Fully Automated Purification of Small Molecules Using Online MicroSPE-UPLC-SPE

Structural annotation of metabolites remains a key challenge in metabolomics, as NMR-based structure elucidation for every unknown UPLC peak is limited by low sensitivity and time-consuming purification. To overcome these constraints, we developed an online microSPE-UPLC platform that enables fully automated, high-throughput peak fractionation. The system allows the injection of up to 1 mL of organic extract onto microSPE cartridges in a 96-well format for metabolite enrichment and cleanup. A dual-pump loading and refocusing strategy ensures quantitative transfer to UPLC, maintaining high chromatographic resolution while collecting narrow fractions on postcolumn microSPE. Fractions can be directly eluted with deuterated solvents for NMR analysis, eliminating drying steps and preserving volatile compounds. This approach enables milligram-scale isolation of natural products per compound within a single day. The workflow was validated using plant and fungal extracts, enabling the successful purification and characterization of several sesquiterpenoids and a diterpenoid.