Determination of trace amounts of phosphate in river water by flow-injection analysis

A flow-injection analysis system for the determination of trace amounts of phosphate in river water has been developed. The phosphate is reacted with molybdate and Malachite Green in acidic medium to form a green species, the absorbance of which is measured at 650 nm. Phosphorus (as inorganic phosphate) can be determined at the level of several ng ml in water. Analyses can be done at a rate of up to 40 per hour.