Microwave digestion for the quantification of inorganic elements in coal and coal ash using ICP-OES

► The use of HF can be offset by higher microwave power for coal and its HTA digestion. ► The use of HF is highly element-specific, as well as depends on sample property. ► The optimised amount for HF is 0.1 ml for real fly ash. ► The recovery of Al in fly ash cannot be achieved through microwave digestion.