Separation was achieved using a Bio-Rad Aminex HPX-87H (9 μm, 300 × 7.8 mm) column coupled to a Bio-Rad micro-guard cation H cartridge (5 μm,30 × 4.6 mm) (Bio-Rad Laboratories, Inc. Hercules, California, USA) eluted isocratically with 0.005 M H2SO4 at a flow rate of 0.4 mL/min at 40 °C.