A New Photometric Method for the Determination of Iron

In the study of many types of biological material it has become of increasing importance to determine accurately extremely small amounts of iron. Since color reactions are, as a rule, very sensitive, calorimetric procedures are particularly useful in the microanalytical field, and several calorimetric methods have appeared in the literature on iron determination. Although the extremely sensitive thiocyanate reaction is widely used for quantitative purposes, and has been the basis for much of our knowledge of iron concentration in biological material, the difficulties of the thiocyanate method have all combined to make investigators welcome the proposal of other processes, and pyrocatechol (l), pyramidon (2), thioglycolic acid (3), dimethylglyoxime (4), the HzFeCh complex (5), a,cr’-bipyridine (6), S-hydroxyquinoline (7), o-phenanthroline (8), ferron (9), etc., have successively been proposed for chromogenic agents, and applied to the quantitative determination of iron. Lutz (10) has shown that acid solutions of ferric ions give a blue-green color with protocatechuic acid, and that ferrous ions give no color under the same conditions. The blue-green color formed by the interaction of ferric ion and protocatechuic acid changes to red in solutions made alkaline, and alkaline solutions of ferrous ions give a red color with the reagent, as does ferric ion under similar conditions. The extreme sensitivity of this color reaction induced the present author to adapt it into a workable and reliable procedure which has been found to be a simple, rapid, and accurate met.hod for t.he determinat,ion of iron in biological materials.