Predict the order of elution for a mixture containing caffeine and benzoic acid, using a reverse phase HPLC. Explain your answer.
Since benzoic acid is more acidic that caffeine, which means it has a lower pH, it is hence more polar. Since for HPLC, the mobile phase is the polar phase, elution of polar compounds will be favoured hence benzoic acid will be eluted first. Is my answer and explanation correct?