In good liquid chromatographic separations, sample molecules are retained only by a single retention. As in reversed phase chromatography, the solute interacts hydrophobically with the non-polar alkyl chain of the column packing. However, in silica-based bonded fillers, some sample components can interact with silanol groups, which is a secondary retention process that tails the peaks. A limited strong matrix is ​​consumed, the column is overloaded with some components, and these overloaded components continue to interact with the secondary matrix. After the action, the desorption process is slow, causing peak tailing. In reversed-phase chromatography, the secondary retention effect is due to the presence of trace amounts of metallic impurities in different types of silica gel groups and column packing.
Secondary retention causes peak tailing is the most common and is a typical example of a strange peak. This peak tailing phenomenon illustrates the difference between the column and the column, and the design of the peak and tail of the packing.
In reversed-phase chromatography, certain basic components can interact with two types of silanol groups, retaining strong and tailing. The most effective way to overcome secondary retention is to add some mobile phase modifier to the secondary retention matrix. interaction. For example, adding a low concentration of 1m mol / L ~ 20mmol / L amines is usually effective. Triethylamine can effectively limit the effect of silanol groups on the sample molecules, and does not affect the use of higher concentrations of triethylamine.
The acidic component has a wide change in slit width, asymmetry, and tailing. The addition of triethylamine does not solve the problem. At this time, the silicic acid groups are combined in the form of a base, and others may be combined in the form of an acid. Different types of silanol groups exist on the surface of the silica gel. Adding 1% acetic acid as a modifier in the mobile phase can reduce the secondary retention effect of the acidic components, and the peak shape of some acidic components will be improved.
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