Detection kit, sealing liquid, method for preserving sealing liquid, and method for detecting sample

A method for detecting a sample in which a target substance contained in a liquid sample is detected, the method comprising:

• a step of adjusting a mixed aqueous solution of a detection reagent reacting with the target substance and the sample;
• a step of filling wells with the mixed aqueous solution of the sample and the detection reagent, by using a fluid device that includes an internal space accommodating the mixed aqueous solution, an injection port and a discharge port communicating with the internal space, and a plurality of wells open to the internal space and accommodating the mixed aqueous solution, by introducing the mixed aqueous solution into the internal space;
• a step of sealing the mixed aqueous solution in the wells with the sealing liquid by introducing an oil-based sealing liquid into the fluid device;
• and
• a step of detecting the target substance by heating the fluid device to allow the target substance and the detection reagent to react with each other,
• wherein a dissolved oxygen amount in the sealing liquid is 100 mg/L or less and a dissolved nitrogen amount in the sealing liquid is 260 mg/mL or less.