Development and validation of a QuEChERS–LC–MS/MS method using an isotope-labelled internal standard for the determination of citrinin in red yeast rice-based supplements and cereals

This study aimed to develop and validate a rapid and reliable QuEChERS– LC–MS/MS for determining citrinin in red yeast rice–based health supplements and cereals. Conventional sonication extraction method, which relies on external standardisation, exhibited poor recovery and accuracy due to matrix effects. A QuEChERS-based procedure using the EN 15662 salt kit, C18 dispersive-solid phase extraction ( d -SPE) sorbent, and internal standard ( 13 C 13 -citrinin) was optimised. Both methods showed excellent linearity (r² ≥ 0.999). Limit of detection and quantification were 0.18 and 0.54 µg/kg for the sonication method, and 0.21 and 0.65 µg/kg for the QuEChERS method, respectively. Recovery experiments in capsules, tablets, and rice showed that the sonication method failed to meet AOAC criteria, whereas the QuEChERS method achieved 91.1–113.2% recovery with relative standard deviations below 7.2%. Treatment of 54 red yeast rice-based supplements and 100 cereals revealed citrinin in two supplement samples (52.87–91.55 µg/kg) and 12 cereal samples (1.79–360.71 µg/kg), with the highest levels in red rice and corn. These findings demonstrate that the QuEChERS method using the EN 15662 salt kit, d -SPE (C18), and internal standard ( 13 C 13 -citrinin) provides accurate, reproducible, and efficient quantification of citrinin in complex food matrices and highlight the need for regulatory limits and standardised analytical methods for cereals.