The maximal mass resolution was 30000, the spray voltage was 3.0 kV, and the tude lens was -100 v. The HPLC column was a 3 mm x 150 mm Inertsil C-18,ODS 3, 3 um column (GL Sciences). The initial solvent system was 20%methanol and 80% water with 0.25% formic acid, at a flow rate of 0.25 mL/min.