A flow injection system with two analytical paths for ammonium determination in soil extracts by conductometry is described. The ammonia generated on line in an alkaline medium is permeated through a hydrophobic membrane (TPFE), collected by a deionized water stream and directed toward the conductivity flow cell. The flow network was designed with two analytical paths in order to increase the analytical throughput. The procedure was used to determine ammonium in 2 mol L-1 KCl soil extracts and allowed 100 determinations per hour with a relative standard deviation (r.s.d) of about 2% and an average recovery of 99.9% for a typical sample with concentration of 2.1 mg NH4+ L1-.
ammonium determination; flow analysis; conductometric detection; analysis of soil extracts
