Laser-induced breakdown spectroscopy (LIBS) is an atomic emission spectroscopy technique that uses a highly energetic, short laser pulse to create a micro-plasma on the sample surface. By analyzing the plasma light emitted from atoms and ions in excited states, LIBS provides both qualitative and quantitative information. In addition to acquiring elemental information from atoms and ions, some recent strategies have focused on monitoring diatomic molecules. This enables access to isotopic information from the emission spectrum of diatomic molecules, a technique known as laser ablation molecular isotopic spectrometry (LAMIS).

This work introduces a novel gas-phase approach for inducing the formation of calcium monofluoride (CaF) diatomic molecules using a methyl fluoride-argon gas mixture in LIBS and LAMIS. By optimizing the instrumental parameters being 0.6 L min -1 of gas flow, 0.25 µs gate delay and fluency of 0.27 J cm -2. CaF molecule formation was successfully achieved within the plasma plume following the ablation of dried liquid samples. The isotopic shift for the X2A2 (0,1) CaF vibronic transition at 583.0 nm was determined to be 292.3 pm. An appropriate selection of the calibration strategy enabled accurate quantification of Ca in real samples, such as tap water and skimmed milk, using external calibration and isotope dilution, respectively. The results were consistent at a 95% confidence level with those obtained via flame atomic absorption spectrometry (FAAS). Partial least squares regression (PLS) analysis was used to improve the accuracy of the isotopic information. This novel approach allows for the determination of Ca in terms of both elemental concentration and isotopic composition, thus broadening the applicability of this technique.