Method for determining diffusion

A method for determining a diffusion feature of a fluidic sample using redox reactions in an electrochemical cell that has at least two electrodes, wherein the first electrode has at least one redox mediator at its surface or in close vicinity of its surface, and the second electrode has an electrode surface free of the at least one redox in the beginning of a test, the method comprising:

• applying an electric potential to a fluidic sample in the electrochemical cell to initiate redox reactions at the two electrode surfaces;
• measuring current associated with the applied potential as a function of time, and
• using a measurement point on a transient part of the measured current at or after a turning point and its associated time to determine the diffusion feature;
• wherein the turning point is the point at which a first transient part ends and a second transient part begins, wherein the first transient part deviates from a Cottrell current decay and the second transient part substantially follows a Cottrell current decay;
• identifying the turning point on the transient part of the measured current;
• using the identified turning point to determine the measurement point that is to be used for determining the diffusion feature, wherein the measurement point is offset in time from the turning point (tturn+Δt, =identified point);
• and
• using the measurement point current and its associated test time to determine simultaneously the diffusion feature and contribution of at least one redox-active substance.