Oxidation of Amino Acids and Aminocarboxylic Acids to Nitrate with Peroxodisulfate

Abstract

As a prior oxidation procedure for the determination of total nitrogen in water based on an electrolytic reduction of nitrate to ammonia, the oxidation of 11 amino acids and 5 aminocarboxylic acids to nitrate with peroxodisulfate was studied spectrophotometrically. With 2 g of potassium peroxodisulfate and 0.8 g of sodium hydroxide, a 15 mL sample solution was heated to 200°C for 1 hour to oxidize these organic nitrogen compounds to nitrate, and to decompose any excess peroxodisulfate to sulfate. By the proposed method, except for histidine and CyDTA, individual amino acids and aminocarboxylic acids containing up to 3.2 mg of nitrogen (3.2 mgN/15 mL) were successfully oxidized to nitrate. Mixtures involving CyDTA or an amino acid having complicated structure were also found to be successfully oxidized to nitrate between 0.42 mgN/15 mL and 2.8 mgN/15 mL. These results suggest that the proposed method can be combined with the electrolytic reduction of nitrate to ammonia to establish an analytical system for the determination of total nitrogen in water.