Methylene Blue Poly(Vinyl Chloride) Membrane Electrode Based on the Methylene Blue-Teteraphenylborate Ion-Pair Complex and Its Application to Pharmaceutical Analysis

Abstract

A methylene blue (MB) poly (vinyl chloride) membrane electrode based on MBtetraphenylborate (TPB) ion-pair complex is described. The linear response covers the range 1x10^?2 - 1x10^?6 mol dm^?3 MB solution, with a slope of 56.5±0.5 mv/decade (pH range 3.0-1 0.0). The detection limit is 7.75x 10^?7 mol dm^?3. The electrode shows stability, good reproducibility and fast response. Interferences from common inorganic cations and some organic bases are negligible. These characteristics of the electrode enabled it to be used successfully for the determination of MB in injection.     

A Neutral Carrier Membrane Calcium-Sensitive Electrode with Wide Working pH Range

Abstract

A poly(vinyl chloride) (PVC) membrane calcium-sensitive electrode based on a new type of synthetic carrier 1,7-di[2-(1-phenylazo)naphtyl]-1,4,7-trioxaheptan is introduced. This electrode exhibited Nernstian response over the concentration range 1.0×10^?1 - 3.0×10^?8 mol/L Ca²⁺ with a slope of 28.8 mV/pCa in calcium ion buffer solutions. The detection limit for calcium ion was 1.0X10^?8 mol/L. The response time varied from 10 to 30 seconds. The working pH range for the electrode was 3.5 - 12.3 when the concentration of Ca²⁺ was 10^?3 mol/L. The lifetime of the electrode was proved to exceed 8 months. It was applied successfully in the determination of calcium ion in river water, mineral water and cosmetic. A method for the determination of total calcium in urine was developed.     

Lead(II)-Selective Membrane Electrode Based on Tetraphenylporphyrin

ABSTRACT

A PVC membrane electrode for Pb² ions based on tetraphenylporphyrin was prepared. The sensor exhibits a Nernstian response for lead ions over a wide concentration range (1.0 x 10^?5-1.0 x 10^?2 M). The limit of detection is 8.5 x 10^?6M. It has a response time of 15 s and can be used for at least three months without any divergence in potential. The proposed electrode shows a fairly good discriminating ability towards Pb² ion in comparison to some alkali, alkaline earth, transition and heavy metal ions. The electrode can be used in the pH range 5.0 to 7.5. It was used as an indicator electrode in potentiometric titration of lead ion.     

Analytical Study of New Creatininium and Tetramethyl-ammonium Cation Selective Membrane Electrodes

Abstract

Two new liquid membrane electrodes which respond to creatininium and tetramethylammonium cations are described. The creatininium cation electrode exhibits rapid and near Nernstian response to creatininium cation activity, at pH 3, in the 10^?3?10^?1 mol/L range. The useful concentration range extends to 10^?4 mol/L. The tetramethyl-ammonium cation electrode exhibits rapid and near Nernstian response to tetramethylammonium cation activity, at pH 2–11.5, in the 2x10^?5? 10^?1 mol/L range. Major interferences for the creatininium electrode are Na⁺, K⁺, NH⁺ ₄ and creatine. The pK_a of the creatininium cation was calculated. A method is described for the potentiometric precipitation titration of tetramethylammonium cation with sodium tetraphenylboron. Amounts of tetramethylammonium in the range 20–200 μol have been determined using Gran's plots, with an average error of about 0.6%.     

Determination of Lysine in Nutrition Sample by Adsorption Voltammetry

Abstract

Lysine can be determined by adsorptive voltammetry after derivatization with acetaldehyde in 1.3 x 10^?2mol/ L borax-NaOH buffer solution (containing 4 x 10^?3mol/ L of CH₃CHO at pH10). The Schiff's base product of the derivation can be adsorbed on a hanging mercury electrode and reduced with peak potential of about -1.33v (vs.SCE) after 120s pre-concentration time. The derivative peak height is linearly proportional to the concentration for lysine in the range 6.0 x 10^?7-1.0 x 10^?5mol/ L. The detection limit is 4.0 x 10^?7mol/ L. Using this method, we have directly determined lysine in nutrition samples without any pre-separation step.     

