Potentiometric-sensor chip, potentiometric assay, and assay kit

A sensor chip comprising:

• a sample inlet that introduces a sample;
• a reference electrode that the sample is made to touch;
• a measurement electrode that has a measuring reagent and is made to touch the sample for measurement of a potential difference from the reference electrode;
• a first flow channel branching from the flow channel stretching from the sample inlet in which the reference electrode is located;
• and
• a second flow channel branching from the flow channel stretching from the sample inlet in which the measurement electrode is located;
• wherein the reference electrode and the measurement electrode are disposed so as for the introduced sample to arrive at the reference electrode earlier than at the measurement electrode.

A potentiometric assay method which uses a sensor chip including a reference electrode and a measurement electrode having a measuring reagent to react with an introduced sample, to measure a potential difference between the reference electrode and the measurement electrode, comprising the steps of:

• introducing the sample;
• making the sample touch the reference electrode;
• after making the sample touch the reference electrode, making the sample touch the measurement electrode;
• detecting time of transition in the potential difference from a discontinuous change to a continuous change;
• and
• calculating a concentration of the sample from the change in the potential difference since the detected time using previously prepared data on relationship between potential differences and concentrations of the sample.

An assay kit comprising:

• a sensor chip that makes a sample touch;
• and
• a measurement device to which the sensor chip is attached to measure a concentration of the sample,
• the sensor chip including:
• a sample inlet;
• a reference electrode that the sample is made to touch;
• a measurement electrode that has a measuring reagent and is made to touch the sample;
• and
• a first terminal for measurement of potentials of the reference electrode and the measurement electrode,
• wherein the reference electrode and the measurement electrode are disposed so as for the introduced sample to arrive at the reference electrode earlier than at the measurement electrode,
• the measurement device including:
• a slot for the sensor chip;
• a second terminal that detects a voltage from the first terminal;
• a memory storing data on relationship between potentials and concentrations of the sample;
• a calculating unit that measures the voltage detected by the second terminal, detects time of a discontinuous change in potential difference between the reference electrode and the measurement electrode and calculates a concentration of the sample from the change in potential difference since the detected time;
• and
• a display unit that displays the concentration calculated by the calculating unit.