Solid-state instrumentation for use with optical-fibre chemical-sensors

Uso de membranas de Nafion para a construção de sensores ópticos para medidas de pH

“…Uma descrição detalhada sobre os componentes empregados no desenvolvimento de sensores ópticos pode ser encontrada em livros texto de Química Analítica Instrumental 18 . Apesar de vários arranjos apresentarem certa complexidade, em vários sistemas 19 é possível utilizar instrumentação de maior simplicidade e de baixo custo, incluindo diodos emissores de luz e fotodiodos.…”

A Simple and Portable Colorimeter Using a Red-Green-Blue Light-Emitting Diode and Its Application to the On-Site Determination of Nitrite and Iron in River-water

“…1 Many researchers have developed LED-based systems not only for colorimeters, 2,3 but also for the detectors of FIA [4][5][6] and CE, 7 or fiber-optic sensors (optodes). 8,9 In this work, we have developed a portable colorimeter that is compact and light (100 × 70 × 50 mm in dimension and 280 g in mass). This colorimeter has a three-emitter LED (RGB, red, green and blue) as a light source and can measure the absorbance corresponding to each emitter, sequentially.…”

“…Signal separation was done by a time-division technique that was widely used. 2,6,8,9 At first, the performance of the colorimeter was checked with several color dyes. After that, it was successfully applied to the on-site determination of nitrogen as nitrite in river-water, 10 and the on-site determination of iron in river-water with the on-site extraction method using methylisobutylketone (MIBK).…”

A Portable Spectrophotometer Using a White-Color Light-Emitting Diode and a Charge-Coupled Device and Its Application to On-Site Determination of Iron

“…20 -100 nm in FWHM). 1,2 Therefore, when applied to colorimeters or fluorometers, they have been used as monochromatic light sources with or without an interference filter. By exchanging LEDs or combining multiple LEDs, measurements at various wavelengths from near UV to infrared could be feasible without a monochromator.…”

“…By exchanging LEDs or combining multiple LEDs, measurements at various wavelengths from near UV to infrared could be feasible without a monochromator. [1][2][3][4][5][6][7] Signal discrimination of multiple LEDs or from ambient light was done by a lock-in amplifier, 5,6 fast Fourier transformation, 3 or time division detection 2,7 with source modulation. Though it is desirable for portable instruments to omit a heavy and bulky monochromator, there is a drawback that the measurement wavelengths are limited by available LEDs.…”