Temperature effects polar compound extraction

This chapter documents enhancements of the efficiency of SFE extraction of alkaloids from plant matrices using basified modifiers. Hence (1) The pure compound solubility of some free bases in pure supercritical C02 has been measured by investigating the effects of temperature, pressure or density of C02 (2) The solubilities of the alkaloidal salts were compared with those of their free bases in order to evaluate the difference of their solubilities influenced by a changing from free bases to salts (3) Polar solvents such as methanol and water, as initial modifiers, were used for the enhancement of the solubilities (4) The solubilities of the salts by non-basified modifiers such as neat methanol or water were compared with those of methanol or water basified with diethylamine (5) The effect of modifiers employed on the desorption of the compounds from a matrix were measured and compared with each other (5) On the basis of the results of pure compound extractability, SFE was performed on alkaloids from the plant... 

Liquid water at elevated temperatures and pressures, but stiU in the subcritical region, is of interest as a solvent in various laboratory and industrial processes. In effect, this means water at a temperature between about 100°C and 373°C, the critical temperature, and at pressures up to 400 bar or greater. Since the dielectric constant of water decreases with increasing temperature, the solubility of many compounds, especially non-polar compounds, increases dramatically at higher temperature. The fact that solubility can be fine-tuned by controlling temperature and pressure makes pressurized hot water a useful tool in various extraction and reaction processes. 

Reversed-phase HPLC can separate polyphenolics of extracts on the basis of polarity. HPLC easily produces better resolution among chemically similar compounds in extracts than conventional chromatographic methods. The operating temperature of the column during reversed-phase HPLC analysis should be controlled for data reproducibility. A change in temperature produces only a minor effect, however, on band spacing in reversed-phase HPLC and produces essentially no effect in normal-phase HPLC (Lee and Widmer, 1996). A range of ambient temperatures is widely used, and elevated temperatures are often applied. The retention times of the peaks are dependent upon the type of column and the combination of various solvents used in the method. 

PHN, ACE, PYR, CHY, B[a]P, and benzo[e]pyrene were separated in a 50 mM borate buffer (pH 9) containing a mixture of 20 mM neutral methyl-(3-cyclodextrin (M(3CD) and 25 mM anionic sulfobutylether-(3-cyclodextrin (SB(3CD) at 30 kV and 30°C. " B[a]P and benzo[e]pyrene were successfully resolved with the other compounds in under 11 min in a 50-cm effective length of capillary without micelles in the mobile phase. The system was also less sensitive to temperature and separation potential. LIE detection with excitation at 325 nm at 2.5 mW from a He/Cd laser coupled to an optical fiber allowed for detection limits in the sub ppb range. The method described above was applied to the analysis of contaminated soil that had been extracted by supercritical CO2 for 20 min at 120°C and collected in methanol/DCM. ° Of the 16 EPA PAH mixtures, eleven compounds were detectable in the low ppb range. Ten of the eleven detectable compounds were measured in the soil extract. When compared to RP-HPLC, CE values were slightly lower but only six compounds were detected by HPLC-FLD. No direct relationship between PAH molecular size, polarity, or volatility with migration order was observed and B[b]F/B[k]F isomers were readily separated. 

The most common supercritical medium is CO2 because of its low critical temperature (31°C) and critical pressure (7.3 MPa), its cost effectiveness, its food grade status, and overall environmental friendliness. However, due to its low polarity, supercritical CO2 (SC-CO2) alone did not perform well in the extraction of phenolic compounds and anthocyanins from grape skins (Mantell et al. 2003 Vatai et al. 2009). A cosolvent, usually ethanol, can be added to SC-CO2 during extraction to enhance polarity. Such a mixture can result in a two-fold increase in phenols and three-fold increase in anthocyanins extracted. Isolation of quercetin might also be improved as SC-CO2 can remove the nonpolar components, thus concentrating the quercetin in the feed material. Water and methanol can also be added as cosolvents to increase the polarity of SC-CO2. 

As the fatty acid composition of coconut oil is independent of the method of extraction, it can be assumed that any health effect purely connected to the fat content may not vary with the type of coconut oil. However, non-lipid components of coconut oil significantly vary with the method of extraction. As most of these minor compounds are polar in nature, then-solubility in coconut oil is higher at high temperatures. Therefore, coconut oil prepared by boiling coconut milk contains higher amounts of phenolic antioxidants compared to other coconut oils. Virgin coconut oil produced under cold conditions can also retain thermally unstable non-lipid matter such as vitamins, some phenolic compounds and several other compounds such as sterols. Copra oil contains lower amount of important non-lipid compounds. Therefore, coconut oil prepared by wet extraction under cold or hot conditions seem to confer better beneficial health effects compared to copra oil. 

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