A Sensitive and Green Plant Waste‐Inspired Fluorescence Switch‐Off Nanoprobe for the Determination of the Antiepileptic Drug Lamotrigine in Human Urine and Pharmaceutical Tablets

An eco-friendly method is proposed to quantify lamotrigine (LTG) across multiple matrices using novel nitrogen-doped carbon dots (N-CDs) derived from Brassica rapa greens via microwave synthesis. These N-CDs exhibit intense fluorescence and excellent water solubility. Their properties were characterized using transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), zeta potential analysis (ζ), Fourier-transform infrared (FTIR), ultraviolet (UV)-visible, and fluorescence spectroscopy. The sensor's stability was evaluated across different conditions. LTG quenched the fluorescence of N-CDs via an inner filter effect. The method demonstrated linearity over the LTG concentration range of 2.0-100.0 μM. The limit of detection (LOD) and limit of quantification (LOQ) were 0.23 and 0.70 μM, respectively. The technique was utilized to quantify LTG in urine and pharmaceutical tablets, with average recovery percentages of 99.62% ± 1.94% and 100.38% ± 1.3%, respectively. The approach was validated with International Council for Harmonization (ICH) guidelines and evaluated for greenness, blueness, redness, and sustainability. The method demonstrates excellent greenness and blueness scores. The good Red Analytical Procedure Index (RAPI) score indicates the method's high precision. The Sustainability of Analytical Methods Index (SAMI) diagram indicates favorable sustainability performance across the Sustainable Development Goals (SDGs).