A bismuth-film electrode (BiFE) ex situ electrochemically deposited onto a copper substrate has been presented for paraquat determination. The bismuth film was electrochemically deposited at an applied potential of À 0.18 V vs. Ag/ AgCl (3.0 M KCl) for 200 s. The analytical curve was linear in the paraquat concentration range from 6.6 Â 10 À7 M to 4.8 Â 10À5 M with a limit of detection of 9.3 Â 10 À8 M. The method presented satisfactory results at a confidence level of 95% and the performance was evaluated in water samples.

Um nefelômetro microcontrolado portátil e de baixo custo é proposto para a determinação de potássio em água de coco e bebidas energéticas. O nefelômetro foi construído utilizando dois LEDs (diodos emissores de luz) como fontes de radiação em 465 nm e 880 nm, dois fotodiodos como fotodetectores e um controlador de interface periférica (PIC) para aquisição e processamento dos dados. O nefelômetro foi utilizado para determinar íons potássio pelo monitoramento do precipitado formado na reação entre íons K + e tetrafenilborato em meio básico na presença de álcool polivinílico. A curva analítica foi linear para potássio na faixa de concentração de 5,0×10 −6 a 5,0×10 −4 mol L −1 , com um limite de detecção de 4,0×10 −7 mol L −1 . Um desvio padrão relativo de 0,2 % para uma solução de potássio 1,6×10 −4 mol L −1 (n = 10) foi obtido. Respostas rápidas e confiáveis e baixo consumo de energia são outras características do nefelômetro proposto.A low-cost portable microcontrolled nephelometer for the determination of potassium in coconut water and energy beverages is proposed. The nephelometer was constructed using two LEDs (light emitting diodes) as radiation sources at 465 nm and 880 nm, two photodiodes as photodetectors, and a peripheral interface controller (PIC) to acquisition and processing data of the nephelometer. The nephelometer was used to determine potassium ions by monitoring the precipitate formed from the reaction between K + and tetraphenylborate anion in a basic medium in the presence of polyvinyl alcohol. The analytical curve was linear in the potassium concentration range from 5.0×10 −6 to 5.0×10 −4 mol L −1 , with a limit of detection of 4.0×10 −7 mol L −1 . A relative standard deviation of 0.2 % for 1.6 × 10 −4 mol L −1 potassium solution (n = 10) was obtained. Fast and reliable responses, low power consumption are other attractive features of the proposed nephelometer.Keywords: microcontroller, nephelometer, light emitting diode, analytical instrumentation, sodium tetraphenylborate IntroductionA nephelometer measures the turbidity of a solution containing suspended particles by directing a beam of light into the sample and sensing the light scattered, usually at right angles (at a 90° angle with respect to the light beam). [1][2][3] This technique has been applied to determine sulfate in water, 4 aqueous drug solubility, 5 and for immunoassays such as of proteins in maternal milk, 6 cystatin-C in serum, 7 and serum myoglobin in patients with acute pancreatitis. 8 Generally, spectrofluorimeters and fluorimeters are analytical instruments widely applied for this purpose. However, components such as high-intensity radiation sources, sophisticated detectors and wavelength selectors, and other optical devices make such equipments expensive. 1,3 Furthermore, these types of equipment are not portable and need microcomputers for control and data acquisition.LEDs (light emitting diodes) are semiconductor devices with p-n junction that exhibit electroluminescence properties when a current passes through them. LED...

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A potentiostat/galvanostat with wireless data transmission and a GPS receiver was applied to in situ flow analyses.

