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Development of a Disposable Amperometric NH Biosensor Based on a Chemically Modified Screen‐Printed Carbon Electrode Coated with Glutamate Dehydrogenase, 2‐Oxoglutarate, and NADH
Author(s) -
Hart J. P.,
Abass A. K.,
Cowell D. C.,
Chappell A.
Publication year - 1999
Publication title -
electroanalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.574
H-Index - 128
eISSN - 1521-4109
pISSN - 1040-0397
DOI - 10.1002/(sici)1521-4109(199905)11:6<406::aid-elan406>3.0.co;2-n
Subject(s) - biosensor , amperometry , detection limit , chemistry , glutamate dehydrogenase , electrocatalyst , chromatography , cofactor , chronoamperometry , electrode , immobilized enzyme , dehydrogenase , inorganic chemistry , nuclear chemistry , electrochemistry , enzyme , biochemistry , cyclic voltammetry , glutamate receptor , receptor
A screen‐printed carbon electrode (SPCE), impregnated with the electrocatalyst Meldola's Blue (MB), has been investigated as the base transducer in a disposable amperometric NH biosensor. The MB‐SPCE detects the cofactor NADH when it is polarized at a potential of only +0.05 V (vs. Ag/AgCl); electrocatalytic oxidation of the cofactor readily occurs at this potential. The device was converted into an NHA biosensor by coating the surface of the MB‐SPCE with glutamate dehydrogenase, 2‐oxoglutarate and NADH. When ammonium ions are present in the sample solution, a decrease in the anodic current occurs as a result of the enzymatic conversion of 2‐oxoglutarate to glutamate which requires NADH. Chronoamperometry was performed on 40 μL aliquots of solutions containing various concentrations of NH 4 + . A 30 s incubation period was used, then the potential was stepped from open circuit to + 0.05 V (vs. Ag/AgCl); response currents were measured from the resulting chronoamperograms at a time of 120 s ( t 120s ). The detection limit was found to be about 2 μM with biosensors containing 4.6 U of enzyme. The stability of these biosensors was examined after storage at 4°C in a desiccator containing silica gel; the response was found to be constant for a period of about 29 days. The proposed biosensors were evaluated on samples of unspiked, and spiked, river water; the recovery and precision data indicated that the devices could be expected to give reliable results for the low levels of NHA normaly expected in rivers.