Determination of iron in chinese herbal medicine based on the fluorescence quenching of rhodamine 6G

A fluorescence quenching method was developed for determination of Fe3+ with rhodamine 6G as fluorescent reagent. Fe3+ reacting with KI in diluted sulfuric acid produced I3- anion which reacted subsequently with rhodamine 6G to form a non-fluorescence compound. As a result, the compound quenched the fluorescence intensity of the system. The fluorescence intensity decreased linearly with the Fe3+ concentration in the range from 20 to 200 μg/L. The detection limit was 8.3 μg/L. This method has been applied to determine the iron in Chinese herbal medicine with satisfactory results.