Experimental Study On Detecting Copper And Cadmium Heavy Metal Element In Water By Collinear Double Pulse LIBS

As a brand new material analysis method, laser induced breakdown spectroscopy technology has great potential application in many fields.But low sensitivity and poor stability drawback are the fatal shortcoming of this technology. In this work, in order to improve the sensitivity of detection, respectively do experiment by collinear double pulse laser induced breakdown spectroscopy(DP-LIBS) and by signal pulse laser induced breakdown spectroscopy(SP-LIBS). Copper and cadmium elements were objects for this study.Results of experiments show that spectral of copper element can clearly be detected at wavelength of 324.7nm and 327.4nm. Spectral of 324.7nm is stronger. Therefore, 324.7nm is chosen as the characteristic analysis spectral line of copper. Spectra of cadmium in the wavelength of 326.11 nm, 340.36 nm, 346.62 nm and 361.05 nm could be detected. The spectral intensity of 361.05 nm was strongest, so choose 361.05 nm as the characteristics analysis spectral line of cadmium.This paper optimized experimental parameters, including laser energy, time delay spectrum signal acquisition, two double pulse laser emission time interval value and so on. The results show that, the optimal single pulse laser energy of copper is 100 mJ and the optimal delay time is1400 ns. The best double pulse laser energy 100 mJ, delay time is 1480 ns and the laser pulse interval is 25 ns. The optimum single pulse laser energy of cadmium is120 mJ and the delay time is 1280 ns. The best double pulse laser energy is 140 mJ, delay time is 1280 ns and two beams of laser emission time interval is 50 ns.Quantitative analysis show that, for copper, single pulse and double pulse detection limits respectively were 22.42ug?ml-1 and 3.5ug?ml-1. For cadmium, single pulse and double pulse detection limits respectively were 76.33ug?ml-1 and 11.32ug?ml-1. Research indicated that using double pulse technology can reduce the limit of detection of LIBS technology. It provided further possibility for the application of the technology.