It would not be very straight forward but I believe you can. Look into literatures about quantitative analysis by XPS. You will have to do some high resolution scans
I would suggest using Electron backscatter diffraction (EBSD). SEM analysis could also help up to some extent since TiB2 and TiB have different crystal structures and morphology. I think attached three articles would be helpful. Best,
Azmi Mert.
Article Spark plasma sintering of functionally graded material in th...
Article Preparation of Titanium Diboride TiB2 by Spark Plasma Sinter...
Article Low-temperature densification of TiB 2 ceramic by spark plas...