Amit Panwar

Chromium(III)-selective electrode based on a macrocyclic compound

A poly(vinyl chloride)-based membrane of 3,10-c-meso-3,5,7,7,10,12,14,14-octamethyl-1,4,8,11- tetraazacyclotetradecane diperchlorate with sodium tetraphenyl borate (STB) as an anion excluder and dibutyl phthalate (DBP), dibutyl butylphosphonate (DBBP), tris(2-ethylhexyl) phosphate (TEP) and tributyl phosphate (TBP) as plasticizing solvent mediators was prepared and investigated as a Cr(III)-selective electrode. The best performance was observed with the membrane having the ligand–PVC–DBP–STB composition 2:10:7:1, which worked well over a wide concentration range (1.77 × 10–6–0.1 mol L–1) with a Nernstian slope of 20 mV per decade of activity between pH 3.0 and 6.5. This electrode showed a fast response time of 15 s and was used over a period of 4 months with good reproducibility (s = 0.4 mV). The selectivity coefficients for mono-, di- and trivalent cations indicate excellent selectivity for Cr(III) ions over a large number of cations. Anions such as Cl– and SO42– do not interfere and the electrode also works satisfactorily in a partially non-aqueous medium. The sensor has been used as an indicator electrode in the potentiometric titration of Cr(III) with EDTA. The practical utility of the membrane sensor has also been observed in solutions contaminated with detergents i.e., cetyltrimethylammonium bromide and sodium dodecyl sulfate. Above all, the membrane sensor has been used very successfully to analyse some food materials for the determination of Cr(III) ion.

New bis-macrocyclic complexes with transition metal ions

Template condensation of benzidine, formaldehyde, ethylenediamine or 1,3-diaminopropane, metal salt and 1-phenyl-1,3-butanedione or 2,3-butanedione in a 1:4:2:2 molar ratio results in the formation of two new series of binuclear pentaaza macrocyclic complexes: dichloro[1,1′-phenylbis(7-methyl-9-phenyl-1,3,6,10,13-pentaazacyclotetradeca-6,9-diene) metal(II)], [M2LCl4] (M = CoII, CuII, FeIII and ZnII) and dichloro[1,1′-phenylbis(8,9-dimethyl-1,3,7,10,14-pentaazacyclopentadeca-7,9-diene) metal(II)], [M2L′Cl4] (M = NiII, CoII, CuII and CdII). Both series were characterized by i.r., 1H-n.m.r., u.v.–vis. spectral studies, conductivity and magnetic susceptibility measurements.

Nickel(II)-Selective Membrane Electrode Based on Macrocyclic Ligand

A polystyrene-based membrane of 3,4:11,12-dibenzo-2,5,10,13-tetraoxo-1,6,9,14-tetraazacyclohexadecane was prepared and investigated as a Ni2+-selective electrode. The best performance was observed with the membrane having polystyrene to ligand composition of 1:6, which worked well over a wide concentration range, 3.16×10−6–1.00×10−1 mol L−1 with a near Nernstian slope of 30.7 mV per decade of activity between pH 2.5 to 7.0. The electrode exhibits a fast response time of 10 s and was used over a period of 2 months with good reproducibility (S=±0.2 mV). The selectivity coefficient values for monovalent, bivalent and trivalent cations indicate excellent selectivity for Ni2+ ions and it also works satisfactorily in a partially nonaqueous medium of methanol and ethanol. The practical utility of the membrane sensor was observed in solutions contaminated with detergents, cetyltrimethylammonium bromide and sodium dodecyl sulfate and the sensor was used successfully to determine nickel in electroplating waste.

Poly(vinyl chloride)-based macrocyclic membrane sensors for magnesium

Poly(vinyl chloride)-based membranes of macrocycles 4,11-dimethyl-2,4,9,11-tetraethyl-1,5,8,12-tetraaza cyclotetradeca-1,8-diene (I) and 4,11-dioxa-2,9-dimethyl-1,5,8,12-tetraaza cyclotetradeca-1,8-diene (II) with sodium tetraphenyl borate (STB) as an anion excluder and dibutyl phthalate (DBP), dioctyl phthalate (DOP), dibutylbutyl phosphonate (DBBP) and 1-chloronaphthalene (CN) as plasticizing solvent mediators were prepared and investigated as magnesium selective electrodes. The best performance was observed having the composition (II)-PVC-STB-DBP in the ratio 2:10:1:7, which works well over a wide concentration range (1.9x10(-6) to 1.0x10(-1) M) with a Nernstian slope of 29 mV per decade of activity between pH 2.5 and 6.5. These electrodes have been found to be chemically inert showing a fast response time of 15 s and were used over a period of 3 months with good reproducibility (S=+/-0.2 mV). The selectivity coefficient values for mono-, di- and trivalent cations indicate excellent selectivity for Mg(2+) over a large number of cations. The electrodes have also been used successfully in partially non-aqueous medium and as an indicator electrode in the potentiometric titration of Mg(2+) with EDTA. Anions such as Cl(-) and SO(4)(2-) do not interfere in the working of the electrode. The practical utility of the membrane sensor has also been observed in solutions contaminated with detergents (cetyltrimethyl ammonium bromide and sodium dodecyl sulphate). Above all, the membrane sensor has been very successfully used to analyse some babyfood products and soft drinks for the determination of Mg(2+).