Agilent 1260 Infinity Quaternary LC equipped with a Phenomenex Gemini NX C18 column (150 × 4.6 mm, 5 µm pore size and 100 Å particle size). HPLC grade formic acid, water and acetonitrile were used for all analyses and were obtained from Merck. Samples were separated using an isocratic elution of 40% v/v acetonitrile in water with 0.1% v/v formic acid over 10 minutes at a flow rate of 1 mL min - 1 , injection volume of 20 µL, detection wavelength of 240 nm, and a column temperature of 40 °C.