Near infra red femtosecond laser ablation : the influence of energy and pulse width on the LA-ICP-MS analysis of monazite

We studied the influence of pulse energy (E-0) and pulse width (tau) of Near Infra Red femtosecond Laser Ablation coupled to Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). A particular emphasis was put on the Pb-206/U-238 and Pb-208/Th-232 repeatability from Moacyr monazite (Itambe, Brazil). Synthetic glass (Standard Reference Material) NIST610 was used as a reference material, as well as a monazite from Manangotry (Madagascar). Pulse energy was investigated in the range E-0 = 0.03 to 0.8 mJ/pulse (tau = 60 fs) while pulse width has been studied from tau = 60 fs to 300 fs (E-0 = 0.1 mJ/pulse). Data suggest that pulse width has no detectable influence on the accuracy and repeatability of measured elemental ratios in the range of 60-300 fs. Observed measurements repeatabilities are 2.5%RSD and 1.8%RSD for Pb-206/U-238 and Pb-208/Th-232, respectively. At 60 fs, the 0.03-0.8 mJ/pulse energy range studied does not induce any detectable change in data accuracy and repeatability. Uncertainties of 1.1-2.8% RSD were obtained for Pb-206/U-238. In the range of E-0 0.1-0.8 mJ/pulse, matrix matched calibration using Manangotry monazite gives a similar good repeatability of 2.4% RSD for Pb-206/U-238. No clear matrix effect could be highlighted