This article describes the retention properties of arsenic (V) and chromium (VI) using a water-soluble polymer based on cationic hydroxyethylcellulose and combined with an ultrafiltration membrane.The polymer was purchased commercially and was characterized by Fourier transform infrared spectroscopy (FTIR).The study of polymer removal capacity of As(V) and Cr(VI) were performed by liquid-phase polymer-based retention technique (LPR).By means of a washing method studied retention as a function of pH, the amount of polymer, and the concentration of As(V) and Cr(VI).The results showed that the retention capacity of both oxy-anions increases with the solution pH.Due to the presence of quaternary ammonium groups in the polymer structure, the retention of As(V) and Cr(VI) was higher at a pH of 9 than that at acidic pH levels, reaching values of 65% for Cr(VI) and 43% for As(V).The study in function of amount of polymer showed that using 75 mg the retention of As(V) was 65%.In the case of Cr(VI) using 50 mg of polymer, 67% retention was obtained.Using low concentrations for arsenic and chromium, maximum retention was found at 65% and 95%, respectively.The maximum retention capacity (MRC) of the polymer was determined by adding As(V) and Cr(VI) to the polymer solution and concentrating in successive steps.FTIR spectra before and after of retention showed differences by the interaction with oxy-anions.