Hydrophobic/hydrophilic fractionation

The hydrophobic/hydrophilic fractionation of organic carbon in ground-water is different than the fractionation of organic carbon in surface water. Table 3 shows that the amount of hydrophobic material in the groundwaters studied was less than 35%, and in surface waters the amount of hydrophobic... 

The optimum water content of most cells is around 80%. Liquid water is absolutely necessary for the stability of the lipid membrane and the hydrophobic regions in proteins. The hydrophilic fractions of the nucleic acids and the proteins require liquid water for maintaining their three-dimensional structures and thus their functionality. 

Figure 13. A few microstructural parameters for Nafion and sulfonated poly(arylene ether ketone)s,i as a function of the solvent (water and/or methanol) volume fraction Xy. (a) the internal hydrophobic/hydrophilic interface, and (b) the average hydrophobic/hydrophilic separation and the diameter of the solvated hydrophilic channels (pores).

Different surfactants are usually characterised by the solubility behaviour of their hydrophilic and hydrophobic molecule fraction in polar solvents, expressed by the HLB-value (hydrophilic-lipophilic-balance) of the surfactant. The HLB-value of a specific surfactant is often listed by the producer or can be easily calculated from listed increments [67]. If the water in a microemulsion contains electrolytes, the solubility of the surfactant in the water changes. It can be increased or decreased, depending on the kind of electrolyte [68,69]. The effect of electrolytes is explained by the HSAB principle (hard-soft-acid-base). For example, salts of hard acids and hard bases reduce the solubility of the surfactant in water. The solubility is increased by salts of soft acids and hard bases or by salts of hard acids and soft bases. Correspondingly, the solubility of the surfactant in water is increased by sodium alkyl sulfonates and decreased by sodium chloride or sodium sulfate. In the meantime, the physical interactions of the surfactant molecules and other components in microemulsions is well understood and the HSAB-principle was verified. The salts in water mainly influence the curvature of the surfactant film in a microemulsion. The curvature of the surfactant film can be expressed, analogous to the HLB-value, by the packing parameter Sp. The packing parameter is the ratio between the hydrophilic and lipophilic surfactant molecule part [70] ... 

The figure shows that hydrophilic lignin derivatives (fraction I) elute in the retention time range 30-80 minutes, compared with 90-140 minutes for the hydrophobic compounds (fractions II-IV). Refractionation by analytical GPC of fractions I-IV (Fig. 9) shows that these fractions encompass wide molar mass ranges. 

Hydrophilic Base Fraction. An aliquot (1-2 mL) of the hydrophilic base fraction was dried under a stream of N2, acidified with HC1, and analyzed for glycine after derivatization with isoamyl alcohol, acetyl chloride, and hep-tafluorobutyric anhydride according to the procedure described by Burleson et al. (23). An aliquot (1-2 mL) of the same hydrophilic base fraction was analyzed for quinaldic acid following the procedure mentioned for the hydrophobic acid fraction. The remaining portion of the hydrophilic base fraction was extracted at pH 10 with 50 mL of methylene chloride. The extract was concentrated to 1 mL and analyzed by GC-FID and GC-MS. 

Wershaw, R. L., Llaguno, E. C., Leenheer, J. A., Sperline, R. R, and Song, Y. (1996b). Mechanism of formation of humus coatings on mineral surfaces. 2. Attenuated total reflectance spectra of hydrophobic and hydrophilic fractions of organic acids from compost leachate on alumina. Coll. Surf. A 108,199-211. 

Sulfur K-edge NEXAFS also detected significant differences between oxidation states in hydrophobic and hydrophilic organic matter (Hundal et al., 2000). Oxidized organic sulfur forms were dominant in the hydrophilic fraction, whereas reduced sulfur forms were dominant in the hydrophobic fraction. 

Provenzano, M. R., Gighotti, G., Cilenti, A., Erriquens, F., and Senesi, N. (2006). Spectroscopic and thermal investigation of hydrophobic and hydrophilic fractions of dissolved organic matter. Compost Sci. Util. 14(3), 191-200. 

Table I shows that the foaming properties of whole casein improved by slight phosphorylation. The lowest phosphorylated form of casein (4 mol P/mol protein) showed higher foam hydration and stability than the native whole casein. However, the highly phosphorylated whole casein (11 mol P/mol protein) showed poor foaming properties. The foam hydration of as-casein deteriorated while that of K-casein improved by phosphorylation. This discrepancy seemed to be caused by a different initial hydrophobic/ hydrophilic balance of the proteins in their native states. However, foam stabilities of all casein fractions were reduced by phosphorylation, with K-casein being only slightly affected.

Single-step preparations of composite polymers have been examined in previous sections. The volume fraction of the continuous phase was, however, relatively small in those cases. In contrast, the present method allows us to prepare composites with larger volume fractions of the continuous phase. Composites with large volume fractions of the continuous phase can also be obtained in a single-step by polymerizing an emulsion or a microemulsion [24]. An emulsion of a hydrophobic (hydrophilic) monomer in another hydrophilic (hydrophobic) monomer can be extremely stable (even thermodynamically stable, and then it is called a microemulsion) if a sufficiently large amount of surfactant is introduced into the system. For an emulsion to be thermodynamically stable, a cosurfactant is in most cases needed besides the surfactant. The latter method was used to prepare composites by employing acrylamide... 

Distribution of Hydrophobic and Hydrophilic Fractions of DOM Derived from Organic Wastes (% of Total DOM)... 

DOM is often fractionated into six fractions hydrophobic acids, bases, and neutral compounds, and hydrophilic acids, bases, and neutral compounds. In the median freshwater, more than 80% of DOC is distributed in a 2 1 ratio between hydrophobic acids and hydrophilic acids, and less than 20% of DOC is evenly distributed between hydrophilic bases and the two neutral fractions. Very little DOC is in the hydrophobic base fraction. In the median freshwater, —60% of DOC is generally distributed in a 3 1 ratio between FAs and HAs. 

Previous studies have established the presence of NHCs in several retort water samples. Leenheer et al. [2] fractionated compounds into hydrophobic/hydrophilic basic and acidic fractions and demonstrated the presence of a number of alky 1-pyri dines and -quinolines by bigh-performance liquid chromatography. Hawthorne and Sieveis [ 3 ] used gas chromatography/mass spectrometry to identify, in 3 retort water/gas condensate sample pairs, a limited number of NHCs in tbe ambient headspace, and many more sucb compounds by an exhaustive purge and trap technique. Also reported in retort water have been a series of Cg to alkyIpyridines t 7 ]. 

---