Low-Consumption and High-Efficiency Isotope Analysis by Microultrasonic Single-Droplet Nebulization Sampling Multicollector Inductively Coupled Plasma Mass Spectrometry

Metal stable isotopes are increasingly applied in various fields, including planetary science and medical research, highlighting the need for isotope analysis methods capable of handling precious and microvolume samples. This study introduces a novel, low-consumption, high-efficiency isotope analysis method using MC-ICP-MS based on microultrasonic single-droplet nebulization (MUSDN). The proposed MUSDN enables the complete nebulization of microliter-sized droplets, delivering high-sensitivity transient analytical signals with a duration of several seconds. Under optimized conditions, MUSDN exhibited significantly enhanced sensitivity compared to conventional pneumatic nebulization, achieving 17-fold and 12-fold improvements for ⁷Li and ⁶³Cu, respectively. The achieved external precisions (2SD) for δ⁷Li and δ⁶⁵Cu were 0.3 and 0.08‰, with single analysis consuming only 1 ng of Li and 2 ng of Cu, respectively. This represents a reduction in sample consumption by 1-2 orders of magnitude compared to conventional PN-MC-ICP-MS while also improving the analysis speed by at least 10-fold due to rapid residual washout. Furthermore, our method demonstrated superior δ⁶⁵Cu analytical precision compared to other high-sensitivity transient analysis methods (0.19‰ with a laser ablation system) with similar sample consumption. Finally, the accuracy of the proposed method was validated through the analysis of geological CRMs, serum CRMs, in-house standard samples, and a series of real serum samples. This novel isotope analysis method provides a promising approach for isotope applications involving precious and microvolume samples.