High-speed mapping of Hg and Se in biological tissue via laser ablation-inductively coupled plasma-mass spectrometry†
While elemental mapping via LA-ICP-MS – i.e. mapping the distribution of elements across the surface of a solid material – has shown a substantial evolution towards higher speed, sensitivity and spatial resolution, some elements show a significantly longer single pulse response (SPR) duration due to their specific physicochemical properties. This work focuses on Hg and Se as such elements in biological tissue and systematically investigates the effects of the instrumental setup, such as the type of ablation cell, mixing bulb and transfer line, on the shape and duration of the SPR profiles. By optimizing the instrumental setup, SPRs with a full peak width at 10% of the maximum peak height (FW0.1M) of 50 ± 2 and 61 ± 4 ms were obtained for 202Hg+ and 77Se+, respectively, when using a laser beam of 20 μm diameter. This constitutes a >5-fold improvement in SPR duration compared to a standard setup, but these SPR durations are still considerably longer than those obtained for, e.g., 65Cu+ (7 ± 1 ms). When selecting the instrument settings and data acquisition conditions for elemental mapping of Hg and/or Se based on the SPR profiles obtained for, e.g., 65Cu+, the pixel acquisition rate attainable was overestimated for 202Hg+ and 77Se+ and significant aerosol carryover or pixel crosstalk occurs, thus leading to smearing effects in the elemental maps. With the optimum setup and adequate selection of all settings, multi-elemental mapping of Hg and Se was performed for a mushroom tissue section, demonstrating a significant improvement in pixel acquisition rate (up to 20 pixels per s).