It is a very insignificant difference. Even 'Atomic absorption' cannot tell any significant difference in oxidation states where the electrons move.

Thus, chemists reduce ferric ions to ferrous ions with Hydroxylamine and react the resulting complex with Orthophenanthroline to get a red color.

If you are going to see ANY difference in the UV try 1st or 2nd order derivative analysis.

UV spectrometer measures the absorbance of light by the double bond in the molecule. The more the double bond, the more the absorbance intensity, and the longer absorption wavelength. These two species has no double bond to distinguish between the two, so you would expect to see no difference in the spectra. A quick search on the internet, which everyone should do before even asking anything in this web board, I found a discussion about this before. see attachment.

generally the solution of Fe2+ is light green while the one of Fe3+ is light yellow, so I think the difference of the spectra in the region 200-700 nm should appear in the visible region (400-700 nm).

Actually i am working on iron oxidizing bacteria. I want to analyse the iron oxidizing activity. how can i show this activity in different incubation time. there are differnt selective media for these bacteria. i have selected winogradsky media. but i am unable to analyse the iron oxidizing activity. plssss guide me.

From my point, I propose that you determine the conc. of Fe3+ at varied incubation time by using the UV-Vis spectrometry at a specific wavelength (this maxium value should be optimized in advance ). Before determining the real sample, the calibration curve should also be established. Alternatively, you can also determine the conc. of Fe 3+ by using ICP-OES or ion chromtography.

can any one provide me this paper 'Fouling of carbon steel heat exchanger caused by iron bacteria' January 1999Materials performance 38(1):55-62