4.5.2. Scanning Electron Microscopy Energy Dispersive X-ray Spectroscopy (SEM-EDX)

Investigation of a sample by SEM does not only produce images but may also provide specific information in respect of the chemical composition of a sample at specific locations in the sample. Energy-dispersive X-ray spectrometry (EDX) is based on the generation of X-rays following the interaction of an electron beam with the atoms in a sample. SEM-EDX has potential applications in NC and NCC use particularly in determining contamination that could arise from milling media. EDX has been successfully used for this application. EDX can also be used to surmise the overall presence of coating agents through determining the presence of coating agent-specific atoms or by observing an increase or reduction in atomic % of pure drug elemental components. EDX was specifically used for both of these applications for the determination of the presence of TPGS 1000 and SDS in NC prepared using the bottom-up method, and the presence of chromium and iron contamination from the steel media milling media during the top-down manufacture of lamivudine-zidovudine NCC [42,111].
