Quantitative extraction

Solution processes of complexes of Mo(VI), W(VI) and V(V) with BPR as well as these complexes in the presence of dodecylpyridiniy chloride from aqueous solutions on aminosilica gels surfaces have been considered. The presence of dodecylpyridiniy chloride increases significantly the sorption degree of metals and broadens pH range of their quantitative extraction. 

This is a slow process, and the extraction time depends on the type of extractor used. With stirring as described in Note 10, practically quantitative extraction of jb-hydroxy phenyl pyruvic acid can be achieved within 6 hours. Extremely long extraction times may cause decomposition of the product. 

Dried or freeze dried samples can be extracted with water-immiscible solvents such as EtOAc or diethyl ether. For quantitative extraction, dried samples are preferably rehydrated at different times for example, 5 to 10 min for dried mangoes, 30 min for lyophihzed red peppers and pasta. Rehydration is followed by extraction with acetone or MeOH. Bixin and norbixin from a mix dry powder of annatto and com can quantitatively be extracted with MeOH followed by acetone. In order to improve pigment recovery, extruded foods require pre-digestion with enzymes to liberate the pigment from the matrix. ... 

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). ... 

Depending on the means of extraction, decreasing the ratio of extraction solvent to plant material may avoid the need for a concentration step. However, quantitative extractions usually require an adequate rate of solvent to material and two or more re-extractions until a clear or faintly colored solution is obtained. ... 

Several SPE procedures reported for triazine compounds are summarized in Table 3, and some are applicable to the quantitative extraction of parent triazine... 

Lopez-Avila and Benedicto combined SEE with ELISA to determine sulfamethazine in powdered milk. Various conditions were tested in order to achieve quantitative extraction of sulfamethazine. Variations in extraction pressure, temperature, extraction period, and the presence of organic modifier resulted in extraction efficiencies of 0-92%. Once optimal extraction conditions had been developed, a commercially available ELISA was utilized to determine sulfamethazine concentrations. The LOD was 2.5 pgkg and satisfactory recoveries were obtained at levels from 5 to 15 pgkg-i. 

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... 

Swagten-Linssen [387] has reported quantitative extraction of crystalline PA6/(Irganox 245, Ultranox 626, 2,4-DTBP) with scC02 as an alternative to dissolution (HFTP)/precipitation (MTBE). 

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... 

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. 

On-line SFE-SFC has also been used for the quantification of erucamide and antioxidants in PE [110]. Cotton et al. [15] have reported quantitative extraction of additives from PP at five different extraction pressures, at a constant flow-rate and temperature. Below 50 atm, extraction was negligible between 50 and 200 atm, Tin-uvin 326 and 770 were extracted, along with small quantities of oligomers. Higher pressures lead to the extraction of all the additives present, with the integrated peak areas conforming well to the actual concentrations. 

Quantitative extraction of PtIV by ra-octylaniline affords a method of separation from Fe111, Co, Ni11, and Cu11 in hydrochloric acid.306 A similar ion-pairing mechanism accounts for extraction by TOPO305 310 and Alamine 304304 (see Tables 5 and 6 for reagent structures) ... 

In summary, studies carried out with tissue surrogates25 highlight some of the problems that must be overcome before proteins extracted from FFPE tissues can be used for routine proteomic studies. First, these studies demonstrate that reversal of protein-formaldehyde adducts does not assure quantitative extraction of proteins from FFPE tissues or vice-versa. It may ultimately turn out that there is no one universal method that can accomplish both tasks, but that instead, each step will need to be optimized separately. Studies with tissue surrogates also suggest that failure to quantitatively extract the entire protein component from FFPE tissues may result in sampling bias due to the preferential extraction of certain proteins. This behavior may be linked to protein physical properties, such as the isoelectric point. The results of our... 

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). 

Romero-Perez AI, Lamuela-Raventos RM, Andres-Lacueva C and Torre-Boronat MC. 2001. Method for the quantitative extraction of resveratrol and piceid isomers in grape berry skins. Effect of powdery mildew on the stilbene content. J Agric Food Chem 49(1) 210-215. 

The sequestered chromium was then eluted from the column with 10.0 ml 0.2 M nitric acid. More than 93% of chromium was recovered in the first 5 ml of eluate by this method. Extraction of 80 ng spikes of Crm from 200 ml aliquots of seawater was quantitative. Neither Crm nor CrVI could be quantitatively extracted. Between 0.15 and 0.19 xg/l total chromium was found in seawater by this method compared to the accepted value of 0.184 0.016 p,g/l. 

The partition of all three types should obey the Nemst law, but in most cases the concentrations of extractable species are affected by chemical equilibria involving them and other components of the system. These must be taken into account when calculating the optimum conditions for quantitative extraction or separation. 

Batch extraction is the simplest and most useful method, the two phases being shaken together in a separatory funnel until equilibrium is reached and then allowed to separate into two layers. If the distribution ratio is large, a solute may be transferred essentially quantitatively in one extraction, otherwise several may be necessary. The optimum conditions for quantitative extraction have been discussed on p. 57. If several extractions are required, it is advantageous to use a solvent more dense than water, e.g. carbon tetrachloride or chloroform, so that the aqueous phase can be left in the separatory funnel until the procedure is complete. 

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. 

Determination of the ionic forms of alkyllead compounds is difficult because of the incomplete extraction of the dimethyl and trimethyl species from sample matrices. Recently a chelation extraction method followed by derivatization to their butyl homologues has overcome all the previous difficulties to achieve quantitative extraction of the dialkyl- and trialkyllead (R=Me, Et) from water samples at nanogram levels [f 8]. 

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 ... 

One of the examples of inclusion complexes formed by intermolecular forces is the C60/PVP complex for the first time described by Yamakoshi et al. (1994). The non-covalent intermolecular nature of forces that stabilizes this complex confirms the fact that fullerene can be quantitatively extracted from its water solution by toluene. 

The assay of potency involves the determination of the API to ensure conformance to label claim. For tablets or capsules, a composite assay requires fO-20 units to minimize tablet-to-tablet variation. In assays, it is critical for the quantitative extraction and recovery of the API meet the typical specification limit between 90.0% and 110.0% of label claim. 

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