Flow injection amperometric determination of trace amounts of ammonium using a gas-diffusion cell as the sample loop

A new flow injection method for the determination of trace amounts of ammonium by using a pyrolytic graphite electrode electrodeposited with a cuprihexacyanoferrate film coated with Nafion film as a sensor is described. A gas-diffusion unit was used to enhance the selectivity and sensitivity. Under optimum analytical conditions, the linear range of the calibration graphs for ammonium were 2–32, 0.8–16 and 0.4–8 µmol l–1 when the accumulation time was 1, 2 and 3 min, respectively. The method has been applied to the determination of ammonium in rain-water samples and recoveries of 96.7–102.2% were obtained. The sr values of seven replicate analyses for all samples were 1.6–2.5%.