Flow injection voltammetric determination of nitrate after reduction to nitrite

Abstract

Nitrate can be determined conveniently by chemical reduction to nitrite, which is then injected directly into an acidic bromide eluent in a flow injection system and monitored using its reduction signal at a glassy carbon electrode held at + 0.3 V versus a saturated calomel electrode. Chemical reduction was best carried out on a batch basis but partial success was experienced in using a method in which a nitrate sample solution was passed continuously through a cadmium sponge column and then through the injection loop of the flow injection valve from which aliquots were injected into the flow injection system. Determinations were also made by injection of nitrate sample solution directly into an acidic bromide eluent and reducing the nitrate on-line with cadmium wire.