Construction and Comparison of UPLC-QE-Orbitrap-MS and UPLC-MSMS Methods for the Detection of Diazepam Residues in Complex Aquatic Matrices

A standardized pretreatment protocol was established for simultaneous determination of diazepam and its metabolites—nordazepam, oxazepam, and temazepam—in aquatic products using liquid chromatography–mass spectrometry. Samples were extracted with 0.2% formic acid in acetonitrile (solid–liquid ratio 1:5, m/v), purified via MCX solid-phase extraction, eluted with 5% ammoniated methanol, and concentrated under reduced pres- sure. The residue was reconstituted in 0.2% formic acid–50% acetonitrile...