Optimization and investigation of parameters for underwater gas-flow fiber-optic LIBS system

Laser-Induced Breakdown Spectroscopy (LIBS), as a promising in situ elemental detection technology, has gained significant attention for its suitability for complex environments. However, its application in underwater environments is hindered by water's impact on the evolution of plasma, making detection more challenging. In this study, a gas-flow fiber-optic LIBS probe was developed for underwater environments. By purging the gas into the water, a solid-gas interface was created where the plasma exhibits properties similar to those in atmospheric conditions. Due to the challenges posed by water and gas refraction in traditional side-view plasma imaging, a multi-fiber coaxial setup was employed to collect and return the plasma's self-emission to an ICCD camera, enhancing probe control. Quantitative analysis of trace Chromium (Cr) elements was performed using the internal standard (IS) method. The working range of the calibration curve is varied from 100 mg/kg to 13800 mg/kg. The limit of detection (LOD) was determined to be 95 mg/kg, with a coefficient of determination (R²) exceeding 0.99.