Spectrophotometric Determination of Iron I. Use of Mercaptoacetic Acid by Ruth

It is the purpose of the research reported in the present series of papers to establish accurate spectrophotometric procedures for the determination of iron, more particularly for use in biochemical and nutrition studies, but applicable generally to the analysis of biological materials, foods, pharmaceuticals, and chemical reagents. Several calorimetric methods for the determination of iron are available, but they lack the rapidity and precision of spectrophotometric methods. Calorimetric procedures are not directly applicable to spectrophotometric work, and are apt under spectrophotometric study to show serious flaws and limitations. In fact, the interferences commonly met in analyses of foods and biological materials make it doubtful whether an investigator desiring accurate results in iron determinations should be satisfied until checks are obtained by at least two different methods. For this reason the present research was designed to adapt for spectrophotometric use a number of the best calorimetric methods for iron, to obtain accurate calibration data over a wide range of iron concentrations, and to establish the validity of these data for determining iron in solutions containing common acids in concentrations that occur in analytical solutions prepared by various wet and dry methods of ashing. This information could be used in testing methods for ashing samples, in studying the effect of interfering substances other than the acids introduced in preparing the analytical solutions, and in devising rapid and accurate methods for determining total iron in foods and biological materials. It also seemed that such work as that outlined was a prerequisite to any successful attack on the problem of developing