Silanols problems caused

Polymeric organic sorbents can reportedly be used at virtually any pH, 2 to 12 [75] or 0 to 14 [73,88], increasing the potential to analyze simultaneously multiresidue samples containing acidic, basic, and neutral compounds. Polymeric sorbents contain no silanol groups and thereby avoid the problems caused by residual silanol groups when bonded silica sorbents are used [73,75],... 

Due to the ambiguity in literature concerning the peak assignment of geminal hydroxyls in infrared spectroscopy, and due to the quantification problems encountered in infrared spectroscopy, caused by the almost complete overlap of the free and geminal hydroxyl band, the NMR results on geminal silanols should be preferred over the infrared results. 

Many of the problems encountered in the analysis of bases by LC are also manifest in CEC. The use of low pHs or reducing the number of acidic silanols leads to extremely low EOFs which may cause excessive retention of concomitantly chromatographed neutral species in addition to the practical consideration of maintaining a "wetted" capillary. These factors have led to a perception that the analysis of bases by CEC is difficult, if not practically impossible. 

Basic analytes may cause problems, as already mentioned.Figure 10.11 explains the reason. If the base is charged as well as the still present and accessible silanol groups (neutral conditions), a mixed retention mechanism is the result with both hydrophobic and ionic interactions, thus leading to tailing and unstable separation... 

A problem that has plagued GC from its beginning has been the physical adsorption of polar or polarizable analyte species, such as alcohols or aromatic hydrocarbons, on the silicate surfaces of column packings or capillary walls. Adsorption causes distorted peaks, which arc broadened and often exhibit a tail (recall Figure 26-5). Adsorption occurs with silanol groups that form on the surface of silicates by reaction with... 

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