Laser-induced breakdown spectroscopy for detection of lead in concrete

Time-resolved laser-induced breakdown spectroscopy was applied for quantitative measurement of lead content in concrete at levels down to 10 ppm. The breakdown was formed at the sample surface by a Q-switched ND:YAG laser operating at a 1.06-mu m wavelength and a repetition rate of 10 Hz. Contamination levels were inferred from the ratio of the integrated emission line of lead to a known reference line of the matrix. The lead contamination can be determined on an absolute scale down to 10 ppm at an optimum delay time of 3.0 mu s. These results were derived from analysis of the temporal evolution of the calibration function within a 0.1- to 19.0-mu s time range. The calibration function exhibits no dependence on the incident laser pulse energy, which was varied from 250 to 400 mJ.