Volatile organic compounds partition coefficient

This experiment provides an alternative approach to measuring the partition coefficient (Henry s law constant) for volatile organic compounds in water. A OV-101 packed column and flame ionization detector are used. 

Bakierowska, A.-M., Trzeszqzynski, J. (2003) Graphical method for the determination of water/gas partition coefficients of volatile organic compounds by a headspace gas chromatography technique. Fluid Phase Equil. 213, 139-146. 

The partitioning of semi-volatile organic compounds between the particle-and gas-phases is commonly described by a partition coefficient (Kp) [44,45] ... 

Kawata et al. [ 128] have described the effects of headspace conditions on recoveries of volatile organic compounds from sediments and soils. Hewitt [129] compared three vapour partitioning headspace and three solvent extraction methods for the preparation of soil samples for volatile organic carbon determination in soils. Methanol extraction was the most efficient method of spiked volatile organic carbon recovery, which depended on the soil organic carbon content, the octanol-water partitioning coefficients of analytes and the extraction time. 

Cox, S.S., Zhao, D. and Little, J.C. (2001b) Measuring partition and diffusion coefficients for volatile organic compounds in vinyl flooring. Atmospheric Environment, 35 (22), 3823-30. 

Headspace-GC-MS analysis is useful for the determination of volatile compounds in samples that are difficult to analyze by conventional chromatographic means, e.g., when the matrix is too complex or contains substances that seriously interfere with the analysis or even damage the column. Peak area for equilibrium headspace gas chromatography depends on, e.g., sample volume and the partition coefficient of the compound of interest between the gas phase and matrix. The need to include the partition coefficient and thus the sample matrix into the calibration procedure causes serious problems with certain sample types, for which no calibration sample can be prepared. These problems can, however, be handled with multiple headspace extraction (MHE) [118]. Headspace-GC-MS has been used for studying the volatile organic compounds in polymers [119]. The degradation products of starch/polyethylene blends [120] and PHB [121] have also been identified. 

Meulenberg, C.J.W. and Vijverberg, H.P.M., Empirical relations predicting human and rat tissue air partition coefficients of volatile organic compounds, Toxicol. Appl. Pharm., 165, 205-216, 2000. 

Recent research has targeted contaminated water and plant interactions. In recent work, partitioning coefficients for contaminants and plant species used in phytoremediation have been determined in the hope of better understanding the fate of compounds, particularly VOCs. Volatile organic compounds were shown to partition between plant biomass, internal... 

The various classes of volatile organic compounds have different distribution coefficients, which aid in their separation and identification. Two equilibrations transfer all alkanes and cycloalkanes into the gas phase, leaving aromatics in the water. Alcohols, acids, aldehydes, and ethers partition little to the gas phase and generally do not interfere in hydrocarbon analyses. If present in amounts that interfere, they can be identified as nonhydrocarbons by their distribution coefficients. They can be analyzed if desired by greatly increasing the gas-to-water ratio. 

Figure 3.22 Representative isotherms for the sorption of volatile organic compounds in plant cuticular matrix at 25°C. Plant matrix-air partition coefficients derived from slopes of the isotherms. [Reproduced with permission from B. Welke, K. Ettlinger, and M. Riederer, Environ. Sci. Technol. 32, 1099 (1998). Copyright 1998, American Chemical Society.]...

Therefore, dust and its associated fine particulate matter tend to become a sink for semi volatile organic compounds (SVOCs) (Butte and Heinzow 1994). Calculations suggest that many SVOCs have long indoor persistence, even after their primary sources have been removed. If the only removal mechanism is ventilation, moderately sorbing compounds (with octanol—air partition coefficients (K a) > 10 ) may persist indoors for hundreds to thousands of hours, while strongly sorbing compounds (Koa > 10 ) may persist for years (Weschler and Nazaroff 2008). 

KLO Kloskowski, A., Chrzanowski, W., Pilarczyk, M., and Namiesnik, J., Partition coefficients of selected environmentally important volatile organic compounds determined by gas-liquid chromatography with polydimethylsiloxane stationary phase, J. Chem. Thermodyn., 37,21,2005. 

But what about the more volatile organic compounds. Even for these compounds there are differences in the degree to which they are absorbable, and the determining factor is the compound s blood gas partition coefficient. To understand how the blood gas partition coefficient governs absorption, consider a vapor enclosed in a cocktail shaker with a bit of water. After the cocktail is shaken, the vapor can partition either into the water or it can primarily remain in the atmosphere within the shaker. In this case, chemicals that remain in the shaker s atmosphere have low blood gas partition coefficients, whereas chemicals found predominantly in the liquid have high values for the coefficient. These tendencies dramatically influence the capacity for absorption, because low values of the blood gas coefficient are indicative of low rates of absorption, whereas elevated coefficient values predict much higher rates of absorption across the lung epithelium. 

Bhatia, S.R. and Sandler, S.l. Temperature dependence of infinite dilution activity coefficients in octanol and octanol/water partition coefficients of some volatile halogenated organic compounds. J. Chem. Eng. Data, 40(6) 1196-1198,1995. 

Spencer and Cliath (1969, 1973) studied the effect of organic matter and clay content on vapor density of various pesticides. In general, they found that subsurface organic matter content and partition coefficients are of primary importance in describing the rate of volatilization for compounds having a high affinity for organic matter. 

Due to their extremely polar character, tetracyclines bind with proteins to form conjugates that are difficult to extract from biological matrices. Use of dilute mineral acids is of great help in dissociating tetracyclines from proteins, but once in aqueous solution, their exfraction into volatile organic solvents for further concentration and cleanup is hampered by the unfavorable partition coefficients. Most of these antibiotics are photosensitive compounds, whereas all of them show poor stability under strong acidic and alkaline conditions with reversible formation of the 4-epi-tetracyclines in weakly acidic conditions (pH 3), and anhydro-tetracyclines in strong acidic conditions (below pH 2). 

Veith, G.D., Macek, K.J., Petrocelli, S.R., Carroll, J. (1980) An evaluation of using partition coefficients and water solubility to estimate bioconcentration factors for organic chemicals in fish. In Aquatic Toxicology, pp. 116-129. ASTM STP 707, Eaton, J.G., Parrish, P.R., Hendricks, A.C., Eds., pp.116-129. Am. Soc. for Testing and Materials, Philadelphia, Pennsylvania. Verhoek, P.H., Marshall, A.L. (1939) Vapor pressures and accommodation coefficients of four non-volatile compounds. The vapor pressure of tri-ra-cresyl phosphate over polyvinyl chloride plastics. J. Am. Chem. Soc. 61, 2737-2742. 

The addition of solvents influences the separation of volatiles from samples by altering their partition coefficients. The sign of the effect depends on the relative polarity of the compounds and solvents involved. Table 4.4 illustrates the effect of the presence of an additional polar solvent such as an alcohol or acetone in an aqueous solution of BTX. As can be seen, the partition coefficient for the three analytes increases in the presence of a polar organic additive [e.g. 5% v/v alcohol (methanol, ethanol, n-propanol, n-butanol)] or acetone in the aqueous solution. Consequently, the additives aid dissolution of polarizable aromatics in water and ultimately decrease the sensitivity by a factor of 2-3. 

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