Combinatorial mixtures of organic solutes for improved liquid/liquid extraction of ions.

Biological systems routinely extract and organize ions in complex yet highly ordered and active systems. Much of this function is attributed to proteins, although recent evidence indicates aggregates of lipids are also capable of molecular recognition. Here we tested the hypothesis that combinatorial mixtures of organic solutes might lead to enhanced liquid/liquid extraction. We started with liquid oleic acid as an organic phase extracting copper ions from water and added a library of additives. By using Bayesian optimization to autonomously direct the combinatorial formulation, we discovered mixtures that enhanced the extraction performance. The main additive that improved the system was octylphosphonic acid. Interestingly, the optimal mixture has a significant improvement compared to this additive alone. This suggests that the combinations of organic solutes are better than using pure components in liquid/liquid extraction. Furthermore, we found that precipitation occurs in the samples showing better extraction efficiency, which has interesting material properties and potential for new types of supramolecular biosensors.