WAY. A portable microcontrolled system is proposed to monitor conductivity, temperature and pH in on-line, in situ and remote way from a water reservoir faraway 200 m. The system comprises two modules: one for data reception (located in laboratory) and another for data acquisition/transmission (located near water reservoir). It uses a microcontroller and a transceiver to remote data transmission/reception by radio frequency. Variations of water parameters were simultaneously monitored without interruption during a period of ten hours with a relative error about 4.0 %. The developed system showed simple, stable, accurate, robust and low-cost to determine parameters of water in field.Keywords: remote monitoring; microcontroller; water analyses. INTRODUÇÃOProblemas relacionados com a poluição das águas se intensificaram após a Segunda Guerra Mundial, quando houve um aumento significativo da urbanização e da industrialização. Nos dias atuais, especialistas acreditam que, em no máximo 20 anos, teremos uma crise associada com a indisponibilidade de água potável semelhante àquela ocorrida em 1973 com o petróleo.1 Neste contexto, o controle de qualidade dos recursos hídricos torna-se de extrema relevância, uma vez que está diretamente correlacionado com a saúde e o bem estar da população, com a conservação do meio ambiente e com diversas atividades econômicas, tais como piscicultura, carcinocultura, agricultura e agropecuária, dentre outras. Dessa forma, parâmetros físicos (cor, turbidez, temperatura, condutividade etc.), químicos (pH, demanda química de oxigênio, oxigênio dissolvido, nitrato, nitrito, fósforo total etc.) e bacteriológicos (demanda bioquímica de oxigênio e coliformes fecais) devem ser periodicamente avaliados, de modo que a qualidade da água possa ser inferida. Em termos gerais, o processo convencional de análise de águas é constituído por três etapas: amostragem, armazenamento e tratamento das amostras e estudo dos fatores intervenientes em sua gestão. Por conseguinte, a manipulação dos parâmetros de controle de qualidade de águas por processos convencionais apresenta desvantagens, 3 como demanda um tempo relativamente longo; torna-se dispendiosa pela necessidade de deslocamento de pessoal para os locais de coleta das amostras, amiúde distantes e de difícil acesso; não possibilita a aquisição de um amplo conjunto de dados necessário para a investigação da evolução temporal dos parâmetros de interesse; durante a etapa de armazenamento, a integridade da amostra pode não ser preservada devido a fatores como efeito de matriz e possíveis atividades biológicas e, não permite a realização de análises em condições reais, o que vem a minimizar a representatividade dos valores obtidos durante as determinações.Os inconvenientes mencionados podem ser superados com o advento de sistemas de monitoramento in situ, on-line e remoto de aquisição de dados. Sistemas desse tipo são caracterizados pela realização do monitoramento de parâmetros de qualidade sem a necessidade da presença regular de um operador. No âmbito da ...

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This study reports on the construction of a turbidimeter employing light emitting diodes as radiation source at a wavelength of 405 nm, a photodiode as detector, a temperature sensor and a microcontroller used for data acquisition and processing. The turbidimeter was applied to determine sulfate concentrations in natural water employing barium chloride as reagent. Potential interferences and recovery studies were performed and an interference of 3.5 % and a recovery between 97.8 and 108 % were estimated. The analytical performance of in situ turbidimeter for the determination of sulfate was evaluated and compared with two commercial spectrophotometers and a good agreement was obtained

Microcontrolled systems coupled biosensors have attracted attention. Here, we describe an automated and portable microcontrolled pumping flow system (µC-PFS) developed to biosensing application. The flow system is fully automatic, portable, it works in battery module and it dispenses the use of microcomputer and the manual operations. This device presents mainly a microcontroller as central processing unit (CPU), an aquarium air pump and three-way solenoid valves to propulsion and the volume control of aliquots inserted in the flow system. Once available its performance, this device was used to pump samples and solution towards a compacted and miniaturized electrochemical flow cell (EFC) employing a multicommutated flow procedure. In the EFC, it was used a biosensor based on acetylcholinesterase immobilized on the gold nanoparticles modified-screen printed carbon electrode, which was used in order to perform the determination of diuron by enzymatic inhibition employing a chronoamperometry. Under the best experimental conditions, the calibration curve for diuron determination was linear in the concentration range from 80 to 1400 nmol/L with a detection limit of 50 nmol/L. Moreover, the proposed system was fully automated, showed precise, with low consumption of sample and waste generation with an analytical throughput of 13/h.