I am a Metallurgical Engineer for a truck manufacturer.  I am developing methods to accurately measure composition of compact graphite iron (CGI) parts as received from the foundry that supplies the parts.  I am interested in accurately measuring Mg content in CGI cast iron.  The European divsion of my  company uses XRF to measure the composition of CGI but the Mg content is not included in these measurements.  I have been told that it is not possible to measure Mg in CGI using XRF due to the inhomogenity of the material.  What other methods can be used? It has been suggested to remelt a sample of CGI and cool it in such a way as to ensure it is homogeneous however this method will burn off the Mg in the sample which defeats the purpose of what I want to measure.  How do other foundries measure Mg?  Do they measure Mg in the final cast product or before casting?

Does anyone have any suggestions?

Thank you in advance.