Quantitative extraction analyses

Quantitative Extraction Analyses. Exhaustive extraction of a sample matrix at a pressure where all of the components of interest are soluble provides the capability for a quantitative analysis. This method is illustrated with the example shown in Figure 9. XAD-2... 

On the other hand, quantitative extraction requires complete and exhaustive extraction and no material can be lost. To assure complete extraction when a food is analyzed for the first time in a laboratory, it is useful to carry out two or three extractions, pool the solvents, and keep separate the next extracts to verify the presence of carotenoids. Usually four to six extractions are enough to remove the carotenoids completely from a sample. The extraction can be carried out in a blender, vortex, or with a mortar and pestle. Accelerated solvent extraction (ASE), an important extraction technique in residue analysis, currently attracts interest due to its short duration, low level of solvent use, and high extraction yield. The average recoveries for all carotenoids with the exception of norbixin ranged from 88.7 to 103.3% using manual extraction and from 91.0 to 99.6% by ASE (70 bar and temperature of 40°C) both extractions were carried out with a mixture of MeOH, EtOAc, and petroleum ether (1 1 1). ... 

Several qualifying features for polymer extract analysis are summarised in Table 2.11. Quantitative separation of polymer and (thermolabile and/or volatile) additives without decomposition of the analyte(s) is difficult for thermoplasts, but even more difficult for... 

Freitag and John [96] studied rapid separation of stabilisers from plastics. Fairly quantitative extraction (>90% of the expected content) of stabilisers from a powdered polymer was achieved by MAE within 3 to 6 min, as compared to 16 h of Soxhlet extraction for the same recovery. MAE and Soxhlet extraction have also been compared in the analysis of cyclic trimer in PET [113]. On the other hand, Ganzler et al. [128] compared the extraction yields for various types of compounds from nonpolymeric matrices for microwave irradiation with those obtained by the traditional Soxhlet or shake-flask extraction methods. Microwave extraction was more effective than the conventional methods, in particular in the case of polar compounds. As expected, the efficiency of the former is high especially when the extraction solvents contain water. With the high dipole moment of water, microwave heating is more... 

Nowadays, MS is often no longer the analytical bottleneck, but rather what precedes it (sample preparation) and follows it (data handling, searching). Direct mass-spectrometric methods have to compete with the separation techniques such as GC, HPLC and SFC that are commonly used for quantitative analysis of polymer additives. Extract analysis has the general advantage that higher-molecular-weight (less-volatile) additives can be detected more readily than by direct analysis of the polymer compound. 

On-line SFE coupled to GC or SFC, according to the thermal stability of the analytes, are both very competitive with classical methods of analysis in terms of sensitivity and analysis time. Since all of the extracted analytes are transferred to the GC system, much higher method sensitivities can be obtained. Several modes of operation are possible utilising on-line SFE-GC, including quantitative extraction of all analytes from a sample matrix quantitative extraction and concentration of trace analytes selective extractions at various solvating powers to obtain specific fractions and periodic sampling (multiple-step extractions) of the effluent at various pressures for qualitative characterisation of the sample matrix. 

Quantitative analysis of multicomponent additive packages in polymers is difficult subject matter, as evidenced by results of round-robins [110,118,119]. Sample inhomogeneity is often greater than the error in analysis. In procedures entailing extraction/chromatography, the main uncertainty lies in the extraction stage. Chromatographic methods have become a ubiquitous part of quantitative chemical analysis. Dissolution procedures (without precipitation) lead to the most reliable quantitative results, provided that total dissolution can be achieved follow-up SEC-GC is molecular mass-limited by the requirements of GC. Of the various solid-state procedures (Table 10.27), only TG, SHS, and eventually Py, lead to easily obtainable accurate quantitation. 

Table 10.32 is a shortlist of the characteristics of the ideal polymer/additive analysis technique. It is hoped that the ideal method of the future will be a reliable, cost-effective, qualitative and quantitative, in-polymer additive analysis technique. It may be useful to briefly compare the two general approaches to additive analysis, namely conventional and in-polymer methods. The classical methods range from inexpensive to expensive in terms of equipment they are well established and subject to continuous evolution and their strengths and deficiencies are well documented. We stressed the hyphenated methods for qualitative analysis and the dissolution methods for quantitative analysis. Lattimer and Harris [130] concluded in 1989 that there was no clear advantage for direct analysis (of rubbers) over extract analysis. Despite many instrumental advances in the last decade, this conclusion still largely holds true today. Direct analysis is experimentally somewhat faster and easier, but tends to require greater interpretative difficulties. Direct analysis avoids such common extraction difficulties as ... 

