Caramelized carbonaceous shell-coated γ-Fe2O3 as a magnetic solid-phase extraction sorbent for LC-MS/MS analysis of triphenylmethane dyes

Carbonaceous shell-coated γ-Fe2O3 nanoparticles (γ-Fe2O3@CNM) were synthesized from glucose caramelization and used as a novel magnetic solid-phase extraction medium for malachite green and crystal violet in environmental water. Malachite green and crystal violet were absorbed on to γ-Fe2O3@CNM by electrostatic and π-interactions. The morphologies, pore structures, surface functional groups, and magnetic properties of γ-Fe2O3@CNM were characterized by TEM, FTIR, hysteresis regression, Brunauer-Emmet-Teller analysis, zeta potential, XPS, and XRD. The magnetic solid-phase extraction procedure was optimized by extraction pH, absorption time, desorption solvent, and desorption time. The absorption capacities (qmax values) for malachite green and crystal violet were 34.2 and 27.9 mg g−1, respectively. After magnetic solid-phase extraction, malachite green and crystal violet were determined by LC-MS/MS. The analytical method was validated with a linear range of 0.02–20 ng mL−1, enrichment factor of 25.8 and 25.4, method detection limit of 0.004 ng mL−1, and intra-day precisions of 2.1% and 2.6% for malachite green and crystal violet, respectively. The relative recovery was found to be 73.4–101.5% for malachite green and 83.1–102.7% for crystal violet upon the application of the magnetic solid-phase extraction method to real water samples from lake, spring, sea, fishpond, and industrial waste.