Method of measuring accuracy of concentration in sending liquid in gradient and liquid chromatograph having function of executing method

A liquid chromatography system comprising:

• a liquid sender that is capable of adjusting a concentration of a second solvent in a mobile phase made of a first solvent and the second solvent to a predetermined setting value and sending the mobile phase;
• an analysis flow path through which the mobile phase from the liquid sender flows;
• a separation column that is provided on the analysis flow path and to separate a sample injected into the analysis flow path;
• a detector that is provided at a position farther downstream than the separation column on the analysis flow path and to detect a component of a sample separated in the separation column;
• and
• a gradient accuracy measurer configured to use an organic solvent containing liquid that does not include a component to be detected by the detector as the first solvent,
• use an organic solvent containing liquid that includes the component to be detected and prevents the separation column from actually holding the component to be detected as the second solvent,
• send the mobile phase while changing a setting value of the concentration of the second solvent in the mobile phase over time,
• find an actual concentration of the second solvent in the mobile phase that is sent at each setting value based on a detection signal of the detector, and
• measure the accuracy of concentration in sending liquid in a gradient.