Maximum extraction

Isolation of the products from complex matrixes (e.g. polymer and water, air, or soil) is often a demanding task. In the process of stability testing (10 days at 40 °C, 1 h at reflux temperature) of selected plastic additives (DEHA, DEHP and Irganox 1076) in EU aqueous simulants, the additive samples after exposure were simply extracted from the aqueous simulants with hexane [63]. A sonication step was necessary to ensure maximum extraction of control samples. Albertsson et al. developed several sample preparation techniques using headspace-GC-MS [64], LLE [65] and SPE [66-68]. A practical guide to LLE is available [3]. 

Extracts of hypericum may vary considerably in terms of the quantity and ratio of their constituents based on the extraction process used. Maximum extraction of hypericin and pseudohypericin is obtained with an 80% methanol solvent at 80°C (Wagner and Bladt 1994). Hyperforin is a lipophilic constituent of hypericum that is present in the oil extract (Chatterjee et al. 1998a). It is not very stable, but its presence is sustained by hot maceration of the flowers and storage in the absence of air (Maisenbacher and Kovar 1992). 

The automated extraction procedure was optimized for maximum extraction efficiency. The extraction parameters investigated were shaking time, shaking speed and solvent/ sample ratio. Three different shaking times (30 min, 60 min, and f20 min), two different shaking speeds (iOO and 190) and two different solvent/sample ratios (0.25 and 0.1667) were examined. These parameters resulted in 12 possible sets of experimental conditions. Twelve spiked water samples were analysed in dupficate, in random order (selected using software), under these experimental conditions. The total volumes and the analyte concentrations were kept constant. 

If, on the other hand, we could convert the free energy change of combustion AG directly to electricity in a suitable galvanic cell, the maximum extractable energy would be... 

Before the extraction procedure may commence, the sample must be prepared in such a way that it is in a condition for extraction of the analyte(s). For analyzing sulfonamide residues in liquid samples such as milk, a pretreatment dilution step with water prior to direct fluorometric detection may be required (207). Dilution of milk with aqueous buffer (208) or sodium chloride solution (209) prior to sample cleanup has also been reported. For the analysis of honey a simple dissolution of the sample in water (210, 211) or aqueous buffer (212) is generally required. Semisolid samples such as muscle, kidney, and liver, require, however, more intensive sample pretreatment. The analyte(s) must be exposed to extracting solvents to ensure maximum extraction. The most popular approach for tissue break-up is through use of a mincing and/or homogenizing apparatus. Lyophilization (freeze-drying) of swine kidney has been carried out prior to supercritical-fluid extraction of trimethoprim residues (213). 

Figure 14.9. Minimum solvent amount and maximum extract concentration. Determined by location of the intersection of extended tielines with extended line RNS. (a) When the tielines slope down to the left, the furthest intersection is the correct one. (b) When the tielines slope down to the right, the nearest intersection is the correct one. At maximum solvent amount, the mix point Mm is on the binodal curve.

We have demonstrated in this paper that two and four samples can be extracted in parallel with supercritical carbon dioxide without significant impact on data quality. Modifications made to an off-line extractor involved addition of a multiport manifold for the distribution of supercritical fluid to four extraction vessels and of a 12-port, two-way switching valve that allowed collection of two fractions per sample in unattended operation. The only limitation that we have experienced with the four-vessel extraction system was in the duration of the extraction. When working with 2-mL extraction vessels and 50-/zm restrictors, and using the pressure/temperature conditions mentioned above, the 250-mL syringe pump allows us a maximum extraction time of 60 min. During this time, two 30-min fractions can be collected with the present arrangement. 

Exhibiting no correlation Pyridine South Wales coals, maximum extraction at 30% volatile matter... 

Sample preparation in NLC and NCE is the most important step in analysis due to the nano nature of these modalities. The sampling should be carried out in such a way as to avoid changes in the chemical composition of the sample. The quantitative values of species depend on the strategy adopted in sample preparation. Extraction recoveries may vary from one species to another and they should, consequently, be assessed independently for each compound as well as for the compounds together. Materials with an integral analyte, that is, bound to the matrix in the same way as the unknown, which is preferably labeled (radioactive labeling) would be necessary, which is called method validation. As discussed above few papers described off- and online sample preparation methods on microfluidic devices. Of course, online methods are superior due to lower risk of contamination and error of methods. Not much work been carried out on online nanosample preparation devices, which need more research. Briefly, to get maximum extraction of analytes, sample preparation should be handled very carefully. 

Hot water is attracting attention as an extraction solvent in the recovery of compounds from plant material as the search for milder and greener" solvents intensifies. The use of hot water as an extraction solvent for milk thistle at temperatures above 100°C was explored. The maximum extraction yield of each of the silymarin compounds and taxifolin did not increase with temperature, most likely because significant compound degradation occurred. However, the time required for the yields of the compounds to reach their maxima was reduced from 200 to 55 min when the extraction temperature was increased from 100 to 140°C. Severe degradation of unprotected (plant matrix not present) silymarin compounds was observed and first-order degradation kinetics were obtained at 140°C. 

The most common chelating agents used to extract metals from water samples are ammonia pyrolidine dithiocarbamate (APDC) and 8-hydroxyquinone. Methyl isobutyl ketone (MIBK) is generally used as a solvent. In a typical extraction, 1 mL of APDC is added to 50 to 100 mL of aqueous sample in a volumetric flask. The pH of the aqueous sample is adjusted for maximum extraction of the analyte of interest. Then 10 mL of MIBK is added (the volumetric ratio of sample to MIBK is usually less than 40) and the mixture is vigorously shaken for 30 seconds. The metal chelate partitions into the organic phase, which floats on the water. More water can be added to raise the organic level into the neck of the flask so that it can be... 

