Calcium‐Selective Electrodes for Measurements in the Presence of Anionic Surfactants

Calcium selective electrodes with various membrane formulations were studied in solutions containing CaCl₂ and sodium dodecylsulfate (NaDS). It is shown that electrodes based on neutral ionophores ETH 1001 and ETH 129 cannot be used as Ca²⁺ ion sensors in these solutions because of strong anion interference from DS^? anion. Among other formulations, that based on calcium bis(tetramethylbutylphenyl)phosphate in tri(2‐ethylhexyl)phosphate appear the most promising. The interpretation of the ISE response in solutions under study relied on a novel approach which considers three forms of calcium: Ca²⁺ free ions, Ca in Ca(DS)₂ precipitate, and Ca²⁺ bound by the DS^? micelles. Data needed for the respective calculations were obtained by DS^? selective electrode based on tetradecylammonium, and Na⁺ selective glass electrode.     

A Heterogeneous Precipitate Based Mn(Ii) Coated Wire Ion-Selective Electrode

Abstract

A new heterogeneous Mn(II) ion selective coated wire electrode (CWISE) based on tetrapyridine Mn(II) thiocynanate as electroactive material has been described. the working pH range of the electrode is 2.3 to 8.8. the electrode shows a linear response in the concentration range 1.0×10^?1M to 1.0×10^?6M. the response time of the electrode is 35 sec. the selectivity coefficient for different cations determined by mixed solution method are:

Fe²⁺(0.05), Cd²⁺(0.05), Ni²⁺(0.01), Co²⁺(0.5), Pb²⁺(0.5), Hg²⁺(0.05), Sn²⁺(0), Zn²⁺(0)

The electrode can be used for the electrometeric determination of Mn(II) ion.     

Potentiometric Titration of Trace Concentrations of Penicillamine Using Ion Selective Electrodes

Abstract

Penicillamine (PA) has shown promise as a therapeutic agent in the treatment of rheumatoid arthritis (RA), and a sensitive analytical procedure applicable to physiological fluids is needed. PA is a metal chelating agent which forms very strong complexes with heavy metal ions (e.g., Hg²⁺, Cu²⁺, Pb²⁺). This characteristic has been applied to the analytical problem presented. The method developed is based on potentiometric titration of the ligand with a metal ion solution utilizing for endpoint detection an indicator electrode selective for this metal ion. The procedure described used lead (II) as the titrant and a lead (II) selective electrode. Demonstrated precision was ±2.0% when 7.5 μg PA was determined in 50 ml solution.     

The Determination of Sodium in Alumina Using a Sodium Selective Ion Electrode

Abstract

A method has been developed for the determination of sodium in alumina using a selective ion electrode. The alumina sample is dissolved in ammonium hydrogen fluoride in platinum crucibles or sintered with boric acid using either platinum, nickel, or zirconium crucibles. Either dissolution technique completely extracts all available sodium. After dissolution, and in the presence of citrate to prevent aluminum hydroxide precipitation, the pH is adjusted to 8.7 with ammonium hydroxide, and the sodium concentration is determined by a sodium selective ion electrode.     

Ionic Diffusion Through Unblended PVC Membranes

Abstract

This work deals with the study of the diffusion of Cl^? ion through pure unblended polyvinylchloride (PVC) membranes of different thickness. Several PVC -tetrahydrofuran ratios and also different internal diameter glass disks have been used to change the thickness of the membrane. A chloride ion selective electrode also constructed in the laboratory is used as the detector. The electrode behaviour was studied by running up a calibration graph prior to membrane positioning. A mean slope of 57 ±1 mV/log.C at 28.0 ± 0.5 °C was obtained and the range of potential values were then known. The detector was very well washed and immediately a membrane was placed directly on its surface and assembled to a rotating disk electrode in order to get a diffusion cell. The receiving compartment in this system has a negligible volume. Therefore, the response of the chloride ion selective electrode is directly proportional to the flux of material through the membrane rather than to the receiving compartment concentration. An almost linear relationship between the Cl^? ion concentration in the range 0.0010 – 0.10 M and its flux through the unblended PVC membrane was found. The chloride ion flux through the PVC membrane in solutions with the ion strength adjusted to 0.1 M was twice to that value obtained without ion strength adjustor (ISA) in the solution. Average rate transport in the range 3.5?10^?7 to 9.6?10^?7 mol/s Cl^? was found at a rotation speed of 1280 rpm.     

