A Review of: “Pharmaceutical Applications of Membrane Sensors by Vasile V. Cosofret and Richard P. Buck CRC Press,Inc., Boca Raton,Florida, U.S.A. 1992, x+431pp. US$95.00/Outside US$114.00, ISBN:0-8493-4406-9”

ABSTRACT

The analytical performance of two modified electrodes (a tyrosinase biosensor and a glassy carbon electrode (GCE) covered with poly[Ni-(protoporphyrin IX)dimethyl ester]) in comparison with the bare electrode has been evaluated in a flow injection system using standard solutions of oleuropein and olive oil samples. The tyrosinase biosensor appeared to be an appropriate device for the selective determination of phenols, moreover it can be easily incorporated in an on-line system. This method was used to evaluate the stability of the samples.     

Preparation,Characterization, and Electrochemical Behaviors of Self-Assembled Monolayer on Gold Electrode Surface with Mercapto-Derivatized Cobaltous Porphyrin

Abstract

5-[4-(3-Mercaptopropyloxy)phenyl]-10,15,20-tris (2-chlorphenyl) porphyrin was utilized for fabricating a self-assembled monolayer (SAM) on a gold electrode. Then cobalt(II) was inserted into the the monolayer by refluxing the cobalt(II) solution in which the pre-assembled porphyrin-modified electrode was immersed. The monolayers were characterized by cyclic voltammetry (CV). Oxidation and catalytic mechanisms of dopamine on the modified electrode were also investigated and elucited respectively. Catalytic currents increased linearly with dopamine (DA) concentration in the range of 1.0 × 10^?9 to 2.0 × 10^?3 mol/L with the correlation coefficient of 0.9989. The modified electrode can be help develop a simple, quick, sensitive, and accurate method for the determination of the biomolecules such as dopamine.     

Perchlorate Ion-Selective Electrodes with the Liquid Membranes of the O-Phenanthroline Chelate or its Related Compounds

Abstract

The metal chelates of o-phenanthroline, a, a′-dipyridyl or bathophenanthroline were used as the ion exchanger in the liquid membrane of the perchlorate ion-selective electrode. The electrode with a nitrobenzene membrane containing tris(bathophenanthroline)ferrous perchlorate is the highest sensitive one and gives a linear Nernstian response up to about 1 × 10 ^?5 M perchlorate. The membrane electrode having the ferrous ion-chelate of o-phenanthroline as an ion exchanger shows an excellent selectivity for perchlorate ion over nitrate or iodide Ion. The effects of the chelate concentration in the membrane and the central metal species of the chelate are examined on the electrode performance.     

Electrolysis at the Interface between Two Immiscible Electrolyte Solutions: Determination of Acetylcholine by Differential Pulse Stripping Voltammetry

Abstract

A three-electrode system with the hanging electrolyte drop electrode (HEDE) was developed for the analytical exploitation of electrolysis at the interface between two immiscible electrolyte solutions (ITIES). The use of the differential pulse stripping voltammetry (DPSV) for the quantitative determination of the species which participates in a charge transfer reaction at ITIES was demonstrated with acetylcholine cation transfer across the water/nitrobenzene interface. Trace concentration of acetylcholine in water in the part per million level (ppm) can be determined. It was concluded that the electrolysis at ITIES represents the perspective method of chemical analysis.     

Determination of Cholic Acids by Ion Selective Liquid Membrane Electrode in Pharmaceutical Products

Abstract

An ion selective electrode based on a liquid membrane, constituted by a solution of tributylcetylphosphonium benzoate in nitrobenzene, is employed to determine cholic acids in pharmaceutical products by calibration curve and standard addition methods. The results are compared with those obtained with enzymatic and calorimetric methods. The proposed technique is simple, rapid and sufficently accurate.     

Silver-Selective Electrode Based on a Direct Modified Electrode Silver Hexacyanoferrate(II) Film

ABSTRACT

A silver hexacyanoferrate(II) modified electrode is introduced as a silver-selective electrode. The electrode was prepared based on a new type of chemically modified electrodes by direct modification of the electrode surface. The electrode response characteristics were investigated by potentiometry. The calibration curve of the electrode shows a linear potentiometric response to Ag⁺ in the range of 10^-7 - 10^-2 M with detection limit of 5 × 10^-8. The modified electrode described in this paper is very simple, low cost and has linear response to Ag⁺ with a slope of 52-55 mV per decade.     

Non-enzymatic sensing of uric acid using a carbon nanotube ionic-liquid paste electrode modified with poly(β-cyclodextrin)

We describe a nonenzymatic electrochemical sensor for uric acid. It is based on a carbon nanotube ionic-liquid paste electrode modified with poly(β-cyclodextrin) that was prepared in-situ by electropolymerization. The functionalized multi-walled carbon nanotubes and the surface morphology of the modified electrodes were characterized by transmission electronic microscopy and scanning electron microscopy. The electrochemical response of uric acid was studied by cyclic voltammetry and linear sweep voltammetry. The effects of scan rate, pH value, electropolymerization cycles and accumulation time were also studied. Under optimized experimental conditions and at a working voltage of 500 mV vs. Ag/AgCl (3 M KCl), response to uric acid is linear in the 0.6 to 400 μΜ and in the 0.4 to 1 mΜ concentration ranges, and the detection limit is 0.3 μΜ (at an S/N of 3). The electrode was successfully applied to the detection of uric acid in (spiked) human urine samples.

