Magnetically N-doped Carbon quantum dots has been synthesized via a simple chemical method and applied as a sorbent for the preconcentration and extraction of trace amounts of Pb²⁺ from water and vegetable samples followed by flame atomic absorption spectrometric detection. The nanoparticles were characterized by X-ray diffraction, UV–vis spectra, Fourier transform infrared spectroscopy, vibrating sample magnetometer analysis and transmission electron microscopy. A central-composite design was used to find the optimum conditions for the preconcentration procedure through response surface methodology. The effects of various parameters such as the pH value, adsorption time, amount of adsorbent, desorption conditions (type, concentration and volume of the eluent and desorption time), sample volume and interfering ions have been studied. Under the optimized conditions, the calibration graph was linear in the range of 0.3–300 μg L⁻¹ (R² = 9992). The detection limit and pre-concentration factor were found to be 0.082 μg L⁻¹ and 265, respectively.