LEAD-SELECTIVE MEMBRANE ELECTRODES BASED ON DITHIOPHENEDIAZACROWN ETHER DERIVATIVES

Three double-armed diazacrown ethers with two thiophene side groups, h enyl-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane (DTDC), enoyl-1,4,10 ,13-tetraoxa-7,16-diazacyclooctadecane (DTODC), and etyl)-1,4,10,13-te traoxa-7,16-diazacyclooctadecane (DTAODC), have been synthesized and u sed as novel neutral lead(II) ionophores in ion selective electrode ap plications. The relationship between the molecular structure of these ionophores and electrochemical properties (linear range, response time , selectivity) of the membrane electrode is discussed. The optimum con ditions for the preparation of the electrodes are described. The optim ized dithenoyldiazacrown had a detection limit of pPb = 5.7, and Nerns tian range with slope 29.2 mV decade(-1) from pPb = 5.0 to 2.7. Mercur y and silver ions are the major interferences. These electrodes are ap plied to potentiometric titrations of lead(II) ions and show promise f or the determination of lead ions in water samples.