In the first section, a surface optical chemical sensor was prepared for determination of mercury(II) ions. The mercury sensing film has prepared by immobilization of PAN as a suitable ligand for Hg(II) on triacetyl cellulose. The optode had a dynamic range 1.00×10 -6 to 9.00×10 -4 mol L ?1 Hg(II) with a limit of detection of 8.0×10 -7 mol L ?1 Hg(II).The influence of potential interfering ions on the determination of Hg(II) was studied. In the second section, a sensitive new bulk optical sensor for mercury(II) is described. This optode is based on the interaction of hexathiacyclooctadecane with Hg(II) in plasticized PVC membrane incorporating chromoionophore V as a lipophilic H + -selective indicator. With the proposed sensor, mercury(II) can be measured in the range of 2.12×10 ?7 to 1.17×10 ?4 mol L ?1 with a limit of detection 2.0×10 ?7 mol L ?1 Hg(II). The sensor showed excellent selectivity for Hg(II). The third introduces a reversible optical chemical sensor for detecting lead ions. The sensor is based on the formation of color complex between Pb(II) with diphenylcarbazone in plasticized PVC membrane. The optode was found to have a long linear dynamic range, 6.89×10 ?6 to 1.07×10 ?2 mol L ?1 Pb(II), and a short response time of 180 s with a detection limit of 6.5×10 ?6 mol L ?1 Pb(II) by batch pectrophotometric method. In addition, the sensor has been incorporated into a home-made flow-through cell for determining lead ions in flowing streams. In the flow system, the linear calibration range was 1.00×10 ?6 to 5.00×10 ?3 mol L ?1 Pb(II). In further sections, tow optical chemical sensors have been developed for the determination of thallium(III) in aqueous solutions using Br-PADAP and PAR complex agents. In the universal buffer with pH 3.0, the optode had been prepared with Br-PADAP, had a linear dynamic range of 2.56×10 -6 – 4.55×10 -4 mol L -1 thallium(III) with a detection limit of 1.1×10 -6 mol L -1 and in the universal buffer with pH 4.0, the optode had been prepared with PAR, had a linear dynamic range of 3.11×10 -6 to 4.66×10 -4 mol L -1 and detection limit of the optode was 1.8×10 -6 mol L -1 . In the last section, an optical chemical sensor has been prepared for the determination of samarium(III) in aqueous solutions based on Br-PADAP. Br-PADAP was used as an ionophore in plastisized PVC membrane. The prepared optode had a linear dynamic range for the samarium concentration of 2.56×10 -6 to 2.61×10 -4 mol L -1 . The lower and upper detection limits of the optode were 1.9×10 -6 and 3.0×10 -4 mol L -1 Sm(III), respectively.