Studi pengembangan binding gel pengikat ortofosfat oleh perangkat diffusive gradient in thin film (DGT) dengan biokomposit coloaded-kitosan-bentonit serta pengaruh anion pada deteksi fosfat = Study of orthophosphate binding gel by diffusive gradient in thin film (DGT) apparatus with co-loaded-chitosan-bentonite biocomposite and anion impact to phosphate detection