ISSN print edition: 0366-6352
ISSN electronic edition: 1336-9075
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The magnetic stir bar as a source of impurities in laboratory blank solutions of the environmental samples subjected to microwave-assisted acid digestion

Vasiliy V. Rosen, Yuliana Andrushchenko, Einat Zelinger, and Orit Gal Garber

The Scientific Service Core Facility (ZBM Analytical Lab), The Faculty of Agricultural, Food, and Environmental Quality Sciences, The Hebrew University of Jerusalem, Rehovot City, Israel



Received: 22 January 2022  Accepted: 8 May 2022



Teflon-coated magnetic stir bars are suspected to be a source of impurities for the laboratory blank solutions. To evaluate the ability of magnetic bars to absorb and release different elements at sub-ppb and above-ppb (µg L−1) level, the experiment with new and used bars was conducted. The bars were subjected to microwave-assisted acid digestion with the soil sample and a series of successive cleaning procedures. The spectrometry analysis of the obtained extracts revealed that most of the elements may be released during subsequent extractions in the ppb-level concentrations, whereas the following elements: Cr, Cu, Sb, Sn, and Pb may be extracted even in elevated concentrations. Electronic microscope inspection of Teflon surfaces demonstrated the multiple defects that probably increase the absorption of the elements. We concluded that the concentration of mineral impurities in the laboratory blank solution prepared in the randomly selected one vessel per sample preparation batch is hardly propagated to the other used vessels. The alternative concept "blank per vessel" was proposed especially for ultra-trace analysis. Also, an additional step in the bar washing procedure was proposed.

Graphical abstract

Keywords: Microwave-assisted acid digestion; Magnetic stir bar; Environmental samples; Icp-OES/MS; SEM/EDS

Full paper is available at

DOI: 10.1007/s11696-022-02276-z


Chemical Papers 76 (9) 5985–5990 (2022)

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