An apparatus for diluting a sample in a liquid chromatography system, comprising: a metering pump having a first pump port and a second pump port; a sample needle having a fluid channel; a sample valve having a plurality of sample valve ports, a first one of the sample valve ports being in fluid communication with the first pump port, a second one of the sample valve ports being in fluid communication with the second pump port, and a third one of the sample valve ports being in fluid communication with the sample needle, the sample valve being operable in one of a first state and a second state, wherein, when the sample valve is in the first state, the sample valve is configured to conduct a solvent to the first pump port and to fluidically terminate the second pump port, and wherein, when the sample valve is in the second state, the second one of the sample valve ports is in fluid communication with the third one of the sample valve ports so that the sample needle is in fluid communication with the second pump port; characterized in that the apparatus further comprises a merge valve in fluid communication with the sample valve for merging a flow of sample with a concurrent flow of mobile phase, the merge valve having a plurality of merge valve ports, the merge valve being operable in one of a first state and a second state, wherein, when the merge valve is in the first state, a first one of the merge valve ports is in fluid communication with a second one of the merge valve ports and wherein, when the merge valve is in the second state, the first one of the merge valve ports is in fluid communication with the second one of the merge valve ports and a third one of the merge valve ports, and wherein the first one of the merge valve ports is configured for receiving the flow of sample, the third one of the merge valve ports is configured to receive the flow of mobile phase and the second one of the merge valve ports is configured for fluid communication with a chromatographic column. a metering pump having a first pump port and a second pump port; a sample needle having a fluid channel; a sample valve having a plurality of sample valve ports, a first one of the sample valve ports being in fluid communication with the first pump port, a second one of the sample valve ports being in fluid communication with the second pump port, and a third one of the sample valve ports being in fluid communication with the sample needle, the sample valve being operable in one of a first state and a second state, wherein, when the sample valve is in the first state, the sample valve is configured to conduct a solvent to the first pump port and to fluidically terminate the second pump port, and wherein, when the sample valve is in the second state, the second one of the sample valve ports is in fluid communication with the third one of the sample valve ports so that the sample needle is in fluid communication with the second pump port; characterized in that the apparatus further comprises a merge valve in fluid communication with the sample valve for merging a flow of sample with a concurrent flow of mobile phase, the merge valve having a plurality of merge valve ports, the merge valve being operable in one of a first state and a second state, wherein, when the merge valve is in the first state, a first one of the merge valve ports is in fluid communication with a second one of the merge valve ports and wherein, when the merge valve is in the second state, the first one of the merge valve ports is in fluid communication with the second one of the merge valve ports and a third one of the merge valve ports, and wherein the first one of the merge valve ports is configured for receiving the flow of sample, the third one of the merge valve ports is configured to receive the flow of mobile phase and the second one of the merge valve ports is configured for fluid communication with a chromatographic column.