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 potential impurities.

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 MET-TA, and found that it was the amidation product of metaraminol and tartaric acid.

Conclusion: The identification, structural elucidation, synthesis and most probable mechanism of formation of MET-TA are discussed in detail in this paper.

背景：药物化合物中的杂质会影响其临床效果并代表潜在的健康风险。为了确保药物的安全性和有效性，有必要调查潜在的杂质。

方法：在本文中，采用二维高效液相色谱联用四极杆飞行时间串联质谱（2D HPLC-Q/TOF-MS）在负电喷雾电离模式下分离和表征了一种新杂质。包含新杂质的峰从第一维色谱系统洗脱，根据其保留时间被切换阀选择性捕获，并转移到与质谱仪相连的第二维色谱系统。我们通过化学合成获得了 MET-TA，其结构通过 MS/MS 表征，并通过核磁共振 (NMR) 进一步证实。

结果：发现杂质为 (2S, 3S)-2,3.-dihydroxy-4-((1R,2S)-1-hydroxy-1-(3-hydroxyphenyl) propan-2-yl)amino)- 4-氧代丁酸，标记为 MET-TA。在这项研究中，我们研究了 MET-TA 的形成机制，发现它是间氨基酚和酒石酸的酰胺化产物。

结论：本文详细讨论了 MET-TA 的鉴定、结构解析、合成和最可能的形成机制。