Gas/diffusion flow injection determination of ammonium ions in river and waste waters by conductometry

An FIA conductometric method for monitoring of ammonium ions in river and w aste waters is proposed. A very good detection limit (x(D) 5.6 mu mol l(-1) ) was obtained at 100/20 s preconcentration/rinsing times and 2 ml sample c onsumption per analysis at the flow rate 0.8 ml min(-1). The detection limi t x(D) can be further improved at longer preconcentration/rinsing times. Pr ecipitation of polyvalent metal ions (mainly Fe(III)) was eliminated by add ition of 0.5 mmol l(-1) EDTA prior to injection. The results are comparable with those obtained by spectrophotometry (Nessler's reagent).