Droplet-based laser ablation ICP-MS for direct elemental screening of oils with minimal sample preparation

A droplet-based laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) method was developed for the direct multi-elemental analysis of oils using minimal sample preparation. Small sample volumes (0.2-10 μL) were deposited onto a flat substrate and analysed directly. The influence of key laser ablation parameters, including fluence, repetition rate, number of laser shots, and droplet volume, was systematically investigated. Under optimized conditions, limits of quantification were in the low μg/g range for most elements, and repeatability typically remained below 8-10 % when internal standardization (In) was applied. The internal standard significantly reduced matrix-related signal variability. Accuracy was assessed using spiked samples, yielding recoveries within 90-110%, and by comparison with conventional ICP-MS after microwave digestion, showing good agreement between both approaches. The method was applied to the elemental screening of 20 commercial oil samples. Although not intended for ultra-trace quantification, the proposed approach provides a rapid, low-consumption, and operationally simple alternative for routine multi-element screening of complex oil matrices.