Extraction reflux

Extracted with 50% MeOH under reflux Extract... 

Extraction efficiencies with shaking and ultrasonic extraction were lower than those with solvent reflux extraction. 

In alluvial soil, there was no great difference in the extraction efficiencies among the various solvent combinations tested, with acetone, acidic acetone or alkaline acetone, for reflux extraction. 

In the soil metabolism study using [ C]pyriminobac-methyl, most of the residual pyriminobac-methyl in soil was extracted by reflux extraction with acetone. ... 

Reflux extraction with acetone has been used for the analysis of rice grain and rice straw including metabolites, and showed good recoveries. ... 

Weigh 40 g (dry weight basis) of the soil sample into a 500-mL round-bottom flask and add 200 mL of acetone-water (3 1, v/v) mixture. Attach a condenser to the flask and perform reflux extraction at 80 °C for 1 h. Filter the extract through a Alter paper on a Buchner funnel with suction into a 500-mL round-bottom flask. Rinse the residue on the funnel with 130mL of acetone, and Alter in the same manner. Combine and concentrate the extract under reduced pressure to 50 mL. Transfer the concentrate into a 200-mL separatory funnel with 10 mL of saturated aqueous sodium chloride... 

Washing/soakinga Shake-flask extraction12 In-vial LSEa Reflux extraction Soxhlet/Soxtec /Soxtherm extraction... 

In liquid-solid extraction (LSE) the analyte is extracted from the solid by a liquid, which is separated by filtration. Numerous extraction processes, representing various types and levels of energy, have been described steam distillation, simultaneous steam distillation-solvent extraction (SDE), passive hot solvent extraction, forced-flow leaching, (automated) Soxh-let extraction, shake-flask method, mechanically agitated reflux extraction, ultrasound-assisted extraction, y -ray-assisted extraction, microwave-assisted extraction (MAE), microwave-enhanced extraction (Soxwave ), microwave-assisted process (MAP ), gas-phase MAE, enhanced fluidity extraction, hot (subcritical) water extraction, supercritical fluid extraction (SFE), supercritical assisted liquid extraction, pressurised hot water extraction, enhanced solvent extraction (ESE ), solu-tion/precipitation, etc. The most successful systems are described in Sections 3.3.3-3.4.6. Other, less frequently... 

Conventional methods of polymer extraction use large quantities of solvents as in shake-flask extraction or a Soxhlet extraction apparatus. For all classical extraction methods, solvent selectivity, in general, is low, i.e. solvents with high capacity tend to have low selectivity. In reflux extractions, which are still quite popular in polymer applications, the polymer is refluxed with a hot solvent, which disperses it to provide a solvent phase containing additives. In these conditions solvents are at their atmospheric boiling point. These methods are lengthy and labour intensive. Fractional extraction is based on solvents with increasing solvent power (cf. also [81]). 

Principles and Characteristics In boiling under reflux procedures a small amount of ground polymer (typically 3g) is placed in a headspace jar (typically 100 mL) and solvent (typically 30 mL) is added. After sealing, the jar is placed in an oven at a temperature where the solvent slowly refluxes. The solvent is, therefore, at the highest temperature possible without applying an external pressure. Consequently, reflux extractions tend to be much faster than Soxhlet extractions. Examples are Soxtec , Soxtherm , FEXTRA and intermittent extraction. Whilst, in theory, partitioning of the analyte between the polymer and solvent prevents complete extraction, this hardly ever constitutes a problem in practice. As the quantity of solvent is much larger than that of the polymer, and the partition coefficients usually favour the solvent, very low additive levels in the polymer result at equilibrium. Any solvent or solvent mixture can be used. 

Applications Caceres et al. [114] compared various methods for extraction of Tinuvin 770 and Chimas-sorb 944 from HDPE pellets, namely room temperature diffusion in CHC13 (20 % extraction), ultrasonica-tion (20% extraction), Soxtec extraction with DCM (nonsolvent) (50 % extraction), dissolution (dichloroben-zene)/precipitation (2-propanol) (65-70% recovery) and boiling under reflux with toluene (solvent) at 160 °C (95 % extraction). By changing conditions (nature of solvent, T, t) similar comparisons do not have much added value. Table 3.6 compares the results of reflux extraction and MAE for additives in LDPE [115]. 

Reflux extraction of additives and wax from polyolefins was reported [116]. Subsequently, the additives were adsorbed onto an adsorbent (Florisil) and the wax was removed from the extract before chromatography. Boiling extractions of SBR are described in ASTM D 1416-89 1 g of rubber is extracted by boiling in two 100 mL portions of 75/25 vol% isopropyl alcohol/toluene. Reflux heating with strong solvents, such as THF, dichloromethane or chloroform has been reported [117]. Reflux extraction has also been used for the 3 h extraction of caprolactam and oligomers from PA6 in boiling methanol. 

