Graphene oxide covalently modified with 2,2 '-iminodiacetic acid for preconcentration of Cr(III), Cu(II), Zn(II) and Pb(II) from water samples prior to their determination by energy dispersive X-ray fluorescence spectrometry

摘要

A novel adsorbent, graphene oxide modified with 2,2'-iminodiacetic acid (GO-IDA), was synthesized by nucleophilic substitution of dimethyl-2,2'-iminodiacetate hydrochloride to the surface of graphene oxide (GO). It was applied in the dispersive micro-solid phase extraction (DMSPE) for the simultaneous preconcentration of selected heavy metal ions from water samples prior to determination by Energy Dispersive X-Ray Fluorescence Spectrometry (EDXRF). The experiments show that at pH 6.5 GO-IDA can be used for quantitative adsorption of Cr(III), Cu(II) Zn(II) and Pb(II) ions from water samples. The adsorption capacities of GO-IDA towards Cr(III), Cu (II), Zn(II) and Pb(II) ions are found to be 117.1, 108.4, 119.6, and 80.7 mg g(-1), respectively. The experimental data are fitted better by the Langmuir model than by the Freundlich model. Under optimal preconcentration conditions the linear response between analyte concentration and fluorescence radiation intensity was observed within 1 - 200 ng mL(-1) for Cr(III) and Cu(II), 1 - 140 ng mL(-1) for Zn(II), and 1 - 100 ng mL(-1) for Pb(II) ions. The uncertainty of the developed method does not exceed 4.3%. The detection limits are 0.11, 0.06, 0.07 and 0.08 ng mL(-1) for Cr(III), Zn(II) Cu(II) and Pb(II), respectively. The enrichment factors obtained for the 50 mL sample volume are in 450 -1465 range. The DMSPE-EDXRF procedure was applied for the determination of Cr(III), Cu(II), Zn(II) and Pb(II) ions in different types of water samples. The accuracy of the procedure was verified by the analysis of Certified Reference Material: NIST 1640a (Trace elements in natural water).