Partitioning with solvent

Analytical methods for parent chloroacetanilide herbicides in soil typically involve extraction of the soil with solvent, followed by solid-phase extraction (SPE), and analysis by gas chromatography/electron capture detection (GC/ECD) or gas chromatog-raphy/mass spectrometry (GC/MS). Analytical methods for parent chloroacetanilides in water are similarly based on extraction followed by GC with various detection techniques. Many of the water methods, such as the Environmental Protection Agency (EPA) official methods, are multi-residue methods that include other compound classes in addition to chloroacetanilides. While liquid-liquid partitioning was used initially to extract acetanilides from water samples, SPE using... 

Propachlor is extracted from plant and animal material with aqueous acetonitrile. After filtration and evaporation of the solvent, the extracted residue is hydrolyzed with base, and the hydrolysis product, NIPA, is steam distilled into dilute acid. The acid distillate is partitioned with dichloromethane. The aqueous layer is adjusted to a basic pH, and NIPA is extracted with isooctane. The extracted residues are cleaned up using a silica SPE column, and NIPA is eluted with isooctane-ethyl acetate (9 1, v/v) solvent mixture. Quantitation is by GC/NPD. 

Concentrate the extracts to about 40 mL at 60 °C under reduced pressure in a rotary evaporator. Transfer the concentrate into a 250-niL separatory funnel, rinse the evaporation flask with 100 mL of aqueous 10% sodium chloride solution and then with 50 irL of dichloromethane, and add the rinsates to the separatory funnel. After shaking the separatory funnel, filter the lower organic phase over anhydrous sodium sulfate into a 250-mL evaporation flask. Repeat partitioning with a second portion of 50 irL of dichloromethane and combine the organic phases. Evaporate the solvent with a rotary evaporator at 40 °C. 

Isoxathion is extracted from plant materials with aqueous acetone. The extracts are concentrated and partitioned with n-hexane after addition of sodium chloride. The n-hexane phase is collected and concentrated after dehydration. The extract is partitioned with n-hexane and acetonitrile. The acetonitrile phase is collected, concentrated, and subjected to Horisil column chromatography. Isoxathion is eluted with diethyl ether-n-hexane after washing the column with the solvent. Isoxathion in the eluate is concentrated and dissolved in acetone and injected into a gas chromatograph for quantitative determination. 

Solvent Extraction Aqueous sample is partitioned with an immiscible organic solvent. Extraction efficiency depends on the affinity of the solute for the organic solvent. All sample types Samples with a high affinity for water are not extracted. Extractions can be performed by a simple single equilibration or by multiple equilibrations with fresh solvent. Solvent impurities concentrated along with sample. 

In recent years, extraction methods for PhACs have usually been based on liquid partitioning with ultrasonic extraction (USE) [43-47], microwave-assisted extraction (MAE) [48], or the more advanced PLE [49-52]. When compared to the other extraction techniques, PLE provides good recoveries, saves time and organic solvent, which makes it become currently a preferred technique for PhAC analyses. 

The operation of a separating funnel depends on partition. A solvent contains some solute. A different solvent, which is immiscible with the first, contains no compound. Because the two solvents are immiscible - which means they do not mix - the separating funnel will show two distinct layers (see Figure 5.15). After shaking the funnel vigorously, and allowing its contents to settle, some of the solute will have partitioned between the two solvents, with some sample passing from the solution into the previously pure solvent 1. 

Samples filtered then extracted with pentane. Solvent dried then partitioned with sodium hydroxide. Organic fraction cleaned up with alumina and silica. 

Adequate precaution and care must be exercised in determining partition coefficients based on the solubility data as S, is not the solubility of substance A in pure Solvent a , but rather the solubility in Solvent a saturated with Solvent cb ... 

A further limitation stems from a detailed examination of the possible reaction coordinate in an Sfjl reaction. Consider a scheme where substrate A may solvolyse to form an intimate ion pair, B, that dissociates and then reacts with solvent. Shiner et al. (1969), Shiner and Dowd (1971) and Shiner and Fisher (1971) have suggested that maximum a-effects will be found where there is a rate-determining conversion of the intimate ion pair into a solvent-separated ion pair, and Murr and Donnelly (1970) have shown how partitioning of the ion pair, B -> A and C, results in an isotope effect in the diphenylmethyl... 

Alternatively, solvent partition or countercurrent techniques may be applied. In order to obtain an isoflavonoid-rich fraction from Erythrina species (Leguminosae) for further purification work, an organic solvent extract was dissolved in 90% methanol and first partitioned with hexane. The residual methanol part was adjusted with water to 30% and partitioned with t-butyl methyl ether-hexane (9 1). This latter mixture was then chromatographed to obtain pure compounds. ... 

Compound Solvent Pressure Partitioning w/o CO2 Partitioning with CO2... 

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