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.

Este artigo demonstra a possibilidade de se realizar uma determinação simultânea de chumbo e cobre em água mineral, de rio e de torneira mediante análise por redissolução potenciométrica empregando um potenciostato lab-made de baixo custo e um método de processamento de sinais baseado em wavelets. As concentrações encontradas para Pb(II) e Cu(II) situaram-se na faixa 3-7 µg L-1. Os desvios padrão relativos foram em média menores que 3%, o que é satisfatório tendo em vista as baixas concentrações dos analitos. Para comparação, a determinação foi também realizada empregando um equipamento comercial de alto padrão (μAutolab Type II, Eco Chemie). As médias e desvios padrão dos resultados foram similares aos obtidos com o potenciostato lab-made. Não foi verificada diferença estatística significativa de acordo com um teste t pareado ao nível de confiança de 95%.

This paper demonstrates the possibility of simultaneously determining lead and copper in mineral, river and tap water by potentiometric stripping analysis using a low-cost lab-made potentiostat and a wavelet-based signal processing method. Pb(II) and Cu(II) concentrations were found to be in the range 3-7 µg L-1. Relative standard deviations were on average smaller than 3%, which is satisfactory in view of the trace concentration. For comparison, the determination was also carried out by using a high-end commercial equipment (μAutolab Type II, Eco Chemie). The average and standard deviation of the results were similar to those obtained with the lab-made potentiostat. No significant statistical difference was verified according to a paired t-test at a confidence level of 95%.

A microcontrolled, portable and inexpensive photometer is described. It uses six light-emitting diodes (LEDs) as radiation sources and a phototransistor as detector, as well as a microcontroller (PIC - Programmable Controller of Interruption). This device provided total autonomy to the proposed photometer, which was successfully applied to determination of Fe2+ in ferrous syrups and of seven clinical biochemical parameters. As the components are cheap (~U$30.00) and easy to find, the proposed photometer is an economical alternative for routine chemical analyses in small laboratories, for research and teaching. Being portable and microcontrolled, it allows doing field chemical analyses.

A lab-made interface for acquisition of instrumental analog signals between 0 and 5 V at a frequency up to 670 kHz at the parallel port of a microcomputer is described. Since it uses few and small components, it was built into the connector of a printer parallel cable. Its performance was evaluated by monitoring the signals of four different instruments and similar analytical curves were obtained with the interface and from readings from the instrument' displays. Because the components are cheap (~U$35,00) and easy to get, the proposed interface is a simple and economical alternative for data acquisition in small laboratories for routine work, research and teaching.