Micro-extraction and determination of transition metals in historical ink

Selective separation of some ecotoxic transition metal ions from aqueous solutions using immobilized macrocyclic material containing solid phase extraction system

A simple flow-based method was developed for the simultaneous separation of certain transition metal ions (Co, Ni, Cu, Zn, Cd) from aqueous systems, which ions show ecotoxic effects when present at elevated concentrations. A silica-gel-bonded macrocycle system, commonly known as molecular recognition technology (MRT) gel, was used for solid phase extraction (SPE) of the target analytes. The collection behavior of the MRT-SPE system was studied based on pH. Fortified deionized water samples containing 250 µg L−1 of each of the elements were treated at the flow rate of 1 mL min−1. The collected analytes were then eluted by 3 M HNO3 and analyzed using inductively coupled plasma spectrometry. Detection limits of the proposed technique were in the range of 0.004–0.040 µg L−1 for the studied metal ions. The validity of this separation technique was checked with spiked ‘real’ water samples, which produced satisfactory recoveries of 96–102%. The non-destructive nature and highly selective ion-extraction capability of the SPE material are the most important aspects of the proposed method and they are the main focus of this paper.