Extraction methods principles

Although on-line sample preparation cannot be regarded as being traditional multidimensional chromatography, the principles of the latter have been employed in the development of many on-line sample preparation techniques, including supercritical fluid extraction (SFE)-GC, SPME, thermal desorption and other on-line extraction methods. As with multidimensional chromatography, the principle is to obtain a portion of the required selectivity by using an additional separation device prior to the main analytical column. 

Owing to the complexity of multi-residue methods for products of animal origin, it is not possible to outline a simple scheme however, readers should refer to methods described in two references for detailed guidance (Analytical Methods for Pesticides in Foodstuffs, Dutch method collection and European Norm EN 1528. ) There is no multi-method specifically designed for body fluids and tissues. The latter matrix can be partly covered by methods for products of animal origin. However, an approach published by Frenzel et al may be helpful (method principle whole blood is hemolyzed and then deproteinized. After extraction of the supernatant, the a.i. is determined by GC/MS. The LOQ is in the range 30-200 ag depending on the a.i.). 

Principles and Characteristics Less well-characterised extraction methods include solvent leaching at high temperature with forced-solvent flow. In the... 

Principles and Characteristics A good extraction method, in addition to quantitative recoveries, ensures a high degree of selectivity. The demands for quantitative and selective extraction are difficult to meet simultaneously. Quantitative extraction with recoveries being independent of the matrix requires a strong extraction fluid. On the other hand, selective extraction is usually associated with fairly mild extraction conditions where only the components of interest are dissolved... 

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]. 

Based on the heat-induced AR principle, DNA/RNA extraction from FFPE tissues can be successfully achieved by a simple heating protocol that allows satisfactory application of molecular analysis using FFPE tissue samples housed in pathology laboratories worldwide. By a combination of improved extraction methods with various innovative techniques of molecular biology, more reliable results of molecular profiling for archival tissue are anticipated. 

The most widely used technique for the separation of large quantities of radioactive material is that of solvent extraction. The principle of the method is that ideally the partition coefficient of a compound between two solvents does not depend on concentration in a given set of conditions. This was shown in an early paper of Graham and Sea-borg (35) who demonstrated that the partition coefficients of gallium and cobalt chlorides between ether and aqueous hydrochloric acid were the same for concentrations of lCTli molar (i. e. no added carrier) as for 1-6xl0 s molar. 

The fermentation broth typically contains 20-30 mg/L of antibiotics, which is to say 30 parts per billion, and must be extracted into concentrated form using solvent extraction. The solvent extraction method was developed by Shell Oil and by Podbielniack and is based on the principle that penicillin is hydrolyzed in aqueous medium to H+ and RCOO ions. Thus, equilibrium in an acidic medium (i.e., one with low pH or high H+ concentration) is favored by the neutral RCOOH form, whereas equilibrium in an alkaline medium (i.e., one with high pH or low H+ concentration) is favored by the RCOO ionic form. The neutral form is more soluble in an organic medium, and the ionic form is more soluble in an aqueous medium. Thus, with amyl acetate as the organic solvent the partition coefficient of penicillin between solvent and water is about 100 at pH 3 and about 1 at pH 6. In the industrial process, the aqueous broth was acidified to pH 3 for the extraction into the organic solvent, and alkalized to a pH 6 for reverse extraction back into an aqueous medium. 

Some of the newer procedures use the same basic principles as the older extraction methods but provide fast and easy-to-use options and generally consume less organic solvent. For the most part, they have higher initial purchase price than the traditional methods. Examples include supercritical fluid extraction, accelerated solvent extraction, and automated solid-phase extraction and microextraction. Modular systems are now readily available that automate these proce-... 

Desired Effluent Quality. This is the single most important factor that decides the ultimate type/combination of equipment required. The criteria used in computing influent quality apply equally in establishing effluent quality Note that analyzers that use solvent-extraction principles measure soluble oil content also. Average solubility of hydrocarbons in water has typically been found to be 20 ppm in Bahrain oil fields. The results obtained with solvent-extraction methods on effluent samples shall be inclusive of dissolved hydrocarbons. For example, a 35-ppm result represents an effluent quality of IS ppm of free floatable od. 

Solid-phase extractions (SPE), in which DOM is selectively concentrated on a solid-phase extractant such as XAD-2 resin or Ci8 adsorbent. In these methods, both inorganic solutes and water are removed concurrently, and a suitable solvent is used to desorb the concentrated, desalted DOM from the solid-phase extractant. In principle, all inorganic solutes may be removed by SPE. 

A complete understanding of SFE and its relation to other extraction methods cannot be made without some knowledge of the basic properties of supercritical fluids and the basic principles of analytical SFE instrumentation. The purpose of this section is to give an introduction to the use of supercritical fluids in analytical-scale extractions while focusing on the application of SFE to pharmaceutical analysis. 

