Sustainable Microextraction for Trace Determination of Aflatoxin M1 in Domestic Waters by High-Performance Liquid Chromatography with Fluorescence Detection (HPLC-FLD): A Computationally Optimized Design

"A rapid and sensitive analytical method for the trace determination of aflatoxin M1 in domestic waters was developed using chitosan as a sorbent and HPLC with fluorescence detection (HPLC-FLD). Computational simulations were employed to pre-investigate sorbent–analyte interactions, and a dominant role of the aflatoxin M1 hydroxyl group in binding to chitosan was revealed. Sample preparation was integrated using dispersive solid-phase extraction and microextraction by packed sorbent (µ-dSPE-PS) techniques in principle. Chromatographic separation was achieved in under 4 min at 25 °C on a reverse-phase C18 column using isocratic elution with acetonitrile–water (70:30, v/v) at 1 mL min−1. Fluorescence detection was performed at 360 nm (excitation) and 440 nm (emission). Linearity was exhibited from 0.2 to 20 pg/mL, with a quantification limit of 0.198 pg/mL. Recoveries were found to range from 98.99–99.98%, with precision between 0.9–1.2%. Among twenty domestic water samples analyzed, aflatoxin M1 was detected in two unspiked samples at concentrations of 11.36 and 12.83 pg/mL. The method was further validated using spiked pooled samples (0.5, 5, and 20 pg/mL), and reliable qualitative and quantitative results were obtained with RSD (relative standard deviation) values between 0.01–0.2%".