A new PVC matrix membrane sensor for determination of praseodymium(III) ion based on bis(salicylaldehyde)thiocarbohydrazone as an ion carrier

The sufficient amounts of bis(salicylaldehyde) thiocarbohydrazone (STCH) as a lipophilic selective element (3%, w/w), sodium nitrobenzene (NB) as a plasticizer (64%, w/w), tetraphenyl borate (NaTPB) as an anionic additive (3%, w/w), and poly vinyl chloride (PVC) as a polymeric matrix (30%, w/w) was employed to form a PVC membrane of a new Pr³⁺ ions selective sensor to apply as an indicator electrode in analytical applications. The best electrode response was observed in the slope (19.5 ± 0.7 mV per decade) over a wide concentrations from lower (1.0 × 10^?6 mol L^–1) to higher (1.0 × 10^?2 mol L^–1) of Pr³⁺ ion solution with a detection limit of 8.5 × 10^–7 mol L^–1. This electrode showed the fast response time about 10 second for praseodymium ion concentration range of 1.0 × 10^–6 to 1.0 × 10^–2 mol L^–1, in the pH range of 2.3–7.9. The matched potential method was applied to study the selectivity of electrode toward Pr³⁺ ions in comparison with many common cations. The results showed the negligible disturbance of all other cations on the proposed praseodymium(III) electrode. The making sensor has been employed successfully as an indicator electrode in the potentiometric titration of praseodymium(III) solution with EDTA at pH 6.0. Moreover the applicability of the sensor was studied in determination of Pr³⁺ ion in mixtures of different ions.     

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.     

Efficient Synthesis of a New Podand and Application as a Suitable Carrier for Silver Ion‐Selective Electrode

A new podand of 1,1′‐thia‐bis‐[1‐(chloroethan‐2‐acetamid‐α‐oxy)] naphtol was synthesized and used as a suitable carrier for Ag⁺ PVC membrane electrode. The electrode exhibited linear response with a Nernstian slope of (59.5±0.8 mV/decade) within a wide concentration range of 1.0×10^?7 to 1.5×10^?2 mol L^?1 silver ions. The electrode had a fast response time of <10 s and detection limit of 8.6×10^?8 mol L^?1 with a working pH range from 3.7 to 9.0. The electrode was highly selective for Ag(I) ions over a large number of cations such as alkali, alkaline earth, and heavy metal ions. The proposed sensor has been applied as an indicator electrode for indirect determination of vitamin B₁ in tablets by determination of Cl^? ions in this compound with a standard solution of Ag(NO₃).     

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.     

Single‐Piece Solid‐Contact Pb2+‐Selective Electrodes Based on Thiophene Oligomer

A single‐piece solid‐contact Pb²⁺‐selective electrode was prepared by adding a thiophene oligomer into the ion‐selective cocktail directly. The one‐step fabrication yielded an electrode with Nernstian response spanning a wide concentration range of 10^?3–10^?8 mol L^?1, and detection limit as low as 5.6×10^?9 mol L^?1. The electrode had a quick response time of approximately 10–15 s and showed excellent selectivity over the most common univalent and divalent cations. The practical application of the proposed electrode has been tested by determining Pb²⁺ in real water samples.     

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.     

Novel potentiometric sensor for the determination of Cd2+ based on a new nano-composite

A novel ion selective carbon paste electrode for Cd²⁺ ions based on 2,2′-thio-bis[4-methyl(2-amino phenoxy) phenyl ether] (TBMAPPE) as an ionophore was prepared. The carbon paste was made based on a new nano-composite including multi-walled carbon nanotubes (MWCNTs), nanosilica and room-temperature ionic liquid, 1-Butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF₆). The constructed nano-composite electrode showed better sensitivity, selectivity, response time, response stability and lifetime in comparison with typical Cd²⁺ carbon paste sensor for the successful determination of Cd²⁺ ions in water and in waste water samples. The best performance for nano-composite sensor was obtained with an electrode composition of 18% TBMAPPE, 20% BMIM-PF₆, 48% graphite powder, 10% MWCNT and 4% nanosilica. The new electrode exhibited a Nernstian response (29.95?±?0.10?mV?decade^?1) toward Cd²⁺ ions in the range of 3.0?×?10^?8 to 1.0?×?10^?1?mol?L^?1 with a detection limit of 7.5?×?10^?9?mol?L^?1. The potentiometric response of prepared sensor was independent of the pH of test solution in the pH range 3.0 to 5.5. It had a quick response with a response time of about 6?s. The proposed electrode showed fairly good selectivity over some alkali, alkaline earth, transition and heavy metal ions.     

