Chemically modified multiwalled carbon nanotube carbon paste electrode for copper determination

A New, MWCNT-Based, Solid-State Thiabendazole-Selective Sensor

Direct potentiometric measurements using solid-state sensors have a great potential for thiabendazole (TBZ) determination, considering simplicity, accuracy, and low cost. Modifying the sensing material of the sensor with multi-walled carbon nanotubes (MWCNTs) leads to improved analytical properties of the sensor. In this study, a new potentiometric solid-state sensor for TBZ determination, based on MWCNTs modified with a sulfate group, and TBZ ion as sensing material was developed. The sensor exhibited a Nernstian response for TBZ (60.4 mV/decade of activity) in a working range between 8.6 × 10⁻⁷ and 1.0 × 10⁻³ M. The detection limit for TBZ was 6.2 × 10⁻⁷ M. The response time of the sensor for TBZ was 8 s, and its signal drift was only 1.7 mV/h. The new sensor is applicable for direct potentiometric determination of TBZ in complex real samples, such as fruit peel. The accuracy of TBZ determination is confirmed using the standard addition method.

Selective detection of Cu2+ ions using a mercaptobenzothiazole disulphide modified carbon paste electrode and bismuth as adjuvant: a theoretical and electrochemical study

Bismuth adsorbed on the MBTS-modified surface facilitates the mass and charge transfer necessary for copper's selective sensing.

A new solid-state anionic surfactant-selective sensor based on functionalized MWCNT

A new solid-state potentiometric sensor for anionic surfactants (AnS) determination was prepared. The sensor material in the liquid membrane was made of multi-walled carbon nanotubes (MWCNTs) chemically functionalized with a quaternary ammonium group and tetraphenylborate (TPB) anion (MWCNT-N⁺(CH₃)₃TPB^-). The response of the MWCNT-N⁺(CH₃)₃TPB^- sensor was Nernstian (59.3 mV/decade of activity) for both AnS investigated (sodium dodecyl sulfate (NaDDS) and sodium dodecylbenzenesulfonate (NaDBS)). The limits of detection were 2.0 ∙ 10^-7 and 1.5 ∙ 10^-7 for NaDDS and NaDBS, respectively, and the average response time was only 5 s. The new MWCNT-N⁺(CH₃)₃TPB^- sensor was very selective for NaDDS compared to anions usually contained in commercial products and is not affected by nonionic surfactants that can also be present in these products. It was tested to determine AnS concertation by the potentiometric titration method in a pH range between 3 and 12 and successfully applied for its determination in three-component mixtures and real systems.

Comparative Electroanalytical Studies of Graphite Flake and Multilayer Graphene Paste Electrodes

In this paper, the fabrication, surface characterisation and electrochemical properties of graphite flake (GFPE) and multilayer graphene (MLGPE) paste electrodes are described. The Raman investigations and scanning electron microscopy were used to analyze and compare structure of both carbon materials. The electroanalytical performance of both electrodes was examined and compared on the basis of the square-wave and cyclic voltammetric behavior of acetaminophen and model redox systems. Results of those studies revealed that GFPE has a larger electroactive surface area and better conductive properties, whilst MLGPE demonstrate better analytical characteristic in case of acetaminophen (AC) determination. AC determination was developed using square wave voltammetry (SWV) and square wave stripping voltammetry (SWSV). For both working electrodes, the process of accumulation enabled us to obtain an extended linear range and to lower the detection limit. In pharmaceutical formulations, AC was determined with good recovery.

A highly sensitive, selective and renewable carbon paste electrode based on a unique acyclic diamide ionophore for the potentiometric determination of lead ions in polluted water samples

Due to the toxicity of lead(ii) to all living organisms as it destroys the central nervous system leading to circulatory system and brain disorders, the development of effective and selective lead(ii) ionophores for its detection is very important. In this work, 1,3-bis[2-(N-morpholino)acetamidophenoxy]propane (BMAPP), belonging to acyclic diamides, was applied as a highly selective lead(ii) ionophore in a carbon paste ion selective electrode for the accurate and precise determination of Pb(ii) ions even in the presence of other interfering ions. Factors affecting the electrode's response behavior were studied and optimized. Scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and FT-IR spectroscopy were used for studying the morphology and response mechanism of the prepared sensor. The lipophilicity of the used ionophore, which contributes to the mechanical stability of the sensor, was studied using the contact angle measurement technique. The selectivity coefficients obtained by the separate solution method (SSM) and fixed interference method (FIM) confirmed the selectivity of the proposed sensor for Pb(ii) ions. The proposed sensor exhibited a Nernstian slope of 29.96 ± 0.34 mV per decade over a wide linear range of 5 × 10⁻⁸ to 1 × 10⁻¹ mol L⁻¹ and detection limit of 3 × 10⁻⁸ mol L⁻¹ for 2 months with a fast response time (<10 s) and working pH range (2.5–5.5). To further ensure the practical applicability of the sensor, it was successfully applied for the lead(ii) ion determination in different water samples and the obtained data showed an agreement with those obtained by atomic absorption spectroscopy. In addition, it was successfully applied for the potentiometric titration of Pb(ii) against K₂CrO₄ and Na₂SO₄.

Due to the toxicity of lead(ii) to all living organisms destroying the central nervous system and leading to circulatory system and brain disorders, the development of effective and selective lead(ii) ionophores for its detection is very important.

Potentiometric Sensors for the Determination of Anionic Surfactants - A Review

Anionic surfactants are important components of many products used in everyday life in all households. They are also applied in various industrial fields at a very large scale. Since they have a negative influence on the environment, it is an imperative to monitor their concentration in aquatic ecosystems. Therefore, it is of great importance to develop new methods for the determination of a wide spectra of anionic surfactants in complex environmental samples in a short time. A comprehensive review of potentiometric sensors for the determination of anionic surfactants in the last 50 years is given with special concern to papers published since 2000, but noting some earlier published important papers. The latest development in use of new ionophores, polymer formulations, and nanomaterials is presented. Additionally, the application of new potentiometric sensors in batch mode or in miniaturized microfluidic methods is discussed.