Bonded phases table

Conditions of activation of the ion exchange sorbent, sample application, sorbent wash, and elution are to a high degree dependent on the nature of the analyte and the bonded phases. Table 9.5 shows a specified overview of the conditions of these steps. 

The separation of positional isomers, i.e., P- and y-tocopherol and to a lesser extent 5,7-dimethyltocol, has been addressed above in different paragraphs. In summary, a complete resolution of P- and y-tocopherol can be achieved by normal-phase chromatography on silica, as well as on diol, amino, and aminocyano bonded phases (Table 3). The three positional isomers have been separated on... 

Appllca.tlons. The first widely appHcable Ic separation of enantiomeric metallocene compounds was demonstrated on P-CD bonded-phase columns. Thirteen enantiomeric derivatives of ferrocene, mthenocene, and osmocene were resolved (7). Retention data for several of these compounds are listed in Table 2, and Figure 2a shows the Ic separation of three metallocene enantiomeric pairs. P-Cyclodextrin bonded phases were used to resolve several racemic and diastereomeric 2,2-binaphthyldiyl crown ethers (9). These compounds do not contain a chiral carbon but stiU exist as enantiomers because of the staggered position of adjacent naphthyl rings, and a high degree of chiral recognition was attained for most of these compounds (9). 

Scientific (Northbrook, IL) contain a silica support with a -y-glycidoxypropylsi-lane-bonded phase to minimize interaction with anionic and neutral polymers. The columns come in five different pore sizes ranging from 100 to 4000 A. The packing material has a diameter from 5 to 10 /cm and yields in excess of 10,000 plate counts. With a rigid silica packing material, the columns can withstand high pressure (maximum of 3000 psi) and can be used under a variety of salt and/or buffered conditions. A mobile phase above pH 8, however, will dissolve the silica support of the column (21). A summary of the experimental conditions used for Synchropak columns is described in Table 20.8. 

The great versatility of HPLC lies in the fact that the stability of the chemically bonded stationary phases used in partition chromatography allows the use of a wide range of liquids as a mobile phase without the stationary phase being lost or destroyed. This means that there is less need for a large number of different stationary phases as is the case in gas chromatography. The mobile phase must be available in a pure form and usually requires degassing before use. The choice of mobile phase (Table 3.6) is influenced by several factors. 

Hydrocarbonaceous bonded phases described in the literature have at vialues ranging frolm 2 to 4. It is believed that among monomeric phases, those having the highest ol values are the best for use in RPC. In Table III the pertinent clttihtcteristics of some monomeric bonded phases are listed. 

The effect of pore size on the retentive capacity of various octadecyl silica bonded phases is illustrated in Fig. 10. Exclusion effects become appreciable when bulky octadecyl groups (see Table V) are attached to the pore wall in 6 nm pore diameter silica (Si-60). As a result, the stationary... 

Among bonded phases of intermediate polarity the so-called cyano phases eqjoy the greatest popularity. Some sflanizing agents which can be used for the preparation of cyano phases are listed in Table VI. Cy-... 

In Table IV various specifications of commercial hydrocarbonaceous bonded phases are listed. It is seen that the conversion of surface sila-... 

The rutile and trirutile compounds of table 8 are characterised by a missing cation order and a cation order which is not vertical to oxygen layers, respectively. 77-bonding may be effective in these lattice types, however (3). As was stated at the end of section F, zJ-effects opposite to those observed for a cation order vertical to oxygen layers are expected in these cases. Indeed the substitution of a d - by a d -cation of high oxidation state is accompanied by a distinct decrease in J, which is larger for the ordered than for the disordered phases (Table 8). 

Tire preferred type of reversed-phase sorbents is Cjg bonded silica (Table 29.4). Using this reversed-phase sorbent, ion-pair separation of lincomycin (154), spiramycin (138), and tylosin (145) residues has also been reported through use of octanesulfonate, heptanesulfonate, and tetrabutylammonium pairing ions, respectively. Phenyl-bonded silica or polymeric stationary phases have also been described for the separation of tilmicosin (133) and lincomycin (146) residues, respectively. 

Liquid chromatographic separation of sedatives and -blockers is usually performed using reversed-phase columns. The preferred type of reversed-phase material is Cig-bonded silica (Table 29.16), but phenyl-bonded silica has also been employed for separation of xylazine and its major metabolite (525). Ion-pair liquid chromatography has also been suggested for separation of carazolol and xylazine residues, by addition to the mobile phase of dodecyl sulfate (522) or heptanesulfonate (520) pairing ions, respectively. 

The structure of SbX3 molecules is trigonal bipyramidal in the vapour phase (Table 20) and this symmetry is retained in the crystal state with some variations in bond lengths. In the case of the iodide the d(Sb—I) is 2.12 A (I—Sb—199°) the crystal consists of hexagonal close packed assemblies of iodine atoms with antimony in the octahedral interstices, but off-centre, giving two different d(Sb—I) distances of 2.87 and 3.32 A. 

Table 2 gives chromatographic data for different classes of enantiomeric dmgs resolved by P-CD bonded phases (8). Drugs for which resolution factors (R) greater than 1.0 were obtained include mephenytoin, ketoprofen, chlorpheniramine, and the barbiturates mephobarbital and hexobarbital. Cyclodextrin-bonded phases provide a rapid and specific technique for the pharmacological evaluation of racemic dmgs. 

Ci8-silica is the most common stationary phase and it separates a wide range of mixtures when the solvent is chosen carefully, as in Figure 25-26. However, it cannot achieve all separations. Table 25-5 is a guide to selecting other bonded phases. 

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