DETERMINATION OF AMMONIUM BY POTENTIOMETRY IN INJECTION IN FLOW COUPLED TO A NEW MICRO DEVICE OF GASEOUS DIFFUSION

Abstract

The determination of ammonium by potentiometry in flow injection coupled to a gaseous membrane microdevice is investigated. A nonactin tubular electrode as an ionophore was used for the detection of ammonium. For this sensor to be selective, a microdevice was built incorporating a gaseous diffusion membrane with the purpose of eliminating interferences. The response of the proposed methodology had a Nernstian response with an angular coefficient of 51.2 mV (R2 = 0.9836) in a range of 0.2 to 5.0 mg L-1. The limits of detection and quantification were calculated in 0.004 (S / N = 3) and 0.010 (S / N = 10) mg L-1. The repeatability of the measurements was determined in 1.3% (n = 10) with a sampling frequency of 13 samples h-1. Under optimum conditions a flow rate of the transporter of 0.5 ml min-1 and a sample volume of 250 µL was obtained. We achieved an integral, selective and reliable system for the determination of ammonium, which may have applications in continuous monitoring in industrial use such as in the fishing sector, vineyards, wines etc. KEY WORDS: Ammonium, Potentiometer, Microdevice, Electrode, Interference.