Rapid Heavy Metals Detection Using LIBS with Concentration Gradient Generators

Surface water, a critical global freshwater resource, faces severe heavy metal contamination threatening ecosystems and human health. Traditional detection methods like ICP-MS are time-consuming and expensive due to complex sample preparation, which is not practical for on-site monitoring. While laser-induced breakdown spectroscopy (LIBS) enables rapid and in situ elemental analysis, its quantitative efficiency in on-site monitoring remains limited by the laborious manual gradient-preparing procedures. Here, we developed a microfluidic-based concentration gradient generator (CGG)-LIBS platform by integrating automated gradient generation with standard addition calibration to enable real-time field quantification of heavy metals in water. The microfluidic CGG device, fabricated via 3D printing, generated six linear concentration gradients (R² > 0.998) through continuous injection mixing. This method integrates multiple steps of solution preparation into a single process, thereby simplifying the experimental procedure while minimizing errors and contamination associated with segmented operations. The trace heavy metals barium (Ba), copper (Cu), and manganese (Mn) were tested using CGG-LIBS, where the results (Ba: R² = 0.999, LoD = 40.9 μg/L; Cu: R² = 0.998, LoD = 71.1 μg/L; Mn: R² = 0.999, LoD = 62.8 μg/L) demonstrated the stable, accurate, and sensitive quantitative determination performance of CGG-LIBS. And the LoDs meet the standard limit of China (GB 3838-2002). Furthermore, comparisons with ICP-MS (<5% relative errors) demonstrated CGG-LIBS's reliability for monitoring natural water systems, as validated through Yangtze River and East Lake water samples. In summary, the CGG-LIBS platform is viable for detecting real water bodies and holds promising application prospects.