ONLINE MONITORING OF PHOSPHATE IN NATURAL-WATER AND EFFLUENT STREAMS USING SEQUENTIAL INJECTION-ANALYSIS

Automation of the molybdenum blue method by sequential injection (SIA) for the on-line monitoring of phosphate in natural waters is presente d. Although sequential injection analysis runs at one fifth the speed of conventional FIA, it presents many advantages such as simplicity of the manifold, robustness and computer compatibility. A reduction in r eagent and sample consumption is also observed. Flow detector fouling does not occur in SIA manifolds as the detector is in contact with wat er between analysis. The proposed SIA analyser is able to monitor phos phate in the range 0-70 mg l(-1) with a standard deviation of 0.9%. Th e detection limit is 0.5 mg l(-1) PO43-.