Chemical bonding of stationary

Deactivation of solid support by chemical bonding of stationary phase. 11... 

Chemical bonding of stationary phases has been shown to increase the stability of the stationary phase compared with conventionally coated films. A chemically bonded phase may be regarded as one that is not extractable by solvents that do not attack the phase. 

Silica particles have surface silanol groups, — SiOH. These are used for chemical bonding of stationary phases by silination reactions with chlorosilanes ... 

Buszewski, B., Gadza-la-Kopciuch, R. M., Markuszewski, M. L, Kaliszan, R. Chemically bonded silica stationary phases synthesis, physicochemical characterization, and molecular mechanism of reversed-phase HPLC retention. Anal. Chem. 1997, 69, 3277-3284. 

Yang, W.-H., Chen, I-L., and Wu, D.-H., Chemically bonded phenylsilicone stationary phases for the liquid chromatographic separation of polycyclic aromatic hydrocarbons and cyclosiloxanes, /. Chromatogr. A, 722, 97, 1996. 

Sandoval, I.E. and Pesek, I.I., Synthesis and characterization of a hydride-modified porous silica material as an intermediate in the preparation of chemically bonded chromatographic stationary phases, AnaZ. Chem., 61, 2067, 1989. 

Table 2 Selection of Commonly Used Ion-Pairing/Dynamic Liquid-Liquid Ion Exchange/ Mobile-Phase Additive Species, Which at pH <7.0 Modify the Retention Characteristics of Unprotected Peptides on Chemically Bonded Hydrocarbonaceous Stationary Phases3-11...

S. N. El-Gizawy, A. N. Ahmed, and N. E. El-Rabbat, High performance liquid chromatographic determination of multivitamin preparations using a chemically bonded cyclodextrin stationary phase, Anal. Lett., 24 1173 (1991). 

S. A. Wise, S. N. Chesler, H. S. Hertz, L. R. Hilpert, and W. E. May, Chemically-bonded aminosilane stationary phase for the high-performance liquid chromatographic separation of polynuclear aromatic compounds. Anal. Chem. 49 (1977), 2306-2310. 

Figure4.3 Formation of chemically bonded silica stationary phases.

Gfeller et al.25 1 used a microparticulate chemically bonded diol stationary phase in combination with an exclusively aqueous mobile phase. It allowed post-column ion-pair derivatiza-tion of the separated alkaloids. By changing the pH and the ionic strength of the buffer, the capacity factors of the alkaloids could be varied. 

Szepesi et al. reported an ion-pair separation of eburnane alkaloids on a chemically bonded cyanopropyl stationary phase. As counter-ion, di-(2-ethyl hexyl)phosphoric acid or (+)-10-camphorsulfonic acid were used in a mobile phase consisting of hexane - chloroform -acetonitrile mixtures (Table 8.8, 8.9). Because of the poor solubility of the latter pairing ion, diethylamine (Table 8.9) was added to the mobile phase. Addition of diethylamine considerably reduced the k1 of the alkaloids, due to suppression of the ionization of the alkaloids. However, due to the strong acidic character of the pairing ion, ion-pairs were still formed under these conditions. The camphorsulfonic acid containing mobile phases were found to be very useful for the separation of optical isomers (Table 8.10, 8.11, Fig.8.8) 6. It was also found that the selectivity of the system could be altered by choosing different medium-polarity solvents (moderator solvents) as dioxane, chloroform or tetrahydrofuran. The polar component of the solvent system affected peak shape. Based on these observations, a method was developed to analyze the optical purity of vincamine and vinpocetine. For the ana-... 

Lumley, B., Khong, T.M. and Perrett, D. (2004) The characterisation of chemically bonded chromatographic stationary phases by thermogravimetry. Chromatographia, 60 (1-2), 59-62. 

Ahmed, A.N. El-Gizawy, S.M. Use of chemically-bonded cyclodextrin stationary phase for high performance liquid chromatographic determination of Feldene capsules. J.Chromatogr.Sci., 1987, 25, 424-426 [column temp 35]... 

C.H. LochmHller, S.F. Marshall and R.W. Wilder. Photoacoustic Spectroscopy of Chemically Bonded Chromatographic Stationary Phases, Anal. Chem.. 52 19-23 (1980). 

A.H.N. Ahmed and S.M. El-Gizawy, Chemically Bonded Cyclodextrin Stationary Phase for the High-performance Liquid Chromatographic Separation and Determination of Sulphonamides, Analyst, 11(1989)4571. 

The inertness of stainless steel columns matches that of fused silica and is derived from a multistep process which utilizes a multilayer pretreatment of the inner surface of the stainless steel. Each layer is chemically stable at elevated temperatures and has the same or higher mechanical properties as the steel tubing. The layers are chemically bonded together. Stationary phases are easily bonded to this stable inert surface, resulting in high-performance columns. 

On the other hand, chiral separation of some fiavonoids was also carried out by HPLC using a chemically bonded chiral stationary phase or more often by the addition of chiral additives in the mobile phase facilitating separation of enantiomers on conventional stationary phases [8, 22, 86]. For the separation of different polyphenols, chromatographic conditions involve almost exclusively the use of a RP C18 column and a binary solvent system containing acidified water using acetic acid, phosphoric acid, or sulfuric acid and a less polar solvent such as methanol or acetonitrile [113-121]. 

Since the early nineties, column manufactures have devoted extensive resources to acquiring technology for the development of chemically bonding a stationary-phase... 

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