Octyl silica

A similar HPLC technique was employed for the investigation of the persistence of MG in juvenile eels (Anguilla anguilla). Extracts were separated in phenyl-hexyl and octyl silica columns (both 50 X 4.6 mm i.d. particle size 3 jun) in series. The mobile phase was composed of 60 per cent ACN and 40 per cent 0.05 M ammonium acetate buffer (pH = 4.5). The flow rate was 0.6 ml/min and analytes were detected at 620 nm. The concentrations of MG and LMG are compiled in Table 3.16. The data prove that this HPLC method can be used for the investigation of the persistence of MG and LMG in animal tissues [106],... 

Fio. 1. Schemdic illustration of the structure of (A) octadecyl and (B) octyl silica. The ciots-hatcbed and the open areas represent the solid iuid open areas of the porous siliceous support. I... 

Fic. 30. Chromatograms iUustrating difference in selectivity due to organic components in the mobile phase. The data were obtained on capped octyl silica (5 Hypersil) with (A) methanol-water (30 30, v/v) or (B) tetrahydroforan-water (23 73, v/v) as the mobile phase. The solutes were (I) p>nitrophenol, (2) pHlinitrobenzene, (3) nitrobenzene, and (4) methyl benzoate. Flowrate, I ml/min column 130 x 4.6 mm i.d. Reprinted with permission from Tanaka ei al. (92). 

Specifications UChrosoi b SI-IUU (silica) UChrosorb HH-K (octyl silica)... 

Oligomers of glycine show little appreciable retention on octyl silica with 20 mM phosphate buffers over the pH range 2.10-7.83 (46), or on octadecyl silica with 100 mM phosphate buffer, pH 2.1 (33), or 5 mM phosphate buffers, pH 2.1, containing hydrophobic alkyl sulfonates (30). It is thus likely that the peptide chain proper makes only a very small contribution to the retention of peptides under these conditions. Based on partition coefficient considerations, oligomers of alanine, and the other nonpolar amino acids, should show a linear dependence of log A on the number of residues. This, in fact, has been observed. For example, the plot of log A versus the number of alanine residues shows (33) a linear dependence with a uniform log A increment due to the methyl group of the aliphatic side chain (Fig. 2), i.e., the effect is additive (45a, 46a). 

CAPACITY RATIOS, k, FOR EBURNANE ALKALOIDS ON OCTADECYL AND OCTYL SILICA PACKINGS WITH DIFFERENT ELUENTS54... 

The thermal stability at 60 °C of CALB-7A was significantly higher than that of the soluble enzyme, with a stabilization factor of 92.15 (Table 2). In a previous study [27], when CALB was immobilized on coconut fiber by covalent attachment at pH 7 and 10, the immobilized enzyme was, respectively, 67- or 364-fold more stable than the soluble enzyme. Making a comparison between the thermal stabilization achieved by adsorption and covalent immobilization, it can be observed that the forces involved in immobilization of CALB on coconut fiber by adsorption are stronger than the bind between enzyme and support, formed dining immobilization by covalent attachment at pH 7. Nevertheless, it is not stronger than the interaction that occurred at pH 10. Other authors [9], when immobilizing CALB by adsorption in octyl silica, obtained a biocatalyst with half-life of around 2 h, which is less stable than CALB-7A prepared in this work (t /2= 8.92 h). 

Stationary phases SI silica gel, CN cyanopropyl silica, AM amino-bonded silica. DIOL diol-bonded silica, C-2 dimethyl silica. C-8 octyl silica, C-18 octadecyl silica, Ce cellulose. AL alumina, Po polyamide coated silica, I-P impregnated with paraffin. I-F impregnated with formamide, I-Ag impregnated with silver nitrate, 1-Pg impregnated with propylene glycol. 

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