The hydrolytic stability of a sterically protected cyanopropyl modified silica phase, used in reversed-phase mode, has been studied. This Zorbax SB-CN stationary phase shows superior hydrolytic stability in comparison with conventional CN stationary phases against intensive flushing with aggressive eluents of high and low pH, plain and also with the addition of an organic modifier. In addition to chromatography and elemental analysis, solid-state NMR was also used to characterize the changes in the properties of these phases. Moreover, the effect of sample volume and nature of the sample solvent on overloading of the SB-CN columns was studied. Volume overloading was already observed, when 10 #x3BC;l of the sample solved in pure organic modifier was injected on the column. On the other hand, if the eluent was used as the sample solvent, no significant loss of column performance could be observed, at least up to 50 #x3BC;l of sample injections.
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