ANALYTICAL AND SEMIPREPARATIVE SEPARATION OF DIASTEREOMERIC LIPIDIC AMINO-ACID CONJUGATES

A series of biologically active peptides and their conjugates with lip idic amino acids were investigated by systematic change of the mobile phase composition using traditional octadecylsilica stationary phase a nd the newly developed Supelcosil(TM) LC-ABZ column. The mobile phases contained various concentrations of methanol and acetonitrile combine d with 0.1% trifluoroacetic acid (TFA). Better peak shapes and higher resolution of the isomers could be observed when the mobile phase cont ained 0.1% TFA. More symmetrical peaks and much higher S values (slope of the log k' vs organic phase concentration plots) were obtained on the special reversed-phase column developed for anionic, basic or zwit terionic compounds. The optimum separation conditions were scaled up t o a semi-preparative reversed-phase column (15 mm i.d.) to collect mg quantities of isomers for further studies.