Background: Impurities in pharmaceutical compounds can influence their clinical effects and represent a
potential health risk. To ensure the safety and effectiveness of a drug, it is necessary to investigate any potential
Methods: In this paper, a new impurity was separated and characterized by two-dimensional high performance liquid
chromatography coupled to quadrupole time-of-flight tandem mass spectrometry (2D HPLC-Q/TOF-MS) in negative
electrospray ionization mode. The peak containing the new impurity, eluted from the first dimension chromatographic
system, was selectively trapped by a switching valve based on its retention time and transferred to the second dimension
chromatographic system, which was connected to the mass spectrometer. We obtained MET-TA by chemical synthesis,
and its structure was characterized by MS/MS and further confirmed by nuclear magnetic resonance (NMR).
Results: The impurity was found to be (2S, 3S)-2,3.-dihydroxy-4-((1R,2S)-1-hydroxy-1-(3-hydroxyphenyl)propan-2-
yl)amino)-4-oxobutanoic acid, labelled as MET-TA. In this study we investigated the mechanism of formation of METTA,
and found that it was the amidation product of metaraminol and tartaric acid.
Conclusions: The identification, structural elucidation, synthesis and most probable mechanism of formation of MET-TA
are discussed in detail in this paper.