Essential oils, separation

Citrus oil dominates this class of essential oil. It is obtained by the cold press method with the exception of lime oil, which is also prepared by steam distillation of essential oil separated during the production of juice.106,107 Aside from bergamot, these oils are primarily monoterpene hydrocarbon mixtures of which (if)-limonene (3) is usually the dominant compound. Since odor contribution of this monoterpene compound is low, it is often removed by distillation or repeated solvent extraction. The resulting oil rich in odor-active compounds is called terpeneless oil and is used extensively. In the case of bergamot and lemon oils, psoralen derivates like bergaptene (64) causing photosensitivity are problematic, and those for fragrance use are rectified to remove it (Table 8). 

There are other cases where steam distillation is responsible for more specific problems of artefact formation which can be avoided if C02-extraction is applied for essential oil separation. One example is the blue colour of distilled German camomile oil. This is caused by the transformation of matricin, which is the genuine plant ingredient, into chamazulene [4]. Both substances have anti-inflammatory properties but the matricin, which is preserved during COj-extraction, is believed to have the better efficacy. Also, the sensitive fragrance of camomile flowers is better preserved in the C02-extract than in the steam distillate. 

Stearopten 1472 The part of an essential oil separated as a solid on cooling... 

Dried cardamom capsules (25g) of four varieties, namely, CCS-1, GG, NKE-12 and RR-1 were crushed and the seeds were separated. The decorticated seeds were hydrodistilled for 3 h in Clevenger apparatus to extract the essential oil. The essential oil separated was collected, dried over anhydrous sodium sulphate and stored in a refrigerator until the analysis was carried out. The percent essential oil content was calculated. The varieties GG recorded maximum essential oil yield (6 %) per capsule weight basis and superior quality with lower 1,8-cineole and high terpinyl acetate contents. 

In any further examination of the essential oils separated by steam distillation from the remaining components of the material to be investigated, the working procedure adopted depends on the amount... 

In the field of essential oils, separation of individual enantiomers and determination of enantiomer excess play an important role in the characterization of plant material, in the investigation of the origin of the essential oil, and in the search of possible adulterations. Reliable assessment of the genuineness of essential oils is a difficult task, since synthetic analogs of essential oil components are commercially available. Therefore, suitable specific methods in the authenticity control of essential oils are of fundamental interest. Two-dimensional GC is a useful technique for both analytical and preparative purposes. After a separation of aroma components on a first column, they are on-line transferred to a second... 

C, b.p. 156 C. The most important of the terpene hydrocarbons. It is found in most essential oils derived from the Coniferae, and is the main constituent of turpentine oil. Contains two asymmetric carbon atoms. The (- -)-form is easily obtained in a pure state by fractionation of Greek turpentine oil, of which it constitutes 95%. Pinene may be separated from turpentine oil in the form of its crystalline nitrosochloride, CioHigClNO, from which the ( + )-form may be recovered by boiling with aniline in alcoholic solution. When heated under pressure at 250-270 C, a-pinene is converted into dipentene. It can be reduced by hydrogen in the presence of a catalyst to form... 

Many spices are processed (2) to produce essential oils, oleoresins, essences, tinctures, extracts, resinoids, etc. These processes separate nonflavor components and further concentrate the aromatic or pungent principles of the spices. Such products allow a wider variety of uses and appHcations of the vital spice components. 

Essences generally are stored separately from the bulk concentrates for stabiHty, and their addition prior to retail packaging is essential to restoring much of the natural fresh flavor of the starting juice otherwise lost during processing. Unlike citms, which affords both an aqueous and an oil-phase essence, only an aqueous-phase essence is obtained for deciduous fmit. Virtually no essential oil is present in the peel or juice in the latter. 

Essential Oils. Volatile oils from plants are referred to as essential oils. The oils can be obtained through steam distillation, solvent extraction, or separation of the oils from pressed fmit. They consist of oxygenated compounds, terpenes, and sesquiterpenes. The primary flavor components of essential oils are oxygenated compounds. Terpenes contain some flavors but are often removed from the essential oil because they are easily oxidized (causiag off-flavors or odors) and are iasoluble. Essential oils are prepared from fmits, herbs, roots, and spices. 

Proper emulsification is essential to the satisfactory performance of a carrier. A weU-formulated carrier readily disperses when poured into water, and forms a milky emulsion upon agitation or steaming. It should not cause oil separation upon heating or crystallization and sedimentation upon cooling. 

Separation of chloroformic fraction of raw material by a polyamide sorbent with the following individual fractions elution and crystallization allowed to study lignans of burdock with IR-, mass- and NMR spectroscopy. In result, aixtiin, arctigenin, lappaols were identified. Sepai ation of essential oils was provided by the method two of State Phaiiuacopeias of the Ukraine. Essential oils were analyzed by the means of gas chromatography. 

In this study in order to eompare the green and yellow leaves of plant they were separately eolleeted and their essential oils were extraeted by water-distillation method and analyzed by GC and GC/MS. The main eonstituents were separated and analyzed by TLC, IR, NMR and UV methods. 

