Strategies for the analysis of coal by laser ablation inductively coupled plasma mass spectroscopy

The potential of laser ablation inductively coupled mass spectrometry (LA-ICP-MS) was investigated for the inorganic characterization of different coal samples pressed into pellets. Reference analysis was performed by microwave-assisted digestion of the ground samples followed by ICP-MS analysis of the resulting solutions. Two different laser ablation sampling procedures were compared. For continuous sampling, three sites of the pellet were sampled for approximately one minute, whereas for sequential sampling 15 sites were sampled for two seconds, respectively. The qualitative results of the two procedures were equivalent, but continuous sampling allowed faster analysis and better precision (RSD about 10%) than sequential sampling (RSD 10-20%). Different normalization procedures with internal and extrinsic standards were investigated and allowed a quantitative determination of Al, Ti, Zn, Ni, and V with measurement uncertainties below 10% and Fe, Si, and Sn with measurement uncertainties below 20%.