Hydrophobic matrices

Burns, M. and Lyddiatt, A., Controlled fluidised bed protein recovery using hydrophobic matrices . The IChemE Research Event, IChemE, Rugby, UK, 1996. 

Lau, S. Y. M., Taneja, A. K., and Hodges, R. S., Effects of high-performance liquid chromatographic solvents and hydrophobic matrices on the secondary and quaternary structure of a model protein. Reversed-phase and size exclusion high-performance liquid chromatography, /. Chromatogr., 317, 129, 1984. 

More elaborate sample preparation is often needed for complex sample matrices, e.g., lotions and creams. Many newer SP technologies such as solid-phase extraction (SPE), supercritical fluid extraction (SFE), pressurized fluid extraction, accelerated solvent extraction (ASE), and robotics are frequently utilized (see Ref. [2]). Dosage forms such as suppositories, lotions, or creams containing a preponderance of hydrophobic matrices might require more elaborate SP and sample cleanup, such as SPE or liquid-liquid extraction. 

Salt (ionic strength) gradients in lEC discussed in Section 5.4.3.3 are frequently used in the separation of complex peptides, proteins, and other biopolymer samples as a complementary technique to RP solvent gradient separations, often in a 2D setup [99,100]. The gradients usually start at a low salt (chloride, sulfate, etc.) concentration and typically run from 0.005 to 0.5 M. A buffer is used to control the pH acetonitrile and methanol may be added to improve the resolution and urea to improve the solubility of proteins that are difficult to dissolve. Ion exchangers with not strongly hydrophobic matrices usually prevent protein denaturation in aqueous mobile phases. 

Fig. 4. Comparison of activity-coupling yield (r %) and yield of grafting for samples of CRL immobilized on silica hydrophobic matrices by different methodologies.

Evaluating odor and flavor taints is frequently done with water, fatty food simulants (oil, chocolate, unsalted butter), hydrophilic powders (sugar, cornflour), or combined hydrophilic-hydrophobic matrices (milk or cream, biscuits) (Kilcast, 2003). The Robinson test often is used to evaluate materials for tainting potential. This test places the test material in a sealed container separated from the food simulant or test food at a relative humidity between 53% and 75%. After about 48 h, the test food is evaluated for taint compared to a control, using a discrimination method (Lord, 2003). Chocolate is frequently used as the food simulant for this test. Intensity of the taint may be evaluated using a... 

The effects of this variable depend on both the matrix and the analytes. Thus, hydrophobic matrices facilitate penetration of supercritical CO, also, because the fluid is water-immiscible, the presence of moisture can make the analytes inaccessible to it. Figure 7.9A illustrates the influence of this variable on the kinetics of extraction of pyrene from natural sludge, both as collected (45 /o moisture) and after air-drying (2% moisture) [40]. However, water added to the sample can facilitate extraction (e.g. that of caffeine from coffee beans. Fig. 7.9B). Natural samples with a high moisture content can plug restrictors as a result of the water they contain freezing at restrictor tips. This problem can be overcome by raising the restrictor temperature, at the expense of losses in the more volatile analytes. 

In the other models, the hydrophobic methyl groups of the polypeptide backbone are envisioned to play more major roles. Generally, methyl groups can assume the role of either spacer molecules, barrier molecules, or hydrophobic matrices for heterogeneous nucleation and propagation. 

Since (NH4)2S04 requires much of the water available for the solvation of proteins, serum proteins may be fractionated on hydrophobic matrices. Doellgast and Plant (1976) chromatographed sera in the presence of 1 M (NH4)2S04 on L-phenylalanyl-Sepharose. IgA is desorbed by lowering the salt concentration to about 20% (800 mM). 

Enzymes best retain their activity on insolubilization when hydrophilic rather than hydrophobic matrices are used. Although many non-carbohydrate matrices have been employed, the hydrophilic nature of polysaccharides must be a major feature contributing to their widespread use for enzyme insolubilization. Presumably, the hydroxyl groups of the polysaccharide resemble water molecules sufficiently to provide the enzyme to be attached with an environment suited to its stability. 

Taking into account their usefulness as adsorbants, clay minerals can be successfully hydrophobized with cationic surfactants [2]. Such hydrophobized matrices can be used for the interlayer adsorption of many organic species such as 1-pentanol. 

Based on the experimental data, it can be concluded that hydrated vermiculite exhibits a very low adsorption capacity for crude oil. On the other hand, anhydrous (expanded) and hydrophobized matrices show high adsorption capacities. The 10% hydrophobized matrix shows a 50% increase in adsorption capacity, in comparison with the expanded one. For adsorption process performed in a water—oil emulsion (50 ppm of oil), the saturation of the soHd hydrophobized matrix is achieved after 60 min. 

SUV Adsorption of detergents from phospholipid-detergent micelles to hydrophobic matrices ... 

Tien, C. L., Lacroix, M., Szabo, P. I. et al. 2003. N-acylated chitosan Hydrophobic matrices for controlled dmg release. 7. Controlled Release 93 1-13. 

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