A novel external calibration strategy using hollow short-tube hydroxyapatite ceramics for elemental quantitative imaging of human teeth by LA-ICP-MS.

Teeth provide retrospective information regarding health status, dietary habits, age, and environmental exposures. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) enables direct solid analysis with high spatial resolution, rendering it well-suited for the microanalysis of teeth. However, accurate quantification is often hampered by the lack of matrix-matched calibration standards. In this work, an external calibration strategy based on hollow short-tube hydroxyapatite ceramics (HAP-T) was established. Due to the one-dimensional tubular architecture, the sintered HAP-T ceramic exhibits high density and mechanical robustness, and its laser ablation behavior was similar to that of tooth samples. The doped trace elements were homogeneously distributed in HAP-T, with relative standard deviations (RSDs) of line scan signals in the range of 7.17-11.07%. The concentrations of doped elements in two synthetic ceramic calibration standards (HAP-T-1 and HAP-T-2) were determined via LA-ICP-MS and pneumatic nebulization ICP-MS (PN-ICP-MS), and excellent consistency was observed between the two analytical techniques. The proposed method was successfully applied to the quantitative elemental imaging of Ca, Mg, Zn, Sr, and Pb in human deciduous tooth sections, achieving high spatial resolution that allows clear visualization of elemental distributions of fine tissue structures including the neonatal line and enamel-dentine junction. These results demonstrate that HAP-T exhibits excellent matrix matching with tooth samples in terms of both chemical composition and laser ablation behavior. This calibration strategy is thus highly promising for the accurate quantitative analysis and elemental imaging of teeth, bones, and potentially other phosphate-based biominerals.