Biosensor based on glutamate dehydrogenase immobilized in chitosan for the determination of ammonium in water samples

Abstract: An optical biosensor based on glutamate dehydrogenase (GLDH) immobilized in a chitosan film for the determination of ammonium in water samples is described. The biosensor film was deposited on a glass slide via a spin-coating method. The ammonium was measured based on β-nicotinamide adenine dinucleotide (NADH) oxidation in the presence of α-ketoglutaric acid at a wavelength of 340nm. The biosensor showed optimum activity at pH 8. The optimum chitosan concentrations and enzyme loading were found to be at 2% (w/v) and 0.08mg, respectively. Optimum concentrations of NADH and α-ketoglutaric acid both were obtained at 0.15mM. A linear response of the biosensor was obtained in the ammonium concentration range of 0.005 to 0.5mM with a detection limit of 0.005mM. The reproducibility of the biosensor was good, with an observed relative standard deviation of 5.9% (n =8). The biosensor was found to be stable for at least 1month when stored dry at 4°C. [Copyright &y& Elsevier]