A simple and rapid screening method for sulfonamides in honey using a flow injection system coupled to a liquid waveguide capillary cell

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Screening and determination of sulphonamide residues in bovine milk samples using a flow injection system

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Determination of tetramethylthiuram disulfide (thiram) for residual analysis in food using spectrophotometry coupled with a solid-phase reactor (SPR) in a flow system

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Gold electrodes from recordable CDs for mercury quantification by flow injection analysis

The development of a new methodology for the construction of very efficient flow cells for mercury detection by potentiometric stripping analysis, employing the thin gold layer of recordable CDs as working electrode is reported. This new source of electrodes (CDtrodes) show very attractive performance, similar to that obtained with commercial gold electrodes, with superior versatility. The low cost of this new source of gold electrodes allows a frequent replacement of the electrode, avoiding cumbersome clean-up treatments. Various experimental parameters have been optimized to yield low detection limits (0.25 ng/mL of mercury for 5 min deposition at 0.3 V) and good precision (standard deviation of 1.9% was obtained for 15 repetitive measurements using 10 ng/mL of mercury). Standard curves were found to be linear over the range of 0.5-100 μg L-1 of mercury. The flow cells developed were used for the quantification of mercury in oceanic and tap water. © Springer-Verlag 2000.

Simple and clean determination of tetracyclines by flow injection analysis

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Evaluation and degradation chemistry of orbifloxacin using LC-MS

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Simulations of Ground-Water Flow, Transport, Age, and Particle Tracking near York, Nebraska, for a Study of Transport of Anthropogenic and Natural Contaminants (TANC) to Public-Supply Wells

The U.S. Geological Survey (USGS) is committed to providing the Nation with credible scientific information that helps to enhance and protect the overall quality of life and that facilitates effective management of water, biological, energy, and mineral resources (http://www.usgs.gov/). Information on the Nation’s water resources is critical to ensuring long-term availability of water that is safe for drinking and recreation and is suitable for industry, irrigation, and fish and wildlife. Population growth and increasing demands for water make the availability of that water, now measured in terms of quantity and quality, even more essential to the long-term sustainability of our communities and ecosystems. The USGS implemented the National Water-Quality Assessment (NAWQA) Program in 1991 to support national, regional, State, and local information needs and decisions related to water-quality management and policy (http://water.usgs.gov/nawqa). The NAWQA Program is designed to answer: What is the condition of our Nation’s streams and ground water? How are conditions changing over time? How do natural features and human activities affect the quality of streams and ground water, and where are those effects most pronounced? By combining information on water chemistry, physical characteristics, stream habitat, and aquatic life, the NAWQA Program aims to provide science-based insights for current and emerging water issues and priorities. From 1991-2001, the NAWQA Program completed interdisciplinary assessments and established a baseline understanding of water-quality conditions in 51 of the Nation’s river basins and aquifers, referred to as Study Units (http://water.usgs.gov/nawqa/studyu.html).

Percolated non-Newtonian flow for silicone obtained from exfoliated bioinorganic layered double hydroxide intercalated with amino acid

A simple and scalable procedure was used to obtain thin, stable, homogeneous, and easy-to-handle films composed of silicone derived from dimethicones containing dispersed hydrotalcite-type materials previously organo-modified with amino acids. The absence of the typical X-ray pattern of the bioinorganic LDH filler suggested an exfoliation process that was further indirectly evidenced by a drastic change in the rheological behavior, which turned from a quasi-Newtonian behavior for the silicone free of LDH filler to an extensive developed gel-like structure for the nanocomposite derivatives. Visualized by the shear-thinning exponent of the complex viscosity in the low-frequency range, the percolation threshold was evident for filler loading as low as <5 w/W%, suggesting the presence of a largely developed interface between the filler and the polymer. The increase of more than one order of magnitude in viscosity was explained by the rather strong attrition phenomenon between the tethered amino acid anions and the silicone chains. UVB radiation absorption profiles make such bioinorganic polymer nanocomposites potentially applicable in skin protection. Thermo-gravimetric analysis revealed significant improvement in the thermal stability, especially in the final step of the polymer combustion, thus underlining the role of the hybrid material as a thermal retardant agent. (C) 2011 Elsevier B.V. All rights reserved.

