J.L. Hidalgo-Hidalgo de Cisneros

Voltammetric determination of trace mercury at a sonogel-carbon electrode modified with poly-3-methylthiophene.

The sonogel-carbon electrode is a new class of sol-gel electrode that exhibit favourable mechanics and electrics properties to be used as electrochemical sensor. In this paper, a modified sonogel-carbon electrode is proposed to determine mercury at trace levels. The modified electrode is obtained by electropolymerization of 3-methylthiophene on the surface of a bare sonogel-carbon electrode. This electrode shows high selectivity and sensitivity and linear response towards Hg(II), with a detection limit of 1.4x10(-3)mgl(-1). The electrode is reusable by a simple chemical cleaning procedure. No deterioration was observed in the electrode response during at least 1 week of successive measurements.

Phenol biosensor based on Sonogel-Carbon transducer with tyrosinase alumina sol–gel immobilization

A new biosensor for detection of phenols, based on tyrosinase immobilization with alumina sol-gel on Sonogel-Carbon transducer, has been developed. The electrode was prepared using high energy ultrasounds directly applied to the precursors. The alumina sol-gel provided a microenvironment for retaining the native structure and activity of the entrapped enzyme and a very low mass transport barrier to the enzyme substrates. Phenols are oxidized by tyrosinase biosensor to form a detectable product, which was determined at -300 mV vs. Ag/AgCl reference electrode. For phenol, the sensor exhibited a fast response which resulted from the porous structure and high enzyme loading of the sol-gel matrix. The linear range was from 5 x 10(-7)M to 3 x 10(-5)M, with a detection limit of 3 x 10(-7)M. The stability of the biosensor was also evaluated.

Stripping voltammetry of silver ions at polythiophene-modified platinum electrodes.

The present work describes the development of a modified platinum electrode for stripping voltammetric determination of silver. The deposition of films based on electropolymerisation of the monomer thiophene was carried out by cycling the potential towards positive values between 0 and 1.6V. The preconcentration process of silver ions was initiated on the surface of the modified electrode by complexing silver with polythiophene (PTH) when a negative potential (-0.5V) was applied; then the reduced products was oxidized by means of differential pulse stripping voltammetry and the peak was observed at 0.17V. Parameters such as pH, supporting electrolyte and number of electropolymerisation cycles were studied. A linear relation between current peak and concentration of Ag(I) was obtained in the range 0.07-1.0mgL(-1). The detection limit for Ag(I) was evaluated to be 0.06mgL(-1). The reproducibility was tested carrying out 11 measurements at different electrodes and the relative standard deviation was 1.5%. The interference of several metals was investigated and showed negligible effect on the electrode response.

Electrochemical behaviour of epinephrine and uric acid at a Sonogel―Carbon L-Cysteine modified electrode

The Sonogel-Carbon electrode is a special class of sol-gel electrode that exhibits favourable mechanic and electric properties to be used as electrochemical sensor. In this study, Sonogel-Carbon modified with L-Cysteine was used to prepare a novel electrochemical sensor. The objective of this novel electrode modification was to seek new electrochemical performances for detection of epinephrine in the presence of uric acid. The response of catalytic current with epinephrine concentration shows a linear relation in the range from 1 x 10(-7) to 5 x 10(-4)M with a correlation coefficient of 0.998, and a detection limit of 8.7 x 10(-8)M. The modified electrode had also been applied to the determination of epinephrine and uric acid in biological samples with satisfactory results. A surface characterisation of this modified electrode was carried out helped by scanning electron microscopy (SEM) and X-Ray energy dispersive spectroscopy (EDS).

New, fast and green procedure for the synthesis of gold nanoparticles based on sonocatalysis

An easy, cheap and green synthetic route, using high-power ultrasounds and sodium citrate dihydrate as non-toxic reducing and stabilizer agent, produces gold nanoparticles in aqueous solution, and at ambient conditions. The time required for the synthesis is 5.5 min. The spherical nanoparticles obtained by this route show a homogeneous size distribution, within the range 5-17 nm, with an average diameter of 10±1 nm. Moreover, 90% of the particles have a diameter ranging from 7 to 13 nm, and their half-life is more than 30 days. The gold nanoparticles synthesized following this route are known as sononanoparticles. Gold sononanoparticles have been characterized by TEM and XRD and their stability has been studied by UV-Vis spectroscopy. Alternative experimental designs are compared to optimize the proposed synthesis procedure.