Observation. The time of observation is about 2-4 hocus for vital preparation and several days for fixed preparations. All the preparations may be analyzed by 3-channel simultaneous detection to receive common complicated interference image of the object and details of its structure (see experiment 1) by receiving 20 visual slices (optical sections) or the complete volume (the information must be also quantitatively extracted) (see experiment 2) by computer modelling the images as well as mathematical analysis (experiments). 

Burford et al. [3] reported a coupled supercritical extraction-gas chromatographic method that can quantitatively extract and determine both gasoline and diesel range hydrocarbons from contaminated soils. The direct transfer of the extract to a gas chromatograph reduced analysis times to about 80min, compared to the 18h required for conventional sonication analysis. 

Consider the analysis of plant material for a pesticide residue by GC. Two grams of the material is chopped up and placed in a Soxhlet extractor (Chapter 11) and the pesticide quantitatively extracted into an appropriate solvent. Following this, the solvent is evaporated to near dryness and the residue is diluted to volume in a 25-mL flask. Then 2.5 pL of this solution and standards is injected in a GC with the following results ... 

The swabs present several problems. With swabs there are many steps that need to be validated to insure an accnrate result. The analyst must be able to quantitatively remove the analyte from the swab. The analyte is added to the swab as a solution, dried, and quantitatively extracted off for analysis. The preferable extraction solntion is the swabbing solvent. The HPLC mobile phase or a mobile phase component could be used, but would necessitate a dilution of the swabbing solution. Standard addition and recovery data of clarithromycin added to different lots of polyester fiber are present in Table 3. ... 

Sun B, Spranger MI (2005) Review quantitative extraction and analysis of grape and wine proanthocyanidins and stilbenes. Ciencia Tec Vitiv 20 59-89... 

An extraction profile is the analysis (usually by chromatographic means) of extracts obtained from a packaging component. A quantitative extraction profile is one in which the amount of each detected substance is determined. 

Prior to phospholipid analysis, it is imperative to extract the lipids from their matrix and free them of any nonlipid contaminants. Phospholipids are generally contained within the lipid fraction, which may be recovered by the traditional Bligh and Dyer or Folch extraction procedure (9,22). In any phospholipid extraction method it is recommended to include a rather polar solvent in addition to a solvent with high solubility for lipids. The former is needed to break down lipid-protein complexes that prevent the extraction of the lipids in the organic phase. Traditionally, mixtures of chloroform and methanol (especially 2 1, v/v) have been recommended. These are washed with water or aqueous saline to remove nonlipid contaminants. Comparing the recovery of phospholipids, Shaikh found that the neutral phospholipids PC, PE, SPH as well as DPG were nearly quantitatively extracted by all solvent systems studied (Table 1), although Bligh and Dyer, in which the lower phase was removed only once, was somewhat worse (23). 

Extraction of fat by supercritical carbon dioxide was investigated as an important option for minimizing the expanded use of frequently flammable and carcinogenic solvents in food analysis. Unfortunately, the presence of moisture in foods has an adverse effect on the quantitative extraction of fat by supercritical fluid extraction (SEE). Hence, samples have to be lyophilized first. The total fat content of freeze-dried meat and oilseed samples was found to be comparable to values derived from Soxhlet-extracted samples (26). Besides, only small amounts of residual lipids could be recovered by an additional extraction of the SFE-extracted matrix by the Bligh and Dyer solvent extraction procedure. As far as the minor constituents are concerned, it was found that the extraction recovery ranged from 99% for PC to 88% for PA. Hence, Snyder et al. concluded that SFE can be used as a rapid, automated method to obtain total fat, including total phospholipids, from foods (26). 

Although the advantages associated with online plasma extraction are attractive, care must be taken to monitor the recovery of dmg-related material during the extraction process. Unlike quantitative plasma analysis, where poor recovery only affects the limit of quantitation, the recovery of all drug-related components in metabolite profiling studies must be high in order to ensure that the quantitative data are meaningful. 

Extraction and Cleanup Procedures. Before the pads were extracted, the bottles containing the exposed pads in DCM were removed from the refrigerator and allowed to warm to room temperature. Then they were shaken for 1 min and the contents decanted into a 125 ml Erlenmyer flask. The pad was extracted 2 more times by shaking for 1 min with fresh 25 ml portions of DCM and the combined extracts refrigerated until analysis. For quantitative extraction, it was necessary that the pads be held in the DCM for at least one day before extraction. 

For example, apple vermouths with different ethanol concentrations (12%, 15%, and 18%), sugar contents (4% and 8%), and levels of spice extracts (2.5% and 5.0%) were prepared and evaluated (Joshi and Sandhu, 2000). Using quantitative descriptive analysis (QDA), flavor profiling was carried out (Joshi and Sandhu, 2009). 

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