Abstract
Intact bacterial cells of Paracoccus denitrificans were immobilized behind a dialysis membrane on the surface of a graphite electrode. Durohydroquinone (DQH 2) was used as an electron transfer mediator between the electrode and respiratory chain of the bacterial cell. The catalytic reduction current based on denitrification reductase activity observed with the electrode was proportional to the concentration of both nitrate and nitrite. In this report, characteristics of the electrode as a nitrate sensor are described. The coefficient of variation of the current measured at concentration of 5 μM nitrate was 3.8% ( n=10). The method has a detection limit of 1 μM nitrate and was applied to determination of nitrate in human urine. No interference of glucose, ascorbic acid, and acetone was observed. The response for nitrite of the electrode decreased in the presence of an inhibitor such as antimycin. When hexacyanoferrate (II), Fe(CN) 6 4−, was used as a mediator, the electrode exhibited nitrite selectivity.
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