Immiscible solvents distillations apparatus

When the distribution ratio is low, continuous methods of extraction are used. This procedure makes use of a continuous flow of immiscible solvent through the solution if the solvent is volatile, it is recycled by distillation and condensation and is dispersed in the aqueous phase by means of a sintered glass disc or equivalent device. Apparatus is available for effecting such continuous extractions with automatic return of the volatilised solvent (see the Bibliography, Section 9.10). 

By analogy to solvent extraction, the column containing the solid adsorbent corresponds to the separatory funnel containing the immiscible organic solvent. The transfer of the solute to the solid adsorbent occurs in an unattended operation requiring no manual effort or additional equipment such as the shakers used in solvent extraction or the distillation apparatus used in some of the automatic extraction devices. This simplicity allows for facile automation either off-line or on-line with the separation and detection procedure (495, 512, 536). 

During operation, the apparatus shown in Fig. 2 requires attention beyond occasional draining of the water trap. It is suitable for a number of preparations in which water is removed by distillation with an immiscible solvent it functions only when the condensate separates into two phases, of which water is the more dense. 

Simultaneous Steam Distillation/Extraction An elegant apparatus was described by Nickerson and Likens ( 5) for the simultaneous steam distillation and extraction (SDE) of volatile components. This device has become one of the mainstays in the flavor field. In this apparatus, both the aqueous sample and water-immiscible solvent are simultaneously distilled. The steam which contains the aroma chemicals and the organic solvent are condensed together, and the aroma compounds are transferred from the aqueous phase to the organic phase. Typical solvents used are diethyl ether, pentane or a mixture thereof normal extraction times are one to two hours. 

This method, specimens and water are heated in a steam distillation apparatus, once the water is boiled, volatile constituents will be carried along with the water vapour and then condensed in to a trap containing water and an immiscible solvent. Water and the solvent will separate into two phases. The volatile oils is dissolved in the solvent. A standard method described in British Pharmacopoeia (BP) 2010, Essential oil in Herbal Drugs, is very useful in determining the total content of volatile oils in herbs. The volatile distillate thus obtained can be used for determination of the constituents either qualitatively or quantitatively. 

Essential oil determination results should always be expressed on a moisture-free basis. Therefore, alongside essential oil determination, moisture content determination of the same plant material also should be carried out using a proper glass apparatus (Dean Stark type). The technique involves distillation of the sample with an immiscible solvent (e.g., xylene and toluene) presaturated with water. Water within the plant material is codistilled with the volatile solvent and condensed into a graduated tube where water collects at the bottom of the tube below the solvent line. Solvent continuously returns to the distillation flask. The volumetric moisture content determination apparatus is shown in Fig. 9.2. 

If the distribution coefficient is sufficiently large, the simplest approach to liquid-liquid extraction is shaking the sample with an appropriate amount of an organic solvent. With smaller distribution coefficients or large sample volumes, continuous extraction or countercurrent extraction is required to achieve a complete separation. The apparatus for continuous extraction causes a liquid immiscible with the sample solution to circulate continuously and in finely divided form through the sample [171]-[173]. Extracted analytes are concentrated by distillation at appropriate times between individual extraction cycles. 

One of the most popular and valuable techniques in the flavor analysis fleld is the simultaneous steam distillation/extraction (SDE) apparatus first described by Likens and Nickerson (17). The apparatus provides for the simultaneous condensation of the steam distillate and an immiscible organic solvent. Both liquids are continuously recycled, and thus the steam distillable-solvent soluble compounds are transferred from the aqueous phase to the solvent. The advantages of this system include the following ... 

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