An ionophore is a compound that can carry specific ions through membranes of cells or organelles. Historically, this term was reserved for biological systems, but ionophores are also used in chemical sensors. An ionophore is the main component determining the membrane selectivity in a potentiometric ion-selective electrode (ISE). The search for new ionophores with a good affinity for various groups of compounds has been going on for decades. These efforts resulted in the development of sensors for determining simple metal cations such as Na + , K + and inorganic anions (F - and CN -) as well as more complex organic cations and anions . Screening of ionophores is usually performed through the fabrication and testing of potentiometric membranes, which is a time-and labor-intensive task that consumes high amounts of the recognition molecule. The ionophore is the most important, but not the only component of the ion-selective membrane. Lipophilic salt reduces the resistivity and maintains the electroneutrality during the sensing process 2, . The most commonly used lipophilic salts are derivatives of quaternary boron (e.g. potassium tetrakis [3,5-bis(trifluoromethyl)phenyl]borate, KTFPB) or ammonium salts (e.g. tridodecylmethylammonium chloride, TDMAC) . All the membrane components are suspended in a plasticized polymer. Plasticizer lowers the polymer's glass transition temperature and significantly affects its conductivity and diffusion rate . It can also enhance interactions with other membrane constituents and analytes, thus improving the overall selectivity of the fabricated sensor. The composition of the membrane i.e., the amount of ionophore, the amount and type of lipophilic salt and plasticizer must be carefully optimized. In addition, the ISE conditioning parameters must be adequately selected because they have a high impact on the repeatability of the results and the lifetime of the sensors.