Reversed-phase liquid chromatography separation and mass spectrometry fragmentation analysis of mitiglinide and three isomers

: The separation of mitiglinide and its three isomer impurities was achieved by reversed-phase ultra-performance liquid chromatography-high resolution mass spectrometry. An ACQUITY UPLC HSS T3 column (100 mm×2.1 mm, 1.8 μm) was used as the stationary phase and water-acetonitrile-n-pentanol (75:25:1, v/v/v; formic acid was added to adjust pH to 1.8) was used as the mobile phase with a flow rate of 0.4 mL/min. According to the exact mass and high resolution mass spectrometry fragmentation (Q Exactive), significant differences were observed in the fragment ion abundance in the secondary mass spectra of mitiglinide and its three isomer impurities. Two of these isomer impurities were newly discovered. The possible fragmentation mechanisms of mitiglinide and its three isomer impurities were also deduced. The limit of detection of the developed method was 1 μg/L. The linearity of the developed method was good from the limit of quantitation (2 μg/L) to 10000 μg/L with a correlation coefficient of 0.9999. The relative standard deviation of the peak area was 2.0%. On the basis of these results, the sources of the mitiglinide isomer impurities were discussed. Isomer impurity 1 was degraded at high temperature, while isomer impurities 2 and 3 were determined to be synthetic impurities. In addition, samples of mitiglinide calcium raw materials were analyzed.