Modification of magnetized MCM-41 by pyridine groups for ultrasonic-assisted dispersive micro-solid-phase extraction of nickel ions

Abstract

Nickel is one of the heavy metals, which is discharged to ecosystem by normal process and human actions. Nickel is regarded as crucial ion in the living creature and is a component of protein structure at very low level. Dispersive micro-solid-phase extraction assisted by ultrasonic waves with a new magnetic material using pyridine-functionalized magnetic nanoporous sorbent was utilized for detection of nickel ions at trace levels in real matrices. Magnetized nanoporous silica (MCM-41) was modified with pyridine groups, and the structure of prepared magnetic nanoporous sorbent was confirmed by instrumental techniques. The applied techniques were Fourier-transformed infrared spectroscopy, X-ray powder diffraction, transmission electron microscopy and thermogravimetry–differential thermal analysis. Preconcentrated nickel using the mentioned sample preparation procedure was monitored by GFAAS at ng L−1 concentrations. To optimize the effect of significant parameters on sorption and desorption of nickel ions using the applied sample preparation procedure, Box–Behnken design was utilized. The influencing parameters in the sorption step are: sorption amount (mg), pH of solution and sonication time (min), and these parameters for desorption step are: volume of eluent (mL), concentration of eluent (mol L−1) and sonication time (min). Optimized data for parameters that obtained by Box–Behnken design were: sample’s pH: 7.5, sonication time for sorption: 8 min, sorbent amount: 24 mg, desorption solvent: HCl 1.2 mol L−1, eluent volume: 420 μL and time of sonication for desorption, 8 min. Relative standard deviation and method detection limit for nickel monitoring under optimized conditions by UA-d-μSPE were observed to be < 6% and 0.008 μg L−1, respectively.