Desenvolvimento de um espectrofometro no infravermelho proximo com transformada de Hadamard

AUTOR(ES)
DATA DE PUBLICAÇÃO

1999

RESUMO

A near infrared spectrophotometer based on Hadamard multiplexed measurements has been developed. The instrument can operate in the range 800 to 1756 nm or 1756 to 2712 nm depending on the dispersion grating position. The spectrophotometer employs a linear mask with 255 elements. Each element is 0.250 mm wide and 4.0 mm height. The spectral measurement can be obtained in a double beam configuration allowing for drift correction of the light source. A spectra can be obtained in a minimum time interval of 8 s and its signal-to-noise ratio is equivalent to that obtained for 127 scans in a conventional instrument. A mechanical light chopper was employed for multiplexed signal modulation and a lock-in amplifier was used for signal recovering. The spectrophotometer can be controlled through a GPIB interface, by using an Advantech board PCI-812-PC or by a serial RS-232C standard interface. The control, data acquisition and data processing program has been written in Visual Basic 3.0. Data can refer to absorbance, transmittance or reflectance measurements. The instrument was employed in the development of analytical methodologies aiming the determination of water in hydrated ethanol and total olefins in parafins C10-C13. The water content of ethanol can be achieved by employing a PLS model that requires only one principal component to describe 99.99% of the data variance. The standard error of prediction (SEP) was 0.01 %. The results allow to predict that the near infrared methodology can replace the densitometry and can be used for in-Iine monitoring of water content in ethanol. The results for total olefins were also good with a estimate of the standard error of prediction equal to 0.05%.

ASSUNTO(S)

espectroscopia de infravermelho analise espectral

ACESSO AO ARTIGO

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