defects in the membrane. Nevertheless, affinity of neutral organic molecules to the mildly hydrophobic polyamide membrane material has been reported in the literature, and may also explain slightly non-ideal permselectivity towards nopinone through BW30 despite its large molecular size. The magnitude of the regressed mass transfer coefficient value represents the most significant compromise between optimising the fit of the Spiegler-Kedem model equations to the experimental data. This is because the magnitude of 𝑘 "# has a profound impact on the buildup of concentration polarisation. While a small 𝑘 "# would fit the model better to large 𝑅 %&' , a larger 𝑘 "# would fit the effective osmotic pressure, which is counteracting the applied pressure, better to large 𝐽 ! , assuming no error in 𝛥𝛱. The 𝑘 "# value obtained as the best compromise was 6.5×10 -6 m 3 m -2 s -1 .