Near Infra Red femtosecond Laser Ablation: the influence of energy and pulse width on the LA-ICP-MS analysis of monazite

Abstract

We studied the influence of pulse energy (E₀) and pulse width (τ) of Near Infra Red femtosecond Laser Ablation coupled to Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). A particular emphasis was put on the ²⁰⁶Pb/²³⁸U and ²⁰⁸Pb/²³²Th 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 E₀ = 0.03 to 0.8 mJ/pulse (τ = 60 fs) while pulse width has been studied from τ = 60 fs to 300 fs (E₀ = 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 ²⁰⁶Pb/²³⁸U and ²⁰⁸Pb/²³²Th, 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 ²⁰⁶Pb/²³⁸U. In the range of E₀ = 0.1–0.8 mJ/pulse, matrix matched calibration using Manangotry monazite gives a similar good repeatability of 2.4%RSD for ²⁰⁶Pb/²³⁸U. No clear matrix effect could be highlighted.