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Biomedical subjects

F Céspedes

Publications and source records attributed to F Céspedes.

6 recordsLinked to original sources
PubMed2005

Simultaneous determination of phenolic compounds by means of an automated voltammetric "electronic tongue".

This contribution describes the simultaneous determination of three phenolic compounds, o-cresol, p-chlorophenol and 4-chloro-3-methylphenol, using direct oxidation and amperometric detection coupled by signal deconvolution, accomplished via chemometric methods. Direct oxidation of phenolic compounds is performed at the surface of an epoxy-graphite transducer, by linear scan voltammetry. Due to strong signal overlapping, artificial neural networks (ANNs) were used during data treatment, in a combination of chemometrics and electrochemical sensors known as an "electronic tongue". To calibrate this system properly, a total of 80 mixed samples were prepared automatically by employing a sequential injection analysis (SIA) system designed to automatically generate the information needed to train the network. The phenolic compound concentration varied from 1 to 70 microM for o-cresol, from 0.5 microM to 140 microM for p-chlorophenol and from 1 microM to 100 microM for 4-chloro-3-methylphenol. A good prediction capability was obtained, with correlation coefficients >0.964 when the obtained values were compared with those expected for a set of 24 external test samples not used for training. The results presented here indicate that this technique is a simple and robust analytical method of environmental interest.

Journal Article↗
PubMed2005

Determination of phenolic compounds by a polyphenol oxidase amperometric biosensor and artificial neural network analysis.

The determination of phenolic compounds is significant given its toxicity, even at very low concentration levels. Amperometric determination of phenols is a simple technique available. Direct oxidation of phenols can be used, but another possibility is the use of polyphenol oxidase (tyrosinase) enzyme biosensors that oxidises the phenolic compounds into their corresponding quinones. Reduction of the resulting quinones accomplishes the amplification of the amperometric signal, as long as the result of the reduction process is the corresponding cathecol, this being able to be oxidised again by the polyphenol oxidase immobilized on the surface of the biosensor. In this communication, simultaneous determination of different phenols was carried out combining biosensor measurements with chemometric tools, in what is known as electronic tongue. The departure information used was the overlapped reduction voltammogram generated with the amperometric biosensor based on polyphenol oxidase. Artificial Neural Networks (ANN) were used for extraction and quantification of each compound. Phenol, cathecol and m-cresol formed the three-analyte study case resolved in this work. Good prediction ability was attained, and so, the separate quantification of these three phenols was accomplished.

Algorithms↗
PubMed1998

Flow injection immunoanalysis based on a magnetoimmunosensor system.

A new immunosensor integrated to a flow system has been developed. It is based on magnetic immunoparticles immobilized on a solid-state transducer using a magnetic field. The described technique renews the immunoparticles reproducibly for each analysis allowing a good measurement precision. The developed experimental approach permits the implementation of an automated immunoassay that is quick (analytical cycle < 30 min) and sensitive in the micromolar concentration range. The system was applied to the determination of rabbit immunoglobulin G as an analyte model.

Animals↗
PubMed1997

Amperometric immunosensors based on rigid conducting immunocomposites.

Novel polishable immunosensors based on rigid biocomposite materials have been constructed. These biocomposites contain graphite powder, rabbit IgG, and methacrylate or epoxy resins. This material acts as a reservoir for the biological molecules and as a transducer at the same time. In order to study the potential analytical properties of this new type of material, a competitive binding assay was developed to determine the RIgG present in a sample with the aid of goat anti-rabbit IgG labeled with alkaline phosphatase. Using phenyl phosphate as a substrate, the phenol produced by the enzymatic reaction was amperometrically detected at 800 mV (vs Ag/AgC1). The surface of the immunosensor can be regenerated by simply polishing, obtaining fresh immunocomposite ready to be used in a new competitive assay.

Animals↗
PubMedDate not supplied

[Thrombolysis in acute myocardial infarct of embolic origin].

Myocardial infarctions which are derived from embolic source have an incidence of 5-13%. They are at risk of systemic embolism. The pathogenesis of myocardial infarction is similar to that of those myocardial infarction whose etiology is atherosclerosis. This make it susceptible to thrombolysis. We report 3 patients with either inactive rheumatic heart disease, coarctation of the aorta or mechanical valvular prosthesis as the probable causes of an embolic infarction. It was located in the posterior-inferior region with a dorsal extension. These patients were treated with intravenous streptokinase. The three of them fulfilled criteria for myocardial reperfusion. Two of them suffered post-infarction angina. In the first case reocclusion of the righ coronary artery was observed; thus a saphenous vein graft was undertaken. In the second, the persistence of thrombus required three month treatment with anticoagulants. The third patient showed not coronary lesions. In conclusion, thrombolytic therapy with streptokinase in acute infarction of embolic origin prevents the progression of ischemic damage and betters the clinical outcome of the patient. Furthermore such disease should be suspected in patients that have risk factors for systemic embolism and normal coronary arteries and with obstruction of a single vessel.

Adult↗