Rmemb was determined by subtracting the electronic resistance (Rel, sum of the contact resistances between stainless steel plungers and PTLs and bulk PTL resistances) from the HFR, the sum of the membrane Rmemb and Rel: 𝑅 𝑚𝑒𝑚𝑏 = 𝐻𝐹𝑅 -𝑅 𝑒𝑙 [ 2 ] The values of tmemb and σmemb for Fumasep® FAA-3 determined in this study are summarised in Table and for Selemion™ AMVN in Table where the quoted uncertainties were derived from the standard error in tmemb.