ANALYTICAL CHEMISTRY IN A DROP.
SOLVENT EXTRACTION IN A MICRODROP
Anal. Chem., 1996, 68, 1817
(Accelerated Article)
Hanghui Liu and Purnendu K. Dasgupta*
Department of Chemistry and Biochemistry
Texas Tech university, Lubbock, TX 79409-1061, USA
(Reviewers' Comments)
A micro (~0.0013 mL) organic
drop is suspended inside a flowing aqueous drop from which the
analyte is extracted. The drop-in-drop system is achieved by a
multi-tube assembly. The aqueous phase is continuously delivered
to the outer drop and is aspirated away from the bottom meniscus
of the drop. After the sampling/extraction period, a wash solution
replaces the sample/reagent in the aqueous layer, resulting in
a clear outer aqueous drop housing a colored organic drop containing
the extracted material. This also results in an automatic backwash.
The color intensity of the organic drop, related to the analyte
concentration, is monitored by a light emitting diode (LED) based
absorbance detector. After the analytical cycle, the organic drop
is removed and replaced by a new one. The performance of the system
is illustrated with the determination of sodium decyl sulfate
(SDS) (a methylene blue active substance (MBAS)) extracted as
an ion-pair into chloroform. This unique micro extraction system
is simple, flexible, permits automated backwashing, consumes only
micro quantities of organic solvents and is capable of being coupled
with other analytical systems. This concept should prove valuable
for preconcentration and matrix isolation in a micro scale.
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