Crown ether-dendrimer based potentiometric Na+ sensor electrode

Poly(vinyl chloride) (PVC)-based membranes of silacrown end grafted carbosilane dendrimer (I) with sodium tetraphenylborate (NaTPB) as an anion inhibitor and dibutylphthalate (DBP), dioctylphthalate (DOP), dibutyl (butyl) phosphonate (DBBP) and 1-chloronaphthalene (CN) as plasticizing solvent mediators were prepared and used as Na+-selective electrodes. Optimum performance was observed with the membrane having I–PVC–NaTPB–DOP in the ratio 1:33:1:65 (w/w). The electrode works well over a wide concentration range 1.5 × 10−6–1.0 × 10−1 M with Nernstian compliance 56.0 mV/decade between pH 5.8 and 9.2 with a fast response time of about 15 s. The selectivity relative to alkali, alkaline earth and transition heavy metal ions is good. The selectivity coefficient values towards potassium ions have been calculated to be 2.3 × 10−4 by utilizing Fixed Interference Method. The proposed electrode could be used for at least 2 months without considerable alteration in its potential. The effect of nonionic surfactants Tween 20, Tween 80, Triton X 100, Span 20 and Span 60 on the potentiometric properties of the sodium selective membrane was also studied.