Functionalization of a SiO2-coated magnetic graphene oxide composite with polyaniline–polypyrrole for magnetic solid phase extraction of ultra-trace Cr(III) and Pb(II) in water and food samples using a Box–Behnken design

A novel polyaniline–polypyrrole functionalized SiO2-coated magnetic graphene oxide composite (MGO/SiO2@PANI–PPy) was prepared as a new magnetic solid-phase extraction (MSPE) adsorbent for separation and pre-concentration of chromium (Cr) and lead (Pb) at trace levels in food and environmental water samples followed by the use of inductively coupled plasma mass spectrometry (ICP-MS). Fourier transform infrared (FTIR) spectroscopy, vibrating sample magnetometry (VSM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) were used to characterize the nanocomposite. Various parameters affecting the extraction yield of heavy metals were optimized using a Box–Behnken design (BBD) through the response surface methodology (RSM). Under optimum conditions, the limits of detection (LODs) were 4.808 ng L−1 for Cr(III) and 3.401 ng L−1 for Pb(II) with relative standard deviations (RSDs) of less than 5% (n = 6). Furthermore, the maximum adsorption capacities of this new sorbent were 188.9 and 213.3 mg g−1 for Cr(III) and Pb(II), respectively. Finally, the developed method was successfully applied for determination of trace Cr(III) and Pb(II) in rice, milk, wine and environmental water samples with recoveries within 95.4–105%.