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1. A liquid chromatograph comprising: a sampling channel in which a sampling needle is provided at a tip; a needle movement mechanism that moves the needle three-dimensionally; a liquid supplier configured to be able to supply at least a mobile phase; an analysis channel provided with a separation column for separating components included in a sample; a pressure valve having an injection port that is fluidly connected with the sampling channel when the needle is inserted and a port connected with the analysis channel, and configured to selectively switched to a loading state and an injecting state, wherein the loading state is a state for fluidly connecting the liquid supplier and the analysis channel not via the sampling channel, and the injecting state is a state for fluidly connecting the liquid supplier and the analysis channel via the sampling channel when a tip of the needle is inserted into the injection port; and a controller configured to control the needle movement mechanism, the liquid supplier, and the pressure valve, wherein the liquid supplier, the analysis channel, and the pressure valve constitute one analysis unit for performing analysis of a sample, and the controller is configured to execute, as an analysis operation in the analysis unit, a sample injection step of bringing the pressure valve into the loading state, sucking a sample from a tip of the needle to hold the sample in the sampling channel, then connecting the sampling channel to the injection port and bringing the pressure valve into the injecting state, and supplying a mobile phase from the liquid supplier, thereby injecting a sample held in the sampling channel into the analysis channel, and an analysis step of separating components of a sample injected into the analysis channel in the separation column by bringing the pressure valve in the loading state and supplying the mobile phase from the liquid supplier, after the sample injection step is ended, in a case where at least a predetermined condition is satisfied, after the analysis step is ended, the controller is configured to execute, as the analysis operation, a system cleaning step of cleaning a liquid flowing route from the sampling channel to the analysis channel by connecting the sampling channel to the injection port and bringing the pressure valve into the injecting state to supply the mobile phase and/or a cleaning liquid from the liquid supplier.
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