Determination of the contents of iron (II), iron (III) and iron complexes in gelatin

Abstract

The determination of the content of iron (II), iron (III) and their complexes in gelatin was investigated by spectrophotometry using 2-nitroso-5-[N-n-propyl-N-(3-sulphopropyl)-amino] phenol (nitroso-PSAP) as a colour reagent. Iron (II) and iron (III) reacted with nitroso-PSAP immediately, and part of their complexes reacted slowly with nitroso-PSAP. Stable complexes such as ethylenediaminetetraacetic acid-iron (EDTA-Fe) did not react with nitroso-PSAP. In alkaline gelatins, iron was mainly in the state of iron (III). The content of unstable iron complexes, the origin of which is the iron combined with protein, was higher in acid bone gelatins than in alkaline bone gelatins. Gelatin has a specific quasi-equilibrium state for iron ion, depending on the properties of the gelatin itself.

Keywords:

• gelatin
• iron (II)
• iron (III)
• unstable iron complexes
• spectrophotometry
• 2-nitroso-5-[N-n-propyl-N-(3-sulphopropyl)amino]phenol