Evaluation of flow injection methods for ammonium determination in wastewater samples

A comparative study of flow injection methods for the determination of ammonium ion in wastewater samples is presented. It includes methods based on the Berthelot reaction and methods based on gas diffusion. Detection is either spectrophotometric or conductimetric. Analytical characteristics of each method are described in terms of reproducibility, sensitivity and selectivity. The performance of several gas permeable membranes to be used in gas-diffusion systems is discussed. The stopped flow approach is also investigated in order to improve the detection limits. Calibration graphs are obtained for each system, with and without that preconcentration step. Finally, a number of wastewater samples are analyzed using the described methods and the results are compared.