Extraction dilute systems

Determination of Na " and Na" ions in raw cosmetic materials was conducted with the developed method of flame photometry. A necessity of development of method of samples preparation arose up in the work process, as this spicily-aromatic raw material contained pectin in amount 0.1-0.5% and that prevented preparation of samples by standard method of extracts dilution and required incineration of analyzed sample, time of analysis was increased in 60 times. It was established that CaCl, solution with the concentration 0,4 % caused destmctions of the carbopol gel. It was established that the addition of 0,1% CaCl, and 0,1% NaCl salts solutions into the system intensified the effect of negative action of these salts onto the gel stmcture and the gel destmcted completely. 

The extraction procedure of silicate species from the aqueous solutions was explained earlier [7]. An amount of 5 ml of solution was quickly poured into 15 ml of a stirred 0.5 N HC1 solution. An amount of 20 ml tetrahydrofuran (THF) was added and stirring continued for 30 min. Addition of 10.7 g NaCl resulted in a phase separation. The THF layer containing the silicate species was separated from the aqueous layer. The extraction with THF of the aqueous layer was repeated and the THF solutions combined to maximize extraction efficiency. Finally THF was evaporated in a rotavap at 20°C. The final products from the concentrated solutions were gel like. The extracts from the diluted systems were powdery. The experimental details on the gel permeation chromatography (GPC) and IR spectroscopy can be found in refs. [2] and [3], respectively. 

Measurements of binary vapor-liquid equilibria can be expressed in terms of activity coefficients, and then correlated by the Wilson or other suitable equation. Data on all possible pairs of components can be combined to represent the vapor-liquid behavior of the complete mixture. For exploratory purposes, several rapid experimental techniques are applicable. For example, differential ebulliometry can obtain data for several systems in one laboratory day, from which infinite dilution activity coefficients can be calculated and then used to evaluate the parameters of correlating equations. Chromatography also is a well-developed rapid technique for vapor-liquid equilibrium measurement of extractive distillation systems. The low-boiling solvent is deposited on an inert carrier to serve as the adsorbent. The mathematics is known from which the relative volatility of a pair of substances can be calculated from the effluent trace of the elutriated stream. Some of the literature of these two techniques is cited by Walas (1985, pp. 216-217). 

The composition of the volatile fraction of bread depends on the bread ingredients, the conditions of dough fermentation and the baking process. This fraction contributes significantly to the desirable flavors of the crust and the crumb. For this reason, the volatile fraction of different bread types has been studied by several authors. Within the more than 280 compounds that have been identified in the volatile fraction of wheat bread, only a relative small number are responsible for the different notes in the aroma profiles of the crust and the crumb. These compounds can be considered as character impact compounds. Approaches to find out the relevant aroma compounds in bread flavors using model systems and the odor unit concept are emphasized in this review. A new technique denominated "aroma extract dilution analysis" was developed based on the odor unit concept and GC-effluent sniffing. It allows the assessment of the relative importance of the aroma compounds of an extract. The application of this technique to extracts of the crust of both wheat and rye breads and to the crumb of wheat bread is discussed. 

An extraction process should take as much of the solute as possible into the extract phase. This objective is expressed as the extraction factor, the ratio of the mass of C in the extract to that in the raffinate, for the single stage (12.3 in the above example). The extraction factor is increased by using a high ratio of solvent to feed and by choosing a system with a high distribution ratio. For the special case of a very dilute system with immiscible A and B and constant distribution ratio, it can be shown that the extraction factor is given by... 

Al/W/O ratio of 4/1/1. The monomer/catalyst ratio necessarily increased with initial monomer concentration. Figure 1 indicates that large amounts of the extractable fraction are formed in polymerizations carried out in dilute systems. 

These methods were developed to quantify and visualize the intensity of aroma as a chromatogram. A specific system named combined hedonic and response measurement (CHARM) was initially developed. Later on, aroma extract dilution analysis (AEDA) (Figure 3), a new method using a conventional GC-O system, was proposed. They share the same strategy aroma extract is diluted to a certain extent and then GC—O methodology is applied. In an AEDA procedure, if such a maximum extent of a dilution that allows the detection of a certain component is times diluted from the original sample, this component is referred to have a flavor dilution (FD) factor of . CHARM value corresponds to FD factor in a CHARM procedure. These values represent the contribution of the volatile the larger these values are, the more important they are considered as key components. 

It should also be noted that many extractive distillation systems exhibit a maximum reflux ratio as well as the conventional minimum reflux ratio. For a given solvent-to-feed ratio, if too much reflux is returned to the column., the solvent is diluted and the separation becomes poorer since not enough solvent is available to soak up component B. 

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. 

