Flow injection and solvent extraction with intelligent segment separation. Determination of quaternary ammonium ions...

Organic solvent segments are introduced into a premixed stream of the sample and an ion-pairing dye by a 3-way valve at regular intervals. The major mechanism of "extraction" in such a system appears to be the adsorption of the ion-pair on conduit walls and subsequent elution by the organic solvent. Following passage through the conduit, the immiscible organic segment is isolated in the loop of a 6-port valve; loop filling is sensed by a pair of conductivity sensors located respectively at the fill and drain ports of the loop and appropriate logic circuitry. The isolated segment is then injected into a purely organic carrier and detected by a suitable optical detector. Results are reported for a number of parametric studies that characterize this system. With immobilized adsorbents on conduit walls for preconcentration, a limit of detection of < 10(-7)M tetrabutylammonium ion can be obtained with bromothymol blue as the ion-pairing agent.