Sulphoxine immobilized onto chitosan microspheres by spray drying: application for metal ions preconcentration by flow injection analysis

Abstract

A new chelating resin based on chitosan biopolymer modified with 5-sulphonic acid 8-hydroxyquinoline using the spray drying technique for immobilization is proposed. The chelating resin was characterized by thermogravimetric analysis (TGA) and X-ray diffraction (XRD) and surface area by nitrogen sorption. The efficiency of the chelating resin was evaluated by the preconcentration of metal ions Cu(II) and Cd(II) present in aqueous samples in trace amounts. The metal ions were previously enriched in a minicolumn and the concentrations of the analytes were determined on-line by flame atomic absorption spectrometry (FAAS). The maximum retention for Cu(II) occurred in the pH range 8–10, and for Cd(II) at pH 7. The optimum flow rate for sorption was found to be 7.2mlmin−1 for the preconcentration of the metal ions. The analytes gave relative standard deviations (R.S.D.) of 0.7 and 0.6% for solutions containing 20μgl−1 of Cu(II) and 15μgl−1 of Cd (II), respectively (n=7). The enrichment factors for Cu(II) and Cd (II) were 19.1 and 13.9, respectively, and the limits of detection (LOD) were 0.2μgl−1 for Cd(II) and 0.3μgl−1 for Cu(II), using a preconcentration time of 90s (n=11). The accuracy of the proposed method was evaluated by the metal ion recovery technique, in the analysis of potable water and water from a lake, with recoveries being between 97.2 and 107.3%.