Organic solvent extraction, comparison

Numerous researchers found lower antimicrobial activity of aqueous extracts in comparison with acetone, methanol, or other organic solvent extracts (Land and Lundstrom 1998 Madamombe and Afolajan 2003 Rankovic et al. 2008 Kosanic et al. 2010). The reason for the weak activity of aqueous extracts is that active substances present in the thaUi of Uchens are insoluble or poorly soluble in water (Kinoshita et al. 1994). 

In a recently published comparison of CO2 with other extraction solvents [5], it is concluded that of all available solvents, CO2 gives extracts with the most natural smell and taste. Grimmett [6] had earlier concluded that the aromas of extracts obtained by liquid carbon dioxide extraction bear a closer resemblance to the original material than those obtained by organic solvent extraction . 

This chapter focuses on the extraction of Brazil nut oil applying supercritical fluid technology and on the comparison of the yield and quality of the oil obtained by this method with those of the oil obtained by other extraction methods such as hydraulic press, organic solvent extraction (petroleum ether and hexane). 

For example, Beynon and Cwm coals when digested in anthracene oil give extraction yields of 68% and 47% respectively. This variation can be explained by reference to the maceral composition of the coals. Beynon coal contains a lower concentration of inertinite than the Cwm coal (Table V). In experiments where relatively pure samples of petrographic species were digested in anthracene oil, exinite and vitrinite were shown to be highly soluble, whilst in comparison the inertinite was almost completely insoluble. Similar variations in reactivity of macerals have been reported from studies of solubility in pure organic solvents (1(3). 

However, the main use of fluorescence has been in the semi-quantitative determination of aromatic hydrocarbons by extraction into an organic solvent, followed by excitation at a standard wavelength and comparison with the emission from a chosen standard. These techniques have been studied by many workers [38-42],... 

A number of analytical methods for the separation of organic mercury compounds use an initial extraction of the organic materials with an organic solvent. Klisenko and Shmigidina [83] then converted both the inorganic mercury held in the aqueous fraction and the organic mercury in the chloroform extract to dithizonate, separated the components on chromatographic columns, and determined the concentration of the various fractions by comparison with reference standards. This method is semi-quantitative at best. 

In the course of our polarographic studies on organic cations we determined the half-wave potentials, 1/2, for various arylmethylium ions [1-11]. The aim of the present work is to extract from these values some new information concerning the relative magnitude of their solvation enthalpies in three very different solvents. A comparison of our results [obtained in methanesulphonic acid (MSA) and dichloromethane (DCM)] with those of Volz and Lotsch [12] [obtained in cyanomethane (CM) solutions] yields some useful conclusions. 

Solvent extraction has many features that make this separation technique applicable for the removal of organic pollutants from wastewater. The organic solutes can be recovered, and there is thus a potential for economic credit to the operation. In comparison with biological treatment, it is not subject to toxicity instabilities. The disadvantage is that, even with solvents having low solubilities in water, solvent losses can be substantial owing to... 

Acetic acid is an important intermediate organic tonnage chemical that may be produced by the petroleum industry and fermentation. The latter process requires the recovery of acetic acid from water solutions, and several techniques have been applied to this separation, including solvent extraction, azeotropic distillation, and extractive distillation. A comparison of economics between azeotropic distillation and solvent extraction combined with azeotropic distillation (Table 10.3) shows that the introduction of... 

The BP utilises formation of a derivative in order to quantify penicillins in formulations. Some penicillins do not have distinctive chromophores a further problem with these molecules is that when they are in suspensions they are not readily extracted away from excipients since they are quite insoluble in organic solvents which are immiscible with water. Using the formation of a complex with the mercuric ion in the presence of imidazole as a catalyst, a derivative of the penicillin structure is produced, which has an absorption maximum between 325 and 345 nm. In the assay, comparison with pure standard for the particular penicillin is carried out rather than relying on a standard A(l%, 1 cm) value. This assay is used by the BP for... 

Comparison to Solvent Extraction. The methodology for using solid adsorbents is described in detail in a later section. Briefly, it involves adsorption and desorption processes. In the adsorption process, the liquid matrix is water containing very small amounts of organic... 

Hewitt, A.D., Comparison of sample preparation methods for the analysis of volatile organic compounds in soil samples solvent extraction vs. vapor partitioning, /. Environ. Sci. Technol., 32(1), 143-149, 1998. 

Volatile organic compounds Comparison of solvent extraction, headspace analysis and vapour partitioning, methanol extraction [88]... 

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