Ultrafast Laser Ablation Processes Allow for Simple Two-Point Calibration Methods to Determine Low-Levels of Boron and Phosphorous in Metallic Alloys

The ablation phenomenon resulting from laser/material interactions with ultra-short pulse lasers (USPL) opens new avenues for elemental analyses with laser ablation mass spectrometry (LA-MS). LA-MS is commonly performed with nanosecond lasers, but thermal effects lead to unwanted fractionation – when more volatile elemental constituents ablate at faster rates than others. This can negatively impact quantification without using carefully selected calibration material. Calibration materials with similar stoichiometry to the sample in question are usually needed (matrix-matched), which are often sparse or non-existent in new and less common materials. Fractionation is substantially mitigated with USPL ablation due to ultrafast electronic ablation, and non-matrix matched (NMM) standards can be utilized for accurate calibration in LA-MS. Using LA-MS with USPL (femtosecond) ablation, trace levels of B and P in three separate NMM reference alloys are examined in-situ. These materials contain levels of B and P with certified values spanning a small range. The small range of three values for both B and P, allow for a low and high calibration point close to the respective middle point for increased accuracy. The experimentally determined middle point value from two-point calibration is compared to the certified value of the respective reference material. The results demonstrate this method is indeed accurate and repeatable for trace-level quantification of B and P in these alloys. Furthermore, this work showcases how the expansion of available reference materials with NMM material, because of USPL ablation processes, allows for more simplistic chemical analysis methods with higher accuracy.