Micro guard cation h guard column cartridge

Samples were either filtered (0.45 μm) or centrifuged (10 min, 14,000 g) and analyzed using a 1200 series high-pressure liquid chromatography system (Agilent Technologies, Santa Clara, CA, USA) consisting of an autosampler with tray cooling, binary pump, degasser, thermostated column compartment, diode array detector (DAD) and refractive index detector (RI) connected in series. The supernatant was injected onto either a 300 mm × 7.8 mm (length × inner diameter) Aminex HPX-87H (Bio-Rad, Richmond, CA, USA) column with 9 μm particle size, 8 % cross-linkage equipped with a 30 × 4.6 mm micro-guard Cation H guard column cartridge (Bio-Rad, Richmond, CA) or onto a 50 × 7.8 mm Rezex™ RFQ-Fast Acid H⁺ guard column (Phenomenex, Torrance, CA, USA) with 8 μm particle size, 8 % cross-linkage or onto a 30 × 4.6 mm micro-guard Cation H guard column cartridge (Bio Rad, Richmond, CA, USA). Compounds were eluted either at 30, 55 or 80 °C at a flow rate of either 0.6 or 1.0 mL using a mobile phase of 5 mM sulfuric acid.