EVALUATION OF FLOW-INJECTION METHODS FOR AMMONIUM DETERMINATION IN WASTE-WATER SAMPLES

A comparative study of now injection methods for the determination of ammonium ion in wastewater samples is presented. It includes methods b ased on the Berthelot reaction and methods based on gas diffusion. Det ection is either spectrophotometric or conductimetric. Analytical char acteristics 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 stoppe d flow approach is also investigated in order to improve the detection limits. Calibration graphs are obtained for each system, with and wit hout that preconcentration step. Finally, a number of wastewater sampl es are analyzed using the described methods and the results are compar ed.