Phase Segmentors

Although most FI determinations involving liquid-liquid extractions are made after separation of the two phases, in some of the more recent contributions, determinations are also made without phase separation, therefore excluding phase separators from the system. 

l Schematic diagram of a merging-tube segmentor. OR, organic phase AQ, aqueous phase Pt, platinum capillary [1]. 

The volume of the droplet formed V, is governed by the interfacial tension To/a-the inner diameter of the capillary //. the acceleration due to gravity g. and the density difference between the two phases Ap, and may be calculated from the equation  

Various factors which influence the segmentation performance of coaxial segmentors using Freon-113. CHCI3. IBMK and CCI4 as test solvents are summarized as follows  

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Departing from the "conventional extraction cell design, Theibolt et al. (11) used a novel phase segmentor and subsequent phase separator in order to extract 4-chlorophenol and phenol from water. On-line SFC was used for subsequent analysis. Recoveries and reproducibilities for the system were not reported, although with a single pass system 100% recovery would not be expected. We too have demonstrated... 

Fig3.13 Schematic diagram of a typical FI manifold for liquid-liquid extraction spectrophotometry. R pump DB. displacement bottle C. carrien R, reagent S. sample SG, phase segmentor EC. extraction coil SR phase separator R. restrictor or impedance coil D. detector W. waste. 

FigJ.15 Schematic diagram of an on-line FI sample cleanup system for a gas chromatograph. OR organic solvent S, aqueous sample SG, phase segmentor EX. extraction coil SP membrane phase separator W, waste DC. desiccator, V, 6-port injector valve B, heater SC. stopcock 1. injection port of gas chromatograph D. detector GC. gas chromatograph [54]. 

T-tube phase segmentor and sandwich-type membrane phase separator. 300 cm long, 0.5 mm i.d. PTFE tubing extraction coil. 

Figure 5.7 A schematic diagram of the online coupling of liquid-liquid extraction with GC. O, 50 ml glass syringe with extraction solvent, flow rate 138 t,lmin S, 50 ml glass syringe with sample, flow rate 1430 xl min PI, phase segmentor E, polymer-coated glass extraction coil (5 m x 0.7 mm id) P2, phase separator with Teflon membrane, 0.2 xm pore size W, waste V, rotary valve with variable loop (load position) C, carrier gas inlet GC, gas chromatography [1 ].

Figure 4.30. Segmentor and separator units used for solvent extraction. In the separator (a) the distance between the end of tube (1) and the orifice of the capillary, through which the organic solvent is introduced, determines the size of the aqueous and organic segments. Thus, by adjusting this distance, the extraction can be optimized, (b) Simple T separator into which a Teflon thread is inserted to facilitate phase separation, (c) Membrane phase separator, furnished with a microphorous hydrophobic membrane (such as Teflon), allowing passage of the organic phase with better than 95% efficiency.

Hitherto, most FI liquid-liquid extractions are performed in a multi-segmented flow comprised of the two immiscible phases. Since the extraction coil is merely an extension of the outlet of the segmentor, the two components may be viewed upon as a single pan in the FI manifold. This pan of the manifold is closely connected with the propulsion system which should meet the demands for the delivery of organic solvents. Although these may be satisfactorily propelled by solvent resistant piston pumps, peristaltic pumps are used more frequently, often making the displacement bottle (cf. Sec. 2.1.1) an indispensable component of this pan of the manifold. 

In the normal FI extraction mode the enrichment factor is limited by the phase ratio which, in turn, is restricted by practical factors. A relatively complex extraction system was described by Atallah et al.[26] in which the continuously pumped sample is extracted by a small volume of oiganic phase trapped in a closed loop which incorporates the segmentor, extraction coil, phase separator and detector flow-cell. A simplified schematic diagram of the circulated extraction part of the manifold in shown in Fig. 

The on-line incorporation of LLE in an analytical system was reported some two decades ago. Typically, an aqueous sample plug is injected into an aqueous car rier. The aqueous phase meets an immiscible organic stream in a segmentor, often... 

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