The role of ion pairing in the chromatographic study of propranolol analogues

The partition coefficients, log P-app(RPLC), for a series of propranolol an alogues have been determined by reversed phase high performance liquid chro matography. The hydrochloride salts and free base log P-app(RPLC) show that charged and uncharged species can partition into the reversed phase. An ex trathermodynamic relationship was found for log P-app(RPLC) measured in two different column stationary phases, C8 and PMOS, suggesting that the same sei of compounds experience a similar trend in these elution systems. The i mportance of using phosphate and/or MOPS buffer is due to the fact that the latter can avoid ion-pairing partitioning, but the former does play the sa me role for PMOS column when the free base is considered.