Spectrophotometric Determination of Trace Iron after Collection and Elution as Its 8-Hydroxyquinoline-5-sulfonate Chelate on Protonated Chitin

A collection and elution method for anionic metal chelate on protonated chitin has been applied to the spectrophotometric determination of iron. Iron is collected as its anionic 8-hydroxyquinoline-5-sulfonate (8-HQ-5-S) chelate on a column of chitin in weak acidic medium. The iron(III)-8-HQ-5-S chelate collected on the chitin is effectively eluted with a small volume of 0.1mol dm-3 ammonia buffer solution (pH 9), and the absorbance of the eluent is measured at 571nm. Beer′s law is obeyed over the concentration range of 0.5 to 5μg of iron in 1cm3 of the eluent. Some metal ions and common inorganic anions do not interfere in concentration range of 100 to 1000 times that of iron, but the tolerance limit for Co, Ni and Cu is low due to the competitive reaction with 8-HQ-5-S. The present method can be applied to the determination of iron in tap and spring water samples.