A comparative study of four 20-membered N2S4-crown ethers as ionophores for polymeric membrane silver selective electrodes

Four 20-membered N2S4-monoazathiacrown ethers have been synthesized and explored as neutral ionophores for Ag+-selective electrodes. Potentiometric responses reveal that the flexibility of the ligands has great effect on the selectivity and sensitivity to Ag+ ions. The electrode based on ionophore 9,10,20,25-tetrahydro-5H,12H-tribenzo[b,n,r][1,7,10,16,4,13]tetrathiadiaza cycloicosine 6,13-(7H,14H)-dione (C) with 2-nitrophenyl octyl ether (o-NPOE) as solvent in a poly(vinyl chloride) (PVC) membrane matrix shows a measuring range of 1.0 × 10−6 to 1.0 × 10−3 mol/L with a Nernstian slope of 54.9 ± 0.3 mV/decade. This electrode has high selectivity for Ag+ with negligible interference from many other cations and can be used in a wide pH range of 3.6-9.2.