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Herein, to monitor the concentration of carbidopa in an aqueous solution, an analytical approach based on electrode surface modification by Pt/SWCNTs as a sensor has been proposed. Pt/SWCNTs was synthesized by polyol strategy and characterized by the TEM method. Results confirmed spherical Pt nanoparticles with a diameter of about 10 nm decorated at the surface of SWCNTs with good distribution. The carbon paste electrode modified (CPEM) with Pt/SWCNTs was fabricated by mixing 12% of nanocomposite as an optimum condition with graphite powder in the presence of paraffin oil as a binder. Carbidopa's oxidation signal was enhanced by about 2.73 times when using the CPEM/Pt/SWCNTs, and its oxidation potential was decreased by about 110 mV. Additionally, the sensor demonstrated a linear dynamic range of 1.0 nM-120 M with a detection limit of 0.5 nM at pH = 7.0 as the ideal condition for monitoring carbidopa. Therefore, carbidopa in water and dextrose saline can be detected using CPEM/Pt/SWCNTs with an acceptable recovery range.

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Tramadol is an analgesic drug that is mainly excreted in the urine. The entry of Tramadol into water samples causes their biological contamination. Therefore, three catalysts such as bismuth ferrite, cobalt-doped bismuth ferrite, and a magnetized Keggin type of polyoxometalate (α-Fe2O3@phosphotungstic acid), were synthesized as photocatalysts to degrade Tramadol in water samples. The morphology and properties of the prepared photocatalysts were evaluated using several techniques. Effects of several factors, including tramadol concentration, pH, hydrogen peroxide concentration, and photocatalyst amount, were studied and optimized by a design experiment procedure based on Box-Behnken design for reducing the number of experiments and cost and investigating the interactions between factors in the photocatalytic degradation process of Tramadol. These factors were optimized for each prepared photocatalyst individually. Under the optimum conditions, the percentages of tramadol degradation and kinetics of the degradation process were evaluated in the presence of each photocatalyst. The tramadol degradation percentages using bismuth ferrite, cobalt-doped bismuth ferrite, and α-Fe2O3 @phosphotungstic acid were 81.10% for 120 min, 90.63% for 80 min, and 91.32% for 80 min, respectively. The rate constants of tramadol degradation were 0.0145, 0.0329, and 0.0312 min-1 for bismuth ferrite, cobalt-doped bismuth ferrite, and α-Fe2O3 @phosphotungstic acid, respectively. The results indicated the highest percentage of tramadol degradation and rate of the degradation process were obtained using α-Fe2O3 @phosphotungstic acid and cobalt-doped bismuth ferrite, respectively.

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A highly sensitive and selective modified electrode was successfully developed for the monitoring of nicotinamide adenine dinucleotide (NADH) in the presence of folic acid. In this regard, a carbon paste electrode (CPE) was functionalized by the nitrogen-doped carbon quantum dots/tin oxide (N-CQDs/SnO2) nanocomposite and 1-butyl-2,3-dimethyl imidazolium hexafluorophosphate ([C4DMIM][PF6]) ionic liquid (IL). The structure and surface morphology of the nanocomposite were characterized by various methods, including field emission scanning electron microscopy, energy dispersive spectroscopy (EDS), high-resolution transmission electron microscopy (HR-TEM), and x-ray diffraction (XRD). The modified electrode displayed powerful and long-lasting electron mediating activity, with well-separated NADH and folic acid oxidation peaks. The sensing response of the developed [C4DMIM][PF6]/N-CQDs/SnO2/CPE platform was evaluated by determining NADH via the voltammetric technique under the optimized operating conditions. The current peaks of the square wave voltammograms of NADH and folic acid increased linearly with enhancing its concentrations within the ranges of 0.003-275µM NADH and 0.4-380µM folic acid. The detection limits for NADH and folic acid were obtained at 0.8 nM and 0.1µM, respectively. Interference species such as glucose, urea, tryptophan, glycine, methionine, and vitamin B12had no influence on the ability of the fabricated modified electrode to detect the target species. The low detection limit, high sensitivity, excellent selectivity, superior stability, and cost-effectiveness made it suitable for the quantification of NADH in the real biological samples with the recovery percent values in the range of 97.5%-103%.