A typical solvent or co-solvent system is selected based on the ability to solvate the analyte(s) relative to the undesired matrix components and the ease with which the solvent can be eliminated after extraction. Co-solvent blends are useful because the polarity (or other properties) can be tailored to that of the analyte(s). Traditional aprotic organic solvents are useful because they can be removed quickly and at low temperatures. Because of the dramatic increase in extraction efficiencies, solvents that have only moderate extraction properties at room temperature and atmospheric pressure can perform quite well under ASE conditions. Because organic-aqueous co-solvents can be used, it is often possible to prepare a solvent that can chemically neutralize the analyte molecule, thereby further facilitating the extraction. Dilute organic acids or bases can be employed for this purpose. Strong mineral acids are generally undesirable because they attack and destroy the stainless steel bombs or other instrument system components. 

Here, the notation MW refers to the molecular weight of solute i and the effective average molecular weights of the extract and raffinate phases, as indicated by the subscripts. For dilute systems, K" IQ (MW a(r ,ai/MWearaa)- Fot theoretical stage or transfer unit calculations, often it is useful to express the partition ratio in terms of mass ratio coordinates introduced by Bancroft [Phys. Rev., 3(1), pp. 21-33 3(2), pp. 114-136 and 3(3), pp. 193-209 (1895)] ... 

This value compares favorably with the value of 35.28 calculated directly from phenol mass ratios taken from extractor internal profile data in the simulation output. The extraction factor [Eq. (15-11)] is then calculated with the dilute system approximation that mphoH = phoh solute-free water and MIBK feed rates of 159,841 and 10,668 Ib/h taken from the simulation output ... 

Procedures for swab samples are described with all kits except the Ridascreen kits. In the BIOKITS assays the swab extract is applied directly to the plate without further preparation, whereas with the ELISA Systems procedures they are treated as liquid samples and need to be heated. The Ridascreen, Veratox, and ELISA Systems kits can be completed in at least half the time of the other assays. This is achieved primarily through shorter incubation times (only 30 min total) and lower extraction dilutions (at least a fourfold difference from the others). The Veratox and ELISA Systems kits also use more test portion to extract from than the Ridascreen kit. This aU means that more extracted protein can be applied to the ELISA plate to illicit a response, which is a prerequisite for a successful detection. The countereffect can be an increased potential for matrix interference or... 

Fresh or previously frozen Xenopus egg extract is supplemented with an energy-regenerating system (150/ig/ml) creatine phosphokinase, 60mAf creatine phosphate) (Blow and Laskey, 1986), cycloheximide to a final concentration of 100 /ig/ml, ATP to a final concentration of 2 mM, and permeabilized Xenopus sperm nuclei at 50 ng DNAZ/ul extract. dNTP pool sizes are readjusted to 50 pM (determined by Blow and Laskey, 1986 Hutchison et ai, 1987) following dilution of the extract. The extent of extract dilution is always kept constant at 20% of the initial volume for all incubations. Samples are incubated at 23°C for the desired time. With Bufo sperm nuclei in homologous egg extract, the sperm suspension is added to extract such that it does not exceed 5% of the total volume of the mixture (Ohsumi and Katagiri, 1991a,b). 

One basic assumption leading to eq. (21) was the Gaussian shape of the field distribution. We had stated that this requires a dense system of moments. In dilute systems (if less than 10% of the surrounding atoms have a moment - see Kittel and Abrahams 1953) the field distribution is close to a Lorentzian shape (Walstedt and Walker 1974). A Lorentzian has no second moment and the distribution width must be characterized by its half width at half maximum. It will not show motional narrowing whether the local field is static or fluctuating, the experimenter will observe exponential relaxation, whose relaxation rate is basically insensitive to the field fluctuation rate 1/r. In this case not much reliable information can be extracted from TF data. Dilute moment systems are therefore usually studied with ZF- and LF pSR. 

Again the kinetic parameters can be estimated in the Lewis ceU (Figure 18.6) as discussed. The reaction kinetics, here derived for acid (HA) extraction, starts with taking into account the equilibrium equation with the 1 1 complex valid in a dilute system ... 

Most solvent-diluent pairs that are essentially completely immiscible become partially miscible as more solute is added (see Section 13.71. This occurs because appreciable amounts of solute make the two phases chemically more similar. Since Eq. (13r2) is usually valid only for very dilute systems, we can usually analyze immiscible extraction systems using constant total flow rates. Thus, the fifth assunption we usually make is... 

This second edition offers new material on methods of sensory detection (nasal through the nose) or (retronasal through the mouth and back of the oral cavity), different flavor release phenomena in the headspace versus the mouth, and matrix in flavor release from oils compared to emulsion systems. Advanced gas chromatographic methods are included, such as solid phase microextraction for the volatile analyses in foods and vegetable oils, gas chromatography-olfactometry, and aroma extraction dilution analyses. 

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