Reversed-phase columns packings

TEST MIXTURES FOR DETERMINING THE RESIDUAL SILANOL CONCENTRATION OF REVERSED-PHASE COLUMN PACKINGS... 

The narrow range of organic modifiers required to elute and desorb polypeptides from the reversed-phase column packing material accounts for the separation of polypeptides from a short C18 capillary column. Because polypeptide elution and separation depend on the accuracy of solvent composition in gradient nano LC, it is very important to use a system that can precisely control the LC modifier concentration even at low percents of organic modifiers in chromatographic elution compositions. 

Some of the characteristic column volumes outlined in the previous argument were determined by Alhedal et al (11) in the examination of a commercially available reverse phase column packing, Zorbax Cs. These authors examined the exclusion properties of the interstitial volume of the column by measuring the retention volume of a number of salts of different molecular volume.The substances used, in ascending order of ion volume, were as follows,... 

Now that reversed phase column packing materials have been used successfully in column liquid chromatography for a number of years, success has also been achieved in thin-layer chromatography in that it is now possible to prepare HPTLC pre-coated plates with the same types of surface-modified sorbents and to use them for separations (2 8, 1, 20). 

All chromatographic separations were made using an ES Industries 0.46 x 15 cm reverse-phase column packed with E. Merck 5 nm Lichrosorb RP-18. A Whatman pre-column (0.21 x 7 cm) packed with C0 PELL ODS (Reeve-Angel) was used to protect the analytical column from both particulate matter and irreversible bonding of injected components onto the stationary phase. The pre-column is also used to dampen mobile phase pulsations from the chromatographic pumps. 

George and Patel investigated some reversed-phase column packing materials for the presence of active silanol groups, by using the columns in the adsorption mode with -heptane as solvent. Four materials were tested for the analysis of theophylline and caffeine. These two compounds were well separated on all materials with the mobile phase acetonitrile - water - acetic acid (95 5 0.2). However, the sequence of caffeine and the internal standard 8-hydro-xypropyltheophylline varied for the columns. 

HPLC has been one ofthe most widely used analytical methods for determining PAHs in complex environmental samples. The development of a chemically nonpolar stationary phase for HPLC has provided a unique selectivity for separation of PAH isomers that are often difficult to separate by GC columns. For example, chrysene, benz[a]anthracene, and triphenylene are baseline resolved with a C-18 reverse phase column packing. A detection limit of subpicogram to picogram levels of PAHs per sample has been achieved by HPLC with fluorescence detector (For and Staley 1976 Furuta and Otsuki 1983 Futoma et al. 1981 Golden and Sawicki 1978 Lawrence and Weber 1984 Marcomini et al. 1987 Miguel and De Andrade 1989 Nielsen 1979 Risner 1988 Tomkins et al. 

Why is a reverse phase column packing desired in many cases ... 

This HPLC procedure uses weak" reversed-phase column packings and inverse-salt gr ents. While it can be consider as a kind of salting out" chromatography, it is also a variation of RPLC 48,49). Retention is related to salt concentration as... 

Suitable samples for reversed-phase columns packed with C, , C, phenyl, or hexyl packings are aromatic hydrocarbons such as toluene, xylene, cumene, naphthalene, acenaphthene, and anthracene and long-chain phthalates such as dihexyl phthalate or dioctyl phthalate. These samples give large retention factors and symmetric peaks with acetonitrile/water mobile phases of high acetonitrile content Typical mobile phases contain 50-70% acetonitrile. The... 

In this case the electrode had a cylindrical geometry (to improve sensitivity) and was placed at the exit frit of a 10-cm long reverse-phase column packed with 3-/im particles (Brownlee Labs,... 

Fekete, S. and Fekete, J. 2011. Fast gradient screening of pharmaceuticals with 5 cm long, narrow hore reversed-phase columns packed with suh-3 micro m core-shell and suh-2 micro m totally porous particles. Talanta 84 416 23. 

Stainless steel. 60 cm X 2 mm I.D., packed with phenyl Corasil (37-50 gm) reversed-phase column packing material Mobile phase... 

In one of the first papers on the HPLC analysis of lipids, Borch reported the successful separation of phenacyl esters of saturated fatty acids, and of cis- and trans-isomers of unsaturated fatty acids, using a microparticulate reversed-phase column packing and UV... 

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