Sorbic acid and benzoic acid and their salts are used as food preservatives (E200, E201, E201, E203 and E210, E211, E212, E213 respectively). The content of such preservatives in flavored bottled water may easily be analyzed by ion exclusion chromatography. This method determines the concentration of the respective acid and does not allow differentiating between the counter cations. The determination of sorbic acids and benzoic acid is achieved by conductivity detection after inverse suppression.