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 d escribed. 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 mu mo l l(-1) when the accumulation time was 1, 2 and 3 min, respectively, T he method has been applied to the determination of ammonium in rain-wa ter samples and recoveries of 96.7-102.2% were obtained, The s(r) valu es of seven replicate analyses for all samples were 1.6-2.5%.