Why Nitrogen can not be detected by EDX?

The absence of elements like nitrogen and hydrogen in energy-dispersive X-ray (EDX) spectra of polyaniline could be due to the limitations of the technique. EDX is primarily used to detect elements with relatively high atomic numbers, and elements like nitrogen and hydrogen have lower atomic numbers, making them more challenging to detect accurately using this method. Additionally, their low atomic masses might result in weaker X-ray emissions that are difficult to distinguish from background noise. Another reason, if nitrogen is low quantity and your edx is set for other high amount element then it no possible to detect nitrogen. Other analytical techniques, such as X-ray photoelectron spectroscopy (XPS), might be more suitable for detecting lighter elements like nitrogen and hydrogen in organic compounds like polyaniline.