Extraction principles volatilization

Dried rhizomes and leaves are used industrially to extract the volatile oil. Dried rhizomes contain 5-6% and leaves contain about 1.0-1.5% oil. Generally, the oil is extractedby steam distillation. Supercritical extraction using liquid carbon dioxide is a relatively new technique for extracting volatile oil and oleoresin. The peculiar turmeric aroma is imparted by ar-turmerone, the major aroma principle in the oil. 

SPME is a patented sample preparation method for GC applications (32-36). The solvent-free technique was developed in 1989 by Janusz Pawliszyn (http. /Avww.science.uwaterloo.ca/ -janusz/spme.html) at the University of Waterloo in Ontario, Canada, and a manual device made by Supelco, Inc. has been available since 1993. In 1996, Varian Associates, Inc., constructed the first SPME autosampler. SPME involves exposing a fused silica fiber that has been coated with a non-volatile polymer to a sample or its headspace. The absorbed analytes are thermally desorbed in the injector of a gas chromatograph for separation and quantification. The fiber is mounted in a syringe-like holder which protects the fiber during storage and I netration of septa on the sample vial and in the GC injector. This device is operated like an ordinary GC syringe for sampling and injection. The extraction principle can be described as an equilibrium process in which the analyte partitions between the fiber and the aqueous phase. 

In principle, extractive distillation is more useful than azeotropic distillation because the process does not depend on the accident of azeotrope formation, and thus a greater choice of mass-separating agent is, in principle, possible. In general, the solvent should have a chemical structure similar to that of the less volatile of the two components. It will then tend to form a near-ideal mixture with the less volatile component and a nonideal mixture with the more volatile component. This has the effect of increasing the volatility of the more volatile component. 

Fixed-roof atmospheric tanks require vents to prevent pressure changes which would othei wise result from temperature changes and withdrawal or addition of liquid. API Standard 2000, Venting Atmospheric and Low Pressure Storage Tanks, gives practical rules for vent design. The principles of this standard can be applied to fluids other than petroleum products. Excessive losses of volatile liquids, particularly those with flash points below 38°C (100°F), may result from the use of open vents on fixed-roof tanks. Sometimes vents are manifolded and led to a vent tank, or the vapor may be extracted by a recov-eiy system. 

Intelligent engineering can drastically improve process selectivity (see Sharma, 1988, 1990) as illustrated in Chapter 4 of this book. A combination of reaction with an appropriate separation operation is the first option if the reaction is limited by chemical equilibrium. In such combinations one product is removed from the reaction zone continuously, allowing for a higher conversion of raw materials. Extractive reactions involve the addition of a second liquid phase, in which the product is better soluble than the reactants, to the reaction zone. Thus, the product is withdrawn from the reactive phase shifting the reaction mixture to product(s). The same principle can be realized if an additive is introduced into the reaction zone that causes precipitation of the desired product. A combination of reaction with distillation in a single column allows the removal of volatile products from the reaction zone that is then realized in the (fractional) distillation zone. Finally, reaction can be combined with filtration. A typical example of the latter system is the application of catalytic membranes. In all these cases, withdrawal of the product shifts the equilibrium mixture to the product. 

The principles behind MAP liquid-phase and gas-phase extractions are fundamentally similar and rely on the use of microwaves to selectively apply energy to a matrix rather than to the environment surrounding it. MAP gas-phase extractions (MAP-HS) give better sensitivity than the conventional static headspace extraction method. MAP-HS may also be applied in dynamic applications. This allows the application of a prolonged, low-power irradiation, or of a multi-pulse irradiation of the sample, thus providing a means to extract all of the volatile analytes from the matrix [477]. 

GC-C-IRMS instrumentation enables the compound-specific isotope analysis of individual organic compounds, for example, n-alkanes, fatty acids, sterols and amino acids, extracted and purified from bulk organic materials. The principle caveat of compound-specific work is the requirement for chemical modification, or derivatisation, of compounds containing polar functional groups primarily to enhance their volatility prior to introduction to the GC-C-IRMS instrument. Figure 14.7 summarises the most commonly employed procedures for derivatisation of polar, nonvolatile compounds for compound-specific stable isotope analysis using GC-C-IRMS. 

The principle of azeotropic and of extraction distillation lies in the addition of a new substance to the mixture so as to increase the relative volatility of the two key components, and thus make separation relatively easy. Benedict and Rup,in(43) have defined these two processes as follows. In azeotropic distillation the substance added forms an azeotrope with one or more of the components in the mixture, and as a result is present on most of the plates of the column in appreciable concentrations. With extractive distillation the substance added... 

In 1985, Ruzicka and Hansen established the principles behind flow injection optosensing [13-15], which has subsequently been used for making reaction-rate measurements [16], pH measurements by means of immobilized indicators [17,18], enzyme assays [19], solid-phase analyte preconcentration by sorbent extraction [20] and even anion determinations by catalysed reduction of a solid phase [21] —all these applications are discussed in Chapters 3 and 4. Incorporation of a gas-diffusion membrane in this type of sensor results in substantially improved sensitivity (through preconcentration) and selectivity (through removal of non-volatile interferents). The first model sensor of this type was developed for the determination of ammonium [13] and later refined by Hansen et al. [22,23] for successful application to clinical samples. 

The effect which each principle operates in the Great Work becomes like this 1. The Body represents the principle of fixity, and it works upon the volatility belonging to the other two 2. the Spirit affords an entrance by opening up the body 3. Water, by means of the Spirit, extracts Eire from its prison, and Fire is the soul [of the Work]. 

Salt was one of Paracelsus tria prima. Like the other principles and the four elements of the alchemists, salt as principle took its qualities as well as its name from the material bodies with the same properties. In a fire analysis, salt was to be found in the non-volatile residue and extracted from the non-soluble earth by water. This real salt demonstrated the more or less universal presence of the salt principle in all such bodies. The presence of SALT as principle accounted for the body s solidity and resistance to fire. In its material manifestation, it was recognized by its solubility and its saline taste. 

The small males of Nephila clavata cohabit with the much larger females in their web, and copulation takes place immediately after the final molt. Olfactometer tests showed that freshly molted females are much more attractive than older ones. Acetone extracts of the body surface of freshly molted females contained the active principle. Miyashita and Hayashi (1996) suggested that the volatile signal may originate from the molting fluid. 

The proximate principles of elemi are a transparent resin having acid properties, soluble in cold alcohol a second rosin taken up by boiling alcohol, bat deposited from the solution on eoolingin a crystalline state , a volatile colorless oil, which, according to Deville, resembles much the essence of turpentine, and of citron in composition, as in its reactions and a bitter extractive. The annexed per centages wore found by BoNAsrnE —... 

Note Valerian consists of the dried rhizome and roots of Valeriana officinalis Linne (Fam. Valerianaceae). It has been employed as an antianxiety agent and sleep aid for more than 1000 years. The drug contains from 0.3 to 0.7% of an unpleasant-smelling volatile oil containing bornyl acetate and the sesquiterpenoids, valerenic acid, and acetoxyvalerenolic acid. Also present is a mixture of lipophilic iridoid principles known as valepotriates. These bicyclic monoterpenoids are quite unstable and occur only in the fresh plant or in material dried at temperatures under 40°C. Although the specific active principals of valerian have not been determined, it is possible that a combination of the sesquiterpenoids and the valepotriates may be involved. The drug may be administered as a tea prepared from 2 to 3 g of the dried herb or equivalent amounts of a tincture or extract may be employed. 

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