Yanduru, Mercy2026-01-282026-01-282025-10-14Yanduru, M. (2025). Development of a green sorbent-based microextraction technique for the determination of trace level aflatoxins in traditionally processed cassava products (Unpublished graduate dissertation). Muni University, Arua, Ugandahttps://dir.muni.ac.ug/handle/20.500.12260/909A research dissertation submitted to the directorate of graduate training, research, and innovations in partial fulfillment of the requirements for the award of a master of science in chemistry of Muni UniversityAflatoxins are a class of naturally occurring mycotoxins that pose a serious threat to food safety and public health due to their potent carcinogenic, mutagenic, and hepatotoxic effects. The detection of aflatoxins in complex food matrices remains challenging due to matrix interferences and the labor-intensive nature of conventional sample preparation techniques. This study aimed at development of a green, sensitive, and efficient analytical method for the quantification of aflatoxins in food samples, employing porous membrane-protected micro-solid phase extraction (µ-SPE) coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS). A series of eco-friendly sorbent materials were synthesized from water hyacinth biomass through chemical activation using eggshell-derived calcium carbonate and phosphoric acid. The resulting materials were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), energy-dispersive X-ray spectroscopy (EDX), and scanning electron microscopy (SEM), and subsequently applied in the micro-solid phase extraction of aflatoxins for trace-level determination. The Taguchi orthogonal array design was employed to optimize key extraction parameters including pH, extraction time, sorbent dosage, ionic strength, and desorption time that influence the extraction efficiency of aflatoxins. Under optimized conditions, the developed method exhibited a linear response in the concentration range of 1–50 ng/mL, with a determination coefficient (R²) between 0.9994 and 0.9999. The method also demonstrated good recovery efficiencies ranging from 80.00% to 92.18%. The method achieved limits of detection (LODs) of 0.08, 0.06, 0.09, and 0.07 µg/kg, and limits of quantification (LOQs) of 0.25, 0.20, 0.30, and 0.22 µg/kg for aflatoxins B₁, B₂, G₁, and G₂, respectively. Good precision was demonstrated, with intra-day and inter-day relative standard deviation (RSD) values ranging from 4.10% to 5.45%. The developed method was successfully applied to the trace-level determination of aflatoxins in 30 cassava flour samples collected from Arua City, Uganda. The analysis revealed that 3.30 % of the preconcentrated samples contained aflatoxin concentrations exceeding the Uganda National Bureau of Standards (UNBS) permissible limit of 10 µg/kg. Aflatoxin B₁ concentrations in the samples were found to be below the maximum allowable limits established by both the European Union (2 µg/kg) and the Uganda National Bureau of Standards (5 µg/kg).This study has established a sensitive and efficient micro-solid phase extraction method for trace level aflatoxins detection in cassava products, indicating contamination levels above safety limits and highlighting the necessity for continuous food safety monitoring.enGreen sorbent-based microextraction techniqueTrace level aflatoxinsPraditionally processed cassava products