Fe(III) Ion‐Selective Membrane Electrode Based on 4‐Amino‐6‐methyl‐3‐methylmercapto‐1,2,4‐triazin‐5‐one

Abstract

An original highly selective and sensitive PVC membrane sensor, working as a Fe(III) ion selective electrode and using 4‐amino‐6‐methyl‐3‐methylmercapto‐1,2,4‐triazin‐5‐one (AMMTO) as an ionophore, has been developed. This cetain sensor demonstrated the following performance; a linear dynamic range between 1.0×10^?6 and 1.0×10^?1 M with a near Nernstian slope of 19.4±0.5 mV per decade; a detection limit of 6.8×10^?7 M; characteristically, the best performance was obtained with a membrane composition of 30% poly(vinyl chloride), 65.5% nitrophenyl octyl ether, 2% sodium tetraphenyl borate and 2.5% AMMTO. Furthermore, the potentiometric response of the developed electrode is independent of the solution pH in the range of 2.2–4.8. The sensor possesses the advantages of short conditioning time, fast response time (<15 s) and, especially, great selectivity towards transition and heavy metal ions and some mono, di‐ and trivalent cations. The electrode can be used for at least 9 weeks without any considerable potential divergence. It was effectively used as an indicator electrode in the potentiometric titration of Fe(III) ions with EDTA and the direct determination of Fe³⁺ in different water samples.     

A New Poly (Vinyl Chloride) Matrix Membrane Electrode for Manual and Flow Injection Determination of Pilocarpine in Some Pharmaceutical Preparations

Abstract

A novel pilocarpinium ion selective membrane electrode is prepared, characterized and used in pharmaceutical analysis. The electrode system incorporates a PVC membrane with pilocarpine-reineckatc ion pair complex as an electroactive material. The electrode exhibits a fast near-Nernstian response for 10^?1-4x10^?5M pilocarpine over the pH range 4-6.5. The electrode displays a good selectivity for pilocarpine with respect to a number of foreign cations. Pilocarpine in various pharmaccutical preparations is determined either by direct potentiometry or potentiometric titration with NaTPB using the proposed sensor. Pilocarpinereineckate membrane is also used in a flow through sandwich cell as a detector for flow injection determination of pilocarpine. Results with an average recovery of 99% and a relative standard deviation of ± 0.3% are obtained. The data compare favorably with those obtained by the standard US Pharmacopeia method.     

Synthesis and characterisation of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) Zr(IV) monothiophosphate composite cation exchanger: analytical application as lead ion selective membrane electrode

A Pb²⁺ ion selective membrane electrode based on poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) Zr(IV) monothiophosphate composite cation exchange material was fabricated using solution casting method. The effect of membrane composition on the proton exchange capacity was investigated by using varying amounts of electroactive material. The membrane with 250 mg of electroactive material and 10 µL of plasticiser exhibited higher proton conductivity. The optimised membrane composition was used for the fabrication of ion selective membrane electrode which exhibited typical Nernstian response towards Pb²⁺ ions in the concentration range 20.70 gL^?1–20.7 µgL^?1 (1 × 10^–1–1 × 10^–7 mol L^?1) with a sub-Nernstian slope of 27.429 mV per decade change in Pb²⁺ ion concentration. The response time of the electrode under study for Pb²⁺ ions was found to be 11 s and the electrode can be used for 120 days without any considerable divergence in response potential. It can also be successfully used in the pH range from 3.0 to 6.5. It was found selective for Pb²⁺ ions in the presence of various monovalent, divalent and trivalent interfering metal ions. It was also employed as an indicator electrode in the potentiometric titration of Pb²⁺ ions using ethylenediaminetetraacetic acid, disodium salt, as a titrant.     

