Studing of selectivity of zinc and cobalt thiocyanate electrodes to thiocyanate ions in presence ClO4− and NO3− E.M. Rakhman'ko†, Yu.V. Matveichuk‡*, V.V. Yasinetski‡  * Corresponding author † Belarussian State University, str. Leningradskay, 14, 220030, Minsk, Belarus ‡ Mogilev State food-stuffs University, av. Shmidta, 3, 2120127, Mogilev, Belarus; Email: Yu_Matveychuk@mail.ru Methods Objects Chem. Anal., Volume 9, No 2, 2014, p. 95-100 https://doi.org/10.17721/moca.2014.95-100
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Abstract

The effect of background concentration of ZnCl₂ and CoCl₂ on selectivity of SCN-ion selective electrodes based on trimethyl- and trinonyloctadecylammonium salts (QAS) with Zn(NCS)₄^2- and Co(SCN)₄^2- have been studied in the presence of interfering nitrate and perchlorate ions. Introduction of ZnCl₂ and CoCl₂ into solution fixes zinc and cobalt coming out of the membrane as a thiocyanate complexes, which have a high affinity towards anion exchange QAS acidocomplexes compared with competing anions. Introduction in solution 3.5 mol/l CoCl₂ increases the selectivity to SCN⁻ on 4 orders, the introduction in solution 5.0 mol/l ZnCl₂ increases the selectivity for SCN⁻ on 5 orders for electrodes based on trimethyl QAS. It is shown that the trinonyloctadecylammonium based electrodes increase their selectivity on 6 and 5 orders, for Zn(NCS)₄^2- (5.0 mol/l background ZnCl₂) and Co(SCN)₄^2- (3.5 mol/l background CoCl₂), respectively .

Keywords: potentiometry, selectivity, tetrathiocyanozincate and tetrathiocyanocobaltate-selective electrode.