Development of an anti-chloride interference and high sensitivity on-line analyzer for analysis of total phosphorus in industrial circulating cooling water

Abstract

An on-line total phosphorus (TP) analyzer was developed to meet the needs for determining the phosphonate concentration in industrial circulating cooling waters with low phosphorus and even phosphorus-free formulations and high Cl− contents. A flow batch analysis technique was used to achieve high sensitivity over a wide range of total phosphorus concentration using a home-made low-power ring-shaped UV on-line digester operating at normal temperatures and pressures and a dual-spectrophotometer detector. The quantification range was 0.36–160 μmolL−1, and the limit of quantification was low enough to detect low, and even no, phosphorus in the treatment reagents. Concentrations of chloride ions up to 700 mgL−1 in the cooling water would not interfere with the digestion. The analyzer was successfully deployed in an open circulating cooling water system. The results from the on-line system agreed well with those of discrete samples analyzed using a conventional analytical method in the factory laboratory.