Determination of uranyl ion by potentiometric titration using an uranyl-selective electrode

Summary A potentiometric titration of uranyl ion is described using an uranyl selective electrode based on a membrane containing a complex of UO₂-bis[di-4-(1,1,3,3-tetra-methylbutyl)phenyl phosphate] as an ion-exchanger and tritolyl phosphate as a solvent mediator. The titrations were carried out with various titrants: sodium hydroxide, potassium fluoride and sodium salts of acetate, oxalate and citrate. The equivalence points were determined by Gran's method. Good results were obtained by using sodium oxalate as a titrant for the determination of uranium in several samples of ammonium diuranate. The results were quite comparable with those obtained by X-ray fluorescence spectrometry.     

Determination of Total Fluoride in Oral Products by Using of Potentiometry With Ion Selective Electrode: A Critical Study

ABSTRACT

In this work, a critical study of the determination of fluoride in oral products with an ion selective electrode was performed. The influence of the type of fluorine compound in the sample as well as the practical factors involved in the analysis were investigated. Fluoride could be determined, directly, in samples where it is in the form of NaF or SnF₂. However, in samples where it is as MFP (sodium monofluorophosphate) an acid treatment was needed for removal of fluoride from the PO₄F^2? ion. In both cases, problems were noted related to the continuous use of the electrode, caused by the adsorption of fluoride ions onto the electrode surface. This problem was solved by using of KOH and Al₂(SO₄)₃ solutions. Good results were obtained for the analysis of real commercial samples.     

Preparation of PbS Nanoparticles by Phase-Transfer Method and Application to Pb2+-Selective Electrode Based on PVC Membrane

Abstract

A novel approach to prepare homogeneous PbS nanoparticles by phase-transfer method was developed. The preparatory conditions were studied in detail, and the nanoparticles were characterized by transmission electron microscopy (TEM) and UV-vis spectroscopy. Then a novel lead ion-selective electrode of polyvinyl chloride (PVC) membrane based on these lead sulfide nanoparticles was prepared, and the optimum ratio of components in the membrane was determined. The results indicated that the sensor exhibited a wide concentration range of 1.0 × 10^?5 to 1.0 × 10^?2 mol·L^?1. The response time of the electrode was about 10 s, and the optimal pH in which the electrode could be used was from 3.0 to 7.0. Selectivity coefficients indicated that the electrode was selective to the primary ion over the interfering ion. The electrode can be used for at least 3 months without any divergence in potential. It was successfully applied to directly determine lead ions in solution and used as an indicator electrode in potentiometric titration of lead ions with EDTA.     

An All‐solid‐state Polymeric Membrane Ca2+‐selective Electrode Based on Hydrophobic Alkyl‐chain‐functionalized Graphene Oxide

An all‐solid‐state polymeric membrane Ca²⁺‐selective electrode based on hydrophobic octadecylamine‐functionalized graphene oxide has been developed. The hydrophobic composite in the ion‐selective membrane not only acts as a transduction element to improve the potential stability for the all‐solid‐state Ca²⁺‐selective electrode, but also is used to immobilize Ca²⁺ ionophore with lipophilic side chains through hydrophobic interactions. The developed all‐solid‐state Ca²⁺‐selective electrode shows a stable potential response in the linear range of 3.0×10⁻⁷–1.0×10⁻³ M with a slope of 24.7±0.3 mV/dec, and the detection limit is (1.6±0.2 )×10⁻⁷ M (n =3). Additionally, due to the hydrophobicity and electrical conductivity of the composite, the proposed all‐solid‐state ion‐selective electrode exhibits an improved stability with the absence of water layer between the ion‐selective membrane and the underlying glassy carbon electrode. This work provides a simple, efficient and low‐cost methodology for developing stable and robust all‐solid‐state ion‐selective electrode with ionophore immobilization.     

A Calcium Ion-Selective Electrode Based on a Neutral Carrier

Abstract

The performance of a liquid-membrane electrode using a synthesized ligand in p-nitroethylbenzene as membrane component is described. Selectivities, working range, lifetime, pH-dependence, and dependence on the dielectric constant of the membrane solvent are discussed. The electrode makes possible the measurement of calcium ion activities in the range of 10^?1 M to 10^?5 M In unbuffered systems with a selectivity of calcium over sodium and magnesium of 175 and 33,000 respectively. The selectivity constants of the cell discussed are heavily influenced by the dielectric constant of the membrane solvent.     

