A foldable and paper-based microfluidic device integrated with LIBS and colorimetric for accurate heavy metals detection

Sensing of heavy metals in water is urgent as heavy metals threaten people’s health. While laser-induced breakdown spectroscopy (LIBS) combined with the standard addition method enables fast elemental analysis in laboratories, its field application is limited by complex sample preparation. To address this limitation, we developed a foldable LIBS-assisted paper-based microfluidic analytical device (LaPAD). This device allows semiquantitative detection via colorimetric reactions, followed by precise quantification using a controlled concentration gradient coupled with LIBS. The foldable LaPAD integrates key laboratory steps (like sample collection, preparation, and standard addition) into a compact and user-friendly format, enabling rapid sample processing and efficient LIBS integration for on-site analysis. Experimental results showed that the colorimetric detection of Cu and Mn was consistent with the expected concentrations. LIBS quantification using standard concentration gradients demonstrated high accuracy (Cu: R² = 0.999, LoD = 924 µg/L; Mn: R² = 0.999, LoD = 890 µg/L). Comparison with ICP-MS showed relative errors < 5 %. These results demonstrate that the foldable LaPAD-LIBS system enables sensitive, accurate, and rapid in situ quantification of heavy metals in real water samples. This method provides a promising tool for large-scale water quality monitoring, offering a practical and efficient solution for environmental analysis.

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