Sustainable synthesis of molecularly imprinted polymers using leuco fuchsin for selective detection of formaldehyde...

Formalin (aqueous formaldehyde) is a well-documented human carcinogen often used as an illegal food preservative. The World Health Organization (WHO) limits the daily intake of formalin to 1.5-14 mg for adults. Higher dosages of formalin can cause death by throat swelling or lung burning. Hence, the need for an instant, selective, and sensitive method for detecting formalin is clear. The present work discusses the efficient synthesis of silica-supported molecularly imprinted polymers (SiO₂@MIPs) for the selective and sensitive detection of formalin using a UV-visible spectrophotometer. This method offers rapid detection with high specificity and sensitivity, enabling timely detection of formalin in food matrices. The synthesized SiO₂@MIPs are characterized using Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX), and a particle size analyzer (PSA). After reaction with SiO₂@MIPs, formalin reacted colorimetrically with leuco fuchsin, resulting in a color change from pale yellow to purple. The adsorption parameters, including the effect of pH, time, and formalin concentration, were also investigated. The adsorption isotherms for formalin in the MIPs and the non-imprinted polymer (NIP) were fitted to the Freundlich isotherm model, and the calculated average binding affinities for formalin were 0.44 and 0.13 mg g^-1 for the MIPs and NIP, respectively. Good recoveries and precision ranging between 98% and 105%, with relative standard deviation (RSD) of <5% (n = 3) in the range 0-10 mg L^-1, were obtained. The Stöber method for silica coating is often considered more environmentally friendly. Iit effectively prevents structural damage to imprinting sites and ensures an adsorption capacity loss of <5% after 3 months, making the approach more sustainable. This method can serve as an alternative to formaldehyde detection in food samples, offering operational efficiency, enhanced selectivity, and environmental benefits.