Determination of Ag, Cu, Mo and Pb in soils and ores by laser-induced breakdown spectrometry

We report the results of an analytical assessment of the determination of Ag, Cu, Pb and Mo by laser-induced breakdown spectrometry in certified and natural soils and ores for the purposes of geochemical exploration. Strong matrix effects were observed in the determination of Mo in soils and ores. The intensity of two Mo lines (313.26 and 550.65 nm) in ore samples was three to five times larger than in soil samples. We corrected such sample-to-sample variations by the selection of internal standards. There was no evidence of strong matrix effects for the other elements. As is typical in atomic emission spectrometry, the linear dynamic range of determination by laser-induced breakdown spectrometry was narrow (1-100 ppm) for the resonance lines as a result of self-absorption. The detection limits of Ag, Mo, Cu and Pb were 0.3, 0.3, 0.6 and 8 ppm, respectively. Such sensitivity is sufficient to determine Mo, Cu and Pb at the level of their crustal abundance.