On-line spectrophotometric determination of phosphate in bioprocesses by sequential injection

Abstract

Automation of a reduced molybdophosphoric acid method by sequential injection (SI) for the on-line monitoring of phosphate concentrations is presented. Simplicity, robustness and computer compatibility of the SI system has made possible the monitoring of a wide range of phosphate concentrations (0.1 to 30 mmol l^–1) without the necessity of mechanical reconfiguration of the manifold. Dilution, when required, was performed in a mixing chamber connected to the selector valve. Decisions about the necessity of dilution were made through software. Real-time data may be provided to process controllers. Results obtained on-line agreed with those obtained off-line. A sampling frequency of 25 per hour is possible. The method was demonstrated in a study of the influence of phosphate concentration on the production of biomass in aerobic fermentations of Saccharomyces cerevisae. The addition of phosphate to the fermentation before its depletion from the medium enhanced the production of biomass by 25 to 35%.