A method performed in a liquid chromatography system includes a metering device pushing a sample into a trap column. The metering device sucks in the sample from a sample reservoir, wherein the sucking in the sample from a sample reservoir precedes the step of pushing the sample into the trap column. The liquid chromatography system also includes a trap column and a metering device, wherein the system is adapted to assume a configuration allowing the metering device to push a sample into the trap column and wherein the metering device is adapted to push the sample into the trap column in this configuration, wherein the system is adapted to assume a configuration allowing the sample to be sucked into the system by means of the metering device. Furthermore, the invention relates to a use of the liquid chromatography system for liquid chromatography, in particular of high-pressure liquid chromatography.