Fig. 1 Schematic sketch (A) of the separation of essential oil components (ca. 500 ng of each component) and reflectance scan of the mixture (B). Menthol (1), caryophyllene epoxide (2), thymol (3), menthyl acetate (4), caryophyllene (5), mixture (G).

Figure 3.5 Two-dimensional GC analysis of tobacco essential oil using non-polar primary and polar secondary separ-ations. The top tr-ace indicates the primary separ-ation, with the four resulting heart-cut cliromatograms shown below being obtained on the transfer of approximately 1-2 min fractions of primary eluent. Reproduced from B.M. Gordon et al. J. Chwmatogr. Sci. 1988, 26, 174 (23).

It is the determination of volatile organic compounds produced from natural products that requires separation techniques that allow isolation of stereoisomers. The most commonly determined groups are the terpene and sesquiterpene species present in essential oils, which are used as key indicators of biological factors such as the growth season, geographic location, climate, etc. These species are also released directly into the atmosphere by very many plants and trees, and make a substantial contribution to global biogeochemical cycles. 

C. Bicchi and A. Pisciotta, Use of two-dimensional gas cliromatography in the dkect enantiomer separation of chkal essential oil components , J. Chromatogr. 508 341-348(1990). 

Figure 4.13 GC X GC analysis of vetiver essential oil column 1, BPX5 column 2, BPX50 (0.8 m in length). The lower trace presents the pulsed peaks obtained from the modulation process, and shows such peaks in a manner that represents the normal cliromatograpliic result presentation. Tliis nace is many times more sensitive than a normal GC trace. In the upper plot, the 2D separation space shows that the BPX50 column is not very effective in separating components of the oils based on polarity, since all the components are bunched up along the same region of 2D time.

We can list the following areas as prime targets essential oil and natural product analysis, chiral analysis (e.g. of fragrances), trace multi-residue analysis, pesticide monitoring, and further petroleum products applications, in fact any separation where simply greater resolution and sensitivity is demanded-which means probably almost... 

Another way to improve the analysis of complex matrices can be the combination of a multidimensional system with information-rich spectral detection (31). The analysis of eucalyptus and cascarilla bark essential oils has been carried out with an MDGC instrument, coupling a fast second chromatograph with a matrix isolation infrared spectrometer. Eluents from the first column were heart-cut and transferred to a cryogenically cooled trap. The trap is then heated to re-inject the components into an analytical column of different selectivity for separation and subsequent detection. The problem of the mismatch between the speed of fast separation and the... 

Mondello et al. (54) have developed some applications of on-line HPLC-HRGC and HPLC-HRGC/MS in the analysis of citrus essential oils. In particular, they used LC-GC to determine the enantiomeric ratios of monoterpene alcohols in lemon, mandarin, bitter orange and sweet orange oils. LC-GC/MS was used to study the composition of the most common citrus peel, citrus leaf (petitgrain) and flower (neroli) oils. The oils were separated into two fractions, i.e. mono- and sesquiterpene... 

Supercritical fluid extraction (SFE) has been extensively used for the extraction of volatile components such as essential oils, flavours and aromas from plant materials on an industrial as well as an analytical scale (61). The extract thus obtained is usually analysed by GC. Off-line SFE-GC is frequently employed, but on-line SEE-GC has also been used. The direct coupling of SEE with supercritical fluid chromatography (SEC) has also been successfully caried out. Coupling SEE with SEC provides several advantages for the separation and detection of organic substances low temperatures can be used for both SEE and SEC, so they are well suited for the analysis of natural materials that contain compounds which are temperature-sensitive, such as flavours and fragrances. 

Often, planar chromatography is used as a preparative step for the isolation of single components or classes of components for further chromatographic separation or spectroscopic elucidation. Many planar chromatographic methods have been developed for the analysis of food products, bioactive compounds from plant materials, and essential oils. 

The separation capacity of a TLC method can be easily improved by use of a two-dimensional high performance TLC technique (2D HPTLC). Various plant essential oils (menthae, thymi, anisi, lavandulae, etc.) have been analysed by 2D TLC with florisil (magnesium silicate) as the adsorbent, using dichloromethane/ -heptane (4 6) in the first direction and ethyl acetate/n-heptane (1 9) in the second direction (69). 

The 2D chromatograms reveal additional components of the natural mixtures. They also give a map of the essential oil, which is helpful in the identification of the components by the position and the characteristic colours of the derivatives on the plate. A further, considerable improvement in the separation performance can be obtained by using overpressured layer chromatography (OPLC). Harmala et al. (70) used 2D OPLC for the separation of coumarins from the genus Angelica. Figure 10.15 shows the one-dimensional (a) and two-dimensional (b) OPLC separations of 16 coumarins. 

Most essential oils appear to be evolved directly in the form of terpenic or non-terpenic compounds separable from the plant tissues in the same form as they exist therein. A considerable number, however, are evolved in the form of complex compounds known as glucosides, in which the essential oil complex is present, but wherein the essential oil itself does not exist in the free state. 

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