Extraction of trace elements in coal for determination by inductively coupled plasma-optical emission spectrometry using N,N-dimethylformamide and ultrasound

Coal usage continues to increase due to global energy demands. Increasing environmental monitoring and concern means that better methods of trace element determination are always required. This study investigated the use of N,N-dimethylformamide (DMF), Triton X-100, HNO3 and ultrasound to extract trace elements (Cr, Mn, Pb, Sr and V) from coal prior to analysis using ICP-OES and ICP-MS. It was found that the proportion extracted was lowest for V (17%) and highest for Pb (100%). Partial dissolution of the coal particles used in the slurries was demonstrated using scanning electron microscopy studies. Trace element determination of two reference material coal samples demonstrated that this method of extraction is effective. Trace elements in three bituminous coals from different seams being mined in South Africa were determined.

► The use of ultrasound proved successful in creating a stable coal slurry. ► The solvent mixture was shown to partially dissolve the coal particles. ► Ultrasonification was an important factor in the slurry development. ► Complete determination of minor, trace and ultra-trace elements was possible.