Aplicações da espectroscopia fotoacustica e ressonancia paramagnetica eletronica a materiais biologicos

AUTOR(ES)
DATA DE PUBLICAÇÃO

1988

RESUMO

In this work we have applied Photoacoustic Spectroscopy (PAS) and Electron Paramagnetic Resonance (EPR) to biological materials. Initially, two methods using PAS in the near-infrared for the determination of adulterant content in binary mixtures of coffee were presented. The basis of the methods is the establishment of calibration curves constructed from the photoacoustic spectra of previously prepared mixtures of coffee and its adulterants commonly utilized in Brazil. We have applied one of the methods for the determination of unknown amounts of adulterants in mixtures of coffee with coffee peal and parchment. The results of the photoacoustic method were in good accordance with the results obtained from the quantitative analysis previously realized by IBC. We have also tried to obtain a systematic method for the classification of the coffee beverages, which is presently realized through the flavour proof (or cup proof). We have employed two different techniques: The EPR and PAS. The results obtained with EPR showed that the rate of free radicals formation during roasting is different for each quality of coffee. This makes possible to use the EPR intensities as an identifier of the different beverages. In the case of photoacoustic spectroscopy we have noted that, in particular, the peak centered at 0,88 mm has different intensities to the different beverages. This allows also the application of this technique for the identification of the different beverages and its correlation with EPR. Finally, we have applied photoacoustic spectroscopy in the visible region for the monitoring of herbicide effects in leaves. In the first case we have applied "Paraquat" to a soybean leaf and the results we have obtained are in good accordance with data registered in the specialized literature. We have concluded that some effects commonly produced by this herbicide were detected and their magnitude and chronology were precisely determined by the Phase Resolved method (PRM). One of these effects was the membranes destruction and consequent loss of water by the leaf (plasmolisys). Another observed effect was the chlorophyll and carotenoid destruction. In another case we have applied three herbicides of the Diphenylether group to the plants Amaranthus and Euphorbia, but only in a few cases regularities of herbicides effects were observed

ASSUNTO(S)

materiais - analise espectroscopia de ressonancia paramagnetica eletronica

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