Sensitive Analysis of Copper in Water by LIBS–LIF Assisted by Simple Sample Pretreatment

Laser-induced breakdown spectroscopy (LIBS) combined with laser-induced fluorescence (LIF) is applied to realize sensitive analysis of trace copper in water for the first time. A wood slice substrate is selected as water absorber to convert liquid sample analysis to solid sample analysis to eliminate drawbacks of the water matrix in direct analysis of liquid samples by the LIBS or LIBS–LIF technique. Copper atoms in the laser-induced plasma are resonantly excited at 324.75 nm from the ground state to a higher state with a tunable dye laser. The fluorescence of copper atoms from this higher state to a lower state at 510.55 nm is selectively monitored with high detection sensitivity. A calibration curve of copper in water analyzed with the LIBS–LIF technique has been built and the limit of detection reaches 3.6 ppb, which is 4–5 orders better than that obtained in direct analysis of aqueous solutions by the LIBS technique. The combination of this simple sample pretreatment method with the LIBS–LIF technique demonstrates rapid, sensitive, and reliable analysis of trace copper in water.