Hi! ChatGPT will answer such a question, I checked. But it is better to look for applications shared on the web by microwave manufacturers.

10 years ago on this portal there was already an exchange of opinions on this subject. And whether they are still current, you have to check for yourself.

https://www.researchgate.net/post/How_do_I_digest_crude_oil_samples_for_ICP-MS_analysis

Z.J.

For microwave digestion of crude oil to determine trace elements by ICP-MS, typically 1 to 8 mL of concentrated nitric acid (HNO3) and optionally 1 mL of hydrogen peroxide (H2O2) are used. The mixture is heated to around 240°C to 245°C for 15 to 25 minutes, then diluted for analysis.

ResearchGate search function found this from 2021. I'm sure there are plenty more out there. Article Determination of iron, nickel, and vanadium in crude oil by ...

There are also ICP manufacturer websites with application notes, and the microwave manufacturers too.

I recommend you to visit the following papers;

Article Microwave-induced combustion of crude oil for further rare e...

Article Microwave-assisted hydrogen peroxide digestion followed by I...

Article Multielement analysis of crude oil produced water by ICP OES...

They are well articulated, have a look they might be very useful