Simultaneous determination of hydrophilic and lipophilic constituents in herbal medicines using directly-coupled reversed-phase and hydrophilic interaction liquid chromatography-tandem mass spectrometry

Limitations in the separation ability of conventional liquid chromatography system remains a challenge in developing a versatile method for simultaneously determining both hydrophilic and lipophilic constituents in herbal medicines (HMs). To measure compounds covering a broad polarity span in HMs, we developed a directly-coupled reversed-phase and hydrophilic interaction liquid chromatography-tandem mass spectrometry system. Samples were firstly separated according to lipophilicity by using a C-18 column. Utilizing a T-piece as connector, the eluent was then pumped into an amide column to get further separation that mainly based on the hydrogen bonding effects. Dan-Qi pair, an extensively used herb-combined prescription in China, was selected to test the practicability and performance of the established system. A total of 27 components, containing 9 hydrophilic and 18 lipophilic constituents, were simultaneously determined using a schedule multiple reaction monitoring method in 15 min. Up to 69.9% content could be monitored in one injection in Dan-Qi pair extract, showing a significant advantage over previous methods. The proposed method was expected to benefit the controllability of herbal medicines.