Development of all solid state chromium(III) selective sensor by using newly synthesized triazole derivative as an ionophore in PVC matrix

Fast chromium determination in pharmaceutical tablets by using electrochemical sensors: Preparation and comparison

In the present paper, three electrodes were prepared with the aim of detecting chromium (III) in pharmaceutical tablets and comparing their capabilities and efficiency. At first, N-(pyridine-2-ylcarbamothioyl) benzamide (NP2YCTB) was synthesized and characterized by 1H NMR, FTIR, and 13C NMR spectroscopy methods. Then, it is used as a sensing material to prepare three types of chromium potentiometry sensors including solid-state electrodes (SSE), coated wire electrodes (CWE) as asymmetric electrodes, and liquid membrane electrodes (LME) as symmetric electrodes. The responses of all electrodes were Nernstian. Field-emission scanning electron microscopy was utilized to investigate the liquid membrane morphology. The presence of chromium (III) in the membrane was proved using Energy-dispersive X-ray spectroscopy and the coordination of NP2YCTB heteroatoms with chromium (III) was confirmed by Fourier transform infrared spectroscopy. The limit of detection for SSE (3 × 10-9 mol/L) was enhanced compared with LME (7 × 10-6 mol/L) and CWE (3 × 10-7 mol/L). The response time of electrodes was very short so it was about 5-6 s for LME and CWE and 5-8 s for SSE. The sensors were used for the potentiometric determination of chromium (III) in pharmaceutical tablets and in the potentiometric titration of it with EDTA.

Chromium measurement in pharmaceutical samples: a comparative study of three new membrane electrodes with different electron-ion exchangers

The present study deals with synthesis of N-(thiazol-2-ylcarbamothioyl) benzamide. It was utilized as a neutral ionophore for designing three types of chromium(III) sensors including coated wire ion selective electrodes (CW-ISEs), ion selective electrodes with liquid internal electrolyte (LIE-ISEs), and solid-state ion selective electrodes (SS-ISEs). UV-visible spectrophotometry was used to confirm the affinity of N-(thiazol-2-ylcarbamothioyl) benzamide to chromium(III). It was found that a membrane with a composition of 2% NaTPB, 8% ionophore, 60% DBP, and 30% PVC showed the best performance and a Nernstian slope of 21.6 mV per decade. Scanning electron microscopy was used to assess the PVC membrane morphology. The existence of chromium(III) in the liquid membrane matrix was proved by energy-dispersive X-ray spectroscopy. Detection limits for SS-ISE (1 × 10^-6 M) and CW-ISE (1 × 10^-6 M) were enhanced relative to LIE-ISE (1 × 10^-5 M). All three electrodes showed a response time of about 5 s. The sensors' applicable pH range was 4.0-6.0. Fourier transform infrared spectra recorded through the electrode membrane showed that chromium(III) ion can interact with sulfur, nitrogen and oxygen atoms of N-(thiazol-2-ylcarbamothioyl) benzamide. The sensors were utilized as indicator electrodes in chromium(III) potentiometric titration with ethylenediaminetetraacetic acid and for directly measuring chromium(III) in some pharmaceutical samples.

Lignosulfonate-Based Conducting Flexible Polymeric Membranes for Liquid Sensing Applications

In this study, lignosulfonate (LS) from the acid sulfite pulping of eucalypt wood was used to synthesize LS-based polyurethanes (PUs) doped with multiwalled carbon nanotubes (MWCNTs) within the range of 0.1-1.4% w/w, yielding a unique conducting copolymer composite, which was employed as a sensitive material for all-solid-state potentiometric chemical sensors. LS-based PUs doped with 1.0% w/w MWCNTs exhibited relevant electrical conductivity suitable for sensor applications. The LS-based potentiometric sensor displayed a near-Nernstian or super-Nernstian response to a wide range of transition metals, including Cu(II), Zn(II), Cd(II), Cr(III), Cr(VI), Hg(II), and Ag(I) at pH 7 and Cr(VI) at pH 2. It also exhibited a redox response to the Fe(II)/(III) redox pair at pH 2. Unlike other lignin-based potentiometric sensors in similar composite materials, this LS-based flexible polymeric membrane did not show irreversible complexation with Hg(II). Only a weak response toward ionic liquids, [C2mim]Cl and ChCl, was registered. Unlike LS-based composites comprising MWCNTs, those doped with graphene oxide (GO), reduced GO (rGO), and graphite (Gr) did not reveal the same electrical conductivity, even with loads up to 10% (w/w), in the polymer composite. This fact is associated, at least partially, with the different filler dispersion abilities within the polymeric matrix.

Exploitation of o-benzoyl benzoic acid as an efficient electroactive material for selective determination of Cr (III) ions in pharmaceutical samples and industrial waste water using carbon sensor

Herein, for the first time, o-benzoyl benzoic acid has been explored as a promising electroactive material for the fabrication of sensitive, precise and accurate carbon paste electrode (CPE) for selective detection of Cr (III) ion. o-benzoyl benzoic acid (o-BBA) as a sensing material and tricresylphosphate (TCP) as a solvent mediator improved the developed sensor performance to get the Nernstian cationic slope of 20.03 ± 0.11 mV decade^-1 within the concentration range of 5.0 × 10^-7-1.0 × 10^-1 mol L^-1. The sensor displayed a fast response time of 12 s reflecting a pH independency over the pH range of 3.1-4.7. Moreover, the reaction between the sensing material and Cr (III) ion on the developed sensor surface was elucidated using the microscopic technique such as scanning electron microscope (SEM) in addition to the energy dispersive X-ray analyzer (EDX). The proposed sensor showed an adequate shelf lifetime (∼33 days). The values of potentiometric selectivity coefficient were obtained by fixed interference and separate solution methods affirming a high distinguishing power of the fabricated sensor toward Cr (III) ions over the other interfering ions. The established sensor could be utilized with a promising success for the Cr (III) ion estimation in the industrial waste water and in the pharmaceutical forms. Additionally, it has been employed as a promising indicator sensor with a superior performance for potentiometric titration of Cr (III) ion against EDTA.