Use of carboxylic group functionalized magnetic nanoparticles for the preconcentration of metals in juice samples prior to the determination by capillary electrophoresis

Nowadays food industry demands reliable and precise methods to resolve problems related to quality and security control. The pretreatment steps, prior to sample analysis, are necessary to extract the target analytes because of the complexities of the food samples matrices. In this work, we have studied, for the first time, the potential of carboxylic group functionalized magnetic nanoparticles to preconcentrate metals from liquid samples before CE analysis. For the extraction of metals, 10 mL of an aqueous sample containing the metal mixture was added to 2 mg carboxylic group functionalized magnetic nanoparticles. Metals retained in the nanoparticles were re-extracted with 200 μL solution consisting of 0.8 mM 1,10-phenanthroline and 0.04% hydroxylamine chloride at pH 2. The electrophoretic buffer used in this work to separate different metals (Co, Cu, Zn, Ni, and Cd) consisted of 30 mM hydroxylamine chloride, 0.30 mM 1,10-phenanthroline, 80 mM urea, 15 mM ammonium chloride, and 0.1% methanol at pH 3.6. Finally, measurements were made at 270 nm. Under the optimized conditions, detection limits for Co, Zn, Cu, Ni, and Cd were 0.004, 0.003, 0.004, 0.008, and 0.009 mg L⁻¹, respectively.