Method for continuously using separation medium

A method for continuously using a separation medium, the method comprising:

• a separation medium filling step of filling a capillary with the separation medium;
• a first pre-run step of applying a voltage in the same direction as that in which electrophoresis is to be performed to the capillary filled with the separation medium to perform a pre-run;
• a first sample injection step of injecting a first-time sample into the capillary subjected to the pre-run;
• a first electrophoretic step of applying a voltage to the capillary into which the first-time sample has been injected to perform first electrophoresis;
• a second pre-run step of applying a voltage in the same direction as that in which electrophoresis is to be performed to the capillary after the first electrophoretic step to perform a pre-run;
• a second sample injection step of injecting a next-time sample into the capillary subjected to the second pre-run step;
• and
• a second electrophoretic step of applying a voltage to the capillary into which the next-time sample has been injected to perform next electrophoresis,
• wherein, after repeatedly performing the second pre-run step, the second sample injection step, and the second electrophoretic step a preliminarily set number of times, the method ends analysis using the separation medium with which the capillary is filled in the separation medium filling step performed once, then returns to the separation medium filling step to replace the separation medium in the capillary, and performs each of the steps including and subsequent to the first pre-run step by using a new separation medium an intended number of times.