Ferrite-calcium alginate as magnetic solid phase extraction adsorbent of copper(ii) ions in water prior to flame atomic absorption spectroscopy

Abstract

A magnetic solid phase extraction (MSPE) procedure using ferrite-calcium alginate (Fe₃O₄-CaAlg) as adsorbent for Cu(II) ions prior to flame atomic absorption spectroscopy (FAAS) was developed. The extraction of Cu(II) ions using Fe₃O₄-CaAlg MSPE is simpler and faster than the conventional method such as solid phase extraction and traditional method such as liquid-liquid extraction. The simple extraction is based on the use of magnetisable adsorbent to extract Cu(II) ions, which can be readily isolated from water samples as a matrix with an external magnet. The adsorbent was prepared by mixing sodium alginate solution with Fe₃O₄ magnetic particles and calcium chloride solution to form magnetic alginate beads. Important parameters influencing the extraction and desorption process including type and volume of desorption solvent, agitation time, extraction time, weight of adsorbent and ample volume were optimized. Under the optimized conditions, calibration graph (external standard method) with coefficient of determination (R²) of 0.974 in the linearity range 20-100 µg/L was observed. Good limit of detection (1.70 µg/L), and limit of quantification (5.6 µg/L) was obtained. Acceptable repeatability (n = 3) with RSDs 2.37% while reproducibility (n = 9) with RSD 5.15% were obtained for Cu(II) ions using the developed MSPE method. Finally, the proposed method was successfully applied for the determination of Cu(II) ion in tap water sample with relative recovery of 78.9% and 4.72% RSD.  However, the proposed method was found to be less suitable for the determination of Cu(II) ion in river water sample with lower relative recovery (45.7% , 1.76% RSD) indicating that the method is sensitive to the matrix.