Use of Rice Husk as a Biosorbent for Analytical Purposes: Physicochemical, Morphological Characterization and Application in Human Breast Milk

The secretion of medicines in breast milk is a crucial topic in clinical medicine. LC-DAD stands out in the literature for its simplicity, cost-effectiveness, and reproducibility. Chromatographic techniques, often coupled with cleaning methods such as μQuEChERS, have proven efficient in analyzing drugs across biological matrices. This study aims to characterize alternative sustainable biosorbents with a high silica content for analytical use, aiming to reduce environmental impact. Commercial sorbents (PSA, C18, GCB) and biosorbents (rice husk (RH), cork, orange bagasse, and passion fruit) were evaluated, with RH presenting superior results. RH was then characterized through laser diffraction, SEM, FT-IR spectroscopy, X-ray diffraction, and thermogravimetric analysis, among others. Key results include SPAN (2.567 ± 0.09), <i>D</i>[4,3] (126 ± 27), and a nonuniform morphology compared to commercial sorbents. RH composition was 27% cellulose, 13% hemicellulose, 9% lignin, and 23% extractives, with notable properties such as WRI (72%) and ZP (-19.2 ± 0.8). Unlike prior studies, this work provides unprecedented physicochemical and morphological characterization of biosorbents, demonstrating RH as a promising and sustainable alternative to traditional sorbents like C18.