A non-mercury electrode for the voltammetric determination of butralin in foods.

A modified electrode was developed with Co-Ag bimetallic nanoparticles stabilized in poly(vinylpyrrolidone) for butralin monitoring. This is the first non-mercury electrode proposed for the quantification of butralin. The bimetallic nanoparticles were characterized by spectroscopic and microscopic techniques, which showed that they are composed of a cobalt core partially covered with silver. The modified electrode was characterized by field emission gun scanning electron microscopy, energy dispersive X-ray spectroscopy and electrochemical impedance spectroscopy. The experimental parameters (pH, supporting electrolyte, accumulation step, pulse technique) were optimized. The calibration plot for butralin obtained by square wave voltammetry was linear in the range of 0.1-1.0 µmol L-1 with limits of detection and quantification of 32 and 106 nmol L-1, respectively. Lastly, the modified electrode was effectively implemented in the quantification of butralin in honey and apple jam samples. The results were in agreement with those furnished by UV-vis spectrometry and endorsed by statistical tests.

Magnetite-platinum nanoparticles-modified glassy carbon electrode as electrochemical detector for nitrophenol isomers.

A glassy carbon electrode was modified with magnetite and platinum nanoparticles stabilized with 3-n-propyl-4-picoline silsesquioxane chloride. This chemically-modified electrode is proposed for the first time for the individual or simultaneous electrochemical detection of nitrophenol isomers. Nanoparticles act as catalysts and also increase the surface area. The polymer stabilizes the particles and provides the electrochemical separation of isomers. Under optimized conditions, the reduction peak currents, obtained by differential-pulse voltammetry, of 2-, 3-, and 4-nitrophenol increased linearly with increases in their concentration in the range of 0.1-1.5µmolL-1. In individual analysis, the detection limits were 33.7nmolL-1, 45.3nmolL-1 and 48.2nmolL-1, respectively. Also, simultaneous analysis was possible for 2-, and 4-nitrophenol. In this case, the separation of the peak potentials was 0.138V and the detection limits were 69.6nmolL-1 and 58.0nmolL-1, respectively. These analytical figures of merit evidence the outstanding performance of the modified electrode, which was also successfully applied to the individual determination of isomers in environmental and biological samples. The magnetite and platinum nanoparticles modified glassy carbon electrode was able to detect nitrophenol isomers at the ppm level in rain water and human urine samples.

Environmentally-friendly in situ plated bismuth-film electrode for the quantification of the endocrine disruptor parathion in skimmed milk.

An in situ bismuth-film electrode (BiFE) together with square-wave cathodic voltammetry (SWCV) was used to determine the concentration of the endocrine disruptor parathion in skimmed milk. The experimental conditions (deposition time, deposition potential and Bi (III) concentration) were optimized for the preparation of the BiFE. A glassy carbon electrode was used as the substrate. The selection of the chemical composition of the supporting electrolyte and the solution pH was aimed at improving the reduction of parathion at the BiFE surface. In addition, the parameters of the square-wave cathodic voltammetry were adjusted to improve the sensor performance. A cathodic current identified at -0.523 V increased linearly with the parathion concentration in the range of 0.2-2.0 µmol L(-1) (R=0.999). The sensitivity of the calibration curve obtained was 4.09 µA L µmol(-1), and the limits of detection (LOD) and quantification (LOQ) were 55.7 nmol L(-1) and 169.0 nmol L(-1), respectively. The performance of the sensor was tested using a sample of skimmed milk with parathion added. The same determination was carried out by UV-vis spectroscopy and the results obtained were used for the statistical evaluation of the data obtained.

Biochemical markers in gastrointestinal malignancies.

The authors review the role of tumor markers in distinguishing benign from malignant conditions of the digestive tract. They also discuss the value of cancer markers to stratify patients in terms of their survival probability, to detect recurrence and to monitor treatment.

Antígeno carcinoembrionários (CEA) na detecçäo e prognóstico do câncer gastrintestinal / Carcinoembryonic antigen (CEA) in the detection and prognosis of gastrointestinal cancer

Neste trabalho foram estudados o papel do antígeno carcinoembrionário (CEA) na distinçäo das condiçöes benignas das malignas do tubo digestivo e o seu valor na avaliaçäo do prognóstico das neoplasias gastrintestinais. Analisaram-se 220 pacientes portadores de câncer no sistema digestivo, sendo 100 de colorretal, 100 de gástrico e 20 de outros, e 70 controles. Na populaçäo controle, foram estimados os valores correspondentes aos percentil 85 e 95, sendo usados para o estabelecimento dos níveis normais do antígeno. Baseado neste critério, foi elaborado um sistema de escore: a) valores < 85 percentil: escore 0; b) 85 < ou = percentil < 95: escore 1; c) percentil > ou = 95: escore 2. Para a estimativa da sensibilidade do CEA, os escores 0 e 1 foram considerados como falsos negativos e o escore 2 como a fraçäo verdadeiramente positiva. Foram detectatos câncer coloretal (57%), tumores gástricos (33%) e outros neoplasmas (35%). As curvas de sobrevida dos pacientes portadores de câncer do intestino grosso revelaram prognóstico inferior naqueles com valores elevados do CEA (escore 2), quando comparados àqueles com níveis normais. Em pacientes com carcinoma do estômago, näo foi demonstrada a significância prognóstica dos valores pré-operatórios circulantes do CEA. Os resultados obtidos confirmaram que o teste do CEA näo deve ser usado como método diagnóstico primário no câncer gastrintestinal, embora seja útil no acompanhamento clínico de pacientes com diagnósticos estabelecidos

[Combination of cancer markers in the detection and prognosis of digestive system tumors]. / Combinação de marcadores de câncer na detecção e prognóstico de tumores do aparelho digestivo.

The role of carcinoembryonic antigen (CEA), gamma glutamyl transpeptidase (gamma GT), phosphohexose isomerase (PHI), pseudouridine (PSD) and acute phase reactant proteins (C-reactive protein (C-RP], alpha 1-acid glycoprotein (alpha 1-AGP) and alpha 1-antichymotrypsin (alpha 1-ACT) in distinguishing benign from malignant conditions of the digestive tract and their value in assessing the prognosis of gastrointestinal neoplasms was evaluated. For each marker it has been possible to produce a simple scoring index derived from the values found in the control population. This work suggests that pre-operative levels of certain cancer markers may be useful in tumor detection and may also give prognostic information additional to pathological staging.