Dispersive micro solid-phase extraction of heavy metals as their complexes with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol using graphene oxide nanoparticles

This article describes a new procedure for multi-element preconcentration of heavy metal ions, specifically of Cr(III), Co(II), Ni(II), Cu(II), Zn(II) and Pb(II) ions. The method is based on dispersive micro solid-phase extraction (DMSPE) of the metal complexes of 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) by graphene oxide nanoparticles prior to energy dispersive X-ray fluorescence spectrometric (EDXRF) determination. The effects of pH, amount of graphene oxide, concentration of complexing reagent, sample volume and sorption time were optimized. The influence of commonly encountered other ions was also investigated. Under optimal conditions, the calibration plots cover the 2 to 150 ng mL(-1) range for each element. The precision (at a 20 ng mL(-1) level for n = 10) is lower than 4.8 %, and the detection limits range is from 0.07 to 0.25 ng mL(-1). The DMSPE-EDXRF procedure was successfully applied to the determination of heavy metal ions in water and spiked water samples with recoveries between 94.4 and 103.5 %.