A scheme of the modified system is depicted in Figure . The modified system based on the commercially available LC-Isolink interface (Thermo Fisher Scientific, Bremen, Germany) coupled to a DELTA V Advantage IRMS (Thermo Fisher Scientific, Bremen, Germany) for continuous flow applications. Eluents and reducing agents were pumped with two separate HPLC pumps (LPG-3400 SD and HPG-3200 SD, Thermo Fisher Scientific, Bremen, Germany). The flow rates for the eluent and reducing agents were both set to 200 µL min -1 .