Partition Solvents/food

Fatty foods (>2% fat) Extraction of fat using sodium sulfate, petroleum ether, by filtering, or by solvents oleanup using solvent partitioning, Florisil GC/ECD No data >85% ( r T sulfate) FDA 1994 (PAM Method 304)... 

COPLAND E L, CLIFFORD M N and WILLIAMS c M (1998) Preparation of (-)-epigallocatechin gallate from commercial green tea by caffeine precipitation and solvent partition . Food Chem, 61, 81-7. 

Food (fish) Grinding with petroleum ether solvent extraction clean-up by liquid-liquid partition, Florisil column chromatography GC/NPD 0.1 ppm Not specified Lombardo and Egry 1979... 

SPME is a sample-preparation technique based on absorption that is useful for extraction and concentration of analytes either by submersion in a liquid phase or exposure to a gaseous phase (Belardi and Pawliszyn, 1989 Arthur et al., 1992). Following exposure of the fiber to the sample, absorbed analytes can be thermally desorbed in a conventional GC injection port. The fiber behaves as a liquid solvent that selectively extracts analytes, with more polar fibers having a greater affinity for polar analytes. Headspace extraction from equilibrium is based on partition coefficients of individual compounds between the food and headspace and between the headspace and the fiber coat-... 

Solid foods can be extracted by means of partition into organic solvents (133). The samples are macerated with aqueous acetone, methanol, or ethanol. The extract is made alkaline with sodium tetraborate, and the solids are separated by filtration or centrifugation after the addition of Celite 545 (135). Foods can also be ground with Celite and 0.1 N hydrochloric acid and washed with chloroform (156). 

Table 13-5 Partition (KG/f) and diffusion (DF) coefficients of several solvents in a selection of liquid, fatty and solid foods at 23 °C. Mr = relative molecular mass. TB = boiling point.

In the above discussion it is assumed that during storage a partition equilibrium is established between the packaging and food. However, this is not always the case. Given the time ti/2, which is the time required for half of solvent contained in the packaging material to be transferred to the food, then one gets ... 

Phase separated polymer mixtures are important in many practical applications, such as confectionery and low-fat foods. Values of the fraction (x) of a component can be replaced by those of the fraction of solvent (Sx) associated with polymer (Morris, 1998) so that Figure 6-22 may be used also to understand the role of solvent partitioning. A key assumption is that there is complete separation of the two polymers in to their respective phases, so that the relative phase volumes (hence, the polymer concentration in each phase) may be characterized by the p-factor, defined as ... 

Sample preparation Water was extracted with hexane for chlorpyrifos (a) and benzene for 3,5,6-trichloro-2-pyridinol (TCP) (b) banana samples were prepared using standard Food and Drug Administration procedures based on extraction, solvent partitioning, and silica gel or alumina column chromatography. 

Furfural is a liquid with a pungent almond-like odor. It is found in food items as a natural product. It is soluble in water to the extent of 86 g 1 at room temperature and the log of its octanol/water partition coefficient is 0.41 indicating that it is more soluble in water than in lipophilic solvents. It has a caramel-like taste and boils at 162°C. As a liquid, its density is 1.16 at room temperature but its vapor density is 3.3, causing it to settle in low places during an environmental release. Its odor threshold is somewhere between 0.024 and 20 mg m ... 

Dietary habits can influence the TK and toxicity of solvents in several ways. The mere bulk of food in the stomach and intestine can inhibit systemic absorption of VOCs. Solvents in the GI tract partition into dietary lipids, largely remaining there until the lipids are emulsified and digested. This substantially delays the absorption of VOCs such as CCI4 and its hepatotoxicity. Increased incidences of cancer have been observed in obese humans possibly due to increase in liver CYP2E1 by ketone body formation. Caloric restriction has clearly been shown to reduce the incidence of cancer. Fasting results in increased P450 activities and reduced GSH, which affect the TK and toxicity of VOCs. Food may contain certain natural constituents, pesticides, and other chemicals, which may enhance or reduce the solvent metabolism. 

To model migration of minor constituents from a polymeric film to a food-simulating solvent requires knowledge of (1) the equilibrium distribution of a migrant between polymer and solvent phases, l.e., the distribution or partition coefficient (K) and... 

Pesticide Residues Pesticide residue analysis often requires elaborate sample preparation procedures and analyte enrichment, which might involve extraction (homogenization, solvent extraction), clean-up (solvent partitioning, GPC, SPE), and analyte derivatization.21 Examples are shown in the environmental applications section. Common pesticide residues found in food crops, vegetables, or fruit are ... 

The primary disposition of carbon disulfide in the environment is related to its use as an industrial solvent and chemical intermediate. Releases from industrial processes are almost exclusively to the atmosphere. Releases of the compound to surface waters and soils are expected to partition rapidly to the atmosphere through volatilization. Hydrolysis and biodegradation do not appear to be important processes in determining the environmental fate of carbon disulfide. It has been detected at generally low levels in ambient air, surface water, groundwater, drinking water, food products, and human milk. Concentrations in environmental media are greatest near source areas (e g., industrial point sources, oceans and marshes, volcanoes). 

Partitioning. A substance may have limited solubility in two mutually immiscible solvents, for instance water and oil. This often happens in foods, for example with many flavoring and bactericidal substances. It then is important to know the concentration (or rather activity) in each phase. For low concentration, the partitioning or distribution law of Nernst usually holds ... 

If the analytes of interest are volatile or semivolatile, solvent extraction is not always necessary, and head-space techniques (HS) can be applied for the analysis, typically utilizing GC as the final analytical step. HS analysis can be defined as a vapor-phase extraction, involving ftrst the partitioning of analytes between a non-volatile liquid or solid phase and the vapor phase above the liquid or solid. The vapor phase is then transferred further and either analysed as vapor or (ad)sorbed to an (ad)sorbent. The head-space techniques have been widely utilized in the analysis of volatiles, such as fi agrances and aroma compounds, in various food and agricultural samples (81-84). The dynamic head-space (DHS), or purge-and-trap technique, is easily coupled on-line with GC. In an on-line system, desorption of trapped analytes for subsequent analysis is usually performed using on-line automated thermal desorption (ATD) devices. 

Toxicity of many substances, their biological uptake and hpophilic storage in the body, their bioconcentrations (movements through the food chain resulting in higher concentrations), and so forth, as well as their fate in the environment can be predicted from their octanol/water partition coefficients, Poet-The partition or distribution coefficient of a substance is the ratio of its solubility in two immiscible solvents. It is a constant without dimensions, and depends on the temperature and pressure. Thus,... 

In foods, the partition of antioxidants between non-aqueous and aqueous phases depends on the solvent properties of the phases and their interaction... 

Solid phase microextraction (SPME) was introduced by Arthur and Pawliszyn over 20 years ago [44]. It is a straightforward, solvent-free, and fast sample extraction method. SPME has become a widely used technique in many areas of analytical chemistry, such as food analysis, environmental sampling, forensics/toxicology, and biological analysis. Recent reviews have been published showing the latest development of this versatile extraction method [45 8]. SPME is based on the partition of the analyte between the extraction phase and the matrix. The technique can be used to monitor analytes in liquid samples or in the headspace and is basically compatible with HPLC and CE, but most applications are made by GC. As indicated by its name, it is not an exhaustive extraction technique and only a fraction of the target analyte is actually extracted. The quantity of analyte extracted is proportional to its concentration, as long as the equilibrium between the analyte in the fiber and the sample is reached. It provides linear results for wide concentrations of analytes (typically from levels of parts per million to parts per billion). 

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