3.1 UPLC-MS/MS analytical conditions
TGC is a novel glycyclcycline, which belongs to third generation tetracycline. Due to high hydrophilic property (Log P=-1.30) of TGC, hydrophilic columns, such as HILIC and T3 column, were firstly tried to perform the separation. However, the peak shape of TGC provided by hydrophilic columns could not meet our expectation. Waters XBridge® BEH Shield RP18 column (3.0×50mm, 2.5μm) could perform the separation with 100% aqueous phase. The 100% aqueous phase was chosen for the retention of TGC according to the high hydrophilic property of TGC, and TGC could achieve symmetric and sharp peak shapes in this chromatographic condition (Figure 1). Quantification of TGC was performed by MRM in positive mode. Therefore, formic acid was added in the aqueous phase to enhance signal response. And ammonium formate was utilized to achieve sharp peak of analyte without tailing. TGC-d9 was used as IS to decrease the effect of matrix.