  Liquid-liquid extraction based on surface nanodroplets, namely
nanoextraction, can continuously extract and enrich target analytes from the
flow of a sample solution. This sample preconcentration technique is easy to
operate in a continuous flow system with low organic solvent consumption and a
high enrichment factor. In this review, the evolution from single drop
microextraction to advanced nanoextraction will be briefly introduced. Also,
the formation principle and key features of surface nanodroplets will be
summarized. Further, the major findings of nanoextraction combined with
in-droplet chemistry toward sensitive and quantitative detection will be
discussed. Finally, we will give our perspectives on the future trend of
nanoextraction.
