Josipa Komljenović

Ion-sensitive behaviour of silver sulphide-based solid-state copper(II) and iodide electrodes in partially aqueous systems

Abstract The response of copper(II)- and iodide-selective electrodes was evaluated in various water-organic solvent mixtures. The copper(II) electrode showed an almost Nernstian behaviour in mixtures with ethylene glycol, tert-butanol, propanol, ethanol and methanol. The experimental slopes in buffered water-acetonitrile mixtures were linear but super-Nernstian. The response of this electrode in mixtures with p -dioxane was neither Nernstian nor linear. The interference of mercury(II) in the direct potentiometric titration of copper(II) with EDTA in solution containing acetonitrile was studied. The behaviour of silver sulphide-based iodide electrode hydrophobized by PTFE in mixtures with ethanol, methanol and p -dioxane was poorer than in water. The potential response of the iodide electrode with a homogeneous membrane (Ag 2 S + AgI) was satisfactory even after prolonged soaking in p -dioxane.

Potentiometric determination of mercury(II) and thiourea in strong acid solution using an ion-selective electrode with AgI-based membrane hydrophobised by PTFE

SummaryThe potentiometric determination of mercury(II) and thiourea (TU) in strong acid solution (pH 0–1) by using an “all-solid-state” ion-selective electrode with (Ag2S 25%, AgI 25% and PTFE 50% m/m)-membrane is described. The linear response, 43 mV(pHg)−1 and 80 mV(pTU)−1, has been obtained in the concentration range from 10−2 to under 10−5 mol/l. By direct potentiometry at pH 0 mercury(II) can be determined in the presence of up to 10−3 mol/l of iron(III). The change in potential in the tested concentration range of thiourea indicates the formation of Ag(TU)1.4+at the exposed surface of the membrane. This stoichiometry is in good agreement with that calculated from the average Ag/TU ratio in the potentiometric titration. The investigated electrode can be used as a good sensor for mercury(II) and thiourea in strong acid media and a wide variety of practical analytical systems.

Use of a multi-purpose solid-state ion-selective electrode body and an agl-based membrane hydrophobised by PTFE for the determination of I– and Hg2+

The design of a multi-purpose “all-solid-state” electrode body is described. The electrode body, which provides solid contact with the ion-selective membrane, can be used with either pressed pellet or metal disc membranes. The preparation and performance of a silver iodide-based pellet hydrophobised by PTFE are described. The pellet (Agl 25%, Ag2S 25% and PTFE 50%m/m) was mounted in the electrode body and examined as an ion-selective membrane for the determination of l– and Hg2+ ions.

Design and properties of flow-through electrode with AgI-based membrane hydrophobized by PTFE; application to flow-injection determination of thiourea

Abstract A multi-purpose solid-state iodide-selective electrode is constructed as a compact tubular sensor; the sensing hole has 2.0 mm i.d. and 1.2 mm length. The behaviour, suitability and incorporation of the tubular electrode into the conduit of a flow-injection system are described. Application of the tubular electrode is exemplified by the determination of thiourea in 0.1 M HClO 4 as supporting electrolyte by using of a flow-injection system. A rectilinear calibration graph is obtained by plotting the peak height versus concentration of thiourea. The detection limit is 20 μM under optimized flow conditions (1.2 ml min −1 , 200 μl samples, 10 −5 M silver ions in the carrier stream).

Flow-injection determination of compounds containing sulfur by using potentiometric tubular sensor

A flow-injection analysis (FIA) setup with flow-through tubular solid-state AgI-based membrane detector, sensitive to the sulfhydryl group, is examined. Application of a flow-injection system is exemplified by the determination of different compounds containing sulfur in 0, 1 M HClO_4 as a supporting electrolyte. For compounds with -SH group, a rectilinear calibration graph is obtained by plotting the peak height versus cencentration of RSH. The experimental slope is in good agreement with the theoretical (59 mV {;p(RSH)};^-1) value postulated on an precipitation process and formation of RSAg into the carrier stream or at the sensing part of the detector. The described FIA setup with utilized sensor can be applied for calculation of the solubility product of RSAg or stability constant of Ag(SR)_n^(1-n)+ complex.

Potentiometric determination of an overall formation constant using an ion-selective membrane electrode: A laboratory exercise for analytical chemistry

The development and application of ion-selective membrane electrodes (ISMEs) continues to be a rapidly growing area of analytical chemistry. However, in the standard analytical chemistry textbook little attention is given to this subject, and there is a gap between the available teaching sources and the research literature.