Passive Sampling, Stable Isotopes: DGT MC-ICP-MS for Isotopic Analysis of Labile Solute Species in Environmental and Life Sciences

Stable isotope ratio analysis of labile (reactive and mobile) solute species by multi-collector (MC) ICP-MS is a cornerstone for tracing sources, pathways, and bioavailability of metals in environmental and biological systems. In practice, the key challenges often occur upstream of the instrument: analytes present at (ultra-)trace levels are susceptible to contamination, complex sample matrices complicate purification, and speciation changes during sampling and sample handling can bias the representativeness of labile-phase isotopic signatures.
This contribution presents the integration of passive sampling by diffusive gradients in thin films (DGT) with MC-ICP-MS as a practical strategy to address these limitations, highlighting recent developments in environmental and life science applications. First, a DGT MC-ICP-MS approach enabling simultaneous quantification of labile Sr and Pb concentrations and isotope ratios in natural waters is presented.1 Field deployment of the DGT passive samplers in the Mur River catchment (Austria) demonstrated up to 10-fold analyte preconcentration while separating critical matrix interferences (Ca and Rb) for 87Sr/86Sr analysis already during sampling, effectively eliminating the need for additional chemical processing prior to MC-ICP-MS. Extending this approach to terrestrial environments, DGT-based sampling accurately captured bioavailable Sr and Pb isotope signatures in soil-plant systems, supporting source tracing applications across environmental forensics and food authentication.2 Second, DGT MC-ICP-MS is translated to non-invasive diagnostics: skin patches based on selective DGT binding layers were designed and characterized to determine Cu isotope ratios in sweat directly on human skin. Results showed quantitative Cu uptake and recovery along with effective isolation from the Na-rich matrix, without causing significant 65Cu/63Cu fractionation. This may open new perspectives for early disease detection in personalized medicine.
Overall, these examples demonstrate how DGT can function as a robust sampling approach for MC-ICP-MS measurements, enabling representative, matrix-resilient, and high-throughput isotopic analysis of labile solute species. Practical considerations for method design and an outlook towards multi-element, multi-isotope analytical platforms for environmental monitoring and medical diagnostics based on DGT passive sampling will be discussed.
1 Wagner S, Santner J, Irrgeher J, Puschenreiter M, Happel S, Prohaska T. Anal. Chem. 2022, 10.1021/acs.analchem.2c00546
2 Wagner S, Santner J, Puschenreiter M, Irrgeher J, Prohaska T. Anal. Bioanal. Chem. 2026, 10.1007/s00216-026-06315-6