Stationary with high silanol activity

These comments demonstrate that the classification of the stationary phases is in line with expectation and is consistent with practical experience. The reproducibility of the values surely depends on the phase and the manufacturer. Therefore, one should expect some variation of the values given here. For the retention factor of a hydrophobic probe, one should expect today a relative standard deviation of around 5%. Kele [16] has demonstrated that the relative standard deviation of the batch-to-batch reproducibility achieved with Symmetry Cjg is as low as 1.3%. The silanol activity can have a standard deviation as high as 15% in... 

Silica gel and aluminium oxide layers are highly active stationary phases with large surface areas which can, for example, — on heating — directly dehydrate, degrade and, in the presence of oxygen, oxidize substances in the layer This effect is brought about by acidic silanol groups [93] or is based on the adsorption forces (proton acceptor or donor effects, dipole interactions etc) The traces of iron in the adsorbent can also catalyze some reactions In the case of testosterone and other d -3-ketosteroids stable and quantifiable fluorescent products are formed on layers of basic aluminium oxide [176,195]... 

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