Studies on shape selectivity of RP C18-columns

Stationary phases with octadecyl groups have been prepared with different c arbon content without and in the presence of water and characterized for th eir selectivity for the shape of various polyaromatic hydrocarbons. It is s hown that both a high hydrocarbon content and a good accessibility of the b onded groups within the pores is required to achieve shape recognition for PAH. High carbon content alone is not sufficient. The two tests for shape s electivity proposed by Sander and Wise as well as by Tanaka are compared. I n most cases the results are similar: A low selectivity with the Sander and Wise test (alpha TBN/BaP < 1) corresponds to a high value with the Tanaka test (alpha TRI/o-TER > 3). However, not in all cases the tests give corres ponding answers. Further studies on molecular recognition are required.