Fluid mixing by fluid supply lines with line-specific fluid pumps for liquid chromatography

A method of providing a mixture of a plurality of different fluids as a mobile phase for a sample separation apparatus, the method comprising:

• providing a plurality of supply lines, each of which is fluidically coupled to a respective one of a plurality of fluid component sources for providing a respective one of the plurality of different fluids;
• providing a plurality of fluid pumps, each of which is associated with a respective one of the supply lines;
• providing a combining point downstream of the fluid pumps and configured to combine the fluids from the supply lines to output combined fluids,
• wherein each one of the plurality of fluid pumps is switchable such that a respective fluid pump, depending on its respective switching state, pushes or does not push a respective fluid from a respective one of the fluid component sources to the combining point;
• operating the fluid pumps to bring respective ones of the fluids to a normalized initial pressure;
• sequentially supplying the fluids from the supply lines to the combining point such that each one of the plurality of fluid pumps, depending on a respective switching state, pushes or does not push a respective fluid from a respective one of the fluid component sources to the combining point,
• wherein the sequentially supplying comprises operating a switching configuration comprising a plurality of switching valves, each switching valve communicating with a respective one of the supply lines and each switching valve positioned between a respective one of the fluid pumps and the combining point, wherein each switching valve is switchable between an open state that allows the respective fluid pump to convey a respective fluid from a respective one of the fluid component sources to the combining point, and a closed state that prevents the respective fluid pump from conveying the respective fluid;
• controlling pushing and not pushing by the fluid pumps, and/or controlling the switching of the switching valves, to controllably define a composition of the combined fluids exiting the combining point;
• and
• operating a fluid conveying device downstream of the combining point as a metering device to further pressurize the combined fluids output from the combining point to a system pressure and to convey the combined fluids to a chromatographic sample separation device.