Selectivity Control of the Separation of Anthocyanins: Replacing Acetonitrile for Methanol in the Mobile Phase

A possibility of replacing acetonitrile for methanol in mobile phases containing an organic modifier, 10 vol. % of formic acid (pH regulator), and water in the separation of anthocyanins by reversed-phase HPLC on a C18 stationary phase (Symmetry®C18) is studied. It is found that in replacing acetonitrile for methanol, it is necessary to use two components of the mobile phase, containing only methanol and only formic acid, as on the joint presence of these substances, a prolonged retention drift is observed, presumably because of the acylation of methanol. It is found that the replacement of acetonitrile for methanol results in small changes in the selectivity of the separation of anthocyanins with identical substituents but different aglycones and with different carbohydrate substituents for one and the same aglycone. There are also no significant differences in the separation efficiency (by the number of theoretical plates) of anthocyanins, which makes it possible to reject expensive acetonitrile in favor of methanol. The developed procedure was applied to determine anthocyanins in cranberry fruits of various degrees of ripeness (by color). The specific features of the anthocyanin composition of cranberry fruits are determined and the need in controlling the composition of the sample solvent for excluding artifact peaks is shown.