Copper(ii)ion determination in water samples using magnetite-calcium alginate sorbent and flame atomic absorption spectrometry analysis

Abstract

Conventional technique such as liquid-liquid extraction (LLE) is widely used in the analysis of Cu(II) ions from water samples. However, LLE is time consuming, tedious, and consume lots of high purity organic solvents. Solid phase extraction (SPE) is an interesting alternative to LLE but it is prone to channelling and is rather expensive. A greener technique such as magnetic solid phase extraction (MSPE) avoids the use of column cartridge and overcome channelling problem. MSPE using magnetite-calcium alginate (Fe3O4-CaAlg) as sorbent is proposed for the extraction of Cu(II) ion from tap and lake water samples and analysis performed using flame atomic absorption spectrometry (FAAS). Characterization of the synthesised sorbent was performed using Fourier transform infrared spectroscopy and scanning electron microscope. The optimum conditions for Fe3O4-CaAlg MSPE of Cu(II) were achieved at a sample solution of pH 6 with 100 mL sample volume and the existence of interfering ions (Na+, K+, Mg2+, and Cl-) was found not to affect the extraction efficiency of the sorbent for Cu( II) ion significantly at the concentrations tested. Other MSPE parameters used were 10 min extraction time, 50 mg sorbent, 10 mL of 0.1 M HNO3 as desorption solvent and 5 min desorption time (sonication assisted). The calibration graph was linear from 20 - 600 ppb with good coefficient of determination (R2 = 0.9998). The LOD (3SD/slope) and LOQ (10SD/slope) of Cu(II) using Fe3O4-CaAlg MSPE with FAAS were in 6.75 and 22.5 ppb, respectively. The LOD achieved with the Fe3O4-CaAlg MSPE with FAAS is applicable to the determination of Cu(II) in real water samples (tap water and UTM lake water). Good relative recoveries and precision were achieved with this proposed method. The Fe3O4-CaAlg has great potential as an alternative sorbent for Cu(II) determination from water samples using the greener MSPE method.