The effect of changes in hydrodynamic conditions on the response of calcium-selective membrane electrodes with a macrocyclic carrier

Shifts of the potentials of a calcium ion-selective electrode based on the complex of 7,19-dibenzyl-2,2,3,3-tetramethyl-7,19-diaza-1,4,10,13,16-pentaoxacycloheneicosane-6,20-dione with calcium tetra(4-chlorophenyl)borate in various membrane solvents caused by changes in hydrodynamic conditions in the measured solution were examined. The use of 2-fluoro-2'-nitrodiphenyl ether as a membrane solvent combined with substitution of benzyl groups with octyl ones in the neutral carrier eliminates this unfavourable phenomenon while preserving the selectivity parameters of the electrode.