Determination of Trace Lead in Plastics by Laser-Induced Plasma Spectroscopy

Abstract

A quantitative analysis of trace lead in plastics was carried out with laser-induced plasma spectroscopy (LIPS). A Q-switched Nd:YAG laser (pulse energy, 90 mJ; pulse width, 10 ns; repletion rate, 10 Hz) was focused on plastic samples in an argon atmosphere, and the emission characteristics of the laser-induced plasma were investigated by changing the argon pressure from atmospheric pressure to 1 Torr. The experimental result showed that the emission intensity of the analysis line (Pb I 405.78 nm) was maximized at a pressure of around 10 Torr. The determination of trace lead in the standard plastic samples (polyethylene and polyvinyl chloride) was carried out in argon at 10 Torr. In the analysis of polyvinyl chloride, time-resolved spectroscopy was used to reduce the effect of the spectral interference with the matrix as well as the background. Linear calibration curves were obtained with detection limits of several tens ppm. The LIPS method was applied to industrial samples.