Journal of Chromatography, 508 (1990) 127-132 Elsevier Science Publishers B.V., Amsterdam - Printed in The Netherlands CHROM. 22 306 zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Chromatographic behaviour of cyclodextrin complexes of NADH and NADP MANABU SENO*, MEILING LIN and KAZUTOSHI IWAMOTO Institute f$!fndustrial Science, Universiiy of Tokyo, Y-22-1, Roppongi, Minato-ku, Tokyo 106 (Japan) (Received January 2nd, 1990) SUMMARY The retention behaviour of NADH and NADP on an ODS-C18 reversed-phase column was investigated by using a 0.05 M phosphate buffer (pH 6) containing CI-, /I- or y-cyclodextrin (CD) as the mobile phase. Three reversible processes were assumed and the partition coefficients, kZ, of inclusion complexes and their stability constants, K, were calculated. The value of k2 is clearly dependent on the molecular weight of the CD. It was established from the calculated values of K that NADH and NADP are liable to form more stable inclusion complexes with /I-CD than a- and y-CDs. NADP has a higher stability constant than NADH owing to the formation of hydro- gen bonds between the phosphate moieties of NADP and the hydroxyl groups of CDs. INTRODUCTION 01-, /I- and y-cyclodextrins (CDs) are cyclic oligosaccharides containing six, seven and eight glucose units, respectively. Because of the dimensions of their non-polar central cavities, CDs act as “hosts”, forming stable inclusion complexes with a variety of “guest” species. The formation of an inclusion complex is based on the ability of the CD to incorporate hydrophobic molecules in its cavity and to form hydrogen bonds between hydroxyl groups at the entrance of the CD cavity and the hydrophilic moieties of the guest molecule’-3. For example, a chiral molecule forms a hydrogen bond with the 2-hydroxyl groups at the entrance of the CD cavity4s5. In addition, many other factors such as Van der Waals force, dipole-dipole interactions and hydrophobic interactions also play important roles in governing the stability of the complex6. In recent years, CD inclusion phenomena have been utilized in high performance liquid chromatographic (HPLC) techniques in two ways: the use of CD-bonded stationary phases as reported by Issaq7 and the use of CD as one component of the mobile phase in reversed-phase liquid chromatography (RP-LC)8p1 I. Cline Love and Arunyanart12 dealt with the latter method and calculated the stability constants, K, of benzene, phenol, o, m- and p-nitrophenol, naphthalene and biphenyl with /?-CD. This paper reports the results of further studies on the determinations of the 0021-9673/90/$03.50 0 1990 Elsevier Science Publishers B.V.