Retention behaviour of some barbituric acid derivatives on a polyethylene-coated silica column.

The retention of 45 barbituric acid derivatives was determined on a polyethylene-coated silica column (PEE) in unbuffered methanol-water eluent mixtures. Each derivative showed a symmetric peak shape in each eluent and the capacity factor decreased monotonously with increasing concentration of methanol in the eluent. Stepwise regression analysis indicated that the retention of barbituric acid derivatives is mainly governed by the molecular lipopholicity and, to a lesser extent, by steric effects of the various substituents. This finding indicates that the polyethylene-coated silica behaves as a real reversed-phase chromatographic support with slightly different retention characteristics.