Construção de um expectrofotometro com transformada de Hadamard e sua aplicação na analise por injeção em fluxo

AUTOR(ES)
DATA DE PUBLICAÇÃO

1993

RESUMO

A fast scanning Hadamard spectrophotometer which is capable to obtain a complete spectra in the visible region in time intervals down to 50 ms has been developed. The spectrophotometer control and data acquisition were performed by a single board microcomputer based on a CPU 8085. This single board sends data, in serial mode, to an IBM PC compatible microcomputer where the Hadamard transform is performed and where emission, transmission or absorption spectra are displayed. AlI computer programs required for instrument control (in ASSEMBLER-8085) and data treatment (in QuickBasic 4.5) were developed. Absorbance measurements of KMnO4 solutions taken in 525 nm showed linearity in the range of 0.0 to 0.8 units. Ten measurements of a KMnO4 solutions whose mean absorbance was 0.250 showed a standard deviation equal to 1.2%. This instrument was employed as detection unit in a Flow Injection Analysis manifold, where acid mixture titrations were performed. The titrations, realized in time intervals up to 5 minutes, were monitored by following the changes in the absorbance spectra of acid-base indicator mixtures. Surfaces, absorbance x time x wavelength, were obtained reflecting the acid mixture composition. Chemometric methods, based on a Partial Least Squares (PLS) multivariate calibration were employed to data reduction and to obtain predictions about acids concentration. Also, the computer programs to multivariate calibration were developed in QuickBasic 4.5. The following acids mixtures were titrated employing the proposed methodology acetic/hydrochloric, citric/tartaric and acetic/benzoic, with mean relative errors in the range of 2.4% to 7.1%.

ASSUNTO(S)

espectrofotometria quimica analitica minimos quadrados

ACESSO AO ARTIGO

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