Extraction of steam distillates by solvents

Extraction of steam distillates by solvents. The apparatus, depicted in Fig. 11,58, 7, may be employed for the continuous extraction of substances which are volatile in steam from their aqueous solutions or suspensions. Solvents of the ether type (i.e., lighter than water) or of the carbon tetrachloride type (i.e., heavier than water) may be used. A reflux condenser is inserted in the Bl9 socket, whilst flasks of suitable capacity are fltted into the lower B24 cone and the upper. B19 cone respectively. For extraction with ether, the flask attached to the upper. B19 cone contains the ether whilst the aqueous solution is placed in the flask fltted to the lower B2i cone the positions of the flasks are reversed... 

Volatile ginger oil obtained from steam distillation has been the subject of many research studies (5-12). However, the thermal degradative effects of steam distillation upon volatile and nonvolatile components of ginger were seldom discussed. Recently, Moyler (1) compared the advantages of liquid carbon dioxide extraction over conventional methods such as solvent extraction or steam distillation by showing reconstructed GC chromatograms which clearly displayed the differences. However,quantitative results showing the differences were not mentioned. 

The simultaneous combination of steam distillation and solvent extraction, usually implemented by a Likens-Nickerson apparatus or its analogues, has also been widely used for the isolation of essential oil. The chemical composition of such essential oils will be analysed by GC-MS [40]. 

Analytical Techniques. Sorbic acid and potassium sorbate are assayed titrimetricaHy (51). The quantitative analysis of sorbic acid in food or beverages, which may require solvent extraction or steam distillation (52,53), employs various techniques. The two classical methods are both spectrophotometric (54—56). In the ultraviolet method, the prepared sample is acidified and the sorbic acid is measured at 250 260 nm. In the colorimetric method, the sorbic acid in the prepared sample is oxidized and then reacts with thiobarbituric acid the complex is measured at - 530 nm. Chromatographic techniques are also used for the analysis of sorbic acid. High pressure Hquid chromatography with ultraviolet detection is used to separate and quantify sorbic acid from other ultraviolet-absorbing species (57—59). Sorbic acid in food extracts is deterrnined by gas chromatography with flame ionization detection (60—62). 

Notes on the preparation of secondary alkylarylamines. The preparation of -propyl-, ijopropyl- and -butyl-anilines can be conveniently carried out by heating the alkyl bromide with an excess (2-5-4mols) of aniline for 6-12 hours. The tendency for the alkyl halide to yield the corresponding tertiary amine is thus repressed and the product consists almost entirely of the secondary amine and the excess of primary amine combined with the hydrogen bromide liberated in the reaction. The separation of the primary and secondary amines is easily accomplished by the addition of an excess of per cent, zinc chloride solution aniline and its homologues form sparingly soluble additive compounds of the type B ZnCl whereas the alkylanilines do not react with sine chloride in the presence of water. The excess of primary amine can be readily recovered by decomposing the zincichloride with sodium hydroxide solution followed by steam distillation or solvent extraction. The yield of secondary amine is about 70 per cent, of the theoretical. 

About 120 chemical constituents have been identified in chamomile as secondary metabolites, including 28 terpenoids, 36 flavonoids and 52 additional compounds [4]. A substantial part of drag effects are determined by the essential oil content. Oil is collected from flower heads, either by steam distillation or solvent extraction, for yields of 0.24-1.90% of fresh or dry plant tissue. Among the essential oil constituents the most active are /-/-a-bisabolol and chamazulene. /-/-a-bisabolol has demonstrated anti-inflammatory, antispasmodic, antimicrobial, antiulcer, sedative and CNS activity. Chamazulene is also anti-inflammatory. Topical applications of chamomile preparation have shown benefit in the treatment of eczema, dermatitis and ulceration [5]. 

Olibanum oil and olibanum resinoid are obtained from frankincense, which is a gum resin collected from the bark of the tree Boswellia carterii Birdw. or B. frereana Birdw. (Burseraceae) growing in Arabia and Somalia. The resinoid is produced by solvent extraction, and steam distillation gives the oil, which is a pale yellow, slightly viscous liquid with a balsamic odor and a faint lemon note. 

