The two podand chelates based on diethylsulfide, 1,5‐bis(2′‐hydroxy‐4′‐nitrophenoxy)‐3‐thiapentane (L1) and 1,5‐bis(8′‐oxybenzopyridine)‐3‐thia pentane (L2), have been synthesized and explored as neutral ionophores for preparing poly(vinyl chloride) based membrane electrodes selective to Pb2+. The addition of anionic additives and various plasticizers has been found to substantially improve the performance of the electrode. The best performance was obtained with the electrode No. 1 having a membrane of ionophore (L1) with the composition PVC:o‐NPOE:ionophore (L1):NaTFPB (%w/w) of 33 : 62 : 3 : 2. The electrode exhibits Nernstian response with a slope of 31.57±0.3 mV decade−1 of activity in the concentration range from 2.0×10−9 to 1.0×10−1 M Pb2+, performs satisfactorily over a wide pH range (1.6–7.0), with a fast response time (5 s).

The two chelates based on calix [4]arene and thiacalix [4]arene have been synthesized and used as neutral ionophores for preparing PVC based membrane sensor selective to Ho 3+ ion. The addition of potassium tetrakis(4-chlorophenyl)borate (KTpClPB) and various plasticizers, viz., NDPE, o-NPOE, DOP, TEP and DOS have been found to improve significantly the performance of the sensors. The best performance was obtained with the sensor no. 6 having membrane of L 2 with composition (w/w) ionophore (2%): KTpClPB (4%): PVC (37%): NDPE (57%). This sensor exhibits Nernatian response with slope 21.10 ± 0.3 mV/decade of activity in the concentration range 3.0 × 10 −8 -1.0 × 10 −2 M Ho 3+ ion, with a detection limit of 1.0 × 10 −8 M. The proposed sensor performs satisfactorily over a wide pH range of 2.8-10, with a fast response time (5 s). The sensor was also found to work successfully in partially non-aqueous media up to 25% (v/v) content of methanol, ethanol and acetonitrile, and can be used for a period of 4 months without any significant drift in potential. The electrode was also used for the determination of Ho 3+ ions in synthetic mixtures of different ions and the determination of the arsenate ion in different water samples.

A silver selective electrode based on TEPQA‐MCM‐41 material was developed and used for the selective determination of Ag+ ion in various samples. The effect of various plasticizers i. e. dimethyl phthalate (DMP), Tris(ethylhexyl)phosphate (TEP), bis‐(2‐ethylhexyl)sebacate (BEHS), bis‐(2‐ethylhexyl)adipate (BEHA) was investigated. The electrode of the composition of 2 : 1 : 77 : 12 : 8 (w/w, %) of TEPQA‐MCM‐41 : NaTPB : Graphite powder : paraffin oil : DMP respectively, works satisfactorily in a wide concentration range of 1.3×10−9 M–1.0×10−1 M for Ag+ ion with a lower detection limit (LOD) of 1.0×10−9 M and has Nernstian slope of 63.4± 1 mV/decay. The electrode can be used in a pH range of 2.3 to 6.7 for a period of 3 months without any divergence in potential response. The selectivity coefficient calculated by fixed interference method indicates the high selectivity of the electrode towards Ag+ ion over other tested cations.

Chemically modified mesoporous silica material (SBA-15) was used for the construction of Tl(I) selective carbon paste electrode. The best response was found with the electrode containing 10% modifier as electrode material. The electrode has a lower detection limit of 6.0 × 10−9 M in a working concentration range of 1.0 × 10−8–1.0 × 10−1 M. The selectivity coefficient calculated by match potential method (MPM) shows the high selectivity of electrode towards Tl(I) over other tested ions. The electrode was successfully applied as an indicator electrode for the titration of 0.01 M TlNO3solution with standards EDTA solution and for sequential titration of mixture of different anions.

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