Quantification of water-soluble moroxydine hydrochloride residue using UPLC-MS/MS: Development and validation in 22 different complex plant-based food samples

In order to overcome the challenge of determining water-soluble moroxydine hydrochloride (MH) from 22 plantbased food matrices with different properties, an extraction pretreatment method was developed in this study using trifluoroacetic acid solutions for high-water-content samples and formic acid solutions for low-water, highoil-content samples. Moreover, the pH was adjusted to 8.5 +/- 0.1 during extraction for high-oil-content samples. An ultra-high performance liquid chromatography - tandem mass spectrometry method was developed to determine MH residues in 22 different foods. The method showed excellent linearity (R2 >= 0.99) with limits of quantification (LOQ) and limits of detection (LOD) for tea at 0.1 mg kg-1 and 0.03 mg kg-1, respectively, and 0.05 mg kg-1 and 0.015 mg kg-1 for other foods. Recoveries ranged from 71 % to 108 %, indicating high precision and applicability for MH residue analysis in plant-based foods.