Linear gradient of buffers A (5% CH3CN in 15 mM sodium borate with 0.1% v/v trifluoroacetic acid, pH 9.4) and B (50% CH3CN in 8 mM sodium borate with 0.1% v/v trifluoroacetic acid, pH 9.4) were used as the mobile phases, and the flow rate was 0.7 mL/min. The solvent gradient...