Desenvolvimento de um fotometro multicanal baseado em um arranjo de diodos emissores de luz

AUTOR(ES)
DATA DE PUBLICAÇÃO

2004

RESUMO

The development of a multichannel photometer based on an array of eight Light Emitting Diodes (LED) is described. Optical fibre bundles were employed to guide the radiation of the LED to the measuring cell and from the cell to the photodiode detector. The instrument was designed to perform measurements in a single wavelength continuously as well as in all wavelengths (470,500, 525, 562, 590, 612, 636 and 654 nm) sequentially, allowing its application in multivariate analysis methods. Evaluation of the photometer indicated drift lower than 2 mV h and a precision better than 0,003 units in measurements of absorbance. The instrument was applied for the simultaneous determination of Zn(lI) and Cu(lI) in metallic alloys and pharmaceutical samples, by employing Multiple Linear Regression (MLR) and for the classification of commercial mineral waters, by using Principal Components Analysis (PCA). The best calibration model, constructed for the first application, presented Root Mean Square Errors of Prediction (RMSEP) of 0.06 and 0.12 mg L for Zn(lI) and Cu(II), respectively. The results obtained with the photometer were compared with those determined by Flame Atomic Absorption Spectrometry (FAAS), showing no significant differences at the 95 % confidence leveI. Mineral water samples were classified according to their respective origins by two Principal Components (PC1 and PC2), which explained 96 and 2 % of the total variance, respectively.

ASSUNTO(S)

instrumentação espectrofotometria quimiometria

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