SEM images of (a) carbon ionic liquid electrode (CILE) (b) MWNT-CILE (c) β-CD/CILE (d) β-CD/ MWNT-CILE. The surfaces of carbon ionic liquid electrode (CILE) (a) and MWNT-CILE (b) were homogenous and no separated carbon layers can be observed; After β- cyclodextrin (CD) was modified on CILE and MWNT-CILE, the surfaces of β-CD modified electrodes (c and d) exhibited loose and porous morphologies.

     

Metal Ion Uptake and Voltammetry on a Dithiocarbamate Containing Polymer Modified Electrode

Abstract

There is a need to expand the range of working electrodes which can be us in analytical voltammetry.

In this work, the synthesis of a thio containing (poly) N-Ethyl Tyramine electrode is described. Cyclic voltammetry, SEM and EPMA were used to characterise the modified electrode.

The ability of this electrode to uptake copper, nickel, mercury or cobalt ions from solution was investigated. Detection limits of the order of 0.1 ppm were estimated using differential pulse voltammetry.     

Poly[Ni(II)Protoporphyrin IX] Modified Electrode for Amperometric Detection of Acetylcholine (Ach) and Choline (Ch)

Abstract

Poly[Ni(II)Protoporphyrin IX] (pNiPP) modified electrode can be used as an alternative method for direct amperometric detection of Acetylcholine (Ach) and Choline (Ch). This response is highly dependent on the electrode potential, that must be higher than +0.4 V versus Ag/AgCl with a maximum at +0.6 V.

Other amino derivatives such as ethanolamine and tetrabutyl ammonium hydroxide did not show amperometric response in the same experimental conditions. On the contrary, KCl shows an increasing amperometric signal in flow injection for a concentration range of 10^?3 to 1 M, indicating certain sensitivity of membrane to Cl^? ions. The lowest detection limit corresponds to the highest cationic volume. The response for acetylcholine is slightly higher than for choline and is almost completely non‐linear for both substrates. The proposed model for the response is Y=(A×X)/(B+X) according to AICc Akaike method.

Choline, in a complex solution, was analyzed by HPLC with the chemically modified electrode as detector.     

Simultaneous Gas Chromatographic Determination of Nitrobenzene and 2,4-Dinitrophenol in Nitrobenzene Manufacturing Plant Wastewater

Abstract

A simple and rapid gas chromatographic procedure is described for the identification and quantification of pollutants in the nitrobenzene manufacturing plant wastewater. The samples were extracted with methylene chloride and subsequently nitrobenzene and 2,4-dinitrophenol were analysed by GC using FID. The method was found to be precise and accurate and applicable for monitoring the effluent treatment system at ppm levels.     

Detection of Nitrite Using Electrodes Modified with an Electrodeposited Ruthenium-Containing Polymer

Abstract

The electrochemical detection of nitrite in flowing solutions using a polymer modified electrode with electrocatalytic properties is described. The modifier was an electrodeposited polymer film of the [Ru(bpy)₂(vpy)₂+²⁺ complex, where bpy is 2,2′ bypyridyl and vpy is 4-vinylpyridine. The modified electrodes showed the ability to enhance the nitrite response and avoid surface fouling. The electrodeposited films exhibited higher mechanical stability than similar chemisorbed coatings.     

Determination of Hydrazine Compounds by Capillary Electrophoresis with a Poly(Glutamic Acid) Modified Microdisk Carbon Fiber Electrode

ABSTRACT

Hydrazine compounds, including hydrazine (HZ), phenylhydrazine (PHZ), semicarbazide (SCZ) and isoniazid (INZ) were separated and determined by capillary electrophoresis (CE) with a poly(glutamic acid) modified microdisk carbon fiber electrode. The modified electrode exhibited highly catalytic activity for hydrazines and has good stability. Linear responses for hydrazines over 2~3 orders of magnitude were obtained. The detection limits for HZ, PHZ, SCE and INZ were 7.8, 8.0, 14.0 and 11.0 fmol, respectively.     

Amperometric Enzyme Based Biosensor For the Detection of Xanthine Via Superoxide

Abstract

An amperometric enzyme modified carbon paste electrode for the detection of xanthinc by the xanthine oxidase catalyzed reaction is described. the product of the enzyme reaction monitored is the highly unstable radical superoxide, detected at O mV (vs SCE) poised potential. A dual working electrode configuration consisting of an enzyme modified carboa paste electrode and an unmodified glassy carbon electrode are utilized for this purpose.     

