Nanoconfined in-situ sampling and extracting switching needle device construction for highly enrichment of polar metabolites in human urine.

Urine, as a non-invasive sampling specimen, offers significant advantages for the diagnosis and treatment of diseases. However, as a water-based matrix, most metabolites in urine are high polarity, which limits the ultrafast extraction and high enrichment of these polar metabolites from urine. Though solvent-based extraction method has demonstrated considerable benefits in extraction rates, the necessity for selecting water-immiscible solvents restricts the extraction of highly polar metabolites.