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Journal of Sensors
Volume 2011, Article ID 980709, 10 pages
Research Article

An Amperometric Biosensor Based on Alanine Dehydrogenase for the Determination of Low Level of Ammonium Ion in Water

1School of Chemical Sciences and Food Technology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, Selangor, 43600 Bangi, Malaysia
2Chancellor Office, Islamic Science University of Malaysia, Bandar Baru Nilai, Negeri Sembilan, 71800 Nilai, Malaysia

Received 4 May 2011; Accepted 30 June 2011

Academic Editor: Michele Penza

Copyright © 2011 Tan Ling Ling et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


An amperometric electrochemical biosensor has been developed for ammonium ( N H 4 + ) ion detection by immobilising alanine dehydrogenase (AlaDH) enzyme in a photocurable methacrylic membrane made up of poly(2-hydroxyethyl methacrylate) (pHEMA) on a screen-printed carbon paste electrode (SPE). The current detected was based on the electrocatalytic oxidation of nicotinamide adenine dinucleotide reduced (NADH) that is proportional to the consumption of N H 4 + ion whilst enzymatic amination of AlaDH and pyruvate is taking place. The biosensor was operated amperometrically at a potential of +0.6 V and optimum pH 7. The N H 4 + biosensor demonstrated linear response to N H 4 + ion concentration in the range of 0.03–1.02 mg/L with a limit of detection (LOD) of 8.52 μg/L. The proposed method has been successfully applied to the determination of N H 4 + ion in river water samples without any pretreatment. The levels of possible interferents in the waters were negligible to cause any interference on the proposed method. The analytical performance of the biosensor was comparable to the colorimetric method using Nesslerisation but with much lower detection limit and linear response range at ppb level.