Synthesis of HNQ-Imprinted Poly(Methyl Acrylate) Using Hybrid Polymerization for the Detection of Lawsone in Henna Powder

In this work, a hybrid polymerization technique, combining sol-gel polymerization with thermal polymerization, was prescribed for the preparation of graphite-supported lawsone-imprinted poly[methyl acrylate (MA)] (PMA@HNQ-G) as a sensing material. The imprinted polymer’s morphology, structure, and imprinting endorsement were thoroughly investigated using various analytical techniques, including field-emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), UV-visible (UV-Vis) spectroscopy, Brunauer-Emmett–Teller (BET) analysis, and energy-dispersive X-ray (EDX) spectroscopy. The pH 6.0 phosphate buffer solution (PBS) was selected for the electrochemical investigation of lawsone (HNQ). Under optimized experimental conditions, the calibration curve was linear over two concentration ranges of 0.05–1.0 and 1.0– $300~\mu $ M with a detection limit of $0.001~\mu $ M and detection quantification of $0.005~\mu $ M by using the differential pulse voltammetry (DPV) technique. To evaluate the practical applicability of the PMA@HNQ-GPE, it was employed for the quantification of HNQ in commercial henna made from the leaves of the henna plant (Lawsonia inermis). The sensor’s response was validated by the partial least squares regression (PLSR) technique that helps to established a robust statistical model to correlate the sensor’s output with the actual lawsone concentrations measured by reversed-phase high performance liquid chromatography (RP-HPLC) technique. The model showed a high prediction accuracy of 95.65% for the detection of HNQ in the cosmetic samples. This approach offers a combination of analytical chemistry (RP-HPLC) and machine learning/statistics (PLSR) to create a validated, reliable method for lawsone detection in cosmetic products, offering potential benefits for quality control and safety assessment in the cosmetic industry.