Application of magnetite-calcium alginate sorbent with flame atomic absorption spectrometry for Lead (II) ions analysis from water samples

Abstract

Magnetite, Fe₃O₄ encapsulated calcium alginate (Fe₃O₄-CaAlg) was proposed as a sorbent in magnetic solid phase extraction (MSPE) of Pb(II) ions from water samples.  MSPE is able to overcome the limitations of liquid-liquid extraction (LLE) and solid phase extraction (SPE).  MSPE use smaller volume fraction of organic solvent for desorption compared to LLE, less tedious than LLE and SPE, and avoids channelling effect as observed in SPE. Pb(II) ions was determined using flame atomic absorption spectroscopy (FAAS) at 283.31 nm.  The as-synthesised Fe₃O₄-CaAlg was characterized using Fourier transform infrared spectroscopy and scanning electron microscopy.  Several MSPE parameters (sample volume, sample solution pH, and effect of selected co-existence ions) influencing the extraction efficiency of Pb(II) ions using the Fe₃O₄-CaAlg sorbent were studied using 50 mg of Fe₃O₄–CaAlg sorbent, 30 min extraction time, 10 mL of 0.1 M nitric acid as desorption solvent and 10 min of desorption time (sonication assisted).  It was found that the Fe₃O₄-CaAlg MSPE of Pb(II) ions was highly dependent on sample solution pH.  Optimum Pb(II) extraction efficiency occurred at pH 6 using 150 mL sample volume and the Fe₃O₄–CaAlg MSPE method was found to be affected by the co-existence of Na⁺, K⁺, Mg²⁺ and Cl^- ions in solution.  The linearity of the Fe₃O₄-CaAlg MSPE method was in range of 60 – 500 µg/L with coefficient of determination of 0.9790.  The limit of detection and limit of quantification were 44.5 µg/Land 76.7 µg/L,respectively.  Repeatability (n = 3) of the Fe₃O₄–CaAlg MSPE method as measured by relative standard deviation was 4.36%.  The Fe₃O–CaAlg MSPE method was applied to two real water samples namely UTM lake and laboratory tap water using optimum conditions.  Lake water recovery for Pb(II) ions (spiked level 400 µg/L) was 110.38% (RSD 3.04%, n = 3) while the recovery for Pb(II) ion from tap water (spiked level 400 µg/L) was 104.2% (RSD 3.53%, n = 3).  Excellent recovery and precision indicates that the proposed Fe₃O₄–CaAlg MSPE method is a good alternative sorbent for Pb(II) ion analysis from water samples.