A 3D-printed portable thermometric platform for on-site determination of hexavalent chromium in environmental waters

Rapid monitoring of hexavalent chromium (Cr(VI)) is essential for environmental safety and public health, yet conventional analytical techniques are laboratory-based and unsuitable for on-site analysis. This study presents a 3D-printed portable thermometric platform that integrates in situ sample pretreatment for the quantitative determination of Cr(VI) in water samples. The detection relies on a thermometric assay in which Cr(VI) modulates the synthesis of catalytic platinum nanoparticles (Pt NPs). Specifically, Cr(VI) inhibits the generation of Pt NPs by consuming ascorbic acid (AA), thereby diminishing the exothermic heat released from the catalytic decomposition of H₂O₂. This temperature variation is transduced into a quantifiable analytical signal by the portable device, enabling rapid analysis without the need for complex instrumentation. The developed platform demonstrated excellent analytical performance, achieving a low limit of detection (LOD) of 0.27 μM, well below the maximum allowable limit (0.96 μM) specified in China's surface water standards, along with high reproducibility. The practical reliability of the platform was confirmed by on-site analysis of water samples collected from nine monitoring sites at Qinglong Lake, which demonstrated satisfactory recovery rates. The proposed platform enables straightforward and cost-effective on-site detection of Cr(VI), thereby facilitating rapid environmental surveillance and regulatory compliance monitoring.