Determination of Pb content in recycled plastic debris by laser-induced breakdown spectroscopy

During several last decades, the usage of plastics has risen steadily across the globe. However, many potentially toxic materials have been used especially in their earlier production. These materials include additions of heavy metals such as arsenic, cadmium, chromium (VI), mercury and lead. Recently, the levels of these heavy metals and other hazardous materials have become controlled by various directives (Registration, Evaluation, Authorization and Restriction of Chemicals - REACH1, Restriction of Hazardous Substances in Electrical and Electronic Equipment - RoHS2 and Waste from Electrical and Electronic Equipment - WEEE3). These restrictions apply also to plastic products made from recycled polymer waste. This post-consumer polymer waste is the most susceptible to an increased heavy metal content. Usually, lead is the heavy metal with the highest concentration.The heavy metal content level needs to be determined reliably and quickly, which is not the case presently. Companies need to wait for a traditional lengthy analysis, which also destroys the sample. Laser Induced Breakdown Spectroscopy (LIBS) provides a drastic improvement in time of measurement and high enough robustness in the sense of precision and accuracy to be considered for this application. This paper presents the capabilities of LIBS to reliably quantify the lead content in polymer post-consumer recycled materials. Using the methodology defined in this work, LIBS can be used directly in-situ to control levels of lead and other toxic substances. In this feasibility work, an accuracy of more than 90% with a relative precision higher than 86% was achieved for the quantification of lead content in standard samples provided by a recycling company using standard multivariate chemometric techniques.

Automated summary

The usage of plastics has steadily increased over the last few decades, but earlier production methods often involved the use of potentially toxic materials, including heavy metals like arsenic, cadmium, chromium (VI), mercury, and lead. Recently, various directives have been put in place to control the levels of these hazardous materials in plastic products, including those made from recycled polymer waste. This paper explores the use of Laser Induced Breakdown Spectroscopy (LIBS) as a reliable and efficient method for quantifying lead content in post-consumer recycled materials. The results showed an accuracy of over 90% and a relative precision of 86% using standard multivariate chemometric techniques.