Dear Manpreet Kaur .

the determination is very simple, please check the publication:

Article Voltammetric Determination of Ni and Co in Water Samples

The described method is for Ni and Co in solution, as a ferrite the digestion would be easily achieved in acidic medium.

Best regards,

WNM

@Wagner Da Nova Mussel

Thank you so much sir for your kind response.

I would like to mention that the method you added is applicable to the solution of Ni and Co. But I have powder sample of NiCo2O4 which is insoluble in water.

Manpreet Kaur

you can characterize your sample with x-ray photoelectron spectroscopy (XPS). I hope this answer will help you. Best luck with your research !!

Dear Manpreet Kaur ,

it is fully applicable to your sample after digestion, as I mention.

In fact it would be one of the most precise, remember you may have variable oxidation states in both metals, Ni and Co. That is why the voltammetric method is the most applicable under such circumstances.

You may do it by X-ray fluorescence, however, you will have no idea of multiple oxidation state in you particular sample.

It is a spinel structure and several cation distribution would be possible, directly influencing the physical-chemistry characteristics, only explicable by the real cation distribution, even the possibility to have some degree of invertion.

good luck

WNM

EDS and XPS are best..

You can do EDAX first and then confirm the phase by XRD technique. This is very trivial.

@dharmadoss Sornadurai

I did the same. But the committee was not satisfied. They kept asking me how did you find that NiCo2O4 is formed.

Manpreet, I think you need to confirm the exact phase formation of NiCo2O4 (ant not other similar phases like NiCo3O5 etc.) in your material, which is a valid question. So, the exact phase match can be determined using Rietveld refinement of XRD pattern of your material.

If you like, you can send me your XRD data in .xrdml/ raw file format. Also, tell me once, which elements/phases are u expecting and other related info, if u have. I can do it..

I think EDS analysis is sufficient for that .You can also tryXPS,AAS ,ICP-MS/OES.

Dear Manpreet Kaur ,

I would not rely on EDS, EDX or EDAX or whatever abbreviations are used.

The reason is that the O-K-alpha has an photon energy of about 525eV.

This means that the escape depth and thus the information depth of the O K-radiation in the presence of Ni and Co is quite small; only about a very few atomic layers.

The situation for the Ni and Co L-radiation is a bit better, but not ideal as well.

So you are quite surface sensitive and thus you will get informations about the surface and surface near stoichiometry of your sample. Any contamination of your sample surface by adsorption of O containing molecules ( e.g. by O2 itself or water) will give errors in the O concentration estimation relative to Ni and Co.

At least a cleaning of the sample surface is necessary; e.g. by sputtering and heating.

Another one accurate technique is Electron Probe Micro Analysis (EPMA).

Dear Dharmadoss Sornadurai ,

in the EPMA a wave lengths dispersive (WDS) or energy dispersive (EDS) spectroscopic technique is used, by which the sample is excited by electrons. The response of the sample is x-ray fluorescence. Thus here the escape depth/ information depth issues, mentioned above, remain the same, especially for low Z elements such as oxygen...

In the EPMA the characteristic X-ray peaks are obtained from the sample and from the amplitudes of the characteristic peaks are used for elemental analysis. Hereafter, there are no comments.

What about standard analytical chemistry, first sample dissolution (or digestion) and then determination of the metals by classical methods (gravimetry, electrochemistry, titration and so on) or atomic spectroscopy (AAS, OES)? This will provide reliable information on the bulk material, something that all the complidated methods using expensive instrumentation are unable to do--they only tell you something about the surface.