The electrode consisted of nitrate reductase held by dialysis membrane onto a Nafion-coated glassy carbon electrode. Methyl viologen was allowed to absorb into the Nafion layer, which acted as a reservoir for the electron mediator. The utility of the electrode to assay fertilizer and water sample for nitrate was demonstrated. The assays conducted with this electrode compared well with colorimetric and potentiometric assays of the same samples. The enzyme nitrate reductase is used to catalyze the reduction of nitrate to nitrite in a protocol requiring microliter volumes of field samples.
Nitrate reductase is commercially available in a stabilized form.
One advantage of the enzyme based nitrate assay is that the reduction of nitrate is easily driven to completion, resulting in a more reliable nitrate determination. Field Determination of Nitrate using Nitrate Reductase. Proceedings of the Symposium on Field Analytical Methods for Hazardous Wastes and Toxic Chemicals, Ed. The most commonly used nitrate test methods involve the reduction of nitrate to nitrite via a copper-cadmium reagent, followed by reaction of the nitrite with the Griess dye reagents. The resulting color is translated into a nitrate concentration by comparison with a calibrated color chart or comparator, or by reading the absorbance in a spectrophotometer.