Hybrid gradient delivery system and operation

A solvent delivery system for use in a liquid chromatography system, comprising:

• a first gradient proportioning valve in fluidic communication with a first plurality of sources of solvent and producing from a mixture of proportions of the first plurality of solvents a first low-pressure gradient stream, the proportions of the first plurality of sources of solvent forming the first low-pressure gradient stream changing overtime in accordance with a first predetermined timetable;
• a first pump in direct fluidic communication with the first gradient proportioning valve to receive and pressurize the first low-pressure gradient stream forming a first pressurized gradient stream and including an output connected to a flow-combining device to move the first pressurized gradient stream to the flow-combining device;
• a second gradient proportioning valve in fluidic communication with a second plurality of sources of solvent, the second gradient proportioning valve producing a second low-pressure gradient stream from a mixture of proportions of the second plurality of sources of solvent, the proportions of the second plurality of sources of solvent forming the second low-pressure gradient stream changing over time in accordance with a second predetermined timetable;
• and
• a second pump operating in parallel with the first pump and in direct fluidic communication with an outlet of the second gradient proportioning valve connected to the flow-combining device to receive and pressurize the second low-pressure gradient stream forming a second pressurized gradient stream and to move the second pressurized gradient stream to the flow-combining device where the second pressurized gradient stream combines with the first pressurized gradient stream to produce a high-pressure gradient stream.

A solvent delivery system for use in a liquid chromatography system, comprising:

• a first gradient proportioning valve in fluidic communication with a first plurality of sources of solvent and producing-from a mixture of proportions of the first plurality of solvents a first low-pressure gradient stream, the proportions of the first plurality of sources of solvent forming the first low-pressure gradient stream changing over time in accordance with a predetermined timetable;
• a first pump in direct fluidic communication with an outlet of the first gradient proportioning valve to receive and pressurize the first low-pressure gradient stream forming a first pressurized gradient stream and including an output connected to a flow-combining device to move the first pressurized gradient stream to the flow-combining device;
• and
• a second pump operating in parallel with the first pump, the second pump including an outlet connected to the flow-combining device to move a pressurized solvent stream to the flow-combining device where the pressurized solvent stream combines with the first pressurized gradient stream to produce a high-pressure gradient stream.