Hello, I am studying about Arsenic and doing experiment to analysis Arsenic in soil by ICP-MS machine. But i don't know how to prepare samples before use that machine. I had read a lot of papers but one has another method and the others has different methods (especially radio of acid we should add). Please help me to know why they have a different standard? Thank you so much

Do you have a supervisor who can answer that question? It is probably going to be best to go with the standard method that your lab currently uses so as to get a consistent comparison with the rest of the results that have come out of your lab. Has anyone else in your group used that machine before? maybe you could ask them which method they used and why and then replicate that for consistency.

Surely that sort of specialised and rather expensive equipment has a designated person to run or oversee it? They should be able to help you.

It seems theres a standard way of sample preparation that I found in the Thermo-Fisher site:

https://www.thermofisher.com/uk/en/home/industrial/spectroscopy-elemental-isotope-analysis/spectroscopy-elemental-isotope-analysis-learning-center/trace-elemental-analysis-tea-information/inductively-coupled-plasma-mass-spectrometry-icp-ms-information/icp-ms-sample-preparation.html