Highly sensitive method for aldehydes detection: Application to furfurals analysis in raisin and bovine milk powder

A pre-column fluorescent derivatization method based on nitrone formation has been applied to determine furfurals (e.g. furfural (F), 5-methyfurfural (5-MF) and 5-hydroxymethylfurfural (5-HMF)) in food samples for the first time. An N-substituted hydroxylamine reagent 4-((hydroxyamino)butyl)-7-hydroxycoumarin (HAHC) was used to react with the aldehyde group of furfurals to form stable nitrone derivatives with high fluorescence intensities. The reactions proceeded under mild conditions in 30 min with high derivatization yields (>93%). A baseline-separation of three furfurals derivatives was subsequently achieved within 25 min on a reversed-phase column. The detection limits were at the low femtomol level (S/N = 3, 20 μL per injection). The linear range of the calibration curve was 0.4-4000 nM with good correlation coefficients (R² ≥ 0.9991). The proposed method was further applied for food sample analysis, such as bovine milk powder and raisin. Satisfactory recoveries were obtained in the range of 94.7%-103.5%. Above all, this pre-column derivatization method is simple, fast and highly sensitive, providing an effective and promising way for future studies of aldehydes in different matrices.