Studies on the potentiometric thallium(III)-selective carbon paste electrode and its possible applications

Determination of Thallium(I) by Hybrid Mesoporous Silica (SBA-15) Modified Electrode

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.

Synthesis and application of nano-sized ionic imprinted polymer for the selective voltammetric determination of thallium

A simple and selective thallium imprinted polymer was synthesized as a chemical modifier for the stripping voltammetric determination of Tl ions. The polymerization process (bulk polymerization) was performed with ethylene glycol dimethacrylate (crosslinking monomer) and methacrylic acid (functional monomer) in the presence of 2,2'-azobis(isobutyronitrile) (initiator). The electrochemical method was based on the accumulation of thallium ions at the surface of a modified carbon paste electrode with Tl imprinted polymer and multi-walled carbon nanotubes. After preconcentration process, the voltammetric measurements were carried out via electrolysis of the accumulated Tl ions in a closed circuit. Under the optimized conditions, a linear response range from 3.0 to 240 ng mL(-1) was obtained. The detection limit and RSD (100.0 ng mL(-1) of Tl) were calculated as 0.76 ng mL(-1) and ±2.7%, respectively. The suggested modified electrode has good characteristics such as excellent selectivity, high sensitivity and suitable stability. Also, it was successfully applied for the electrochemical determination of trace amounts of Tl in the environmental and biological samples.

Carbon paste electrodes in electroanalytical chemistry

An overview is given dealing with the applications of carbon paste electrodes in equilibrium potentiometry as well as in electrochemical stripping analysis using both voltammetric and potentiometric modes. Various modifications of carbon pastes and carbon paste-based biosensors are also mentioned. The main emphasis in this article is directed at summarizing recent results of the authors' research group during the past few years.

Chemically modified carbon paste electrode for the potentiometric flow injection analysis of piribedil in pharmaceutical preparation and urine

A new carbon paste electrode selective for piribedil (PD) was prepared and fully characterized in terms of composition, usable pH range, response time and thermal stability. The electrode active recognition is by liquid ion-exchange mechanism via the use of piribedil phosphomolybdate as ion-exchanger dissolved in tricresyl phosphate as a more suitable solvent mediator for the paste. The modified electrode showed a Nernstian slope of 58.4+/-0.6 mV over the concentration range of 7.5 x 10(-7) to 1 x 10(-3)M with an average recovery of 98.3-101.0% and R.S.D. of 0.45-1.31%. The electrode exhibits good selectivity for PD with respect to a large number of inorganic cations, organic cations, sugars and amino acids. The developed electrode was successfully used for the potentiometric determination of PD in its aqueous solutions, pharmaceutical preparation, and urine in batch and flow injection analysis (FIA).

Chemically Modified Carbon Paste Electrode for the Potentiometric Determination of Dicylomine Hydrochloride in Batch and in FIA Conditions

A carbon-paste electrode for dicyclomine hydrochloride (DcCl) was prepared and fully characterized in terms of composition, life span, usable pH range and temperature. The electrode was applied to the potentiometric determination of dicylominium ion in its pure state and in pharmaceutical preparations in batch and flow injection conditions and in biological fluids using standard additions method. The electrode is based on a mixture of two ion-exchangers, namely, dicyclominium-phosphomolybdate and dicylominium-tetraphenylborate, dissolved in dioctyl phthalate as pasting liquid. The modified electrode showed a near-Nernstian slope of 58 +/- 2 mV over the concentration range of 1.2 x 10(-5)-1.6 x 10(-2) M with an average recovery of 97-102% and a RSD of 0.090-1.00. The electrode exhibits good selectivity for DcCl with respect to a large number of inorganic cations, sugars, amino acids and organic substances of biological fluids. Potentiometric titrations of DcCl with several titrants have been monitored using this modified carbon paste electrode as an end-point indicator electrode.