Abstract
An environmentally friendly analytical procedure of pre-concentration of
cobalt, nickel, and copper according to the rules of green chemistry has been
developed. The proposed method is based on using chitosan for sorption of trace
elements from water samples. The novel modification of the sorption process is the
combination of an ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate
[BMIM][PF<sub>6</sub>]) with chitosan. Ionic liquid partly decreases the
crystallinity of the chitosan. The crystalline regions of the polymer are not
accessible to metal ions. Although the ionic liquid cannot completely disrupt the
crystalline domains of chitosan, it may gain in the reactive groups of the chitosan,
even at the center of the particle. Consequently, the sorption of metal ions by
chitosan is significantly improved. In this paper, adsorption characteristics of
cobalt, nickel, and copper using newly developed sorption are studied. The effect of
pH and time of chitosan activation, as well as sorption, salt concentration, some
metals ion concentrations, and the amount of adsorbent on the extent of adsorption,
are investigated. Chitosan with adsorbed metal ions was dissolved in acetic acid.
After evaporation a solvent film formed and was then analyzed using X-ray
fluorescence spectrometry (XRF). As it meets the criterion of thin samples for XRF
analysis, the matrix effects can be neglected. With the proposed procedure we
obtained detection limits of 7 ng mL<sup>-1</sup> for cobalt, 5 ng mL<sup>-1</sup>
for nickel, and 4 ng mL<sup>-1</sup> for copper.
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