Hej Angela,

if you want to analyze a water sample you can distinguish between Fe2+ and Fe3+ using the "phenatroline method" and measure the concentration at a photometer. Fe2+ is forming an orange colored complex. So you will analyze first the Fe2+ and to another aliquot of the same sample ascorbic acid must be added so that all remaining Fe3+ will be reduced, then you measure Fe2+ again and the difference to the first measurement is the Fe3+. It is important that you fix the water samples immediately with sulphuric acid and not with hydrochloric acid since the formation of iron(III)-chloro complexes favor the oxidation of Fe2+! The advantage of this method is the low detection limit for iron (0.01 mg/L). If you want to analyze a solid sample you should also use sulphuric acid and not hydrochloric acid for the extraction. I mean you can also do the extraction in a glove box but this might be rather cumbersome, the more so as extracts must be centrifuged and filtrated before of analysis. You can google the phenatroline method for details and will also find videos as good guidance.

Good luck,

Dominik

ICP-MS is  useful technique for the determination of Fe2 and Fe3 in same sample.

Mossbauer spectroscopy would help to determine this. Google the details or I can direct you to well-known researchers.

Please refer :

Igneous pathogenesis  A Global Tectonic approach, B.M.Wilson, Springer.

Michael is right. It totally depends on conc., matrix, etc.  XPS spectroscopy is also there with Mossbauer spectroscopy.

madam 

Angela Rincon Arias

please refer 

1. http://www.sciencedirect.com/science/article/pii/S0003267097003310

 One way is to measure total Fe by AAS, and Fe3+ with SCN-

There are quite many methods to do that. In all you need to determine the total amount of Fe i.e. using AAS and one ion directly. Depending on concentration Fe+2 is easily determined using REDOX titration for example with H2O2. There are also colorimetric methods for both or if you have the equipment ion chromatography

by  complexsation  of  one of  them Fe+2  then separation  it   from  other ion  Fe+3

you  can  complexation  with  8-hyroxy  quinoline

ICP-OES will only give total iron. You could just speculate based on the sample characteristics (oxic/anoxic, high pH/low pH, ...) if it is rather Fe2+ or Fe3+.

Please see discussion of question

"How do I measure both ferrous and ferric iron in water in a more accurate way?"

Here, several techniques are described. I prefer to use phenanthroline. It can be used to photometrically determine ferrous iron (Fe2+) and after addition of ascorbic acid it can be used to determine total iron (ferric iron will be reduced to ferrous iron by ascorbic acid). By this technique, both can be measured in one sample: take a subsample for ferrous iron, another subsample for total iron (add ascorbic acid here). The difference between both readings is ferric iron.

Hej Angela,

if you want to analyze a water sample you can distinguish between Fe2+ and Fe3+ using the "phenatroline method" and measure the concentration at a photometer. Fe2+ is forming an orange colored complex. So you will analyze first the Fe2+ and to another aliquot of the same sample ascorbic acid must be added so that all remaining Fe3+ will be reduced, then you measure Fe2+ again and the difference to the first measurement is the Fe3+. It is important that you fix the water samples immediately with sulphuric acid and not with hydrochloric acid since the formation of iron(III)-chloro complexes favor the oxidation of Fe2+! The advantage of this method is the low detection limit for iron (0.01 mg/L). If you want to analyze a solid sample you should also use sulphuric acid and not hydrochloric acid for the extraction. I mean you can also do the extraction in a glove box but this might be rather cumbersome, the more so as extracts must be centrifuged and filtrated before of analysis. You can google the phenatroline method for details and will also find videos as good guidance.

Good luck,

Dominik