ATOMIC FLUORESCENCE SPECTROSCOPIC METHODS FOR ULTRATRACE ELEMENTAL ANALYSIS USING A HIGH- REPETITION RATE TUNABLE DYE LASER AND FURNACE SAMPLE ATOMIZATION

AUTOR(ES)

Ricardo Queiroz Aucélio

DATA DE PUBLICAÇÃO

1999

RESUMO

The goal of this work was to develop ultrasensitive methods based on Electrothermal atomization laser-excited atomic fluorescence (ETA-LEAFS) to determine Ge, In, Pb, Pt and Tm in complex samples such as biological and environmental. The ultimate goal was to achieve high sensitivity and high selectivity with little sample manipulation and simple sample calibration procedures. For In, Ge, and Pt sensitive determination methods (femtogram limits of detection) using a standard graphite furnace technique were developed. High sensitivity was achieved by the proper choice of experimental parameters and instrumental design. A high repetition rate copper vapor pumped dye laser was employed to probe more efficiently the transient atom population generated in the atomizer. Tube atomizers with front illumination detection scheme was employed to increase the number of fluorescent atoms detected, improve the dynamic linear range and decrease interferences from the surrounding atmosphere. Experimental parameters were optimized to maximize the signal to noise ratio. Special care concerning imaging and sample atomization conditions was taken to minimize the noise level reaching the detection system. Improvements in the sample atomization efficiency and minimization of interferences were achieved by the choice of the best atomization technique, graphite material, use of matrix modifiers. Efforts are made to improve sensitivity and minimizing interferences by choosing between wall and platform techniques, and optimizing furnace parameters to eliminate sample matrix components. For Pb, a porous graphite filter was used to develop a filter furnace LEAFS method allowing the determination of this element by simple calibration curve method in whole blood with minimum sample manipulation. A graphite tube lined with rhenium foil was employed for the determination of Tm. The performance of the rhenium lined tube was compared with pyrolytic graphite, graphite tubes coated with carbide forming elements, and graphite tubes lined with W and Ta foils. A better performance in terms of sensitivity, reproducibility and long term stability was achieved.

ASSUNTO(S)

quimica analitica elementos traco laser-excited atomic fluorescence; spectrometry métodos óticos de análise laser instrumentação analítica atomização eletrotérmica de amostra espectrometria de fluorescência atomica amostras ambientais fluídos biológicos

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