12 research outputs found
Ozonated water and chlorine effects on the antioxidant properties of organic and conventional broccoli during postharvest
Electroanalytical determination of 4-nitrophenol by square wave voltammetry on diamond electrodes
The anodic voltammetric behavior of 4-Nitrophenol on a Boron-doped diamond electrode in aqueous solution has been studied using square wave voltammetry. After optimization of the experimental conditions, that model molecule was analyzed in pure water solutions using a Britton-Robinson buffer with pH 6.0 as the supporting electrolyte. Oxidation occurs at 1.0 V vs. Ag/AgCl in an irreversible two-electron process controlled by adsorption of the species. The detection limit (DL) obtained was 2.8 mug L-1. This result was comparable to that obtained from reduction of the molecule at -0.8 V vs. Ag/AgCl under the same experimental conditions (DL = 4.2 mug L-1). Both DL values are within the limits required by the legislation for drinking water (30 mug L-1). The combination of square wave voltammetry and diamond electrodes has proved to be an interesting and desirable alternative for the analytical determination of organic molecules
Electroanalytical determination of 4-nitrophenol by square wave voltammetry on diamond electrodes
Electroanalytical determination of carbendazim and fenamiphos in natural waters using a diamond electrode
In this study, a method for electroanalytical determination of carbendazim (CBZ) and fenamiphos (FNP) in natural and spiked water was developed using square wave voltammetly in Na2HPO4 0.1 mol L-1 as supporting electrolyte. the calibration curve for carbendazim detection presented good linearity in the concentration range of 0.50 to 15.0 mu M, with a sensitivity of 0.080 A/mol L-1 and a linearity of 0.998. the oxidation of fenamiphos on BDD electrode shows a dynamic range of concentration of 0.5 to 25.0 mu M and sensibility of 0.14 A/mol L-1. the recovery experiments showed values between 70 and 100% for spiked samples thus indicating the feasibility of the electroanalytical methodology to quantify CBZ and FNP in pure or natural waters. (C) 2012 Elsevier B.V. All rights reserved.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento CientÃfico e Tecnológico (CNPq)Fundação para o Desenvolvimento da UNESP (FUNDUNESP)Universidade Federal de São Paulo, Dept Ciencias Exatas & Terra, Inst Ciencias Ambientais Quim & Farmaceut, BR-09972270 Diadema, SP, BrazilUniv Camilo Castelo Branco, Sao Jose Dos Campos, SP, BrazilUniv Fed Pelotas, Ctr Ciencias Quim Farmaceut & Alimentos, Pelotas, RS, BrazilUNESP, Dept Chem & Biochem, Inst Biosci, Botucatu, SP, BrazilUniversidade Federal de São Paulo, Dept Ciencias Exatas & Terra, Inst Ciencias Ambientais Quim & Farmaceut, BR-09972270 Diadema, SP, BrazilFAPESP: 2008/50588-6FUNDUNESP: 0049/11-DFPWeb of Scienc
Renewable nanocomposite layer-by-layer assembled catalytic interfaces for biosensing applications
A novel, easily renewable nanocomposite interface based on layer-by-layer (LbL) assembled cationic/anionic layers of carbon nanotubes customized with biopolymers is reported. A simple approach is proposed to fabricate a nanoscale structure composed of alternating layers of oxidized multiwalled carbon nanotubes upon which is immobilized either the cationic enzyme organophosphorus hydrolase (OPH; MWNT−OPH) or the anionic DNA (MWNT−DNA). The presence of carbon nanotubes with large surface area, high aspect ratio and excellent conductivity provides reliable immobilization of enzyme at the interface and promotes better electron transfer rates. The oxidized MWNTs were characterized by thermogravimetric analysis and Raman spectroscopy. Fourier transform infrared spectroscopy showed the surface functionalization of the MWNTs and successful immobilization of OPH on the MWNTs. Scanning electron microscopy images revealed that MWNTs were shortened during sonication and that LbL of the MWNT/biopolymer conjugates resulted in a continuous surface with a layered structure. The catalytic activity of the biopolymer layers was characterized using absorption spectroscopy and electrochemical analysis. Experimental results show that this approach yields an easily fabricated catalytic multilayer with well-defined structures and properties for biosensing applications whose interface can be reactivated via a simple procedure. In addition, this approach results in a biosensor with excellent sensitivity, a reliable calibration profile, and stable electrochemical response
Effects of soil tillage and mulching on thermal performance of a Luvisol topsoil layer
Important energy exchanges at soil surface
regulate the thermal environment within top soil layer and the boundary layer above it. By this reason, the application of mulches or the modelling of micro relief by soil tillage are common practises to modify the thermal regime of a soil.
The aim of this study is to compare the effect on thermal behaviour of a Luvisol resulting of soil tillage and the application of stubble mulch and, different amounts of straw mulch. For this purpose, experiments were performed from January to May 2007 in a field sowed with winter wheat.
Temperatures were measured with copper-constantan (Type T) thermocouples placed over straw and over stubble, at soil surface and at 2, 4 and 8 cm depth. Temperatures above canopy were also recorded.
Daily mean temperatures and temperature
amplitudes in the top soil layer covered by straw mulch were smaller than those verified either by stubble mulch or with soil tillage. Daily minimum temperatures in mobilized plots or
covered by stubble mulch were smaller than those verified in plots covered by straw mulch, therefore being the former treatments more susceptible to frost than the later ones.
Thermal differences between the four plots decreased significantly with wheat growth. Implications of these techniques of soil temperature control for crop growth are
also discussed
A immunosensor for the diagnosis of canine distemper virus infection using SPR and EIS
Canine distemper virus (CDV) is a viral disease that affects dogs and many other carnivores. Clinical diagnosis of CDV is difficult due to the broad spectrum of signs that may be confounded with other respiratory and enteric diseases of dogs. Laboratory analysis is required to diagnose suspected cases. In this study, surface plasmon resonance (SPR) and electrochemical impedance spectroscopy (EIS) methodologies were developed for the detection of canine distemper virus simultaneously. The assay exhibited high specificity, as all the negative controls were not mistakenly detected. The CDV concentration was determined from successive injections into the apparatus, with a linear range from 1.1 to 116.0 ng mL-1. The system exhibited good reproducibility with 4.5% variation between runs after regeneration of the coated surface with a solution of 0.1 M glycine-HCL (pH 3.0). The capacitance and resistance values of the modified interface were calculated from EIS data using an equivalent circuit. It was possible to measure CDV in highly concentrated viruses with good specificity and reproducibility. © 2013 The Royal Society of Chemistry
Effects of Protein A in Detection of Canine Distemper Virus through immunosensor construction
We have developed a detection system to canine distemper virus (CDV) by employing surface plasmon resonance (SPR) and compared the effect of oriented and random immobilization. Several parameters, such as the surface concentration of immobilized antibodies, antigen binding capacity, and the maximum surface concentration of immobilized antibody were optimized. The maximal antigen binding capacity was obtained by means of a SPR-sensor immobilized via protein A, which leads to an end-on orientation. CDV at 0.1 ng/mL can be detected using protein A. Urine analysis showed that all samples contained detectable levels of CDV, but the results revealed an improvement in sensitivity of the assay when it is specifically oriented. The described method is simple, fast, selective, and sensitive to the biorecognition element. The results emphasize how important it is to attach proteins on surfaces in such a way that their binding sites are oriented toward the solution phase.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de NÃvel Superior (CAPES