Water quality determination device, water quality determination method, and flow cell

A water quality determination method comprising:

• a first detection step of receiving a light emitted from a first light emitting unit toward a flow path by a first light receiving unit through the flow path;
• and
• a second detection step of receiving a light emitted from a second light emitting unit toward the flow path by a second light receiving unit through the flow path, wherein
• the first light emitting unit and the first light receiving unit are disposed opposite each other through the flow path,
• the second light emitting unit and the second light receiving unit are disposed opposite each other through the flow path,
• an optical path length from the second light emitting unit to the second light receiving unit is longer than an optical path length from the first light emitting unit to the first light receiving unit.

A flow cell comprising:

• a container body having an inlet and an outlet for a liquid, and a flow velocity control path provided in a region between the inlet and the outlet;
• a light emitting unit capable of emitting a light toward the liquid flowing in the flow velocity control path;
• and
• a light receiving unit that receives the light emitted from the light emitting unit, wherein
• the flow velocity control path includes:
• a control path inlet into which the liquid flowing in from the inlet is inflowed;
• and
• a control path outlet from which the liquid flowing into the control path inlet is outflowed, wherein
• an opening area of the control path inlet and an opening area of the control path outlet are equal.