Hydraulic part of the gradient elution system

Depending on the pumping system, two devices can be used. In one instance, the two solvent streams coining from two different pumps are mixed, and in the other the solvent to be pumped through the column is selected by one or two electrovalves. 

We can group together devices that have an electrovalve after the pumping system. 

Step gradients. The Siemens step-gradient system is shown in Fig, 6. Two solvents, A and B, are contained in two 220-nil holding coils (b, c), connected 

Gradients generated with pneumatic pumps. The DuPont gradient elution accessory and the Jobling Model JL 921 gradient generator are similar and use 

When the proportioning valve a is opened, solvent A flows directly from the pump to the mixing chamber. When the valve b is opened, the solvent A is pumped to 

---