abstract ion selective electrodes (ises) are electrochemical sensors that respond selectivity to the activity of ionic species. an ion-selective electrode is an electrochemical device that uses a thin selective membrane or film as the recognition element, and is an electrochemical half-cell equivalent to other half-cells of the zeroth (inert metal in a redox electrolyte). in common methods of chemical measurements (batch methods), sample is placed in a vessel and the detector is placed into sample without flowing. flow injection analyses (fia) are chemical measurements, which are carried out in flowing samples. in fia, sample passes front of the detector only for a few moments; thus, the response time for detector should be very low. flow injection technique (fit) is the first way for automation of analytical chemical methods. the automation of analytical methods is necessary for cost, simplicity of operation and reliability reasons. some detectors are inherently more suitable than others in the interfacing, and therefore are used more frequently in fia system. these include, spectrophotometers, atomic absorption, inductively coupled plasma (icp), electrochemical detectors. a large variety of electrochemical detectors have been used in fia, including those based on potentiometry (fip), amperometry, volametry and chronopotentiometry. the use of ion-selective electrodes (ise) in fia seems very attractive because of a number of advances, such as simple, low cost instrumentation, little or no pretreatment of the sample, no interference from sample color and turbidity, reliability, compatibility, capability, etc. ion selective electrodes respond rapidly and reproducibly in a fip system, they seem to exhibit nearly nerstian behavior, selectivity coefficients obtained in this dynamic mode are often improved in favor of the main (mother) ion. in addition, automated analyzers can be based on fia systems using potentiometric sensors due to the simplicity, low reagent consumption and high sample processing capability. some barium compounds released during industrial processes dissolve easily in water and are found in lakes, rivers, and streams. because of their water-solubility these barium compounds can spread over great distances. based on the selectivity order obtained from solution studies, calix[4]crown-6 was used as a suitable lipophilic ionophore for the construction of a new pvc-membrane electrode for selective and sensitive determination of ba2+ ions. while there is no report definitely indicating cd2+ ion as an essential trace element in biological processes, it is well known that this element is highly toxic to a wide variety of living organisms, including man. thus, in recent years, a number of ion-selective electrodes for cadmium assay have been reported in the literature, while none of which is used in flow injection potentiometric determination of cadmium ion. thus, in this work, we used 1,3-bis(2-cyanobenzene)triazene as a suitable lipoiphilic neutral ionophore for the preparation of pvc-membrane coated graphite electrode (cge) for selective determination of cadmium ion in solution under batch and flow injection modes. the determination of trace transition metals is important in the context of environmental protection, food and agricultural chemistry. in next works we report on the flow injection potentiometric determination of cobalt and copper ions using a novel highly selective and sensitive coated graphite electrode based on 7-[(5-chloro-8-hydroxy-7-quinolinyl)methyl] - 5,6,7,8,9,10 - hexahydro - 2h - 1,13,4,7,10 - benzodioxatriazacyclo pentadecine-3,11 (4h,12h)-dione, and 5,11,17,23-tetra-propyl-thio-methyl-calix[4]arene respectively. carbon nanotubes (cnts) due to their special physicochemical properties such as ordered structure with high ratio, ultra-light weight, high mechanical strength, high electrical conductivity, high thermal conductivity, metallic or semi-metallic behavior and high surface area have been recently used for the preparation of different sensors. while they have many of the same properties as other types of carbon, cnts offer unique advantages including enhanced electronic properties. therefore, cnt-based sensors generally have higher sensitivities, lower limits of detection, and faster electron transfer kinetics than traditional carbon electrodes. finally we used cnts to improve detection limit and sensitivity ise for determination of mercury and cerium based on 7,10,13-triaza-1-thia-4,16-dioxa-4,16-dioxo-2,3,17,18-dinaphto-cyclooctadecane, and 2-((e)-{[(e)-2-({(e)-[2-hydroxy-3-(4-morpholinylmethyl) phenyl] methylidene} amino) ethyl] imino} methyl)-6-(4-morpholinyl methyl) phenol, respectively.