This Technical Specification specifies three methods of digestion for solid recovered fuels:
a) microwave assisted digestion with hydrofluoric, nitric and hydrochloric acid mixture;
b) hot water bath digestion with hydrofluoric, nitric and hydrochloric acid mixture, after ashing of the SRFs sample;
c) oven digestion with nitric, perchloric and hydrofluoric acid mixture.
Instrumental determination of As, Ba, Be, Cd, Cr, Co, Cu, Pb, Mn, Mo, Ni, Sb, Se, Tl, V, Zn is performed by Inductively Coupled Plasma with optical or mass detection or graphite furnace Atomic Absorption Spectrometry. Hg can be analysed only after the microwave assisted procedure or, alternatively, by a direct analysis method.
The effectiveness of the digestion can be verified by qualitative X-ray fluorescence (XRF) analysis on the remaining residue. If necessary an alternative digestion method (among those proposed) is used.
Method a) is recommended for general use, but the amount of the test portion can be very low in case of high concentration of organic matter.
Method b) is recommended for SRFs with high organic matter concentration that can be difficult to digest with the other methods. This method is not suitable for mercury.
Method c) is recommended for SRFs samples for which the other methods leave a significant insoluble residue.