Barium(II)-PVC Membrane Sensor Based on 4-4′-Methylenediantipyrine as a Neutral Carrier

Abstract

A highly selective and sensitive poly(vinyl chloride) membrane electrode, using 4-4′-Methylenediantipyrine as an ionophore, has been prepared and examined as a Ba²⁺-selective electrode. The influence of the anion excluder (sodium tetraphenyl borate, NaTPB) and the effect of the plasticizers dibutyl phthalate (DBP), nitrobenzene (NB), and benzyl acetate (BA) were studied. The best performance was obtained with the sensor having a membrane composition (w/w) of (MAP, 2.0%), (PVC, 30%), (NB, 66%), (NaTPB, 2.0%) with a wide working concentration range of 1.0 × 10^?6 to 1.0 × 10^?2 M between the pH values of 3.4 and 10.6. Furthermore, a Nernstian slope of 29.7±0.3 mV/decade of activity was demonstrated with a response time of 15 s. The sensor could be used over a period of 2 months with no potential divergence, revealing a good selectivity for a broad variety of cations including alkali, alkaline earth, heavy and transition metals. Regarding the practical applicability of this sensing device, it was successfully applied for the Ba²⁺ ions detection in a lithophone pigment and as an indicator electrode in the potentiometric titration of the under study cations.     

Highly Selective and Sensitive Triiodide PVC‐Based Membrane Electrode Based on a New Charge Transfer Complex of 2‐(((2‐(((E)‐1‐(2‐Hydroxyphenyl) Methylidine) Amino) Phenyl) Imino) Methyl) Phenol for Nano‐Level Monitoring of Triiodide

Abstract

A highly selective and sensitive triiodide sensor based on a 2‐(((2‐(((E)‐1‐(2‐hydroxy phenyl) methylidine) amino) phenyl) imino) methyl) phenol with iodine (CTC) as membrane carrier was developed. The electrode revealed a Nernstian behavior over a very wide triiodide‐ion concentration range (5.0×10^?8–1.0×10^?2 M), and relatively low detection limit (3.0×10^?8 M). The potentiometric response is independent of the pH of solution in the pH range of 3.0–10.0. The electrodes manifest advantages of low resistance, very fast response (<12 s), and most importantly, good selectivities relative to a wide variety of inorganic and organic anions, including iodide, bromide, chloride, fluoride, sulfite, sulfate, cyanide, thiocyanate, and acetate. In fact, the selectivity behavior of the proposed triiodide ion‐selective electrode shows great improvements compared to the previously reported electrodes for the triiodide ion. The proposed membrane sensor can be used for at least 6 months without any significant divergences in the potential. The electrode was successfully applied as an indicator electrode in the titration of triiodide with thiosulfate ion.     

Determination of Total and Fluoride Bound Aluminium in Tea Infusions by Ion Selective Electrode and Flame Atomic Absorption Spectrometry

ABSTRACT

Speciation of metallic compunds is important especially for their bioavailability. In this present study fluoride bound aluminium species were determined in tea infusion. Total aluminium was measured using flame atomic absorption spectrometry (FAAS). Free fluoride and total fluoride were measured by fluoride selective ion electrode (FISE) with the assistance of TISAB buffer solution used for adjustment of pH and total ionic strength, and ALCOA buffer solution which decomposes all of the Al-fluoride complexes in solution.

During the studies, the effects of pH and time on the formation of Al-F complexes and interference of some metal ions found in tea infusion such as Al³⁺, Mg²⁺, Fe²⁺, Fe³⁺ and Mn²⁺ on the concentration of free fluoride were investigated. The concentration of each Al-fluoride complexes in tea fusion were determined indirectly by calculation using pF-Mole Fraction Diagram. It was found that 1.13±0.15 mg 1^? of 12.00±0.86 mg 1^? total aluminium is fluoride bound aluminium, which means that appoximately 10% of total aluminium in tea infusion is complexed with fluoride.     

