Monosegmented micro-volume liquid-liquid flow-extraction system based on intermittent pumping and spectroscopic detection

A micro-volume liquid-liquid flow-extraction system with on-capillary spect roscopic detection has been developed, exploiting the surface-enhanced capa city of small plugs of organic solvent to extract analytes from aqueous sam ples in 250 mu m i.d, silica columns. The organic solvent plug is monitored directly, while in the capillary, and a ceramic piston pump is used, allow ing exact volumes of the aqueous sample and the organic solvent to be pulse d into the capillary. This pulsed flow increases the extraction efficiency. Sample and organic solvent volumes used in the trials reported here were i n the ranges 180 nl-5.6 mu l and 50 nl-3 mu l, respectively. The utility of the system was demonstrated by extracting pharmaceutical samples containin g caffeine (2.65 mu l) with chloroform (254 nl). This system is suitable fo r analyses where only small amounts of sample are available, e.g. for drug screening. (C) 2000 Elsevier Science B.V. All rights reserved.