Gas/Diffusion Flow Injection Determination of Ammonium Ions in River and Waste Waters by Conductometry

Abstract

An FIA conductometric method for monitoring of ammonium ions in river and waste waters is proposed. A very good detection limit (xD 5.6 μmol l-1) was obtained at 100/20 s preconcentration/rinsing times and 2 ml sample consumption per analysis at the flow rate 0.8 ml min-1. The detection limit xD can be further improved at longer preconcentration/ rinsing times. Precipitation of polyvalent metal ions (mainly Fe(III)) was eliminated by addition of 0.5 mmol l-1 EDTA prior to injection. The results are comparable with those obtained by spectrophotometry (Nessler's reagent).