The ashing procedure produces cellular oxidised -residues rich in Na 2 O, CaO, MgO, Fe 2 O 3, SiO 2, Ca(PO 4) 2, Mg(PO 4) 2, etc., which are detected by X-ray microanalysis with 2-4 times sensitivity gained after incineration of sample, due to increased mineral concentration and reduced nonspecific background radiation.