A New Silver(I) Potentiometric Sensor Based on a Calix[4]arene Substituted at the Narrow Rim by Amide/Phosphoryl Groups

Abstract

AbstractA coated‐wire type silver ion‐selective electrode has been constructed using a modified p‐tert‐butyl‐calix[4]arene by amide‐phosphoryl groups, named 5, 11, 17, 23‐tetra‐tert‐butyl‐25, 27‐bis(diethylcarbamoylmethoxy)‐26,28‐bis(diphenylphosphinoylmethoxy)calix[4]arene (Calix), as neutral carrier. A plasticized PVC membrane containing 30% PVC, 60% ortho‐nitrophenyloctylether (NPOE), 2% sodium tetraphenylborate (NaTPB) and 8% “Calix” was coated on a graphite rod. The prepared electrode exhibited a linear Nernstian response over the range 1 × 10−6 to 1 × 10−2 M with a slope 58.4 (±0.2) mV per decade change and a detection limit of 6.3 × 10−7 M. The working pH range of the sensor is 4‐6.7. It is found that the dynamic response time of the electrode to achieve a steady potential was very fast (∼11 s). The selectivity of the sensor relative to NH4+, Li+, Na+, K+, Ca2+, Sr2+, Ba2+, Mn2+, Pb2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Fe3+, La3+, Sm3+ and Th4+ was examined. The prepared electrode exhibits adequate stability with good reproducibility (57.6 ± 0.5 mV per decade change for 10 weeks). It was successfully used as an indicator electrode in potentiometric titration of silver ions with standard solution of EDTA. The sensor was also used for silver ion measurements in various synthetic samples.