Milk-Derived Carbon Nanodots for Dispersive Micro-Solid Phase Extraction of Copper at Trace Levels from Vegetable Samples

Carbon nanodots were synthesized from bovine milk using a hydrothermal method. In order to investigate the structure of the synthesized material, characterization was performed by Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and scanning transmission electron microscopy (STEM). The material was used as a nanosorbent for the dispersive micro-solid-phase extraction of copper at trace levels. The quantification of copper was conducted using a high-resolution continuum source flame atomic absorption spectrometer (HR-CS FAAS). The optimal working conditions were a pH of 6.0, a nanosorbent mass of 5 mg, a desorption time of 3.5 min. and a desorption agent of 2 mol L−1 HNO3. The detection limit and limit of quantification were determined to be 0.4 ng mL−1 and 1.2 ng mL−1 respectively, with relative recoveries ranging from 92% to 102%. The relative standard deviation (RSD) was 3.4% and the linear range was from 1.8 to 100 ng mL−1. This method is highlighted for its speed, high sensitivity, and environmentally friendly approach, making it a practical option for detecting copper levels in vegetables.