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

Abstract

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 s_r values of seven replicate analyses for all samples were 1.6–2.5%.