STRONTIUM (II)-SELECTIVE ELECTRODE BASED ON A MACROCYCLIC LIGAND

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Abstract
A poly(vinyl chloride)-based membrane of 2,9-dimethyl-4,11-diphenyl-1,5,8,12-tetraazacyclotetradeca-1,4,8,11-tetraene with sodium tetraphenylborate (STB) as an anion excluder and dibutyl phthalate (DBP), tris(2-ethylhexyl) phosphate (TEP), dibutyl butylphosphonate (DBBP), and tributyl phosphate (TBP) as plasticizing solvent mediators was prepared and investigated as a Sr(II)-selective electrode. The best performance was observed with the membrane having the ligand-PVC-DBP-STB composition 1:4 : 1:1, which worked well over a wide concentration range (1.4 × 10−6−0.1 mol L−1) with a Nernstian slope of 28.6 mV per decade of concentration between pH 4.0 and 10.0. This electrode showed a fast response time of 12 s and was used over a period of 100 d with good reproducibility (s= 0.3 mV). The selectivity coefficients for monovalent, divalent and trivalent cations indicate excellent selectivity of Sr(II) ions over a large number of cations including Ca(II) and Ba(II). Anions such as Cl− and SO4 2 do not interfere ...