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A new electrochemical platform was suggested for the sensing of the dasatinib (DA) anticancer drug based on paste electrode modification (PE) amplified with Fe3O4-SWCNTs nanocomposite and 1-hexyl-3-methylimidazolium tetrafluoroborate (mim-BF4-). The new platform showed a linear dynamic range from 0.001-220 µM with a detection limit of 0.7 nM to determine DA at optimal condition. Electrochemical investigation showed that the redox reaction of DA is relative to changing the pH of solution. Moreover, Fe3O4-SWCNTs/mim-BF4-/PE has improved the oxidation current of DA about 5.58 times which reduced its oxidation potential by about 120 mV at optimal condition. In the final step, Fe3O4-SWCNTs/mim-BF4-/PE was used as an analytical platform to determine the DA in tablets and a dextrose saline spike sample, and the results showed recovery data 99.58-103.6% which confirm the powerful ability of the sensor as an analytical tool to determine the DA in real samples.

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Electrochemical sensors have shown great appeal for the simultaneous analysis of pharmaceutical compounds. In this way, the presence study described first electroanalytical sensor for simultaneous determination of adrenalone and folic acid. The two-amplified voltammetric sensor was developed by modifying carbon paste electrode (CPE) with NiO/SWCNTs composite and 1-butyl-3-methylimidazolium methanesulfonate (1B3MIMS) and used for simultaneous determination of adrenalone and folic acid. The NiO/SWCNTs was synthesised by a fast and low-cost precipitation strategy and then characterised by EDS, FESEM and XRD methods. The results confirmed a particle size range of ⁓ 26.93-33.87 nm for NiO nanoparticle decorated at SWCNTs. The cyclic voltammetric investigation showed that oxidation potentials of adrenalone and folic acid depend on changing the pH value. The maximum oxidation current for the simultaneous analysis of two compounds occurred at pH = 7.0. In this condition, the sensor showed linear dynamic range 0.01-400 µM and 0.3-350 µM for determination of adrenalone and folic acid, respectively. The NiO/SWCNTs/1B3MIMS/CPE was then used as an ultrasensitive electroanalytical sensor for determination of adrenalone and folic acid in injection samples with recovery ratio between 98.2-103.66 %.

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Based on a selective complexation of N'-(2-oxo-1,2-di(pyridin-2-yl)ethylidene)furan-2-carbohydrazide (L) with Gd(III) ions, it was used as a selectophore in construction of a Gd(III) selective PVC membrane sensor. Different compositions for the membrane were tested. The o-nitrophenyloctyl ether (NPOE) was used as suitable plasticizer, and a mixture of sodium tetraphenyl borate (NaTPB) and oleic acid (OA) as anion excluders. The proposed sensor displayed a Nernstian behavior with the slope of 19.9 ± 0.6 mV decade(-1) in concentration range of 1.0 × 10(-6) to 1.0 × 10(-2)mol L(-1). Detection limit was 4.2 × 10(-7)molL(-1) and response time was ~10s. Applicable pH range of the electrode was 4.2-8.0. Lifetime of the sensor is at least 10 weeks. Analysis of certified reference materials confirmed the accuracy of the proposed electrode.

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A novel Dy(III) ion-selective PVC membrane sensor was made using a new synthesized organic compound, 3,4-diamino-N'-((pyridin-2-yl)methylene)benzohydrazide (L) as an excellent sensing element. The electrode showed a Nernstian slope of 19.8 ± 0.6 mV per decade in a wide concentration range of 1.0 × 10(-6)-1.0 × 10(-2) mol L(-1), a detection limit of 5.5 × 10(-7) mol L(-1), a short conditioning time, a fast response time (<10s), and high selectivity towards Dy(III) ion in contrast to other cations. The proposed sensor was successfully used as an indicator electrode in the potentiometric titration of Dy(III) ions with EDTA. The membrane sensor was also applied to the F(-) ion indirect determination of some mouth washing solutions and to the Dy(3+) determination in binary mixtures.

