In my view they are both suitable but expensive!

Why not do the classical C,H,N,S,O elemental analysis?

Thanks for your suggestion. Please how do I analyse C,H,N,S,O

C,H,N,S,O is usually done in so-called "C,H,N-analysers". The bulk material is burned (combustion and pyrolysis) and the resulting gases, such as CO2, H2O, NO2, SO2 are collected and quantitatively analysed. Any commercial analytical lab is offering such measurements, see e.g. Pascher Lab in Remagen, Germany (brochure attached). Of course, these labs offer also more sophisticated methods.

https://www.ncbi.nlm.nih.gov/pubmed/15274755