We further investigated the efficiency loss related to step 2, i.e., the step in which the freshly activated molecule partitions into the chloroform phase, and step 3, i.e., the step in which it leaves the chloroform again. We tested several transporter molecules differing in their partitioning coefficient and their interface-crossing rate. Specifically, next to the charge-neutral Cbz-D, we tested the polar nitro-phthalic anhydride and the negatively charged sulfo-phthalic anhydride (Fig. ). Again, we found no evidence of assembly before and after fueling by a turbidity measurement, confirming that nitro-and sulfophthalic acid were well-dissolved (Fig ). Both nitro-and sulfophthalic acid successfully crossed the hydrophobic barrier after activation with EDC. However, sulfo-phthalic acid was only transported with a 0.2% efficiency, showing the importance of partitioning in chloroform. In contrast, the polar nitro-phthalic acid molecules were transported roughly as effectively as Cbz-D (Fig. , Fig. ). We used the model to understand the role of the partitioning coefficient and interface crossing on the transport. The transfer rate across the interface quantifies the kinetics at which equilibration occurs at the interface. The efficiency of the transportation process is directly proportional to this rate. As a measure for the partitioning coefficient, we used the excess chemical-potential difference, which quantifies the change in the energy when a molecule crosses the water-oil interface into the oil. Figure depicts the transport efficiency after 8 days as a function of the excess chemical-potential difference. The transport efficiency decreases if it is unfavorable for molecules to enter the chloroform, represented by an interaction difference of -8 kBT. Conversely, with a high attractive interaction difference of +8 kBT, molecules remain trapped in the chloroform, hindering efficiency after 8 days. The ideal scenario is in between, ensuring effective transport by avoiding extremes hindering transfer. In the model, sulfo-phthalic acid partitions weaker into the chloroform at a drastically reduced interface-crossing rate, potentially due to its permanent negative charge, and transports with a low efficiency.