Opopanax oil and opopanax resinoid are obtained from the resin of Commiphora erythraea Engl. var. glabrescens Engl., a tree growing in Somalia (Burseraceae). The resinoid is prepared by solvent extraction, and steam distillation of the resin gives the essential oil, which is a yellow to greenish-yellow liquid with a warm, sweet, balsamic odor. 

Aldehydes and Ketones. The best derivative from which an aldehyde can be recovered readily is its bisulphite addition compound, the main disadvantage being the lack of a sharp melting point. The aldehyde (sometimes in ethanol) is shaken with a cold saturated solution of sodium bisulphite until no more solid adduct separates. The adduct is filtered off, washed with a little water, then alcohol. A better reagent is freshly prepared saturated aqueous sodium bisulphite solution to which 75% ethanol is added to near-saturation. (Water may have to be added dropwise to render this solution clear.) With this reagent the aldehyde need not be dissolved separately in alcohol and the adduct is finally washed with alcohol. The aldehyde is recovered by dissolving the adduct in the least volume of water and adding an equivalent quantity of sodium carbonate (not sodium hydroxide) or concentrated hydrochloric acid to react with the bisulphite, followed by steam distillation or solvent extraction. 

Turpentine and Rosin The major naval stores products are turpentine, primarily composed of volatile terpenes, and rosin, mainly a mixture of resin acids. Principally the same products, but in different proportions, can be recovered by tapping resin-rich trees or by steam distillation or solvent extraction of wood residues and especially stumps. Today, however, the most important source for turpentine and rosin is the tall oil recovered after pulping of pine wood (see Section 10.3.1). 

Extraction of Essential Oils from Plants. Essential oils are aromatic substances widely used in the perfume industry, the pharmaceutical sector, and the food and human nutrition field. They are mixtures of more than 200 compounds that can be grouped basically into two fractions a volatile fraction, which constitutes 90-95% of the whole oil, and a nonvolatile residue, which constitutes the remaining 5-10%. The isolation, concentration, and purification of essential oils have been important processes for many years, as a consequence of the widespread use of these compounds. The common methods used are mainly based on solvent extraction and steam distillation. SFE has been used for the extraction of essential oils from plants, in an attempt to avoid the drawbacks linked to conventional techniques (57). Such is the case with the extraction of flavor and fragrance compounds, such as those from rose (58), rosemary (59), peppermint (60), eucalyptus (61), and guajava (62). The on-line coupling of the extraction and separation ietermi-nation steps (by SFE-GC-FID) has been proposed successfully for the analysis of herbs (63) and for vetiver essential oil (64). 

Steam distillation is the main commercial extraction procedure for the production of essential oils from almost any type of plant material. Solvent extraction is also used commercially and yields a resinoid, concrete or absolute according to the solvents and techniques used (see Chapter 4). Both steam distillation and solvent extraction are used on a laboratory scale to produce oils and extracts for analysis. Other methods of extraction, such as supercritical fluid extraction (SFE), which uses supercritical CO2 as the extraction solvent, are now being developed and used on both commercial and laboratory scales. The extracts produced by SFE may contain different materials from the steam-distilled oil because of the solvating power of C02 and the lower extraction temperature, which reduces thermal degradation. The C02 extract may therefore have an odour closer to that of the original material and may contain different fragrant compounds. The choice of extraction procedure depends on the nature and amount of material available, and the qualities desired in the extract. Solvent extraction is better suited to small sample amounts or volatile materi-... 

Qccurance and Identification. An early report of cotton volatile composition by Minyard et al. (44) involved steam distillation of large quantities of leaves and flowers. Major compounds identified included the monoterpenes a-pinene, B-pinene, myrcene, trans-B-ocimene, and limonene ( 4). Several other monoterpene hydrocarbons were also present in low concentration. Since that report, many other terpenes have been identified in cotton essential oil steam distillates and solvent extracts. These compounds include cyclic hydrocarbons such as bisabolene, caryophyllene, copaene and humulene (45-47), the cyclic epoxide caryophyllene oxide (45), cyclic alcohols such as bisabolol, spathulenol, and the aromatic compound... 

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