Flow injection analysis of inorganic polyphosphates

Flow injection analysis is applied to the determination of orthophosphate and polyphosphates, such as diphosphate and triphosphate. A strongly acidic solution containing molybdenum(V) and molybdenum(VI) is used as the carrier so that hydrolysis of polyphosphates and color development of the resultant orthophosphate can be achieved simultaneously. For complete chemical reaction, the temperature of the reaction coil is maintained at 140° C. Application of a back-pressure coil is then necessary to eliminate the noise caused by gas bubbles. Total amounts of inorganic polyphosphates can be determined at a sampling rate of 45 samples per hour with a relative standard deviation of less than 1%. In addition, the flow injection system is shown to be useful as a post-column detector for high-performance liquid chromatography of inorganic polyphosphates. The efficiency of this system is compared with that of an air-segmented flow system.