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.