The impedance of the series combination of a ZARC element (Section 2.2) and a generalized Warburg element (Section 2.1) is given by Given that the ZARC and Warburg timescales are separated with the ZARC timescale being much lower than the Warburg timescale, the admittance, 𝑌(𝑓; 𝑅 ∞ , 𝑅 ct , 𝜏 ZARC , 𝜙, 𝐴, 𝛼), can be approximated as