Optical trapping suspension-assisted LIBS for liquid analysis

Laser-induced breakdown spectroscopy (LIBS) for liquid analysis faces challenges of energy dissipation and poor reproducibility due to the bulk liquid environment. Here, we present an optical trapping suspension-assisted LIBS (OTS-LIBS) approach that confines laser-sample interaction to a single levitated microdroplet in air, isolating the plasma from the liquid environment. This design suppresses quenching and ensures stable excitation, leading to higher plasma temperature and electron density, prolonged lifetime, and lower excitation thresholds compared to conventional static (SL-LIBS) and multi-droplet (MD-LIBS) methods. The relative standard deviation (RSD) is reduced by 21.5–30.7%, reaching 11.75% for Ca and 11.99% for Na. Signal-to-noise ratio (SNR) improves by 1.6- to 2.5-fold, reaching 22.43 for Ca and 108.97 for Na. Calibration linearity is enhanced with R c 2 > 0.97, and limits of detection (LoD) for Ca and Na are 118 ppm and 621 ppm, respectively, representing reductions of 58.6–80.2%. These results demonstrate that OTS-LIBS offers a robust platform for rapid, non-contact, multi-element liquid analysis.