A frozen-suspension external calibration strategy for quantitative imaging of Ce in fresh animal soft tissues by CLA-ICP-MS.

A simple and reliable external calibration strategy was developed for quantitative elemental imaging of fresh animal soft tissues using LA-ICP-MS coupled with a cryogenic ablation cell (CLA-ICP-MS). The suspension prepared with powder of certified reference material of animal tissue was frozen in the cryogenic cell and then used as the external standard. Compared to the traditional external standard preparation methods such as tabletting method, the proposed strategy has a controllable solid-liquid ratio, which not only ensures a high matrix matching with fresh animal tissue samples, but also shows a significant sensitizing effect (signal intensity increased by 1.3 times to 8.2 times). With simple and reliable process, the proposed method can ensure good dispersion and acceptable long-term stability of external standards for suspensions, which overcomes the shortcomings of gelatin standards easily deteriorated by moisture absorption. The method was validated with animal reference materials, yielding relative errors below 10% for most elements and limits of detection (LODs) ranging from 0.1 ng g-1 (Ba) to 1872 ng g-1 (K). Applied to imaging Ce distribution in mouse spleen after CeO2 NP exposure, the results was similar to the previous study, demonstrating the method's potential for investigating toxicological mechanisms of metal NPs.