RETENTION INDEXES OF PHENOLS FOR INTERNAL STANDARDS IN REVERSED-PHASE HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY - APPLICATION TO RETENTION PREDICTION AND SELECTIVITIES OF MOBILE PHASES AND PACKING MATERIALS

The retention indices of previously reported phenols were calculated by means of the least-squares method on the basis of n-alkyl 4-hydroxybenzoate scales and applied to retention predictions and selectivities of mobile phases and packing materials. A simple method was established which predicts the retention times of phenols as candidates for internal standards in reversed-phase high-performance liquid chromatography. Relationships between log k' and the numbers of carbon atoms in the alkyl chain of n-alkyl 4-hydroxybenzoates, which are standard compounds for calculating retention indices, showed excellent linearity under all the tested conditions. The retention time of each phenol was calculated from the retention data for one marker solution consisting of uracil, methyl 4-hydroxybenzoate and ethyl 4-hydroxybenzoate and the retention index of each phenol. The experimentally observed retention times and predicted values agreed to within 10% relative error under several conditions. Using this technique, approximate retention times of phenols can be predicted easily and promptly. In addition, selectivities of the mobile phase and packing materials for phenols are discussed.