Asymmetry Due to Secondary Interactions

As has been discussed previously, a number of different interactions give rise to retention on HPLC columns that can be exploited to separate analytes. In a well designed column, normally one major type of interaction will be exploited, and other interactions will be suppressed in order to keep separations simple, predictable, and efficient. A good example of this is traditional RP HPLC, in which the main interactions are hydrophobic interactions between solutes and a nonpolar, C18 derivatised silica stationary phase. 

An additional source of secondary sites may be derived from irreversibly retained components from previous samples. These may form a contaminated layer at the top of the column rich in secondary sites and may give rise to significant taiUng. Again, strategies for dealing with this problem are considered in Chapter 10. 

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In this section, we will deal with the major contributions to the asymmetry of peaks. We will first deal with asymmetry due to overloading, and then we will deal with asymmetry due to secondary interactions. 

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