A frozen suspension external calibration strategy for elemental quantitative imaging of fresh plant soft tissues by LA-ICP-MS with cryogenic ablation cell

A simple and reliable external calibration strategy of LA-ICP-MS for fresh plant soft tissues was developed. The prepared plant suspension was frozen by the designed cryogenic ablation cell and used as external standard for quantitative elemental imaging analysis of fresh plant tissues. The controllable water content of the prepared external standards provides a similar matrix with fresh soft tissues, and a homogeneous elemental distribution could be ensured due to the fine grinding particle sizes. More interestingly, the presence of water increased the signal intensity produced by the suspension by a factor of 1.6 (Pb) to 66.6 (La) compared to that of the pressed cake. The excellent dispersing property and advantage of long-term use were achieved owing to the employment of 0.1% PAANa as suspending agent. A series of plant reference materials were analyzed, and the relative errors of most elements were less than 10 %, indicating that there is a reliable accuracy of the proposed method. The limits of detection (LODs) ranged from 0.1 ng·g⁻¹ (La) to 1279 ng·g⁻¹ (S). This method was used for elemental imaging analysis in rice leaves under arsenic stress, and the results were consistent with previous studies, which mean that the proposed method could provide technical support for researchers in the fields of agriculture and environment.