Can Laser-Ionisation Time-of-Flight Mass Spectrometry Be a Promising Alternative to Laser Ablation/Inductively-Coupled Plasma Mass Spectrometry and Glow Discharge Mass Spectrometry for the Elemental Analysis of Solids?

At the beginning of the age of laser-ionisation mass spectrometry (LIMS) increasing numbers of publications were observed. However, later the method began to run into obstacles associated with poor reproducibility of analysis and large variations in elemental sensitivities so that the wide interest of the scientific community in the method faded away. However, the results described here show that the current knowledge of laser plasma processes, together with modern technical solutions to ion separation and quantification with time-of-flight (ToF) mass spectrometry, allow one to overcome the above-mentioned obstacles in LIMS. Thus, the performance in direct-sampling solid analysis demonstrated by the LAMAS-10M instrument is similar to that typically obtained by laser ablation/inductively-coupled plasma mass spectrometry (LA-ICP-MS) and glow-discharge mass spectrometry (GD-MS) methods. At the same time, there are additional advantages, including compactness of the instrument, absence of the need for expensive consumables and freedom from mass line interferences. Direct-sampling elemental LIMS is discussed as a promising alternative to LA-ICP-MS and GD-MS. Existing and prospective approaches to designing direct-sampling laser-ionisation mass spectrometers are theoretically justified. Factors affecting the main performance criteria, such as reproducibility, correctness, variations of relative sensitivity factors, linear dynamic range and resolution are considered. The demonstrated reproducibility, resolution, low-ppb limit of detection and one order-of-magnitude variation in elemental sensitivity are not the limit for direct-sampling laser-ionisation mass spectrometry of solid samples. Ways of improving LI-ToF-MS instrumental performance are discussed and theoretically justified.