a multi - dimensional liquid analysis system includes a flow splitter for separating mobile phase outflow from a first dimension liquid analysis system into first and second liquid split outlet flows . volumetric flow rate control of the split outlet flows is provided by a flow control pump which withdraws one of the split outlet flows from the flow splitter at a controlled withdrawal flow rate to define the other split outlet flow rate as the difference between the outflow rate from the first dimension system and the withdrawal flow rate . in this manner , accurate and consistent flow division can be accomplished , which is particularly useful for multi - dimensional liquid analysis .