Zeta-potential measurement jig

A zeta-potential measurement jig, to be used for an electrophoretic mobility measuring device, comprising:

• a frame body including:
• a first holding wall and a second holding wall, which are arranged in such a manner as to be opposed to each other, and the first holding wall has a first opening and the second holding wall has a second opening, and the first opening and the second opening are aligned with one another at a position opposite to one another;
• and
• a bottom wall configured to couple a lower end of the first holding wall and a lower end of the second holding wall to each other;
• an intermediate block which is arranged above or below a cell in such a manner as to be adjacent to the cell, the cell being arranged between the openings at substantially the same level as that of the openings, and
• a cell retainer, which is arranged above the intermediate block between the first holding wall and the second holding wall, and is configured to press the cell and the intermediate block toward the bottom wall,
• wherein at least one of the first holding wall or the second holding wall has one of a first groove or a first protrusion to be elastically fitted into a first support groove, which is configured to support the intermediate block on a lateral side, and
• wherein the intermediate block has another one of the first groove or the first protrusion.