PROBLEM TO BE SOLVED: To establish a method for obtaining a qualitative marker of a high reproducibility by adding a standard substance to an unknown sample, obtaining a migration time of the standard substance by capillary zone electrophoresis, and converting the migration time of the standard substance to an effective mobility given that a velocity of a seepage flow is linearly dependent on the time.
SOLUTION: A standard substance is added to an unknown sample. A capillary electrophoresis is carried out to obtain a migration time of the standard substance. Supposed that a velocity of a seepage flow is linearly dependent on the time, the migration time of the standard substance is converted to an effective mobility. In the conversion method with the use of a virtual seepage flow, a velocity Veof,hyp of the virtual seepage flow is obtained as a linear function of the time from migration times tA and tB of two standard substances of mobilities mA and mB according to Veof,hyp=at+b. Thereafter, a velocity of the unknown sample is obtained from a migration time t of the unknown sample. A difference from the velocity Veof,hyp of the virtual seepage flow is obtained and divided by an average potential gradient E of a capillary.