Abstract: A unified ion-exclusion chromatography (IEC) system for monitoring anionic and cationic nutrients like NH+4, NO-2, NO-3, phosphate ion, silicate ion and HCO-3was developed and applied to several environmental waters. The IEC system consisted of four IEC methodologies, including the IEC with ultraviolet (UV) detection at 210 nm for determining NH+4on anion-exchange separation column in OH- form connected with anion-exchange UV-conversion column in I- form in tandem, the IEC with UV-detection at 210 nm for determining simultaneously NO-2 and NO-3 on cation-exchange separation column in H+form, the IEC with UV-detection at 210 nm for determining HCO-3on cation-exchange separation column in H+form connected with anion-exchange UV-conversion column in I- form in tandem, and the IEC with visible-detection based on molybdenum-blue reaction for determining simultaneously silicate and phosphate ions on cation-exchange separation column in H+ form. These IEC systems were combined through three manually-driven 6-port column selection valves to select each separation column to determine selectively the ionic nutrients. Using this sequential water quality monitoring system, the analytical performances such as calibration linearity, reproducibility, detection limit and recovery were also tested under the optimized chromatographic conditions. This novel water quality monitoring system has been applied successfully for the determination of the ionic eutrophication components in sub-urban river waters.

Key words: anionic and cationic nutrients, column selection valve, water eluent, ion-exclusion chromatography (IEC)