In a direct injection type automatic sampler, a sampling needle having a liquid sample collected from a sample vessel by using suction force of a pump is inserted into an injection port. Then, a flow path-switching valve is rotated to switch a flow path to make a flow of mobile phase liquid pass through a loop to thereby introduce the collected sample into a column. The injection port is directly incorporated in the flow path-switching valve.
The present invention relates to a sample injection device, a sample injection method, and a liquid chromatograph that control the flow of a mobile phase using a switching valve. The sample injection device includes a port connected to a separation column, a pump for supplying a mobile phase, first and second sample injection needles, a syringe, and a valve configured to selectively connect the first sample injection needle to the pump or the syringe and to connect the second sample injection needle to the pump. When the first sample injection needle is attached to the port, the first sample injection needle is connected to the pump through operation of the valve. When the second sample injection needle is attached to the port, the first sample injection needle is connected to the syringe and the second sample injection needle is connected to the pump.
