Abstract : In this thesis, I have introduced a simple method for the construction of an optical chemical sensor (optode) for the determination of Pd(II) ions in aqueous sample solutions by the use of a plasticized PVC-based polymeric membrane film, incorporating 4,4'-Bis-(dimethylamino)thiobenzophenone (Thio-Michler's Ketone, TMK) as the palladium chromophore (the palladium sensing element) and KTPClPB as anionic additive. The proposed optical sensor possessed a stable and fast absorbance signal, and was found to be highly selective towards Pd(II) ions with significant absorbance signal change at 436 nm, upon the exposure to aqueous solutions containing varying levels of Pd(II) ions. The sensing film was able to determine Pd(II) ion concentrations in aqueous sample solutions with a high selectivity over a wide dynamic range of 9.4×10-8 – 2.8×10-4 M, at a pH of 2.8 with a detection limit of 9.4×10-9 M. The proposed optode was able to tolerate high concentrations of several metal ion interferents, and was used in the analysis of several samples. The samples were reanalyzed using a reference spectrophotometric method...