Figure 21.5 Gas extraction. Also called the dynamic purge-and-trap method. Principle of a gas/solid extraction column. A chemical transformation used to detect an aldehyde hy deriva-tivization (testing polluted atmosphere, Supelco Inc.).

The headspace technique, a static gas extraction method, is particularly suitable for the enrichment of volatile compounds. It enables the analysis of solid and liquid samples by direct sampling from the gas phase, and can be directly combined with gas chromatography. This principle is based on the distribution of analyte between the matrix and gas phase. It has been used successfully to determine volatile sulfur compounds from various matrices, such as wastewater, body fluids, plants, and animal fatty tissue. 

Kaufmann et al. developed a bipolarity extraction method based on principles similar to those of the QuEChERS technique. With the use of this isolation technique, polar and non-polar residues remained in the aqueous phase and underwent clean-up by SPE on a mixed-mode Oasis HLB cartridge. The residues were subsequently analyzed by UPLC-MS/MS. Extracts isolated using the bipolarity approach required a lengthy SPE procedure prior to analysis. Kaufmann stated that extracts produced at the end of the procedure contained less matrix components compared to QuEChERS. However, it can be concluded that... 

In principle, any extraction method can be optimized accordingly as long as suitable and validated expressions for protein release and enzyme inactivation rates are available. In practice Eqs. 2.5 and 2.6 can be complex and depend on many operational variables (Currie et al. 1972). If both protein release and enzyme inactivation are assumed to proceed according to first order kinetics ... 

The principle of extraction method used to separate PTC and product is based on solubility of quaternary ammonium salt in alkaline aqueous solution. " For example, tetrabutylammonium bromide is soluble to the extent of 27% in dilute (1% NaOH) aqueous solutions, but when the solution is made more concentrated (15% NaOH), the solubility of Bu4N Br decreases to 0.07%. When the products are obtained in PTC system, they can be usually separated from PTC by distillation method. PTC catalyst in the distillation residue may sometimes be reusable. With quaternary ammonium salts as catalysts, temperatures above 100-120 C usually result in partial or total decomposition of the quaternary salts to trialkylamines and other products. Mieczynska et al. and Monflier et al. investigated the hydrogenation and hydroformylation under phase transfer catalytic conditions. They found that the yield of aldehydes obtained in hydroformylation of 1-hexene strongly depends on solvent 24% in toluene, 53-86% in toluene-water-ethanol mixture and 77-94% in water-ethanol solution. The mixture of water-ethanol as a solvent was also found to be the best for hydrogenation of 1-hexene (96% of hexane). Conversion of Ph2PCH(CH3)(COOH) phosphine into sodium salt Ph2PCH(CH3)(COONa) yields aldehyde in toluene, 92% in toluene-water and 94% in toluene-water-ethanol mixture. 

The basic requirement for SFE to be useful is that it should be quantitative. Consequently, reHable methods must be developed based on good imderstanding of the extraction process. In principle, an extraction method consists of an extraction step (1) and a collection step (2), both equally important (Figure 3). 

See alsa Chemometrics and Statistics Multivariate Calibration Techniques. Color Measurement. Extraction Solvent Extraction Principles. Flow Injection Analysis Detection Techniques. Food and Nutritional Analysis Water and Minerals. Kinetic Methods Principles and Instrumentation Catalytic Techniques. Optical Spectroscopy Detection Devices. Spectrophotometry Overview Derivative Techniques Biochemical Applications Pharmaceutical Applications. Spot Tests. Water Analysis Overview. 

Plasmon Surface Resonance. Based on the principle of plasmon surface resonance, Biacore Life Sciences has developed a kit assay optimized for cobalamin analysis in food items (Biacore 2005). The recommended extraction method is autoclaving in add followed by filtration or centrifugation. As the extraction is carried out manually before analysis on the instrument, we expect that other extraction methods may work equally well (see Section 26.3.1). 

When factor analysis has been done to determine the factors that affect the survival of SMEs in the province, the factors were extracted using principle component to see how many of the 23 variables could be factors. It was considered by eigenvalue that exceeds 1.0 the eigenvalue is indicative of the ability of the emerging factors to explain the variability of the original variables. Besides, in this research, we also applied the Varimax rotation method and the KMO statistics, which are used to measure the suitability of the information available, and KMO > 0.6 would be considered suitable data to use for factor analysis techniques. The results showed that the KMO = 0.8123, which was over 0.6, so the information was appropriate to use technical analysis. The results showed there were live factors that had eigenvalue over 1.0, so the analysis grouped the factors into live factors as in Table 3. 

---