Column packings encapsulated

Figure 18-6. UPLC chromatography of benzodiazepines on a 14.5-cm x 50- xm column packed with l- xm polybutadiene-encapsulated non-porous zirconia particles. Eluent pH 7 buffer-acetonitrile 68 22 at 100°C. Peaks 1, uracil 2, clorazepate 3, fluni-trozepam 4, clonazepam 5, chlordiazepoxide 6, oxazepam 7, clorazepate 8, diazepam. (Reproduced from reference 53, with permission from Elsevier.)...

FIGURE 4.5 Chromatograms of a-phenylethanol enantiomers nsing (a) SFC and (b) open tubular column GC. Conditions (a) 12 cmx250 p.m ID capillary packed with 5-p.m porous (300 A) silica particles encapsulated with fS-CD polymethylsiloxane (10% w/w) and end-capped with HMDS, 30°C, 140 atm, CO2, FID, 10 cmxl2 p.m ID restrictor, (b) 25 mx250 p.m ID cyano-deactivated capillary cross-linked with fi-CD polymethylsiloxane (0.25 xm df) 130°C He FID. (Reprinted from Wu, N. et al. 2000. J. Microcol. Sep. 12 454-461. With permission.)... 

Miwa and Yamamoto (31) described a simple and rapid method with high accuracy and reliability for the determination of C8 0-C22 6 fatty acids, which occur in esterified forms in dietary fats and oils and in living cells [the biological effects of routinely consumed fats and oils are of wide interest because of their impact on human health and nutrition (28,29), in particular, the ratio of cu-3 polyunsaturated fatty acid to w-6 polyunsaturated fatty acids (w-3/cu-6) seems to be associated with atherosclerosis and breast and colon cancers (30)]. They report improved separation of 29 saturated and mono- and polyunsaturated fatty acids (C8-C22), including cis-trans isomers and double-bond positional isomers, as hydrazides formed by direct derivatization with 2-nitrophenylhydrazine hydrochloride (2-NPH HC1) of saponified samples without extraction. The column consisted of a J sphere ODS-M 80 column (particle size 4 /xm, 250 X 4.6-mm ID), packed closely with spherical silica encapsulated to reach a carbon content of about 14% with end-capped octadecyl-bonded-spherical silica (ODS), maintained at 50°C. The solvent system was acetonitrile-water (86 14, v/v) maintained at pH 4-5 by adding 0.1 M hydrochloric acid with a flow rate of 2.0 ml/min. Separation was performed within only 22 min by a simple isocratic elution (Fig. 6). The resolution of double-bond positional isomers, such as y-linolenic ( >-6) and a-linolenic acid ( >-3) hydrazides and w-9, >-12, and >-15 eicosenoic acid hydrazides was achieved by use of this column. 

Pellicular packings may also consist of a fully functionalized layer encapsulating solid particles, where there is no physical attachment of the active layer to the core particles [7] or as colloidal particles bearing charged moieties (latex) electrostatically bound to a solid core functionalized with groups of opposite charge [8] (Fig. 1). Most of the anion-exchange columns in use today for either carbohydrate or ion chro-... 

Sephadex G-50 (medium) (Phase Separations, Pharmacia, Sweden). The solid is dispersed in PBS buffer for swelling and the dispersion is subsequently degassed under vaccum. Gel chromatography columns are packed and used for ARSL separation from non-encapsulated molecules (as described in detail in the following section). 

Silica gel or silica-based chemically bonded or encapsulated phases with octadecyl, octyl, phenyl, cyanopropyl, aminopropyl or spacer bonded propanediol substituents. Column length 15-25 cm with an internal diameter of 1-6 mm (4-5 mm most common) and a particle size of 5 or 10 pm. Packed capillaries 15 cm - 2 m, internal diameter 250 pm, particle size 3, 5,10 or 15 pm. 

Shen, Y., Reese, S. L., Rossiter, B. E. et al. (1995) Silver-complexed dicyanobiphenyl-substi-tuted polymethylsiloxane encapsulated particles for packed capillary column supercritical fluid chromatography. J. Microcol. Sep., 1, 279-87. 

---