Retention regularities of alkanols and other small organic molecules on 13X zeolite under HILIC conditions

Abstract

The retention regularities on a column packed with microspherical zeolite 13X particles were studied for different classes of compounds (alkanes, aromatic substances, oxygen-, nitrogen-, chlorine-, and sulfur- containing compounds) under conditions of hydrophilic interaction liquid chromatography (HILIC) using methanol and acetonitrile as mobile phases. In general, the retention (logk’) of studied substances having kinetic diameter less than zeolite pore size is proportional to their polarity. The retention of organic substances was compared for 13X and mesoporous silica columns. A special attention was paid to the retention of n- and iso-alcohols homologues, for which a electrostatically induced sieving effect was observed. It was found that retention factors (k’) of solutes on 13X depend strongly on flow rate of the mobile phases indicating the presence of kinetic selectivity effect for the micrporous adsorbent. For the first time the baseline separation was obtained for the low homologues of n-alkanols. Also, selective separation of methanol and methanol-d₄ (selectivity α = 1.274; resolution of peaks R_S = 1.32) is achieved on 50 × 4.6 mm I.D. column with acetonitrile as the eluent.