Polychlorinated biphenyls hydrophobic

Maruya, K.A. and R.F. lee. 1998. Biota-sediment accumulation and trophic transfer factors for extremely hydrophobic polychlorinated biphenyls. Environ. Toxicol. Chem. 17 2463-2469. 

Zajicek, J.L. Tillitt, D.E. Huckins, J.N. Petty, J.D. Potts, M.E. Nardone, D.A. 1996, Application of Enzyme-Linked Immunosorbent Assay (ELISA) for Measurement of Polychlorinated Biphenyls (PCBs) from Hydrophobic Solutions Extracts of Fish and Dialysates of Semipermeable Membrane Devices (SPMDs). In Environmental Immunochemical Methods, ACS Symposium Series 646 American Chemical Society Washington, D.C. Chapter 26, pp 307-325. 

In 1990, the applicability of cyclodextrin-modified MEKC (CD-MEKC) was successfully explored for the first time by adding a neutral CD to the micellar solution for the separation of highly hydrophobic and closely related compounds such as chlorinated benzene congeners, polychlorinated biphenyl (PCB) congeners, and tetrachlorodibenzo-p-dioxin (TCDD)... 

Haque, R. and Schmedding, D.W. A method of measuring the water solubility of hydrophobic chemicals solubility of five polychlorinated biphenyls. Bull. Eviron. Contam. Toxicol., 14(1) 13-18.1975. 

For halogenated aromatic hydrocarbons like polychlorinated biphenyls (PCBs), polychlorinated dibenzofurans (PCDFs), and polychlorinated dibenzo-p-dioxins (PCDDs) the binding to the aryl hydrocarbon (Ah) receptor regulates their toxicity [89]. The Ah receptor controls the induction of one of the cytochrome P450 enzymes in the liver. Toxic responses such as thymic atrophy, iveight loss, immu-notoxicity and acute lethality are associated ivith the relative affinity of PCBs, PCDFs and PCDDs for the Ah receptor [89]. The quantitative structure-activity relationship (QSAR) models predicting the affinity of the halogenated aromatic hydrocarbons ivith the Ah receptor describe the electron acceptor capability as well as the hydrophobicity and polarizability of the chemicals [89[. 

Liquid-liquid extraction and sorbent accumulation are the most commonly employed isolation-concentration methodologies. In their ideal forms, these methods readily extract or accumulate relatively hydrophobic compounds such as polynuclear aromatic hydrocarbons (PAHs) or polychlorinated biphenyls. However, when HPLC is likely to be the method of choice, the compounds are likely to be highly polar or ionic. In these common cases, adaptation of the traditional methodology can readily serve to carry out the necessary isolation. 

In most wastes and wastewater, polychlorinated biphenyls (PCBs) and particulate matter are found in the aqueous phase. The fraction of PCBs associated with each phase depends on the hydrophobicity. The congeners containing more chlorine substituents have a stronger tendency to associate with particulate. PCBs sorbed to surfaces such as diatomaceous earth are not oxidized by aqueous OH at an appreciable rate relative to the reaction rate of OH with solution-phase PCBs. Sedlak and Andren (1994) performed a quantitative evaluation of the effect of sorption to particulate matter on the rate of PCB oxidation by OH. The transformations of three PCB congeners — 2-monochlorobiphenyl (MClBp) 2,2, 5-trichlorobiphe-nyl (TrCIBp) and 2,2, 4,5,5 -pentachlorobiphenyl (PeCIBp) — were studied at an initial concentration of 1 pM of PCB solution. Data from the experiments were compared with predictions from quantitative kinetic models that used independently determined data on reaction rates and OH concentrations. 

As more chlorines are added in the polychlorinated biphenyl series (PCBs), the measured log Poct values taper off asymptotically to a maximum value of 8.55 (de Bruijn, 1989). This is most probably due to the fact that the l(h3M octanol which is present in the water phase is much greater than the amount of PCB, and it acts as a detergent/ sequestering the miniscule amount of any solute with log P>7.5. Of course, this may make measured octanol/water an improved model for many actual environmental systems. River water with a heavy load of sediment will adsorb hydrophobic solutes and appear to solvate them better than pure water. The only real problem in calculating the log Poct of PCBs whose log P<7.0 is allowing for the decreased hydrophobicity of chlorines in the ortho position. Again, most programs handle this reasonably well, as the examples in Table 5.6 show. 

