Acid digestion of aromatic organic samples - ICP-MS analysis

[rodrigaoman]

Hello everyone!
I need to analyse the inorganic contend of organic sample.
My real case is: I have to identify/quantify metal trace in a very pure ethyl centralite (N,N-diethyl-diphenylurea) sample by ICP-MS.
The problem is that ethyl centralite is insoluble in water and I have tried nitric acid digestion, but it didn't work. It turned yellow and didn't solubilize. Organic solvents cannot be used to solubilze samples to inject in the ICP-MS. I have read that nitric acid digestion is not recommended for high aromatic samples, like mine.

What other type of acid digestion could I used in my sample in order to analyse trace metals by ICP-MS (nitric acid doesn't work).

Hope someone can help.

Best regards!

Rodrigo

[Don_Hilton]

You may want to get perchloric acid involved. In looking around I noticed http://www.inorganicventures.com/tech/t ... ic-samples which may give some ideas or at least a direction to start looking. And, note the safety precautions.

[krickos]

Hi

Seem to recall a variant of the nitric acid/perchloric acid variant. Basicly Sample is digested with sulphuric acid (conc.) and H2O2 is added dropwise to the slow boiling slurry to avoid potential foaming and fast reactions. After completion of reaction the majority of acid is carefully boiled off and residue is quantatively transfered with diluted acid to a suiteble vessle.

Again be careful.

[jerole]

Hi,

If you have a microwave for digestions you can use HNO3/H2O2 to digest organic matter, Perchloric acid should work too but you have to be careful.

Some ICP-MS have the option to introduce organic solvents directly with special kits. Depending on the instrument you can nebulize up to 100% methanol. If your compound is soluble in methanol maybe this is an option and you avoid sample contamination by the acids/H2O2.

[rodrigaoman]

Hi

Seem to recall a variant of the nitric acid/perchloric acid variant. Basicly Sample is digested with sulphuric acid (conc.) and H2O2 is added dropwise to the slow boiling slurry to avoid potential foaming and fast reactions. After completion of reaction the majority of acid is carefully boiled off and residue is quantatively transfered with diluted acid to a suiteble vessle.

Again be careful.

Thank you all for replying me.
What's the best way of working it out?

I add concentrated H2SO4 over 0,5 g of the sample, mix and then drop H2O2?
Or should I add H2O2 over 0,5 g of the sample first and then add H2SO4?

Should I heat?

What's the sequence? Time?
What's the best proportion betweent H2SO2 and H2O2?

You guys are amazing. Hope you answer me back and I'll it and put results here.

[oscarBAL]

Hi Rodrigo; peroxide digestion is quite good for a lot of compounds I do not how how it will work in terms of recovery with your sample but for this kind of digestion you can find alot of information form Hach company I used a dijestor from them very nice and cheap but you can't analyze may samples. please see the manual have a lot of usefull information.

As in any other digestion please be extracarefull!

http://www.hach.com/fmmimghach?/CODE%3A2313018568%7C1

Oscar.

[AICMM]

Rodrigo,

I am out of my league here (of all things good and gas chromatographic....) but have you considered combustion as a possibility? Either a Parr bomb or a microwave. If I recall correctly some Brazilians presented a seminar at Pittcon last year on just this type of application. I will see if I can find and post the a portion of the abstract(s.)

The other suggestion I would have, if you have access to a decent academic library, is to look up digestion and Los Alamos National Laboratory. They have done digestions on these types of materials before for ICP-MS analysis.

Best regards,

AICMM