Using a continuous flow apparatus, extraction of maleic acid and phthalic acid by from their mixture supercritical carbon dioxide (scCO 2 ) saturated with Trioctylamine, have been performed at temperatures of 35, 45, and 55 K in the pressure range of (100-350) bar and flow rate of 0.2 mL min -1 of liquid CO 2 flow rate. Since organic acids are polar compounds and can hardly be extracted by scCO 2 , trioctylamine as an ion-pair forming reagent was used to increase the extraction amount of the acids. The amount of extraction of maleic acid and phthalic acid increased with pressure up to 250 and 200 bar, respectively, where it reaches a plateau at different temperatures. The amount of extraction of maleic acid by scCO 2 -TOA was higher than the amount of extracted phthalic acid. The amount of the acids extracted was also increased with increasing temperature. The amount of extracted acids by scCO 2 -TOA was much higher than the solubility of them in neat scCO 2 . Moreover, the extraction selectivity of maleic acid to phthalic acid (? = y 1 /y 2 ) of 7.3 was achieved at 318 K and pressure of 250 bar. The method was established as a selective and green extraction method for dicarboxylic acids such as maleic and phthalic acids.