 High pH: 40 °C, 1 mL/min flow rate, using a mobile phase gradient of water containing aq. ammonium bicarbonate (10 mM, adjusted to pH 10 with 0.88 M aqueous ammonia) and acetonitrile. 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.