High-performance liquid chromatography reversed-phase materials

Commercially available poiybrominated aromatic ethers have been analyzed by reversed phase high performance liquid chromatography. NMR spectra of material isolated by preparative methods served to identify the observed peaks as congeners of tetrabromo to nonabromo diphenyl ether. A bromination pathway was clearly indicated. 

In 1979, it was stated that poiybrominated aromatic ethers have received little attention (ref. 1). That statement is still applicable. Analyses to characterize this class of commercial flame retardants have been performed using UV (refs. 1-2), GC (refs. 1-6), and GC-MS (refs. 1-4). The bromine content of observed peaks was measured by GC-MS, but no identification could be made. The composition of poiybrominated (PB) diphenyl ether (DPE) was predicted from the expected relationship with polyhalogenated biphenyl, a class which has received extensive attention. NMR (refs. 3-6) was successfully used to identify relatively pure material which had six, or fewer, bromine atoms per molecule. A high performance liquid chromatography (HPLC) method described (ref. 1) was not as successful as GC. A reversed phase (RP) HPLC method was mentioned, but no further work was published. 

Identification and quantification of natural dyes need high performance analytical techniques, appropriate for the analysis of materials of complicated matrices containing a small amount of coloured substances. This requirement perfectly fits coupling of modern separation modules (usually high performance liquid chromatography in reversed phase mode, RPLC, but also capillary electrophoresis, CE) with selective detection units (mainly mass spectrometer). 

In this unit, methods for reversed-phase high-performance liquid chromatography (HPLC) are described for the analysis of polyphenolics. HPLC analysis can be employed in an easy and fast manner to obtain an accurate elucidation and quantification of individual polyphenolic compounds found in plant-based materials. The separation of each polyphenolic is based on the polarity differences among polyphenolics with structural similarities and uses various combinations of mobile and stationary phases. 

The following table provides a summary of the general characteristics of the most popular stationary phases used in modem high-performance liquid chromatography.1 7 The most commonly used phases are the bonded reverse phase materials, in which separation control is a function of the mobile (liquid) phase. The selection of a particular phase and solvent system is an empirical procedure involving survey analyses. The references provided below will assist the reader in this procedure. 

Various workers [23-32] have studied the application of high performance liquid chromatography to the determination of PAHs in water samples. Hagenmaier et al. [31] used a reversed phase high-pressure liquid chromatography procedure for the determination of trace amounts of polycyclic aromatic hydrocarbons in water. Different column packing materials were tested, in conjunction with non polar stationary phases of various polarities, for separation efficiency, detection limits and long-term stability. The method was suitable for concentrations as low as 2ng L 1 in a IL sample. Compounds... 

In recent years several sensitive and specific methods for the simultaneous determination of ephedrine alkaloids in plant material have been published. These include thin-layer chromatography (292,426), gas chromatography (251), straight-phase and reversed-phase high-performance liquid chromatography (253, 255, 302, 355, 427), isotachophoresis (303, 356), and 13C-NMR (304). Resolution of enantiomeric alkaloids by HPLC has been achieved on chiral stationary phases (417, 418) or after derivatization with a chiral agent on an achiral stationary phase (419). Chromatographic separation and analytical detection of... 

C. Dewaele and M. Versele, Influence of the particle size distribution of the packing material in reversed-phase high-performance liquid chromatography, J. Chromatogr. 260 (1983), 13-21. 

As reversed-phase high-performance liquid chromatography is the most common mode of HPLC, many efforts have been made by chromatographers to introduce hydrophobic moieties on the zirconia surface. Polybutadiene-coated zirconia (PBD-Zr02) was proven to be an excellent reversed-phase packing material.PBD-Zr02 has excellent pH and thermal stability and is efficient for... 

Solid-state Si and CPMAS NMR have been used to characterize three different reversed-phase materials for high-performance liquid chromatography, obtained by sorption of poly(methyloctylsiloxane) onto bare silica, titanized silica and zirconized silica pores and to study the coupling of y-methacryloxypropyltrimethoxysilane on experimental nano-porous silica fillers. 

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