Bismuth modified gold nanoelectrode ensemble for stripping voltammetric determination of lead

Use of carbon black based electrode as sensor for solid-state electrochemical studies and voltammetric determination of solid residues of lead

For the first time carbon black based electrode modified with paraffin was applied as a sensor on voltammetry of immobilized microparticles (VIMP) approach for determination of lead solid residues in hair dye samples. The solid microparticles of Pb(II) (Pb(CH₃COO)_2(s)) immobilized into the carbon paste sensor containing carbon black and paraffin were firstly reduced at initial potentials and further reoxidized at around -0.60 V during anodic scan. Electroanalytical parameters as well as supporting electrolyte composition, and pH were also evaluated. An analytical curve in 0.2 mol L^-1 phosphate buffer solution (pH 5.0) from 0.04 to 3.2 μg (R² = 0.999) with detection and quantification limits of 4 and 13 ng, respectively, were achieved. The method was applied to quantify lead solid residues in hair dye samples without previous mineralization or complex sample pre-treatment. Besides adequate repeatability, stability and selectivity of the developed sensor based on VIMP features, the method using carbon black based sensor was considered advantageous comparing to the results recorded by a spectrometric method (relative error lower than 8%) from several analytical viewpoints.

Comparison Study of Voltammetric Behavior of Muscle Relaxant Dantrolene Sodium on Silver Solid Amalgam and Bismuth Film Electrodes

Voltammetric behavior of muscle relaxant dantrolene sodium (DAN) was studied and the voltammetric methods for its determination using polished and mercury meniscus modified silver solid amalgam electrodes (p-AgSAE and m-AgSAE) as well as using bismuth film electrode (BiFE, ex situ plating on GCE) have been proposed. These working electrodes represent the most commonly used alternatives to mercury ones which come wrongfully into disfavor because of alleged toxicity of mercury. Within this work, the obtained results of DAN determination have been completed by corresponding statistical parameters and also some electrochemical characteristics of AgSAEs and BiFE were assessed, especially in comparison with the mercury electrodes.

Nanobiosensing with Arrays and Ensembles of Nanoelectrodes

Since the first reports dating back to the mid-1990s, ensembles and arrays of nanoelectrodes (NEEs and NEAs, respectively) have gained an important role as advanced electroanalytical tools thank to their unique characteristics which include, among others, dramatically improved signal/noise ratios, enhanced mass transport and suitability for extreme miniaturization. From the year 2000 onward, these properties have been exploited to develop electrochemical biosensors in which the surfaces of NEEs/NEAs have been functionalized with biorecognition layers using immobilization modes able to take the maximum advantage from the special morphology and composite nature of their surface. This paper presents an updated overview of this field. It consists of two parts. In the first, we discuss nanofabrication methods and the principles of functioning of NEEs/NEAs, focusing, in particular, on those features which are important for the development of highly sensitive and miniaturized biosensors. In the second part, we review literature references dealing the bioanalytical and biosensing applications of sensors based on biofunctionalized arrays/ensembles of nanoelectrodes, focusing our attention on the most recent advances, published in the last five years. The goal of this review is both to furnish fundamental knowledge to researchers starting their activity in this field and provide critical information on recent achievements which can stimulate new ideas for future developments to experienced scientists.

Trace level voltammetric determination of lead and cadmium in sediment pore water by a bismuth-oxychloride particle-multiwalled carbon nanotube composite modified glassy carbon electrode

Two multiwalled carbon nanotubes-based composites modified with bismuth and bismuth-oxychloride particles were synthesized and attached to the glassy carbon electrode substrate. The resultant configurations, Bi/MWCNT-GCE and BiOCl/MWNT-GCE, were then characterized with respect to their physicochemical properties and electroanalytical performance in combination with square-wave anodic stripping voltammetry (SWASV). Further, some key experimental conditions and instrumental parameters were optimized; namely: the supporting electrolyte composition, accumulation potential and time, together with the parameters of the SWV-ramp. The respective method with both electrode configurations has then been examined for the trace level determination of Pb(2+) and Cd(2+) ions and the results compared to those obtained with classical bismuth-film modified GCE. The different intensities of analytical signals obtained at the three electrodes for Pb(2+) and Cd(2+) vs. the saturated calomel reference electrode had indicated that the nature of the modifiers and the choice of the supporting electrolyte influenced significantly the corresponding stripping signals. The most promising procedure involved the BiOCl/MWCNT-GCE and the acetate buffer (pH 4.0) offering limits of determination of 4.0 μg L(-1) Cd(2+) and 1.9 μg L(-1) Pb(2+) when accumulating for 120 s at a potential of -1.20 V vs. ref. The BiOCl/MWCNT electrode was tested for the determination of target ions in the pore water of a selected sediment sample and the results agreed well with those obtained by graphite furnace atomic absorption spectrometry.

Electrochemical oligonucleotide-based biosensor for the determination of lead ion

The possibility of utilization of gold electrodes modified with short guanine-rich ssDNA probes for determination of Pb(2+) was examined. Interaction between guanine residues and lead ion followed by formation of G-quadruplex structures was confirmed by electrochemical impedance spectroscopy investigations. An external cationic redox label, methylene blue, was employed in voltammetric measurements for analytical signal generation. It was shown that due to the G-quadruplex formation, the oligonucleotides in the recognition layer fold, which enhances the electron transfer between methylene blue and the electrode surface. The MB current signal rises proportionally to the lead ion concentration in the range from 0.05 to 1μmol/L. The developed biosensor demonstrated high selectivity towards Pb(2+) ion, with only minor response towards interfering metal cations. The calculated limit of detection was of 34.7nmol/L. The utilization of the biosensor for Pb(2+) determination in real samples of water was also tested.

Arrays of microelectrodes: technologies for environmental investigations

Within this work it is our intention to provide an overview of the use of arrays or microelectrodes in the characterisation of environmental samples. Electrochemical methods are often a relatively simple and inexpensive alternative to spectroscopic or chromatographic methods for the analysis of a wide range of analytes. Arrays of microelectrodes display a number of advantages over simple planar macroelectrodes and the reasons for this will be detailed within this work. We will also describe some of the most common methods for constructing microarrays. The application of these arrays for analysis of environmental samples such as soil and water for heavy metal contamination has been the major focus of research in this field and comprises much of this review. However other systems will also be detailed such as determination of various anions or other samples such as pesticides.