Quantitative analysis of Fe-based samples using ultraviolet nanosecond and femtosecond laser ablation-ICP-MS

Abstract

The quantification capabilities of iron-based samples were investigated using three commercially available ultraviolet (UV) nanosecond (ns) and femtosecond (fs) laser ablation systems coupled to inductively coupled plasma mass spectrometry (LA-ICP-MS). A comparison of three pulsed laser ablation systems (ArF* excimer, Nd:YAG and Ti-sapphire) with different wavelengths and pulse time durations (15 ns, 4 ns and 150 fs, respectively) was performed. Minor and trace elements were determined using 57Fe as internal standard element. Using similar spatial resolution for all laser systems and commonly applied operating conditions for each system, higher ion-signals (25–30%) and more stable elemental ratios (10% TRSD) were obtained for UV-fs-LA-ICP-MS. Scanning electron microscope images and particle size distributions measured for UV-ns-LA systems showed a bimodal distribution formed by nano-sized agglomerates and micro-sized molten spherical particles. In contrast, due to reduced thermal effects achieved using ultra-short pulses, the particle size distribution measured using UV-fs-LA showed a broad monomodal distribution (nano-sized agglomerates in the range of 50–250 nm). Matrix-matched (within metallic samples) and non-matrix matched calibrations were applied for the analysis of Fe-based samples, using a silicate glass (SRM NIST 610) as non-matrix matched calibration sample (glass-metals). Improved analytical results in terms of precision and accuracy were obtained using femtosecond laser ablation when using similar matrices for calibration. Moreover, non-matrix matched calibration used for quantification provides more accurate results (5–15%) in comparison with both UV-ns-LA-ICP-MS (5–30% using Nd:YAG laser and 15–60% using ArF* laser).