Solvent extraction and photometric determination of nitrite with some aromatic ortho diamines

Abstract

Nitrite reacts with diamines and gives sensitive color reactions with certain aromatic ortho diamines. With nitrite in an acidic medium, both 3,3′-diaminobenzidine and 3,4-toluenediamine give yellow colored solutions, while 4,5-diamino-o-xylene gives a green colored solution. The molar absorptivity is approximately 3500 for 3,3′-diaminobenzidine, 2900 for 3,4-toluenediamine, and 1050 for 4,5-diamino-o-xylene. The reactions are not very sensitive; however, the reaction products can be extracted by some organic solvents such asn-butyl oriso-amyl alcohol. No analytical method for determining nitrite based on solvent extraction is known. The factors affecting the color development have been studied. Nitrite reacts with diamines at a 1 to 1 ratio. Most common ions do not interfere, but oxidizing substances must be absent. Tartrate and EDTA may be present as masking agents. Nitrate may be determined after its reduction with a metal such as magnesium. The rate of reduction has been studied with the help of a nitrate ion electrode. Nitrite can also be titrated photometrically using 3,3′-diaminobenzidine as a titrant.