Extraction techniques scheme

Polymer/additive analysis then usually proceeds by separation of polymer and additives (cf. Scheme 2.12) using one out of many solvent extraction techniques (cf. Chapter 3). After extraction the residue is pressed into a thin film to verify that all extractables have been removed. UV spectroscopy is used for verification of the presence of components with a chromophoric moiety (phenolic antioxidants and/or UV absorbers) and IR spectroscopy to verify the absence of IR bands extraneous to the polymer. The XRF results before and after extraction are compared, especially when the elemental analysis does not comply with the preliminary indications of the nature of the additive package. This may occur for example in PA6/PA6.6 blends where... 

Normally an extraction technique is selected to give the highest recovery for a wide range of pollutants. Therefore, the extract will most likely contain a high proportion of co-extracted material. Many of the clean-up techniques have been tailored into a series of multi-residue schemes in order to maximize the use of each sample [189,402,453,454,478-481]. This is of particular value when the maximum amount of chemical information is required for each sample. 

Matrix solid-phase dispersion (MSPD) is the extraction method of choice for the analysis of solid samples, such as plant material, foodstuffs or tissue samples [26]. This method has been developed especially for solid or viscous matrices. MSPD is preferable to other extraction techniques, because the solid or viscous sample can be directly mixed with the sorbent material of the stationary phase [27]. As the carotenoid stereoisomers stay bound in their biological matrix until the elution step, they are protected against isomerisation and oxidation [28]. The extraction scheme of MSPD is shown in Figure 5.2.1. 

Aminoquinolines 62 have been prepared in a two-step, one-pot, three-component reaction of 2-azidobenzophenones, secondary amines and arylac-etaldehydes [110]. The microwave-assisted reaction proceeded via the initial formation of enamines 59. Subsequent addition of 2-azidobenzophenones 60 afforded the triazoline intermediates 61, which underwent thermal rearrangement and cyclocondensation to furnish 2-aminoquinolines 62 (Scheme 41). Direct comparison with conventional thermal conditions demonstrated the superiority of microwave dielectric heating in terms of yields (73% vs. 31% of heterocycle 63 after 10 min at 180 °C). Furthermore, the formation of by-products due to decomposition of azide 60 was diminished in the microwave-assisted synthesis. Purification of the products was achieved using solid-phase extraction techniques. 

In a subsequent study, solvent partitioning and solid-phase extraction techniques were used to produce a partial ly -pur If led extract (15). The first step In the purification scheme Involved partitioning of a highly oonoentrated ethanol 1c extract of house fly ovaries between chloroform and water. Further processing of the chloroform layer (I.e., evaporation, solvent exchange, and filtration through a bed of Porapac Q) eventually produced a methanol 1c extract with a 23-fold Increeee In OH activity over the crude extract. 

The quinoline scaffold and derivatives occur in a large number of natural products and drug-like compounds. A method for microwave-assisted synthesis of 2-aminoquinolines has been described by Wilson et al. [62]. The process involves rapid microwave irradiation of secondary amines and aldehydes to form enamines, then addition of 2-azidobenzophenones with subsequent irradiation to produce the 2-aminoquinoline derivatives (Scheme 10.27). Purification of the products was accomplished in a streamlined manner by using solid-phase extraction techniques to produce the desired compounds in high yields and purity. Direct comparison of the reaction under thermal and microwave conditions, using identical stoichiometry and sealed reaction vessels, showed the latter resulted in improved yield. 

The concentrations of individual PAH in water systems range from less than 1 ppt (pg per g) in pure ground water supplies to greater than 1 ppm (pg per g) in heavily contaminated sewage. Therefore, some preconcentration and extraction techniques are required to raise the concentrations to levels at which identification and quantitative analysis are possible. Because PAHs may only represent as little as 0.01% of the total organic fraction present in the water sample, the analytical scheme must be devised so that the PAHs can be analyzed without the interference from the other pollutants. Since the concentrations are so low, serious errors may occur from losses or contamination during sampling or the analytical... 

Scheme 16.34. Microfluidic and fluorous extraction techniques for oligosaccharide synthesis.

Heat extraction techniques for solid sample preparation in GC are static and dynamic headspace analysis (SHS, DHS, HS-SPME and HSSE), thermal desorption (TD-GC, TD-GC-MS), pyrolysis and thermochromatography. Nomenclature is not unambiguous as to DHS, TD and PT. The terminology purge-and-trap is usually preferred for the simplest dynamic technique in which it is not necessary to subject the sample to either solvents or elevated temperatures. Scheme 2.7 shows the family of headspace sampling techniques. Headspace sorptive extraction (HSSE) and HS-SPME represent high capacity static headspace. 

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