A Novel Hg(II) PVC Membrane Sensor Based on Simple Ionophore Ethylenediamine Bis‐Thiophenecarboxaldehyde

Abstract

A mercury (II) ion‐selective polyvinyl chloride (PVC) membrane sensor based on ethylenediamine bisthiophenecarboxaldehyde (EDBT) as a novel nitrogen‐ and sulfur‐containing sensing material was successfully developed. The ionophore was produced through Schiff's base formation between ethylenediamine and 2‐thiophenecarboxaldehyde. These two reagents have the advantages of low cost and simple chemical compounds. Ortho‐nitro phenyl pentyl ether (o‐NPPE) as solvent and sodium tetraphenyl borate (NaTPB) as a lipophilic salt were chosen. The sensor exhibited a good linear response of 30.0±0.4 mV per decade within the concentration range of 10^?7–10^?2 and a detection limit of 7.0×10^?8 mol L^?1 Hg(II). The sensor showed good selectivity and fast response for the mercury (II) ion with respect to some alkali, alkaline earth, transition, and heavy metal ions. The EDBT–based sensor was suitable for aqueous solutions of pH range from 2.0 to 4.5. It can be used for about 3 months without any considerable divergence in potential. The formation constant of ionophore complex with Hg(II) ion was calculated by using the segmented sandwich membrane method. The structure of both the ionophore and its Hg(II) complex were examined using infrared spectra and elemental analysis. The proposed sensor was applied for the determination of Hg(II) content in some dental amulgum alloys and as an indicator electrode for potentiometric titration of Hg(II) ion with EDTA solution, as well as with I^?, OH^?, and IO₃ ^? ions. In addition, the solubility products of the previous ions were determined by using this sensor.     

Lead-Selective Membrane Potentiometric Sensor Based on a Recently Synthesized Bis(Anthraquinone) Sulfide Derivative

Abstract

A new PVC membrane electrode for lead ions, based on bis[(1-hydroxy-9,10-anthraquinone)-2-methyl]sulfide as membrane carrier, was prepared. The sensor exhibits a Nernstian response for Pb²⁺ over a wide concentration range (5.6 × 10^?3-4.0 × 10^?6 M). It has a response time of about 30 s and can be used for at least 3 months without any divergence in potentials. The proposed membrane sensor revealed good selectivities for Pb²⁺ over a wide variety of other metal ions. It was used as an indicator electrode in potentiometric titration of lead ion.     

PPb Level Monitoring of Dy(III) Ions by a Highly Sensitive and Selective Dy(III) Sensor Based on a New Asymmetrical Schiff's Base

Abstract

A Dy(III) ion‐selective membrane sensor has been fabricated from polyvinyl chloride (PVC) matrix membrane containing a new asymmetrical Schiff's base [(E)‐N‐(2‐hydroxybenzylidene)benzohydraide] or BBH as a neutral carrier, sodium tetraphenyl borate (NaTPB) as an anionic excluder and nitrobenzene (NB) as a plasticizing solvent mediator. The membrane sensor displays linear potential response in the concentration range of 1.0×10^?2–1.0×10^?6 M of Dy(III). The electrode exhibits a nice Nernstian slope of 20.1±0.8 mV/decade in the pH range of 3.0–8.0. The sensor has a relatively short response time in whole concentration ranges (<20 s). The detection limit of the proposed sensor is 8.0×10^?7 M (～128 ng/mL), and it can be used over a period of six weeks. The selectivity of the proposed sensor with respect to other cations, (alkali, alkaline earth, transition and heavy metal ions) and especially lanthanid ions, is excellent. The practical utility of the sensor has been demonstrated by using it as an indicator electrode in the potentiometric titration of Dy(III) with EDTA.     

Lead Ion‐Selective Polypyrrole Solid‐Contact Electrode Based on Crown Ether

Abstract

The lead(II) ion selective solid‐contact electrode based on polypyrrole film, covered with a polyvinyl chloride membrane has been prepared. Polypyrrole film was used as a mediating layer of the solid‐contact electrode due to the conductivity. Crown ether has been used as ionophores in polyvinyl chloride cocktail solutions. This solid‐contact electrode based on benzo‐15‐crown‐5 exhibited Nernstian‐response within 30 s response time over concentration range, 1×10^?1～5×10^?7 M. The selectivity of this electrode to other metal cations was comparatively good. This electrode showed much better results, such as detection range, slope, response time and reproducibility than conventional ion selective electrode and coated wire electrode.