Mediated Amperometric Biosensor for the Determination of Ammonium

A mediated amperometric biosensor based on bi- layer glutamate dehydrogenase (GLDH)/diaphorase immobilized on screen printed carbon paste electrode (SPCE) for the determination of ammonium has been described. In this work the electrochemical oxidation of NADH was used as indicator reaction for the quantification of ammonium concentration. The use of ferrocene carboxaldehyde as an electron transfer mediator lowered the oxidation potential of NADH to + 0.4 V vs. Ag/AgCl. Parameter optimization improves the analytical performance of the biosensor within the linearity range of 2.5 mu M to 500 mu M with the detection limit of 2.5 mu M. The reproducibility of the fabricated biosensor was also evaluated and it was found to be good with a relative standard deviation (RSD) of 4.17% (n= 5). A good agreement with the Indothymol method was obtained for the measurement of ammonium in water samples.