The time required for the analyte to move through the effective length of the capillary, Leff, that is, from the sample introduction point to the detection point.
Source:
PAC, 2004, 76, 443. 'Terminology for analytical capillary electromigration techniques (IUPAC Recommendations 2003)' on page 448 (https://doi.org/10.1351/pac200476020443)