Super-sensitive detection of sodium in water using dual-pulse laser-induced breakdown spectroscopy

Laser-induced breakdown spectroscopy (LIBS) has been used for the detection of trace species in water. LIBS has the capability to be used for a real-time, in-situ analysis during power-plant operation. To improve the detection limit of the LIBS technique, a dual-pulse cross-beam scheme (DP-XB) was adopted. In this paper, we discuss the effects of the detector gate delay time, dual pulse interval, laser irradiating energies, and irradiating position for DP-XB LIBS. The signal-to-noise ratio (S/N) was optimized when the laser irradiating energies were 240/200 mJ, while the detector gate delay and pulse interval were 4∼8 μs and 8 μs, respectively. The linear correlation between the Na concentration and the fluorescence intensity was obtained from 1 to 100 ppb and the limit of detection (LOD) for Na was 0.14 ppb.