The mobile phase consisted of 0.1% (v/v) formic acid in water (eluent A) and of acetonitrile: 0.1% formic acid (1:1, v/v) (eluent B). The gradient program was as follows: 0 to 40 min, 10% to 38% of B; 40 to 60 min, 38% to 48% of B; 60 to 70 min, 48% to 100%...