An unsegmented extraction system for flow injection analysis

In the system described, the two phases are fed into a module containing a PTFE membrane so that no segmentation takes place, i.e., each phase is fed to only on one dise of the membrane. The groove depth on the “aqueous” side of the membrane is 0.4 mm and on the “organic” side 0.8 mm. This latter groove is filled with a porous support of polyethylene. Caffeine, sodium dodecyl sulphate and sodium dioctylsulphosuccinate samples (40—500 μl) were injected into an aqueous carrier stream which was merged and mixed with an aqueous reagent before it was fed into the module. The maximum extraction efficiency varied with the flow rate but was in the range 8–18% and was obtained by injecting sample volumes larger than 400 μl. By injecting 40 μl of sample, the efficiency dropped by a factor of 1.5–7, depending on the character of the analyte. The system is suitable for coarse liquid-liquid extraction of concentrated samples because neither segmentation nor separation of the phases is required.