A COMPARISON OF SOME PYRIDYL-SUBSTITUTED PYRAZINES AS ANALYTICAL REAGENTS

A comparative study of six 2-pyridyl and 2-(6-methyl-pyridyl) derivatives of pyrazine as chromogenic reagents of the ferroin and cuproin types has established 2,3,5,6-tetrakis(2'-pyridyl)pyrazine as a highly sensitive reagent for iron(II); 2,3-bis(2'-pyridyl)-5,6-dihydropyrazine and 2,3-bis[2'-(6'-methyl pyridyl)]-5,6-dihydropyazine both show high sensitivity and characteristic high selectivity in their reactions with iron(II) and copper(I) respectively-the reaction with copper(I) being almost as sensitive as that given by bathocuproine. The ease with which the highly coloured metal chelates can be extracted into immiscible solvents to give stable solutions makes these reagents useful for the determination of traces of iron and copper. © 1969.