  Cleaner analytic technique for quantifying compounds in dense suspension is
needed for wastewater and environment analysis, chemical or bio-conversion
process monitoring, biomedical diagnostics, food quality control among others.
In this work, we introduce a green, fast, one-step method called nanoextraction
for extraction and detection of target analytes from sub-milliliter dense
suspensions using surface nanodroplets without toxic solvents and pre-removal
of the solid contents. With nanoextraction, we achieve a limit of detection
(LOD) of 10^(-9) M for a fluorescent model analyte obtained from a particle
suspension sample. The LOD lower than that in water without particles 10^(-8)
M, potentially due to the interaction of particles and the analyte. The high
particle concentration in the suspension sample thus does not reduce the
extraction efficiency, although the extraction process was slowed down up to 5
min. As proof of principle, we demonstrate the nanoextraction for
quantification of model compounds in wastewater slurry containing 30 wt% sands
and oily components (i.e. heavy oils). The nanoextraction and detection
technology developed in this work may be used as fast analytic technologies for
complex slurry samples in environment industrial waste, or in biomedical
diagnostics.
