A quantitative analysis of trace heavy metals (lead, cadmium, mercury, and chromium) in plastics was carried out with laser-induced plasma spectroscopy (LIPS). A Q-switched Nd: YAG laser beam (pulse energy, 90 mJ; pulse width, 10 ns; repetition rate, 10 Hz) was focused on plastic samples in an argon atmosphere at a pressure of 10 Torr, and the emission spectra of the laser-induced plasma were measured using time-resolved spectroscopy. The experimental results showed that time-resolved measurement of a spectrum with a delay time of 0.4 μs after the laser pulse was effective for reducing the effect of the spectral interference with matrix as well as the background. Under the above conditions, the standard plastic samples (polyethylene and polyvinyl chloride) were analyzed for trace elements of lead, cadmium, mercury, and chromium, and the linear calibration curves with a slope of unity were obtained. The detection limits are plastic material and element-dependent, but are on the order of 10 ppm.
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