Desenvolvimento de um espectometro de emissão para a região do infravermelho proximo / Development of an emission spectrometer for the near infrared region

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

Despite the wide analytical application of near infrared (NIR) spectroscopy, there are few works in litetature about near infrared emission spectroscopy (NIRES) or its exploitation for analytical purposes. This work describes a development of a new NIRES instrument based on an acousto-optical tunable filter (AOTF) as wavelength selector. The instrument is also constituted by an electrical heater as excitation source, a modulated radio-frequency (RF) generator to control AOTF, a PbS detector, a lock-in amplifier to acquire the detector signal, and a microcomputer to control the instrument and to acquire the emission data. The detector was positioned in front of the output window of AOTF in order to measure an emission intensity related to both diffracted beams modulated over the nondiffracted beam, leading to gains in signal to noise ratio. The NIR emission spectra were obtained by heating a few microliters or miligrams of sample to a constant temperature between 150 and 250 °C and scanning the RF signal frequency. The NIR emission spectra were applied, for instance, to characterize materials used in liquid chromatography according to the type and amount of coating material, specific surface area and thermal stability; to determine the oxidative stability of vegetable oils at frying temperatures; to classify new lubricant oils according to their chemical constitutions an used lubricant oils according to their milage; to distinguish crystalline forms, as demonstrated for titanium dioxide; to distinguish different types of Portland cements; and to evaluate the soybean oil content in mixtures with olive oil.

ASSUNTO(S)

instrumentação espectroscopia de emissão near infrared filtro optico-acustico sintonizavel emission spectroscopy acousto-optical tunable filter instrumentation infravermelho proximo

ACESSO AO ARTIGO

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