Low-pressure gradient device

A low-pressure gradient device comprising:

• a reciprocating pump for sending a liquid by suctioning and discharging the liquid;
• a first suctioning flow path for introducing a first mobile phase into the reciprocating pump;
• a second suctioning flow path for introducing a second mobile phase into the reciprocating pump;
• a meeting portion where the first suctioning flow path and the second suctioning flow path meet each other;
• an inlet flow path connecting the meeting portion and the reciprocating pump;
• solenoid valves respectively provided on the first suctioning flow path and the second suctioning flow path to carry out opening and closing of the respective flow paths at different times;
• orifices provided as flow path sections having smaller diameters than the other portions of the respective suctioning flow paths between the solenoid valves and the meeting portion on the respective suctioning flow paths;
• and
• a connecting block having the meeting portion and at least a part of each of the suctioning flow paths,
• wherein the solenoid valves are attached to the connecting block with respective packings and connected to the respective suctioning flow paths through flow path holes of the respective packings, each of the packing, being sandwiched between the respective solenoid valve and the connecting block, and each of the flow path holes having a constant cross-section, and wherein the orifices are the flow path holes themselves of the respective packings.