Use of silica gels modified with benzyldimethyltetradecylammonium in ion chromatography

The adsorption of benzyldimethyltetradecylammonium (Zephiramine) on differe nt silica gels was studied. It was shown that the maximum adsorption of Zep hiramine is observed for silica gel grafted with phenyl groups. With exampl es of Zephiramine, cetylpyridinium chloride, and cetylmethylammonium chlori de, it was demonstrated that the retention of inorganic anions on ion excha ngers is determined by the degree of shielding of the quaternary nitrogen a tom in the molecule of the modifier. For silica gels modified with differen t modifiers, the retention of anions increases in the order Zephiramine > c etylpyridinium chloride > cetylmethylammonium chloride. It was found that i norganic anions are not retained on silica gels with C2H5, C8H17, and C18H3 5 groups modified with Zephiramine; however, the retention of anions and se lectivity of their separation significantly increased on the silica gel con taining phenyl groups and modified with Zephiramine.