Novel Membrane Potentiometric Thiocyanate Sensor Based on Tribenzyltin(IV) Dithiocarbamate

A novel PVC membrane ion‐selective electrode based on tribenzyltin(IV) dithiocarbamate [Sn(IV)–TBDTB] as neutral carrier was developed for thiocyanate (SCN^?) determination. The electrode exhibits a near‐Nernstian response for SCN^? with a slope of 62.8±2.0 mV per decade over a wide concentration range 1.0×10^?1–2.0×10^?6 mol L^?1 and a detection limit of 1.0×10^?6 mol L^?1 in MES–NaOH buffer, pH 6.0, at 25 °C. The electrode prepared with 1.5 wt.% Sn(IV)–TBDTB, 32.5 wt.% PVC and 66.0 wt.% 2‐nitrophenyloctyl ether (o‐NPOE) shows optimal response characteristics. Anti‐Hofmeister selectivity sequence for a series of anions shown by the electrode was as follows: SCN^?>Sal^?>I^?>ClO >phCOO^?>CH₃COO^?>Br^?>Cl^?>NO >NO >Citrate>SO₄^2?. The useful pH range for the electrode was found to be 3–7 with a response time 30–40 s. The electrode has been used for direct determination of thiocyanate in wastewater with satisfactory results.     

Application of 1,4-Diaminoanthraquinone as a New Sensing Material for Fabrication of a Iron(III)-Selective Modified Carbon Paste Electrode

In the present work, a novel sensitive electrochemical potentiometric sensor for sensing Fe³⁺ ions based on 1,4-diaminoanthraquinone (DAQ) as a hydrophobic selector element was prepared to implement as an ion selective carbon paste electrode in the aqueous solutions. The adequate amounts of ionophore (5%), paraffin oil (25%) as a binder, Nanosilica (NS: 0.5%) multi-wall carbon nanotubes (MWCNTs: 1%) as a modifier, and graphite powder (68.5%) as an inert matrix was occupied to form the paste. This new FeCP sensor demonstrated a Nernstian slope of 19.7 ± 0.7 mV per decade over widish linear range between 1.0 × 10^–8 to 1.0 × 10^–2 mol L^–1 at working pH range of 1.9–5.0 in the optimized conditions. The average elapsed time to response of electrode was about ~6 s for concentrations from lower (1.0 × 10^?8 mol L^–1) to higher (1.0 × 10^?2 mol L^–1) of Fe³⁺ ion solution. The selectivity of electrode toward Fe³⁺ ions in comparison with other cations was studied by matched potential method. The making FeCP sensor has been put to use successfully as an indicator electrode in analytical applications such as the potentiometric titration and determination of iron(III) ion in blend of different ions.     

Cyanide ion selective solid contact electrode based on nickel complex of N,N′-bis-(4-phenylazosalicylidene)-o-phenylene diamine ionophore

A cyanide ion selective poly(aniline) solid contact electrode based on nickel complex of N,N′-bis-(4-phenylazosalicylidene)-o-phenylenediamine ionophore was successfully developed. The electrode exhibits a good linear response of 58.7 mV/decade (at 20 ± 0.2°C, r ² = 0.998) with in the concentration range of 1 × 10^?1.0-1 × 10^?6.0 M cyanide. The composition of this electrode was: ionophore 0.300, polyvinylchloride 0.300, 2-nitrophenyloctyl ether 0.670 (mass). This 2-nitrophenyloctyl ether plasticizer provides the best response characteristics. The electrode shows good selectivity for cyanide ion in comparison with any other anions and is suitable for use with aqueous solutions of pH 4.6–6.3. The standard deviations of the measured emf difference were ±1.92 and ±1.87 mV for cyanide sample solutions of 1.0 × 10^?2 M and 1.0 × 10^?3 M, respectively. The stabilization time was less than 183 s and response time was less than 38 s.     

Electro-Catalytic Oxidation of Ascorbic Acid at a Cobalt-Salen Polymer Modified Electrode and Analytical Applications

ABSTRACT

The preparation and electrochemical characteristics of electrodes modified by cobalt complexes of N, N' - bis(salicylidene)-ethane -1, 2- diamine (salen) are described. A cobalt-salen polymer film modified electrode has strong electro-catalytic effects for the oxidation of ascorbic acid. The anodic peak potential of ascorbic acid shifted negatively for 400 m V. The catalytic reaction rate constant determined by rotating disk experiments is 7.08×10⁵ mol s^?1 cm^3. The catalytic mechanism and the effect of film thickness are discussed. A sensitive voltammetric response for ascorbic acid was obtained covering a linear range from 1.0×10^?6 to 1.0×10^?3 mol-L^?1 The modified electrode showed good stability and reproducibility. The electrode was used to the determination of ascorbic acid in fruit juices and showed promising results compared with conventional methods. The electro-catalytic effect of several metal-salen complexes and a similar Schiff base derivative for ascorbic acid was compared.     

