Analytical Sciences

Digestion of Plastic Materials for the Determination of Toxic Metals with a Microwave Oven for Household Use

Hiroki SAKURAI,* Junji NORO,** Akira KAWASE,*** Masanori FUJINAMI,* and Koichi OGUMA*

*Department of Applied Chemistry and Biotechnology, Faculty of Engineering, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
**Research Department, Nissan ARC, Ltd., 1 Natsushima-cho, Yokosuka 237-0061, Japan
***SII Nano Technology Inc., 2-15-5 Shintomi, Chuo-ku, Tokyo 104-0041, Japan

A rapid sample-digestion method for the determination of toxic metals, cadmium, chromium, and lead, in polyethylene and polyvinyl chloride has been developed by using a microwave oven for household use. An appropriate amount of the sample taken in a PTFE decomposition vessel was mixed with nitric acid or nitric and sulfuric acids. The vessel was heated in a microwave oven by a predetermined operating program. The digested sample was diluted to a definite volume with water after evaporating most of the nitric acid. The precipitate, if formed, was filtered off by a membrane filter. The metals were determined by ICP-AES. The sample digestion required 5 min (for 20-mg sample) to 25 min (for 60-mg sample). The analytical results obtained for cadmium, chromium, and lead in a polyethylene certified reference material, BCR-680, digested with nitric acid, were in good agreement with the certified values.

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