Scheme 1.
Working scheme representing the function of the LC system with two parallel flow channels for multiple consecutive sample injections. For the first injection, the switching valves are in Position 1 and LC separation take place on Column 1 connected to the flow channel leading to the mass analyzer. Simultaneously, Column 2 is being equilibrated with the initial mobile phase. After 90 seconds the valves are switched to Position 2, and the second injection is performed on Column 2, now eluting to the mass analyzer.