If you want to use absorption spectroscopy, it depends on whether or not the heavy atom under investigation have significant absorption at the X-ray wavelength you have at home lab. If that is the case, you should be able to see the absorption and tell whether or not the heavy atom has been incorporated [1].
I think there are other spectrometry and chromatography ways of doing it too [2]. For more information you can check the following references: [1]. Ascone,I. and Strange,R. (2009) Biological X-ray absorption spectroscopy and metalloproteomics. J. Synchrotron Radiat., 16, 413-421. [2]. Garcia,J.S. et al. (2006) Trends in metal-binding and metalloprotein analysis. Talanta, 69, 1-15.