Use of Gas Diffusion Electrode for the In Situ Generation of Hydrogen Peroxide in an Electrochemical Flow-By Reactor

Hydrogen peroxide is a powerful oxidant that finds application in several areas, but most particularly in the treatment of industrial wastewaters. The aim of the present study was to investigate the effects of applied potential and electrolyte flow conditions on the in situ generation of hydrogen peroxide in an electrochemical flow-by reactor with a gas diffusion electrode (GDE). The electrolyses were performed in an aqueous acidic medium using a GDE constructed with conductive black graphite and polytetrafluoroethylene (80:20 w/w). Under laminar flow conditions (flow rate = 50 L/h), hydrogen peroxide was formed in a maximum yield of 414 mg/L after 2 h at -2.25 V vs Pt //Ag/AgCl (global rate constant = 3.1 mg/(L min); energy consumption = 22.1 kWh/kg). Under turbulent flow (300 L/h), the maximum yield obtained was 294 mg/L after 2 h at -1.75 V vs Pt//Ag/AgCl (global rate constant = 2.5 mg/ (L min); energy consumption = 30.1 kWh/kg).

Fast Determination of Ciclopirox in Pharmaceutical Products by Amperometry in Flow and Batch Injection Systems

Amperometry coupled to flow injection analysis (FIA) and to batch injection analysis (BIA) was used for the rapid and precise quantification of ciclopirox olamine in pharmaceutical products. The favourable hydrodynamic conditions provided by both techniques allowed a very high throughput (more than 300 injections per hour) with good linear range (2.0200 mu mol L-1) and low limits of detection (below 1.0 mu mol?L-1). The results obtained were compared with titration recommended by the American Pharmacopoeia and also using capillary electrophoresis. Good agreement between all results were achieved, demonstrating the good performance of amperometry combined with FIA and BIA.

Paper-Based Analytical Device for Electrochemical Flow-Injection Analysis of Glucose in Urine

This article describes a new design for a paper-based electrochemical system for flow injection analysis. Capillary wicking facilitates a gravity-driven flow of buffer solution continuously through paper and nitrocellulose, from a buffer reservoir at one end of the device to a sink at the other. A difference in height between the reservoir and the sink leads to a continuous and constant flow. The nitrocellulose lies horizontally on a working electrode, which consists of a thin platinum layer deposited on a solid support. The counter and reference electrodes are strategically positioned upstream in the buffer reservoir. A simple pipetting device was developed for reliable application of (sub)microliter volumes of sample without the need of commercial micropipets; this device did not damage the nitrocellulose membrane. Demonstration of the system for the determination of the concentration of glucose in urine resulted in a noninvasive, quantitative assay that could be used for diagnosis and monitoring of diabetes. This method does not require disposable test strips, with enzyme and electrodes, that are thrown away after each measurement Because of its low cost, this system could be used in medical environments that are resource-limited.

Continuous enzymatic interesterification of lard and soybean oil blend: Effects of different flow rates on physical properties and acyl migration

Continuous enzymatic interesterification is an alternative to chemical interesterification for lipid modification technology which is economically viable for large scale use. A blend of 70% lard and 30% soybean oil was submitted to continuous enzymatic interesterification in a glass tubular bioreactor at flow rate ranging from 0.5 to 4.5 mL/min. The original mixture and the reaction products obtained were examined to determine melting and crystallization behavior by DSC, and analyzed for regiospecific fatty acid distribution. Continuous enzymatic interesterification changed the mixture, forming a new triacylglycerol composition, verified by DSC curves and variation in enthalpy of melting values. The regiospecific distribution of fatty acids was changed by flow variations in the reactor. In the continuous enzymatic interesterification reaction the flow rate of 4.5 mL/min, was more advantageous than slower flow rates, reducing acyl migration and increasing process productivity. (C) 2011 Elsevier B.V. All rights reserved.

