Ultra‐High‐Throughput Nanoliter‐Scale Liquid‐Liquid Extractions and Reaction Mixture Purification

Miniaturizing chemical processes to the nanoliter scale is essential for reducing costs, increasing throughput, and enabling massively parallel experimentation with tens of thousands of samples. However, purification at this scale remains a major issue. Conventional methods like liquid-liquid extraction (LLE) are not applicable at nanoliter volumes without expensive and complex instrumentation, and even then, not at such extreme throughput. The droplet microarray (DMA) platform enables high-throughput synthesis in nanoliter droplets confined to hydrophilic spots on a superhydrophobic surface. Yet, purification of compounds at this small scale and high throughput remains challenging. Here, a novel approach is presented for parallel purification of thousands of microliter- to nanoliter-sized droplets via LLE. The method exploits the ability of hydrophilic spots to retain aqueous droplets under both air and organic solvents. By immersing the entire DMA into an organic solvent, all droplets simultaneously contact the organic phase, enabling rapid, parallel, single-step extraction across the entire array. This process eliminates the need for individual pipetting or complex phase separation equipment, making it scalable, cost-effective, and compatible with miniaturized, ultra-high-throughput workflows down to 15 nL volume and up to tens of thousands of parallel extractions.