Improved sequential injection method for phosphate quantification within a wide dynamic range with in-line pre-concentration to monitor soil leachates

Phosphate is a well-known contaminant and its content is an indicator of water quality, so it is important to have an efficient monitoring of the soil leaching process. In this work, an automatic, low cost flow analysis method, capable of real-time monitoring of the soil leaching processes using spectrophotometric detection, based on the molybdenum blue reaction, was developed. The developed methodology for phosphate determination was based on the molybdenum blue reaction and includes an on-line solid phase extraction (SPE) step, involving an AG1-X8 anionic exchange sorbent. The described SI method enabled phosphate determination within a wide range, 1–80 µM, with a detection limit of 0.52 µM. It was successfully applied to leachates from laboratory scale soil columns (LSSC) and one sample analysis was carried out in triplicate, in less than 10 minutes.