Ion-Selective Electrode for the Determination of Furaltadone

ABSTRACT

A Furaltadone (FD) ion-selective PVC membrane electrode based on the ion-pair complex of FD with sodium tetraphenylborate was prepared with dioctyl phthalate as a plasticiser. The electrode exhibits a linear response with an approximate Nernstian slope (50 mV decade^?1 at 20 ⁰C) with the concentration range 2.18 x 10^?5–2.18 x 10^?4 FD. The effects of ionic strength and pH of the test solution on the electrode performance were studied. The electrode exhibited very good selectivity for FD with respect to a large number of inorganic and organic cations of biological importance. The standard addition method and potentiometric titration were used to determine the FD in pure solution and in pharmaceutical preparations with satisfactory results.     

Analytical Determination of N-(2-Mercapto Propionyl)Glycine (Tiopronin) by Voltammetric Methods

Abstract

The anodic processes which occur at the mercury electrode in N-(2-mercaptopropinyl)glycine (tiopronin) solutions are studied by polarographic techniques (d.c., d.p. and a.c₁.), controlled potential coulometry and cathodic stripping voltammetry. According to the observed electrochemical behaviour the overall electrode process is the formation of a mercury(II)-mercaptide. Adsorption on the electrode of both the mercaptide and the free thiol is present. The d.p.p. peak at -0.58 V or the voltammetric stripping peak at -0.56 V are used for the analytical determination of N-(2-mercaptopropionyl)glycine within the concentration ranges 7.0 10^?5 - 6.8 10^?6 mol 1^?1 or 3.0 10^?7 - 1.0 10^?9 mol I^?1, respectively. Calibration functions are reported in both cases. The interference of several organic compounds is described.     

One-step construction of an electrode modified with electrodeposited Au/SiO2 nanoparticles, and its application to the determination of NADH and ethanol

A new electrode was developed by one-step potentiostatic electrodeposition (at ?2.0 V for 20 s) of Au/SiO₂ nanoparticles on a glassy carbon electrode. The resulting electrode (nano-Au/SiO₂/GCE) was characterized by scanning electronic microscopy, X-ray photoelectron spectroscopy and electrochemical techniques. The electrochemical behavior of dihydronicotinamide adenine dinucleotide (NADH) at the nano-Au/SiO₂/GCE were thoroughly investigated. Compared to the unmodified electrode, the overpotential decreased by about 300 mV, and the current response significantly increased. These changes indicated that the modified electrode showed excellent catalytic activity in the oxidation of NADH. A linear relationship was obtained in the NADH concentration range from 1.0?×?10^?6 to 1.0?×?10^?4 mol?L^?1. In addition, amperometric sensing of ethanol at the nano-Au/SiO₂/GCE in combination with alcohol dehydrogenase and nicotinamide adenine dinucleotide was successfully demonstrated. A wide linear response was also found for ethanol in the range from 5.0?×?10^?5 to 1.0?×?10^?3 mol?L^?1 and 1.0?×?10^?3 to 1.0?×?10^?2 mol?L^?1, respectively. The method was successfully applied to determine ethanol in beer and biological samples.     

Novel Gadolinium PVC‐Based Membrane Sensor Based on Omeprazole as an Antibiotic

A novel gadolinium ion‐selective electrode based on the antibiotic omeprazole as membrane carrier was prepared. The electrode has a linear dynamic range between 1.0×10^?1 and 1.0×10^?5 M, with a Nernstian slope of 19.3 ± 0.3 mV decade^?1 and a detection limit of 5.0×10^?6 M. The potentiometric response is independent of the pH of the solution in the pH range 4.0–10.0. The electrode possesses the advantages of short conditioning time, fast response time and especially, very good selectivity over a large number of other cations. The electrode can be used for at least 2 months without any considerable divergence in potentials. It was used as an indicator electrode in potentiometric titration of Gd(III) ions with EDTA.