A GC-MS calibration curve was established for the conversion of recorded GC-MS signals to nopinone concentrations. For this purpose, calibration standards were prepared at eight known nopinone concentrations using pure MeOH solvent and no water for dilution, as the instrument was expected to show little sensitivity towards the amount of water in solution when measuring nopinone content. As the experimentally collected permeate samples were expected to have a low nopinone content, calibration curve generation focussed on nopinone concentrations ranging from 0.005 to 0.05 mol l -1 . For completion, calibration standards were also prepared at higher concentrations of 0.1 mol l -1 and 0.45 mol l -1 . The latter corresponds to a nopinone concentration of 62 g l -1 , equivalent to the concentration of the feed solution to the membrane unit during experimental runs.