The first 2.5 ml of collected permeate were discarded as hold-up volume during all experimental runs. Subsequently, permeate samples were collected in separate tubes at 5 ml intervals and the permeation time of each sample was recorded. It was assumed that the volumes of all 5 ml batches were sampled precisely, and that permeation times were recorded with negligible errors. Due to time constraints, it was not possible to collect more than 60 ml of permeate volume per experimental run. At the end of each run, the system was depressurised via a relief valve, and the retentate was collected in a separate vial. All samples were stored at room temperature. A sketch of the experimental set-up is shown in Figure . (Illustration by Dr Sameer P. Khare; University of Bath).