Simple derivatization of aldehydes with d-cysteine and their determination in beverages by liquid chromatography–tandem mass spectrometry

We describe a simple derivatization method to determine aldehydes. This method is based on derivatization with d-cysteine and consecutive liquid chromatography–tandem mass spectrometry (LC–MS/MS). The optimum derivatization conditions of aldehydes with d-cysteine were 10 min at 50 °C and pH 7.0. The formed alkyl thiazolidine-4-carboxylic acid derivatives were directly injected in LC–MS/MS. In the established condition, the method was used to detect eight aldehydes in beverages. The limit of detection (LOD) and limit of quantification (LOQ) of the aldehydes were 0.2–1.9 μg L−1 and 0.7–6.0 μg L−1 and the relative standard deviation was less than 2.0% at concentrations of 0.1 mg L−1 and 1.0 mg L−1 with the exception of octanal. All the beverage samples had detectable levels of methanal (0.033–0.145 mg L−1), ethanal (0.085–2.12 mg L−1), propanal (ND to 0.250 mg L−1), butanal (ND to 0.003 mg L−1), pentanal (ND to 0.471 mg L−1), hexanal (ND to 0.805 mg L−1), heptanal (0.019–3.91 mg L−1) and octanal (0.029–0.118 mg L−1).

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► This study describes a new derivatization method of aldehydes in water matrix with d-cysteine.
► The optimum derivatization conditions were 10 min at 50 °C and pH 7.0.
► The formed alkyl thiazolidine-4-carboxylic acid derivatives were directly injected in LC–MS/MS.
► The LOD and LOQ of the eight aldehydes in beverages were in range of 0.2–1.9 μg L−1 and 0.7–6.0 μg L−1, and RSD was less than 2.0%.
► All the beverage samples had detectable levels of almost all aldehydes.