Extraction Coils

It facilitates the transfer of material through the interfaces of segmented flow in the extraction coil, the length of which, together with the flow rate, determines the duration of the actual liquid-liquid extraction. 

It splits, in a continuous manner, the segmented flow from the extraction coil into two separated phases (phase separator). 

In the extraction coil (EC), when the extraction reaction is based on the formation of metal chelates and the ligand is dissolved in the organic solvent. Here the reaction and the transfer of the chelate take place simultaneously. 

Conventional oontinuous LLE requires the use of three basic units viz. a segmenter, an extraction coil and a phase separator, in order to achieve the sequential formation of aqueous-organio phase segments, mass transfer between the two types of segments and olean separation of the acceptor phase to be led to the detector, respectively, [2]). 

This manifold has been used for the USALLE of paracetamol from suppositories [17]. Hydrolysis of the analyte prior to reaction with o-cresol in the alkaline extractant medium was also favoured by US (the entire sample plug was irradiated in EC). Hydrolysis and formation of the reaction product displaced the extraction equilibrium, thus favouring extraction into the aqueous phase. The influence of the variables related to the dynamic manifold (namely, flow rate and sample volume), chemical variables (namely, NaOH and o-cresol concentrations) and temperature was studied using the univariate method on account of their independence on the other hand, those related to US (namely, probe position, radiation amplitude and pulse duration) were the subject of a multivariate study in which the latter two exhibited an insignificant but positive effect. Positioning the probe closest to the extraction coil was found to maximize extraction efficiency. The positive effect of US on extraction and analyte hydrolysis provides the overall enhancement shown in Fig. 6.4A, which shows the results obtained in the presence and absence of US. The time required for the development of the method was significantly shorter than that required by the United States Pharmacopoeia (USP) method. In addition, the latter produces emulsions that need about 30 min for phase separation after extraction. 

FIGURE 12.8 Schematic diagram of the CFLME system. (From Liu, J.-F., Chao, J.-B., and Jiang, G.-B., Anal. Chim. Acta, 455, 93, 2002. With permission.) S, sample solution R, 0.5 M sulfuric acid O, organic solvent A, acceptor W, waste PI, P2, peristaltic pumps P3, piston pump MC, mixing coil EC, extraction coil VI, V2, 6-port valves SLM, SLM device PDA, detector, 240 nm. 

Fig. 6.15. Experimental set-up for high-pressure liquid-liquid extraction. LS liquid sample, SR solvent reservoir, PP piston pump, HPP high-pressure pump, CP confluence point, EC extraction coil, R restrictor. (Reproduced with permission of Springer-Verlag.)...

Fig.l Schematic representation of SIA-HPLC-detector system 1 the dialysis unit 2 the extraction (dilution, concentration, derivatization) unit 3 the HPLC-D unit. SV is the selection valve EC is the extraction coil D is the detector. 

FIGURE 8.14 Flow diagram of a flow injection system with wetting film extraction. S = sample C = aqueous carrier stream Org = organic solvent Ec = extraction coiled reactor SP = solvent added for single phase establishment Me — mixing coiled reactor D = detector. For details, see text. 

Fig. 5.14 Continuous segmented assembly with liquid-liquid extractor for the determination of various amines by ion-pair formation. AC, mixing coils EC, extraction coils PS, phase separator. (Reproduced from [32] with permission of Springer Verlag).

Figure 4.29. FIA manifold for the determination of trace metals by solvent extraction with dithizone in carbon tetrachloride. The aqueous sample S is injected into the aqueous carrier stream AQ, to which at (a) the organic phase ORG is continuously added and after passing through the extraction coil (b), made of Teflon tubing, the organic phase is again separated at point (c) and carried on through the flow cell for spectrophotometric measurement.

Therefore, the dispersion process within the extraction coil should, according to the arguments raised in discussing Fig. 4.31, be less significant when the film is thinner. Experimental results reveal that this is... 

An extraction coil in which the analyte is transferred from one phase to the other. 

Fi >3.6 Schematic diagram showing him formation in a liquid-liquid extraction coil tubing, a. static conditions b. flow conditions. AQ, aqueous phase OR. organic phase F. organic him 1201. 

In order to achieve high phase transfer factors, the extraction coil lengths are usually substantially longer than normal FI reaction coils. This feature would have been a principle source of analyte dispersion in the extraction system however, the phase... 

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. 

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