Table 3.6 Relative efficiencies of microwave-assisted and reflux extraction techniques for additives in LDPE ...

For the extraction of rubber and rubber compounds a wide variety of solvents (ethyl acetate, acetone, toluene, chloroform, carbon tetrachloride, hexane) have been used [149]. Soxtec extraction has also been used for HDPE/(Tinuvin 770, Chimassorb 944) [114] and has been compared to ultrasonic extraction, room temperature diffusion, dissolution/precipitation and reflux extraction. The relatively poor performance of the Soxtec extraction (50% after 4h in DCM) as compared with the reflux extraction (95% after 2-4 h in toluene at 60 °C) was described to the large difference in temperature between the boiling solvents. Soxtec was also used to extract oil finish from synthetic polymer yam (calibration set range of 0.18-0.33 %, standard error 0.015 %) as reference data for NIRS method development [150]. 

Table 3.28 Comparison of microwave and reflux extraction solvent efficiencies for additives in LLDPE...

I were obtained in 10 min for both 20- and 30-mesh grinds. Ten-minute extractions are sufficient to ensure that all additives have been extracted, but it is brief enough that smaller, more volatile additives are not lost. Recovery and precision data for several other additives in II were also reported. Extraction results with microwave heating in isobutanol or isopropanol compared with a 60 min reflux extraction also show good reproducibility (<3 % RSD for all additives analysed). 

The OSM MAP can be effectively applied to most of the organic additives for polyolefins. Its validity has been tested by comparing the OSM with traditional reflux extraction procedures for primary AOs (phenols), secondary AOs (aliphatic and aromatic phosphites ... 

Figure 3.21 Comparison of SFE and reflux extraction (according to ASTM D 1416) for styrene-butadiene rubbers. After Sekinger et al. [395]. Reprinted with permission from Rubber Chemistry and Technology. Copyright (1996), Rubber Division, American Chemical Society, Inc.

PP/Uvasil 299 fibres were analysed by 1II NMR after dissolution (toluene)/precipitation (methanol) and PP/Uvasil 299 pellets after reflux extraction with precipitation (methanol) of the oligomers [619]. The dried extracts were redissolved in CDCI3, containing the DMP internal standard. The method allows quantification of the high-MW HALS at very low levels (0.044 0.001 %). 

Bruns, L. E. "Plutonium - Uranium Partitioning by a Reflux Extraction Flowsheet," in "Proceedings, ISEC 71," Society of Chemical Industry, London, 1971, Vol. 1, p. 186. 

Table 1 shows the results of extraction of Radiata pine under hot compressed water system in two cases that is, the case using compressed water only and the case with % NaOH aqueous solution, together with the conventional reflux extraction case. 

Soxhlet extractor. A laboratory apparatus consisting of a glass flask and condensing unit used for continuous reflux extraction of alcohol- or ether-soluble components of food products. Named after its inventor, a German chemist. 

The analytical procedures used for TS and VS determinations are those described in Standard Methods for Examination of Water and Wastewater , 16th Edition, 1985. M.B.A.S. analysis were carried out using the same procedure described for water samples after a previous extraction step with methanol in a Soxhlet. This extraction method was found to be more reproducible than reflux extraction, for the latter did not guarantee a total anionic surfactant recovery. 

The hot water extractable soil B method is based on refluxing air dry soil for 10 minutes with deionised water at a 1 2 soil/solution ratio. After replacing liquid lost during reflux, extracts are filtered while hot and allowed to cool. The first of the two analytical finishes is a colorimetric procedure which utilises azomethine-H (Rayment Higginson 1992). It is preferred when ICPAES is not available. Other colorimetric procedures for determining B, including carminic acid (Hatcher Wilcox 1950) and curcumin (Hayes ... 

Refer to Figure E16-1, p. 552. Ten grams of oregano leaves is reflux extracted with /-butyl methyl ether for 20 minutes, and the solvent evaporated at room temperature overnight. The CCC column is filled with stationary phase, and then mobile phase is passed into it. Standards of both thymol and carvacrol are run, and 20 1-minute fractions are collected. The content of each fraction is determined at 276 nm, and their partition ratios are determined. The sample residue is taken up in 5 mL of mobile phase and 0.50 mL is added. The peak area is compared to that shown in Figure El 6-2, p. 552, which was obtained under the same conditions. 

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