a) The HPLC system (e.g. Aijiren II Prime) should consist of a quaternary gradient pump, an autosampler (100 μL maximum loop capacity) and a diode array detector with 60 mm path length for the highest sensitivity and 10 mm path flow cell. b) C18 column (e.g. Poroshell SB-C18 column, 3.0 × 100 mm, 2.7 μm or equivalent).