 Formic: 40 °C, 1 mL/min flow rate, using a mobile phase gradient of water containing 0.1% formic acid (v/v) and acetonitrile containing 0.1% formic acid (v/v). Gradient conditions were initially 1% of the acetonitrile mixture, increasing linearly to 97% over 1.5 min, before remaining at 97% for 0.4 min, then rising to 100% over 0.1 min.