SOLVENT EXTRACTION-FLOW INJECTION WITHOUT PHASE-SEPARATION THROUGH THE USE OF THE DIFFERENTIAL FLOW VELOCITIES WITHIN THE SEGMENTED FLOW

A simple and robust flow injection extraction system has been developed. The system exploits the wetting film of the organic phase which forms on the walls of the hydrophobic Teflon tubing. This wetting film is stationary and thus reduces the average linear velocity of the organic flow. Any component extracted into the organic phase requires more time to pass through the extraction coil than the unextracted components. Using organic solvents such as hexanol, which have a high viscosity and low interfacial tension, the differential flow velocities can yield a separation in time between unextracted and extracted components. After the separation is complete, methanol addition homogenizes the segmented flow prior to its passage through the flow cell of an absorbance detector. Thus the need for a phase separator has been eliminated. Large aqueous-to-organic phase ratios, high flow rates, and long extraction coils enhance the resolution between the unextracted and extracted components. The active components in motion sickness tablets were determined with an analytical precision of 2.5-4.0% and a throughput of 12 analyses/h.