Separation of analytes determined in positive modewas carried
out on a 3.5m SymmetryShield RP18 2.1mm×150mm column
(Waters) at a flowrate of 0.2mLmin−1 at 45 ◦C. In the final method,
eluent A consisted of pure (Milli-Q) water and B of methanol, both
containing 5mMof ammonium acetate. Linear gradientwas as follows:
0 min, 5% B; 1min, 50% B; 30 min, 100% B; 36 min, 100% B;
37 min, 5% B; and 47 min, 5% B. Separation of analytes determined