Preconcentration and ultra-trace determination of hexavalent chromium ions using tailor-made polymer nanoparticles coupled with graphite furnace atomic absorption spectrometry: ultrasonic assisted-dispersive solid-phase extraction

Abstract

We describe ultrasonic assisted-dispersive solid-phase extraction based on tailor-made polymer (UA-DSPE-TMP) nanoparticles for selective extraction of Cr(VI) ions. Ultrasound is a robust method to facilitate extraction of target ions in the sorption step and elution of target ions in the desorption step. The TMP nanoparticles used in UA-DSPE-TMP were prepared by precipitation polymerization. TMP nanoparticles were synthesized using methacrylic acid as a functional monomer, ethylene glycol dimethacrylate as a crosslinker, 2,2′-azobisisobutyronitrile as an initiator, 1,5-diphenylcarbazide as a ligand, methanol as the solvent, and Cr(VI) as a template ion, through a precipitation polymerization technique. TMP nanoparticles were characterized by Fourier-transformed infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy (SEM), elemental analyses and energy-dispersive X-ray spectroscopy. The effect of influencing parameters on extraction of Cr(VI) by the prepared TMP nanoparticles was evaluated and optimized. The optimum conditions for the method were: pH of solution = 1.0; sonication time for sorption = 10 min; TMP amount = 10 mg; type and concentration of eluent: NaOH/EDTA 0.5/0.1 mol L⁻¹; volume of eluent = 200 μL; sonication time for desorption = 2 min. Under the optimized conditions, the limit of detection and relative standard deviation for the detection of Cr(VI) by the method was 8.0 ng L⁻¹ and <7%, respectively.