I assume you're referring to a porous/high surface area electrode because you mentioned analytes going "into" it. If it's a glassy carbon electrode, you should use mechanical polishing with aluminum oxide slurry. If it's platinum or gold, you can use cyclic voltammetry in 0.5 M H2SO4.
Dear Effat: It is not so much the penetration of contaminants inside the electrode. You have some alternatives, between them, scan from 0 V up to +1,5 V ( during 2 or 3 minutes) the electrode in NaOH 1 M. After, wash very well with abundant water. Previously, you must clean with diamond paste, to clean using ultrasonic and polish the surface carefully. In this case, you must obtain a signal, with few current density of double layer and without any peak.
Also, the before pocedure not only clean, funcionalyze the electrode surface. This means enrich with electrones the surface and benefit The electronic transference.