Sonosynthesis of gold nanoparticles from a geranium leaf extract.

A rapid in situ biosynthesis of gold nanoparticles (AuNPs) is proposed in which a geranium (Pelargonium zonale) leaf extract was used as a non-toxic reducing and stabilizing agent in a sonocatalysis process based on high-power ultrasound. The synthesis process took only 3.5 min in aqueous solution under ambient conditions. The stability of the nanoparticles was studied by UV-Vis absorption spectroscopy with reference to the surface plasmon resonance (SPR) band. AuNPs have an average lifetime of about 8 weeks at 4 °C in the absence of light. The morphology and crystalline phase of the gold nanoparticles were characterized by transmission electron microscopy (TEM). The composition of the nanoparticles was evaluated by electron diffraction and X-ray energy dispersive spectroscopy (EDS). A total of 80% of the gold nanoparticles obtained in this way have a diameter in the range 8-20 nm, with an average size of 12±3 nm. Fourier transform infrared spectroscopy (FTIR) indicated the presence of biomolecules that could be responsible for reducing and capping the biosynthesized gold nanoparticles. A hypothesis concerning the type of organic molecules involved in this process is also given. Experimental design linked to the simplex method was used to optimize the experimental conditions for this green synthesis route. To the best of our knowledge, this is the first time that a high-power ultrasound-based sonocatalytic process and experimental design coupled to a simplex optimization process has been used in the biosynthesis of AuNPs.

Determination of Mercury Using a Novel Sonogel‐Carbon 3‐Methylthiophene Electrode

Abstract A solid Sonogel‐Carbon electrode was modified for the determination of Hg (II) in industrial waste water. 3‐Methylthiophene (3MT), pyrrol, poly‐3‐methylthiophene (P3MT), polypyrrol, and C18 were used for the chemical modification. The obtained composite electrodes were tested for their response to Hg(II); the best results were observed for the 3MT monomer modification with a detection limit of 10−2 mg · l−1 and 3 weeks lifetime of use. A linear relationship between anodic peak height and concentration inside the range of 0.07–0.42 mg · l−1 was obtained. A study of interferences due to other heavy metal is also included.

Analytical Study of Hygiene Hazards Involved in Naval Industry Welding Processes

Abstract The metal contents of welding fumes produced at the shipyard Astilleros Espanoles in Puerto Real, Spain, were investigated to assess the hygiene hazards in order to improve health conditions at the factory. Personal and environmental samples were collected on a cellulose or polyvinylchloride filter with the aid of a sampler in compliance with National Institute for Occupational Safety and Health standard methods. Quantitative metal determinations were carried out by flame atomic absorption spectroscopy. A microscopic examination was also achieved to assess shape and size of metal particles. The results obtained for metals and particles were compared with established threshold limit values, and conclusions were drawn according to the type of welding procedure, sampling place, and use of fume extractor.

Electrochemical Analysis of Mercury Using a Kryptofix Carbon‐Paste Electrode

Abstract Successful applications of different analytical procedures to determine quantitatively mercury in aqueous media can be found in recent literature. Fundamentally it has made use of Cold Vapour Atomic Absorption Spectrometry (CV‐AAS), X‐Ray Fluorescence or UV Spectrophotometry, Inductively Coupled Plasma Atomic Emission Spectrometry (ICP‐AES), or Inductively Coupled Plasma Mass Spectrometry (ICP‐MS), which are the techniques commonly used for trace measurement of heavy metal in the laboratory. In this paper a new and alternative methodology to determine quantitatively mercury in aqueous media is reported. A kryptofix carbon‐paste electrode has been used to determine voltammetrically mercury. The detection limit for mercury was evaluated to be 0.12 µg/l.