FI-ICP-OES determination of Pb in drinking water after pre-concentration using magnetic nanoparticles coated with ionic liquid

Accurate measurement of trace metals in environmental, biological and medical samples often requires the application of enrichment and/or isolation procedures. Among the many pre-concentration and/or matrix separation techniques available, solid phase extraction procedures (SPE) are most widely employed. In the last years, surface functionalized magnetic-nanoparticles have been introduced, which offer distinct improvements compared to conventional column-based SPE approaches. In the present work, a Flow-Injection (FI) procedure for on-line separation of magnetic nanoparticles from aqueous sample solutions with subsequent ICP-OES analysis is proposed. Silica-coated magnetic cobalt nanoparticles covered with an outer layer of ionic liquid were used as sorbent material. After analyte extraction, the particle suspension was directed through an electromagnetic trap, thereby the analyte loaded particles were separated from the sample solution. For analysis, the electro-magnet was switched off and the particles were transferred with the carrier solution to the ICP-OES used for element-specific online analysis. Compared to batch-wise methods, the FI-approach offers an additional enrichment step and requires less manual sample manipulation. Applicability of the proposed FI-ICP-OES procedure was demonstrated by the analysis of Pb in the reference material ERM-CA022a and tap-water samples collected from different districts in Vienna, Austria.