Aim: 
To develop a UHPLC–MS/MS method for the quantification of 12 constituents in rat plasma afteroraladministration of Zhuanggu Guanjie. Methods: 
Constituent separation was performed on a C18column,and the mass spectrometric detection was performed in multiple reaction monitoring mode witha positive–negative ionization mode. 
Results: 
The method was successfully applied to the pharmacokineticstudy of these 12constituents after rats taking Zhuanggu Guanjie capsules.The results showed thatpsoralen,isopsoralen and aspersaponin VI were the keyeffective components and had high exposure.

Conclusion: 
A rapid,simple and sensitive ultra-high-performance liquid chromatography coupled withtriple quadrupole mass spectrometry method for the detection of 12 components in rat plasma after taking Zhuanggu Guanjie was developed and applied in this pharmacokinetics study.

Experimental
Chemicals & reagents
The standard compounds of psoralen,isopsoralen,aspersaponinVI,verbascoside,naringin,epimedinB,epimedinC,quercetin,osthole,quercitrin,neobavaiso?avone,formononetin and chloramphenicol(internalstandard;purity>98%) were purchased from Chengdu Pufei De Biotech Co.,Ltd(Chengdu,China).The structure patterns of these 12 analytes and IS are shown in Figure1.
The ZGC was manufactured by China Resources Sanjiu Medical & Pharmaceutical Co.,Ltd(Shenzhen,China).Each1.0g ZGC contains psoralen 0.22mg,isopsoralen0.23mg,aspersaponinVI3.88mg,verbascoside0.072mg,