Laser co-sourced plasma emission–absorption spectroscopic for ppb-level heavy metals detection in coal ash

Sensing of heavy metals in coal ash is urgent for human health and environmental protection. However, conventional methods require chemical digestion, which cannot achieve both real-time and accuracy. Here, we demonstrate a novel optical sensing approach, called laser co-sourced plasma emission–absorption spectroscopic dual detection (LCSP-EASD), which innovatively couples the complementary and strongly correlated emission and absorption spectra of the same plasma. The emission spectrum mode enables the sensor to have comprehensive multi-element analytical capabilities, while the absorption spectrum mode enhances the detection sensitivity by utilizing the specific absorption of elements. The synergistic effect significantly enhances the performance of comprehensive, specific, real-time, and sensitive sensing of heavy metals. The experimental measured heavy metals in the pyrolysis products under different conditions closely matched the standard results, which verified the feasibility to detect heavy metals in coal ash. The results demonstrate that the limits of detection for Cr, Pb, Se, and Hg decreased to 2.14, 2.24 ppm, 464, and 119 ppb, respectively, which meet the standard limit of China (GB15618-2018). Compared with the TXRF, it has a 2.3 times enhancement in optimal sensitivity and 2 orders of magnitude shortened in experiment duration. Furthermore, comparisons with reference methods (< 5% relative errors) demonstrated its reliability for monitoring coal ash, as validated through real fly ash samples. In summary, as a novel synergistic spectral integration technique based on a co-sourced plasma, it has the advantages of sensitivity and real-time performance, unlocking its possibility in the industrial field, especially in areas where both sensitivity and efficiency are required.