The extraction of a metal ion is studied as a function of one of the variables [HA] or [B], keeping the concentration of the other in excess as compared to that of the metal ion. The extraction of the metal ion is then followed as a function of [HA]/[M] or [B]/[M] and the ratio for the maximum extraction gives the stiochiometry of the extracted adduct26,27. Choice of proper experimental conditions and a high value for the adduct formation constant are necessary for successful application of this method. 

Manufacturers provide operating characteristics of photovoltaic modules in standard conditions, which are defined by a solar irradiance value equal to 1000 W/m2 and a photovoltaic module temperature equal to 25°C. The most important of them is the maximum power that can be obtained at these conditions and is used for the determination of the photovoltaic module nominal power. However, in a considered site, solar irradiance changes during the day. In addition, depending on the environmental conditions, due to the internal thermal losses of the photovoltaic module, its temperature also varies. As a result, the maximum extracted power is usually lower than that provided by the manufacturers. 

Egg yolk powder contains normally 56% total lipids (consisting of triglycerides, lecithine and cholesterol), 30% protein, ash and some other substances. From these substances only triglycerides and cholesterol are soluble in C02 and can be separated from protein and lecithin. For all tests with egg yolk powder the same raw material was used. The maximum extractable yield was 40% with a twenty hour test at 500 bar. 

In the Orient, numerous natural products have long been used in folk medicine. Also, in recent years some pharmaceutical industries and universities in Korea are placing their efforts on the quantification of cytotoxic phytochemicals from the natural resources. As a part of those efforts, the present authors are involved on the two-fold critical evaluations of the possible implementation of the supercritical fluid extraction(SFE) to obtain extracts from the natural resources one is the establishment of the optimum SFE condition for each sample resource which gives maximum extraction yield and cytotoxicity, and the other is the high-purity isolation of some specific compounds from the SFE total extracts. 

The regenerated extraction gas leaves the second regeneration column at its head and is cooled down in (WT3) to a temperature of approximately 20°C. Depending on the type of extraction solvent the buffer vessel (KP) contains liquid phase in equilibrium state with gas or merely gas of high density. In the last case a pressure controlled pneumatic pump feeds fresh solvent into the circular process. If a gas/liquid equilibrium is achieved in the buffer vessel the gas pressure remains constant until a minimal amount of liquid remains there. For this purpose two optical sensors are introduced into the buffer vessel registrating the minimum and maximum extraction liquid level If the level falls below minimum, fresh liquid extraction solvent is refilled. 

Maximum extraction occurs from 1 to 3 M HNO3 into o-nitrophenyl-hexyl-ester and the following separation factors were measured with respect to trivalent americium for 1 mM ligand concentration and 10-4 M metal ions Sf(Am/Ln or Cm) = 2.00 (La), 52 (Ce), 1.72 (Nd), 2.78 (Sm), 5.15 (Eu), 7.15 (Cm). Following this study numerous CMPO-substituted calix[4]arenes have been synthesized and tested. 

In a report by Nakahara et al., the extraction efficiency of various methods for 6-AM and morphine was compared. Finely cut hair samples were placed into solutions of methanol, 0.1 M HCl, methanol-5 M HCl (20 1), helicase, or methanol-trif-luoroacetic acid (TFA) (9 1). Extraction was performed overnight following ultrason-ication for 1 h, except for the methanol extract, which was sonicated for 14 h. Methanol-TFA was found to be the best solvent for extracting 6-AM and morphine with minimal hydrolysis and maximum extraction efficiency. Nakahara et al. noted that heroin was not detected in heroin users hair by this method, possibly due to hydrolysis to 6-AM. The extraction rates of 6-AM and morphine from heroin users hair with methanol-TFA reached a plateau after 8 to 10 h. 

Since the effluents from nuclear fuel reprocessing plants also contain Amflll), we studied NDSX of Am(lll) using the HFC module [17,18], and the acidic extractant PC-88A (2-ethyUiexylphosphonic acid mono-2-ethylhexyl ester). The results of the smdies are summarized in Figure 33.12. At 30% PC-88A concentration, a maximum extraction of 90% was achieved. Amflll)... 

In any case, the energy released through this mechanism of transfer must have an average value in the order of the energy gap between the valency and conduction bands, but may not exceed the maximum extraction energy"of an electron from the valency band. If the AH of an endothermic reaction or of the endothermic step of a reaction is greater than this... 

The usual effect of increasing the acid concentration is reported to be an increase in the (due to increased amounts of the extractable MA3 in the aqueous phase) followed by a decrease in the (due to formation of the extractant-HNC adduct), resulting in a maximum extraction at an acid concentration between 2 and 6 M. However, one study has noted an increase in americium extraction at nitric acid concentrations from 12 to 16 M. These data are not consistent with the usual view of americium distribution dependence on nitric acid and nitrate concentration, and the authors hypothesize that a TBP HN03 adduct, which is a stronger extractant for americium than TBP alone, is formed above 8 M HNO3 and an organic-phase complex of Am(N03)3 (TBP mHNC ) is formed rather than Am(N03)3 nTBP (26). While one may not absolutely discount this possibility, additional factors such as the extraction of HAm(N03) and deviations from ideal activities in such concentrated acid solutions should definitely be considered. 

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