MODIFICATION OF MIXED RETENTION MECHANISMS FOR AROMATIC AMINE AND PYRIDINE-DERIVATIVES IN RP-HPLC

Silanophilic interactions of aromatic amine and pyridine derivatives in reversed-phase liquid chromatography have been modified for improved selectivity and resolution. Silanol groups on octadecyl silica columns were modified using borate or acetate salts which masked silanophilic retention of model compounds. Further treatment of modified columns using soluble salts of transition metals produced columns containing 2 to 6 mg of metal ions. Slopes of DELTA k versus 1/g adsorbed metal ion were 92 to 3040 g** minus **1. Values for complexation constant K//A were 1. 5 multiplied by 10**3 left bracket M** minus **1 right bracket for 4-picoline at concentrations of 0. 42 and 0. 43mM respectively in 70% methanol:30% water solvent. Retention and resolution were similar to those obtained using metal complexes as mobile-phase dopants.