The present invention is directed to solubilizing compounds, a device and a method for solubilizing and removing carboxylic acids and especially fatty acids from oils, fats, aqueous emulsion, aqueous media and organic solutions. Devices utilizing the inventive method shall be used for separating carboxylic acids from oils, fats, aqueous emulsion, lipophilic media or organic solutions, respectively by preparing an aqueous micro- or nanoemulsion of the carboxylic acids especially the fatty acids and the solubilizing compound which contains at least one amidino and/or gianidino group. Solubilization effects of solubilizing compounds combined with the inventive use of separation methods for carboxylic acids can be used to treat persons in need of removal of fatty acids or analyze carboxylic acids from blood or process other solutions in food, pharmacy, chemistry, bio fuel industry or other industrial processings.