The retention properties of nucleobases in alkyl C8-/C18- and IAM-chromatographic systems in relation to log Pow

In order to evaluate the differences in the partition properties of 35 structurally congeneric nucleobases of biological interests in octanol-water biphasic, alkyl C(8)/C(18), and IAM systems, a comparative chromatographic study was performed. Comparing with the reversed-phase C(8)/C(18) retention data, most of the purines possessed weaker IAM retention except for those with specific H-bond and/or electrostatic interactions. Quantitative correlations between the experimental log P(ow) literature values and the IAM, C(8), and C(18) log k were evaluated (R(2)=0.943, 0.794, and 0.767, respectively). Although IAM retention correlated significantly better (larger R(2) value) with the log P(ow) values statistically, the latter was revealed apparently behaving more like (slope approaching unity) alkyl C(8)/C(18) retention and hence also has the same shortcoming in under-representing analytes capable of forming short-term H-bond/electrostatic interactions with polar head-groups of phospholipids. A chemically meaningful structure-retention model (q(2)=0.824 and R(2)=0.968) was derived, in which the hydrophobic interaction is identified as the underlying factor for the retention of purines in IAM system modulated non-trivially by H-bond/electrostatic interactions.