A LED Based Photometer for Solid Phase Photometry: Zinc Determination in Pharmaceutical Preparation Employing a Multicommuted Flow Analysis Approach

In this work, a LED (light emitting diode) based photometer for solid phase photometry is described. The photometer was designed to permit direct coupling of a light source (LED) and a photodiode to a flow cell with an optical pathlength of 4 mm. The flow cell was filled with adsorbing solid phase material (C-18), which was used to immobilize the chromogenic reagent 1-(2-thiazolylazo)-2-naphthol (TAN). Aiming to allow accuracy assessment, samples were also analyzed employing ICP OES (inductively coupled plasma optical emission spectrometry) methodology. Applying the paired t-test at the 95% confidence level, no significant difference was observed. Other useful features were also achieved: linear response ranging from 0.05 to 0.85 mg L-1 Zn, limit of detection of 9 mu g L-1 Zn (3 sigma criterion), standard deviation of 1.4% (n = 10), sampling throughput of 36 determinations per h, and a waste generation and reagent consumption of 1.7 mL and of 0.03 mu g per determination, respectively.

A LED based photometer for solid phase photometry: zinc determination in pharmaceutical preparation employing a multicommuted flow analysis approach

Neste trabalho é proposto um fotômetro baseado em LED (diodo emissor de luz) para fotometria em fase sólida. O fotômetro foi desenvolvido para permitir o acoplamento da fonte de radiação (LED) e do fotodetector direto na cela de fluxo, tendo um caminho óptico de 4 mm. A cela de fluxo foi preenchida com material sólido (C18), o qual foi utilizado para imobilizar o reagente cromogênico 1-(2-tiazolilazo)-2-naftol (TAN). A exatidão foi avaliada empregando dados obtidos através da técnica ICP OES (espectrometria de emissão por plasma indutivamente acoplado). Aplicando-se o teste-t pareado não foi observada diferença significativa em nível de confiança de 95%. Outros parâmetros importantes encontrados foram faixa de resposta linear de 0,05 a 0,85 mg L-1 Zn, limite de detecção de 9 µg L-1 Zn (n = 3), desvio padrão de 1,4 % (n = 10), frequência de amostragem de 36 determinações por h, e uma geração de efluente e consumo de reagente de 1,7 mL e 0,03 µg por determinação, respectivamente.

From anionic polymerization in continuous flow to macromolecular architectures and stimuli-responsive surfaces

The thesis can be divided in four parts and summarized as follows:(i) The investigation and development of a continuous flow synthesis procedure affording end-functional polymers by anionic polymerization and subsequent termination in one reaction step and on a multigram scale was carried out. Furthermore, the implementation of not only a single hydroxyl but multiple orthogonal functionalities at the chain terminus was achieved by utilizing individually designed, functional epoxide-based end-capping reagents.(ii) In an additional step, the respective polymers were used as macroinitiators to prepare in-chain functionalized block copolymers and star polymers bearing intriguing novel structural and material properties. Thus, the second part of this thesis presents the utilization of end-functional polymers as precursors for the synthesis of amphiphilic complex and in some cases unprecedented macromolecular architectures, such as miktoarm star polymers based on poly(vinyl pyridine), poly(vinyl ferrocene) and PEO.(iii) Based on these structures, the third part of this thesis represents a detailed investigation of the preparation of stimuli-responsive ultrathin polymer films, using amphiphilic junction point-reactive block copolymers. The single functionality at the block interface can be employed as anchor group for the covalent attachment on surfaces. Furthermore, the change of surface properties was studied by applying different external stimuli.(iv) An additional topic related to the oxyanionic polymerizations carried out in the context of this thesis was the investigation of viscoelastic properties of different hyperbranched polyethers, inspired by the recent and intense research activities in the field of biomedical applications of multi-functional hyperbranched materials.