Reduction of Nitrate to Nitrite by Using Zinc Powder for Determination of Total Nitrogen in Sea Water

The reduction of nitrate to nitrite by using a filter disk (pore size 0.45 mu m; phi 25 mm) loaded with 0.5 g of zinc powder was investigated. When a 20 mL of sample, to which 0.1 g of ammonitim sulfate and 0.2 mL of 1 g/L EDTA solution were added, was filtrated with filter disk at 15 mL/min, nitrate was reduced to nitrite with ca. 93% efficiency. Nitrite in the filtrate was determined by naphthylethylenediamine spectrometry. The precision of repeated tests (n = 10) was ca.1 % on the nitrate standard solution (0.15 mu gN/mL). Good results were obtained in recovery tests using sea water treated with potassium peroxydisulfate.