Preconcentration and voltammetric behaviour of Ag + at carbon paste electrodes modified by N-benzoyl-N',N'-di-i-butyl-thiourea

Abstract

The preconcentration of silver at carbon paste electrodes (CPE) modified with N-benzoyl-N',N'-di-i-butyl-thiourea and its subsequent voltammetric determination is studied with test solutions. The preconcentration of silver at the surface of the modified CPE succeeds as well with open circuits as with applied potentials. The amount preconcentrated depends on the electrode potential with a maximum at +0.1 V vs. Ag/AgCl, thus enabling the preconcentration of silver without cathodic treatment. The detection limit is in the order of 10(-4) mmol/l Ag(+). The surface reactions during the preconcentration are discussed. It is assumed that silver complexes of the modifier are formed in a fast reaction followed by a slow reaction with participation of silver and of carbon surface groups.

Complexes of podand-containing bis(dithiophosphonate) ligands with cobalt(II), nickel(II) and cadmium(II): recognition of CH2Cl2

“…Ligands containing two essentially different complexing groups simultaneously, for example a chelating fragment and a macrocycle or its open-chain analogue, have drawn the attention of researchers as potential bimetallic catalysts [1], models for the study of intracomplex redox processes [2][3][4][5] and reagents for supramolecular synthesis [6,7].…”

Evaluation of Microelectrode Arrays for Amperometric Detection by Scanning Electrochemical Microscopy

“…The thick film technology is suitable even for medium sized quantities while thin film processes are profitable only for very high unit numbers [8]. Pastes or inks can be modified by different filling materials (graphite or insulators), redox mediators [9,10], complexing agents [11], catalysts [12,13], or enzymes [14,15] to give materials with a wide range of chemical properties and can be made compatible with thick film technology.…”

Complexes of crown-containing N-thioacylamido(thio)phosphates with Zn(II) and Co(II) cations

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Reaction of the potassium salts of N-acylamido(thio)phosphates [4 0 -benzo-15-crown-5]NHC(S)NHP(Y)(OiPr) 2 (Y = S, HL I ; Y = O, HL II ) with Zn(II) and Co(II) cations in aqueous EtOH leads to complexes of formulae Zn(L I,II À S,Y) 2 (Y = S, 1; Y = O, 2) and Co(L I -S,S 0 ) 2 (3), while interaction of the potassium salt of [4 0 -benzo-15-crown-5]C(S)NHP(O)(OiPr) 2 (HL III ) with Zn(II) in the same conditions leads to a complex of composition Zn(HL III )(L III -S,O) 2 (4).Compounds containing two essentially different complexing groups simultaneously -a chelating fragment and a macrocycle -draw the attention of researchers as potential bimetallic catalysts [1], models at studying intracomplex redox processes [2][3][4][5] and reagents for the synthesis of supramolecular compounds [6,7].Presence of the exocyclic functional groups in a molecule of crown-ether, interacting with atoms of a cycle or metal cations, increases complexing selectivity and complexing ability in relation to metal ions, and results in a change of the hydrophilic-hydrophobic balance and surface-active properties [8,9].Earlier, we had reported about bis-thioureas, containing diaza-18-crown-6 and diaza-15-crown-5 [10], thiourea on the basis of monoaza-18-crown-6 [11] and thiophosphorylated thiobenzamide [12], containing a benzo-15-crown-5 cycle, possessing the ability for complexes with alkaline and transition metal cations.Combination of crown-ether and thioacylamido(thio)-phosphate fragments C(S)NHP(Y) in one molecule opens greater opportunities for the synthesis of various supramolecular coordination compounds. Herein, we present complexes of Zn(II) and Co(II) cations (1-4) with ligands HL I-III (Scheme 1) [13].

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“…Compounds containing two essentially different complexing groups simultaneously -a chelating fragment and a macrocycle -draw the attention of researchers as potential bimetallic catalysts [1], models at studying intracomplex redox processes [2][3][4][5] and reagents for the synthesis of supramolecular compounds [6,7].…”