Zinc(II) PVC-based membrane sensor based on 5,6-benzo-4,7,13,16,21,24- hexaoxa-1,10-diazabicyclo[8,8,8]hexacos-5-ene

The 5,6-benzo-4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8,8,8]hexacos-5-ene (BHDE) was used as an excellent ionophore in construction of a Zn(II) PVC-based membrane sensor. The best performance was obtained with a membrane composition of 30% poly(vinyl chloride), 64.5% nitrobenzen (NB), 2.5% BHDE and 3% sodium tetraphenylborate (NaTPB). This sensor shows very good selectivity and sensitivity towards zinc ion over a wide variety of cations, including alkali, alkaline earth, transition and heavy metal ions. The sensor revealed a great enhancement in selectivity coefficients for zinc ions, in comparison to the previously reported zinc sensors. The proposed sensor exhibits a Nernstian behavior (with slope of 29.1 ± 0.4 mV per decade) over a wide concentration range (1.0 ´ 10-6-1.0 ´ 10-1 mol L-1) with a detection limit of 6.3 ×10-7 mol L-1 (41.2 ng mL-1). It shows relatively fast response time, in the whole concentration range (< 10s), and can be used for at least 10 weeks in a pH range of 2.8-7.3. The proposed sensor was successfully used in direct determination of zinc ions in wastewater of industrial zinc electroplating companies, and also as an indicator electrode in titration with EDTA.