Experimental The system included a JEOL AccuTOF™ time-of-flight mass spectrometry system and an Agilent 1100 HPLC. All instruments were controlled by a JEOL MassCenter™. All solvents used were of HPLC grade. The standard solutions were purchased from Cerilliant (Round Rock, TX) and further diluted with mobile phase A. The HPLC and MS conditions are listed in Table 1.