Molecular masses up to 270 000 u in coal and coal-derived products by matrix assisted laser desorption ionization mass spectrometry (MALDI-m.s.)

Abstract

This paper describes the application of matrix assisted laser desorption ionization (MALDI) to coals and coal-derived materials using sinapinic acid as the matrix. The mass range of molecules in coal and coal-derived materials has been extended by a factor 100 compared with prelaser desorption mass spectrometric measurements. A peak of intensity is observed for coals and coal-derived materials in the mass range 1000–5000 u which is sample dependent. The upper mass ranges of the spectra vary according to sample, ranging from over 260 000 u for Point of Ayr coal and 200 000 u for a coal tar pitch, to 20 000 u for a maceral concentrate liquefaction extract. These results confirm earlier results using laser desorption mass spectrometry and are in broad qualitative agreement with size exclusion chromatography results. Detailed quantitative agreement, however, requires further work. The implications of this work for the debate on coal structure and models of coal conversion are considerable.