Gradient proportioning valve

A gradient proportioning valve (GPV) for liquid chromatography comprising:

• a plurality of inlet ports configured to receive a plurality of solvents;
• a manifold connected to each of the plurality of inlet ports configured to mix the plurality of solvent in a controlled manner to provide a solvent composition, the manifold including a plurality of conduits internal to the manifold, each of the plurality of conduits receiving solvent through a respective one of the plurality of inlet ports;
• an actuation mechanism having a piston located within a bored structure surrounding the piston, the actuation mechanism configured to open and close at least one of the plurality of conduits in a controlled manner wherein the piston and the bored structure have a tight tolerance configured to create a fluid tight seal when the actuation mechanism closes the at least one of the plurality of conduits, wherein the tight tolerance creates a clearance of less than 6 microns between the piston and the bored structure;
• and
• a common outlet port configured to receive the solvent composition,
• wherein the GPV is configured for setting a desired precision solvent composition in liquid chromatography systems, to provide a continuous stream of a compositionally accurate mixture of solvents, wherein the GPV includes no integral accumulator chambers,
• wherein the piston is configured to rotate about the bored structure to open and close the at least one of the plurality of conduits in the controlled manner.