EFFECT OF pH AND ANION INTERFERENCES ON DETERMINATION OF ORTHOPHOSPHATE SPECIATION BY DIFFUSIVE GRADIENT IN THIN FILM (DGT) TECHNIQUE

Abstract

The diffusive gradient in thin film (DGT) is an analytical method on separation and determination of phosphate. The surface analysis of gel was used in the scanning electron microscopy (SEM) that show the chemical and physical interaction in diffuse gel and oxide gel. The response of DGT device in speciation of phosphorus as H2PO4 -, HPO4 2and PO4 3showed a linear correlation between concentration and accumulation of phosphate with the concentration of 0.2 -1.0 mgL -1 . Species of H2PO4give a linear correlation of 0.9792 with regression linear at y = 9.8825x -0.0503. The HPO4 2give a linear correlation of 0.8872 with regression linear at y = 7.2143x -0.7545. The species of PO4 3give a linear correlation of 0.9769 with regression linear at y = 7.5558x -0.1828. The phosphorus accumulation from different speciation showed H2PO4 -˃ PO4 3-> HPO4 2 with accumulation was 9.6525 µg, 7.1589 µg, and 6.8783 µg, respectively. The DGT can response of phosphate with various pH at 2-12 and showed the species of phosphate as H2PO4 -, HPO4 2and PO4 3-. The optimum response show at the pH of 4 that shows the species of H2PO4 -. Anion interference was studied in this research including SO4 2-, NO3and CO3 2-. Effect of anion sulfate, nitrate and carbonate can reduce of phosphate accumulation in DGT device in the range of anion concentration from 0.05 to 0.25 mgL -1 . The interferences of NO3 -, SO4 2-, CO3 2at 0.25 mgL -1 can reduce of phosphate accumulation with the efficiency of 64.64 %, 25.10 %, and 7.57 %, respectively. The effect of NO3 -˃ SO4 2-˃ CO3 2in the accumulation of phosphate in the binding gel of DGT unit.