Analytical Sciences

Flow Systems Including Pervaporation for Spectrophotometric Monitoring of Ethanol in Industrial Fermentations

Ivanildo LUIZ de MATTOS * and Elias Ayres Guidetti ZAGATTO

Centro de Energia Nuclear na Agricultura, Universidade de São Paulo, P. O. Box 96, Piracicaba-SP 13400-970, Brazil

A flow injection system exploiting pervaporation was developed for spectrophotometric determination of ethanol. It was applied to monitor a molasses fermentation process by real time analysis of sample aliquots taken off from the fermentor unit. Moreover, it was adapted for on-line monitoring. The system yields precise results (RSD <1.5%) at concentrations from 1.00 and 10.0%(v/v) ethanol; Beer's law is followed (r=0.99946, n=5) and sampling frequency is 20 h -1 . For an on-line determination, controlled standard additions were performed for the proper correction of any matrix effects. Results were compared with those provided by HPLC, and the agreement between them corroborated the applicability of the pro-posed procedures for large scale analysis and/or for the quality control of molasses fermentation in the sugar-alcohol industry. (Keywords: Flow injection spectrophotometry, pervaporation, biotechnology, ethanol, process control)

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