Metal Contaminants in Commercial Thiazine Dyes

Abstract
The iron, potassium, sodium and zinc contents of commercial samples of the thiazine dyes azure A (C.I. 52005), azure B (C.I. 52010), azure C (C.I. 52002), methylene blue (C.I. 52015), new methylene blue (GI. 52030), polychrome methylene blue, thionine (C.I. 52000) and toluidme blue (C.I. 52040) have been determined by atomic absorption spectrophotometry. The metal concentrations varied widely in the 38 samples examined—iron, potassium, sodium and zinc together comprised between 0.02% and 25.35% of individual samples.