to 6.0, and its detection limit was found to be:0.8 × 10^?7M. The selectivity of the proposed electrode towards some of the metal cations present in lanthanum(III) cation solutions was tested, and the experimental results showed a good selectivity towards this metal cation.     

Silver(I)-selective membrane electrodes based on sulfur-containing podands

Some podands, acyclic polyethers, were utilized as membrane active components to prepare Ag(+)-selective polymeric membrane electrodes. The thiapodand-based electrodes exhibited considerable selectivity toward Ag(+) over other heavy metal ions including Cd(2+), Pb(2+), Cu(2+) and Hg(2+). Also, good selectivity over alkali and alkali earth metal ions were observed. Response slopes, pH effects, response time, and signal baseline return of the sensor systems were studied in static mode and/or in a flow-injection system. The Ag(+)-selectivity was explained by the soft-soft interaction of the Ag(+) ion with the sulfur donor atoms as well as the stacking interaction between aromatic end groups of the host molecule on complexation.     

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-).     

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.