Disopyramide-Selective Membrane Electrode∗

Abstract

A liquid membrane electrode based on disopyramide - dipicrylamine ion - pair complex, dissolved in nitrobenzene as solvent was proposed for the determination of disopyramide - an antiarrhythmic drug. The linear response covers the range from 10^?2 - 5 × 10^?6 M disopyramide solution, with a slope of 51.0 mV/decade (pH range 3.0 to 7.0). The detection limit is 4.7 × 10^?8 M. The electrode shows a good stability, reproducibility and fast response. The selectivity of the electrode is good. The strong interfering ion is thiamine (Vitamin B₁). These characteristics of the electrode made it to be used for the determination of disopyramide through direct and indirect potentiometric methods. Through indirect potentiometric method, disopyramide - as active substance can be determined with an average recovery of 99.98% and a relative standard deviation of 0.24%, and also this method can be used for its determination in pharmaceutical formulations such as capsules and ampoules with a relative standard deviation less than 1%. The electrode can be used at the dissolution tests of disopyramide capsules. The physical processes are numerically simulated by typical equations. The apparent first - order rate constants for disintegration and dissolution processes were calculated.

     

Impedance Spectral Studies of Hemoglobin Immobilized on Au‐colloid Modified Self‐Assembled Monolayer Electrode

Abstract

The immobilization of Hemoglobin (Hb) on Au‐colloid associated with a 4‐Aminothiophenol monolayer on a gold electrode was studied. The electrochemical behaviors of the modified electrode was characterized and investigated by electrochemical impedance spectroscopy (EIS) and cyclic voltammograms (CVs). Differnces among each modifying steps were observed. The results implied that Au colloid enlarged the surface of modified electrode so as to increase the immobilization amount of Hb. Some parameters of EIS have been discussed to fit results. This method shows good correlation for detection of Hb in a broad linear range and exhibits low detection limit.     

Catalase Like Activity of Iron Phthalocyanine Incorporated in a Carbon Paste Electrode

Abstract

The electrochemical oxidation of hydrogen peroxide has been investigated using a modified carbon paste electrode, by incorporating iron phthalocyanine. This offers interesting properties due to the catalase like activity of the electrode.

The utilization of this type of electrode permits the quantitative determination of hydrogen peroxide at concentrations down to 5x10^?5 M.     

Sensitive Detection of NADH by Ferrocenylalkanethiol Functionalized Multiwall Carbon Nanotubes Electrodes

Abstract

The 6-ferrocenylhexanethiol (FcC₆SH) functionalized multiwall carbon nanotubes (MWNTs) modified glassy carbon electrode (FcC₆SH/MWNTs/GCE) was easily fabricated and used for the sensitive detection of NADH. Cyclic voltammetric and amperometric methods were used to study the behavior of NADH on the FcC₆SH/MWNTs/GCE. A broader linear response range to the NADH concentration from 5 µM to 1.5 mM with a correlation coefficient of 0.9982 was obtained. The detection limit was 0.54 µM. The synergetic effects of FcC₆SH and MWNTs make the modified electrode highly sensitive to NADH. In addition, the modified electrode can decrease the fouling of the electrode surface.     

Amperometric Biosensors Based on Platinum Nanowires

Abstract

Platinum nanowires (PtNW) were prepared by an electrodeposition strategy using nanopore alumina template. The nanowires prepared were dispersed in chitosan (CHIT) solution and stably immobilized onto the surface of glassy carbon electrode (GCE). The electrochemical behavior of PtNW‐modified electrode and its application to the electrocatalytic reduction of hydrogen peroxide (H₂O₂) are investigated. The modified electrode allows low potential detection of hydrogen peroxide with high sensitivity and fast response time. As an application example, the glucose oxidase was immobilized onto the surface of PtNW‐modified electrode through cross‐linking by glutaric dialdehyde. The detection of glucose was performed in phosphate buffer at –0.2 V. The resulting glucose biosensor exhibited a short response time (<8 s), with a linear range of 10^?5?10^?2 M and detection limit of 5×10^?6 M.     

Hemoglobin Modified Carbon Paste Electrode: Direct Electrochemistry and Electrocatalysis

Abstract

A new hemoglobin (Hb) modified carbon paste (CP) electrode was fabricated by simply mixing the hemoglobin with carbon powder and paraffin homogeneously. To prevent the leakage of Hb from the electrode surface, a Nafion film was further applied on the surface of Hb-carbon composite paste electrode. Direct electrochemistry of hemoglobin in the paste electrode was easily achieved, and a pair of well-defined quasi-reversible redox peak of heme Fe(III)/Fe(II) couple appeared with the formal potential (E^0′) as ?0.335 V (vs. Saturated calomel electrode; CE) in pH 7.0 phosphate buffer solution (PBS). The fabricated Hb modified electrode showed good electrocatalytic ability to the reduction of trichloroacetic acid (TCA) and H₂O₂.     

质子惰性介质中硝基苯在铂微盘电极上的电化学行为

采用循环伏安法, 以铂微盘电极为工作电极, 铂片为辅助电极, 饱和甘汞电极为参比电极, 研究了硝基苯在含有四丁基高氯酸铵(TBAP)电解质的N,N-二甲基甲酰胺(DMF)有机溶液中的电化学行为, 并探讨了扫描速度和底物浓度等因素对硝基苯电化学特性的影响. 结果表明,该反应属扩散控制的准可逆反应.