Semiautomated fluorometric analysis of riboflavin in nutrient premixes containing reduced iron

A simple, rapid, and reproducible semiautomated method is described for routine analysis of riboflavin in premixes containing high levels of reduced iron. Reduced iron is separated from premixes by a magnet before digestion with sulfuric acid solution. The presence of ferrous sulfate, ferric pyrophosphate, and sodium ferric pyrophosphate in premixes did not affect the analytical results for riboflavin. Pretreating sample extracts with potassium permanganate and hydrogen peroxide gave variable results for riboflavin. Possible causes and mechanisms of iron interferences in fluorometric riboflavin analysis are briefly discussed. The procedure developed is capable of analyzing 40 samples/hr.