Poster, D.L. and J.E. Baker. 1996a. Influence of submicron particles on hydrophobic organic contaminants in precipitation. 1. Concentrations and distributions of polycyclic aromatic hydrocarbons and polychlorinated biphenyls in rainwater. Environ. Sci. Technol. 30 341-348. 

The analytical availability of hydrophobic organic micropollutants could be reduced to a high extent in the presence of DOM. Gjessing et al. (2007) showed that the analytical recovers of polychlorinated biphenyls (PCBs) was also affected by the quality and the nature of DOM. 

Webb, R.G., McCall, A.C. (1972) Identities of polychlorinated biphenyl isomers in Aroclors. J. Assoc. OfFic. Anal. Chem. 55, 746. Weber Jr., W.J., Voice, T.C., Pirbazari, M., Hunt, G.E., Ulanoff, D.M. (1983) Sorption of hydrophobic compounds by sediments, soils and suspended solids-H. Water Res. 17(10), 1443-1452. 

PGC sorbents have even more highly homogeneous hydrophobic surfaces than GCB sorbents. PGCs are macroporous materials composed of flat, two-dimensional layers of carbon atoms arranged in graphitic structure. The flat, homogeneous surface of PGC arranged in layers of carbons with delocalized n electrons makes it uniquely capable of selective fractionation between planar and nonplanar analytes such as the polychlorinated biphenyls [92,94,95],... 

Regardless of one s position in this debate, it is apparent that the use of compounds that show persistence in the environment must be carefully examined and monitored. Any compound that is persistent and hydrophobic (lipophilic or fat soluble) will be subject to the process of biomagnification and may present special problems. In addition to DDT and other chlorinated pesticides, another example is provided by the polychlorinated biphenyls (PCBs). These compounds have two benzene rings bonded together, with varying numbers of chlorines substituted on the rings. One example is provided by the following structure ... 

Gobas et al. [30] in 1989 investigated the bioconcentration potential of polychlorinated biphenyls (PCBs), polybrominated benzenes (PBBzs) and poly-brominated biphenyls (PBBs), and other super-hydrophobic chemicals, such as decachlorobiphenyl and Mirex. These authors also pointed out the importance of bioavailability for bio concentration of super-hydrophobic chemicals. Their study showed that the bioavailable fraction of the super-hydrophobic chemical decachlorobiphenyl can be as low as 3 % and of Mirex can be as low as 2.2 %. For decachlorobiphenyl, a BCF was found that was one to two orders of magnitude lower than the true BCF. 

The Hydrophobic Effect Hydrophobic Sorption Hydrophobic ( water-hating ) compounds, for example, hydrocarbons and chlorinated hydrocarbons such as the polychlorinated biphenyls are soluble in many nonpolar solvents but not readily soluble in water. Because of the incompatibility of the hydro-phobic substance with water, these substances have a tendency to avoid contact with water and seek to associate with nonpolar environments such as the surface of a mineral or an organic particle (Tanford, 1980). The sorption of hydro-phobic substances to solid materials (particles, soils, sediments) that contain organic carbon may be compared with the partitioning of a solute between two solvents—water and the organic phase. 

The extraction of Polychlorinated Biphenyls (PCBs) from water may effectively be accomplished with C-18 and a reversed-phase mechanism. The method is similar to the PAH method and consists of isolation of the analytes from a 1 -L sample, followed by elution with ethyl acetate followed by methylene chloride. The combination of solvents is needed for the hydrophobic nature of PCBs. The disk is cleaned with the elution solvents before addition of the sample. 

Micellar electrokinetic chromatography (MEKC), a modified CE, enabled the separation of electrically neutral analytes. However, highly hydrophobic compounds including PAHs, corticosteroids, fat-soluble vitamins and polychlorinated biphenyl (PCB) congeners could not be separated by MEKC in electrophoretic medium of sodium dodecylsulfate (SDS) [59]. The use of CDs to the SDS solution can remarkably improve the resolution of analytes. For example, a mixture of water-soluble and fat-soluble vitamin or esterom can be successfully separated by MEKC by the addition of y-CD in the SDS electrophoretic medium [60]. 

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