Flow injection gas-diffusion amperometric determination of trace amounts of ammonium ions with a cupric hexacyanoferrate

A new flow injection method for the determination of trace amounts of ammonium ions was developed by using a glassy carbon electrode electrodeposited with a film of cupric hexacyanoferrate coated with Nafion film as the sensor. The electrode gives sensitive but not selective response to potassium and ammonium ions. A gas-diffusion unit was used for the separation of ammonium and potassium ions and high selectivity and sensitivity for ammonium ions can be obtained. The method is simple and sensitive. Under optimum analytical conditions, the linear range of the calibration graph for ammonium ions is 2-40 muM. The method has been applied to the determination of ammonium ions in lake water and rain water samples. Recoveries of 94.4 to 104.4% were obtained. The relative standard deviations of seven replicate analyses for all samples were 1.1-2.3%.