Puja Saxena

Tetraazacyclohexadeca Macrocyclic Ligand as a Neutral Carrier in a Cr Ion-selective Electrode

A polystyrene-based membrane of 2,10-dimethyl-4,12-diphenyl-1,5,9,13-tetraazacyclohexadeca-1,4,9,12-tetraene macrocyclic ionophore was prepared and investigated as Cr(III)-selective electrode. The best performance was observed with the membrane having the polystyrene-ligand-dibutylphthalate-sodiumtetraphenyl borate composition 1:4:1:1 with a Nernstian slope of 19.0 mV per decade of concentration between pH 3.0 and 6.5. This electrode has been found to be chemically inert and of adequate stability with a response time of 20 s and was used over a period of 100 d with good reproducibility (S= 0.3 mV). The membrane works satisfactorily in a partially non-aqueous medium up to a maximum 30% (v/v) content of methanol and ethanol. The potentiometric selectivity coefficient values indicate that the membrane sensor is highly selective for Cr(III) ions over a number of monovalent, divalent and trivalent cations. The membrane electrode has also been successfully used to determine Cr3+ in various food materials.

A highly selective thallium(I) electrode based on a thia substituted macrocyclic ionophore.

A new highly Tl(I)-selective PVC membrane electrode based on tetrathia macrocycle 6,7: 14,15-dibenzo-5,8,13,16-tetraoxo-1,4,9,12-tetrathiacyclohexadecane [Bz(2)O(4)(16)aneS(4)] (I) as membrane carrier, o-nitrophenyloctyl ether (o-NPOE) as solvent mediator and potassium tetrakis(p-chlorophenyl)borate (KTpClPB) as lipophilic additive has been developed. The best performance was given by the membrane of macrocycle (I) with composition 3:120:1.5:50 (I:o-NPOE:KTpClPB:PVC). This electrode exhibits a Nernstian response to Tl(I) ions in the concentration range 1.0x10(-1)-2.23x10(-6)M with a slope of 58.2mV/decade of concentration and a detection limit of 1.58x10(-6)M. The response time of the sensor is 12s and can be used over a period of 4 months with good reproducibility. The proposed electrode revealed good selectivity over a wide variety of other cations including alkali, alkaline earth, heavy and transition metals. The electrode works well over a pH range of 3.2-11.5 and in partially non-aqueous medium with up to 30% organic content. The sensor was also used as an indicator electrode in potentiometric titration of Tl(I) ions with KI solution.

A bromide selective polymeric membrane electrode based on Zn(II) macrocyclic complex

A novel bromide ion-selective PVC membrane sensor based on 2,3,10,11-tetraphenyl-1,4,9,12-tetraazacyclohexadeca-1,3,9,11-tetraene zinc(II)complex (I) as carrier has been developed. The electrode exhibited wide working concentration range 2.2 x 10(-6) to 1.0 x 10(-1)M and a limit of detection as 1.4 x 10(-6)M with a Nernstian slope of 59.2+/-0.5 mV per decade. The response time of electrode was 20s over entire concentration range. The electrode possesses the advantages of low resistance, fast response and good selectivities for bromide over a variety of other anions and could be used in a pH range of 3.5-9.5. It was successfully used as an indicator electrode in the potentiometric titration of bromide ions with silver ion and also in the determination of bromide in real samples.

Strontium(II)-selective electrode based on a macrocyclic tetraamide.

A new PVC membrane electrode based on 5,7,12,14-dibenzo-2,3,9,10-tetraoxa-1,4,8,11-tetraazacyclotetradecane (I) as an ion carrier, o-nitrophenyloctyl ether (o-NPOE) as solvent mediator and sodium tetraphenylborate (NaTPB) as lipophilic additive was fabricated and investigated as Sr(2+)-selective electrode. The best performance was exhibited by the membrane having composition 8:200:4:120 (I:o-NPOE:NaTPB:PVC). The electrode exhibited a Nernstian response for strontium ion over a wide concentration range 3.98 x 10(-6) to 1.0 x 10(-1)M with a slope of 29.0+/-0.1 mV/decade of concentration and a detection limit of 2.82 x 10(-6)M. It showed a response time of less than 10s and could be used for at least 3 months without any divergence in potential. The proposed electrode showed a good discriminating ability towards strontium(II) ion over a wide variety of other metal ions including alkali, alkaline earth, transition, and heavy metal ions. The electrode can be used in the pH range of 2.5-10.5 and in mixtures containing up to 35% (v/v) non-aqueous content. It was used as an indicator electrode in potentiometric titration of strontium ion against EDTA.

Lead‐Selective Potentiometric Sensor Based on Macrocyclic Ionophore [Pyo2(16)Diene N6]

Abstract Polystyrene‐based membrane of 2,3,4:10,11,12‐dipyridine‐1,3,5,9,11,13‐hexaazacyclohexadeca‐2,10‐diene with sodium tetraphenyl borate (STB) and dibutyl phthalate (DBP) as anion excluder and plasticizing agent was prepared and investigated as Pb(II)‐selective electrode. The best performance was observed with the membrane having the polystyrene‐ligand‐DBP‐STB composition 1:6:1:1, worked well over a wide concentration range (1.41 × 10−6 to 1.00 × 10−1 mol L−1) with a Nernstian slope of 29.0 mV per decade of concentration between pH 3.0 and 6.0. The limit of detection is 1.0 × 10−6. This electrode has been found to be chemically inert and of adequate stability with a response time of 15 s and was used over a period of 100 d with good reproducibility (S = 0.3 mV). The membrane works satisfactorily in a partially nonaqueous medium up to a maximum 30% (v/v) content of methanol, ethanol, and acetone. The potentiometric selectivity coefficient values indicate that the membrane sensor is highly selective for Pb (II) ions over a number of monovalent, divalent, and trivalent cations. The practical ability of the membrane sensor has also been observed in solutions contaminated with detergents (i.e., cetyltrimethylammonium bromide and sodium dodecyl sulfate). The membrane electrode has also been successfully used to determine Pb2+ in real samples. Supported by the Council of Scientific and Industrial Research (CSIR), New Delhi, India.