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A new ion-selective electrode for Sm(3+) ion is described based on the incorporation of N,N',N"-tris(4-pyridyl)trimesic amide (TPTA) in a poly(vinylchloride) (PVC) matrix. The membrane sensor comprises nitrobenzene (NB) as a plasticizer, and oleic acid (OA) as an anionic additive. The sensor with the optimized composition shows a Nernstian potential response of 19.8 ± 0.5 mV decade(-1) over a wide concentration range of 1.0 × 10(-2) and 1 × 10(-6)mol L(-1), with a lower detection limit of 4.7 × 10(-7)mol L(-1) and satisfactor applicable pH range of 3.6-9.2. Having a short response time of less than 10s and a very good selectivity towards the Sm(3+) over a wide variety of interfering cations (e.g. alkali, alkaline earth, transition and heavy metal ions) the sensor seemed to be a promising analytical tool for determination of the Sm(3+). Hence, it was used as an indicator electrode in the potentiometric titration of samarium ion with EDTA. It was also applied to the direct samarium recovery in binary mixtures.

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In this research, we report a new Ho(3+)-PVC membrane electrode based on N-(4,5-dimethyl-2-(picolinamido)phenyl)picolinamide (H(2)Me(2)bpb) as a suitable ion carrier. Poly vinylchloride (PVC)-based membrane composed of H(2)Me(2)bpb with oleic acid (OA) as anionic additives, and o-nitrophenyloctyl ether (NPOE) as plasticized solvent mediator. The sensor exhibits a Nernstian slope of 20.1 ± 0.2 mV decade(-1) over the concentration range of 1.0 × 10(-6) to 1.0 × 1(-2) mol L(-1), and a detection limit of 5.0 × 10(-7) mol L(-1) of Ho(3+) ions. The potentiometric response of the sensor is independent of the solution pH in the range of 3.5-9.4. It has a very short response time, in the whole concentration range (<10s), and can be used for at least eight weeks. The proposed electrode shows a good selectivity towards Ho(3+) ions over a wide variety of cations, including alkali, alkaline earth, transition and heavy metal ions. To assess its analytical applicability the proposed Ho(3+) sensor was successfully applied as an indicator electrode in the titration of Ho(3+) ion solutions in certified reference materials, alloy samples and for the determination of the fluoride ion in two mouthwash preparations.

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This paper presents the optimization of instrumental and solution parameters for determination of tamoxifen in urine and plasma and formulation by fast Fourier transform square wave voltammetry (SWV) using a gold microelectrode in flow-injection system. The samples are subjected by the same buffer solution and are injected in the flow-injection apparatus. By applying a novel square wave voltammetry method to perform as a sensitive method the voltamograms are recorded. The method used for determination of tamoxifen by measuring the changes in admittance voltammogram of a gold ultramicroelectrode (in 0.05 mol L(-1) H(3)PO(4) solution) caused by adsorption of the tamoxifen on the electrode surface. The best sensitivity was achieved using a frequency of 600 Hz and a medium composed of 0.05 mol L(-1) phosphate buffers at pH 2.0. The best performance was obtained with the pH value of 2, pulse amplitude 25 mV, frequency 600 Hz, accumulation potential of -100 mV and accumulation time of 0.5s. Furthermore, signal-to-noise ratio has significantly increased by application of discrete fast Fourier transform (FFT) method, background subtraction and two-dimensional integration of the electrode response over a selected potential range and time window. Calibration plots are given for solutions containing 1.0 x 10(-11) to 3.0 x 10(-6)mol L(-1) of tamoxifen. The detection limit is calculated to be 3.0 x 10(-12)mol L(-1) ( approximately 2 pg mL(-1)). The relative standard deviation at concentration 2.0 x 10(-8)M is 6.1% for five reported measurements.

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Highly selective and sensitive poly(vinyl chloride) (PVC) membrane electrodes based on 6-methyl-4-{[1-(2-thienyl)methylidene]amino}3-thioxo-3,4-dihydro-1,2,4-triazin-5-(2H)-one (MATDTO) as new carriers for gadolinium ion-selective electrode was reported. The membrane solutions containing PVC, o-nitrophenyl octyl ether (NPOE) as plasticizer, sodium tetraphenyl borate (NaTPB) as lipophilic ionic additive, and MATDTO, displays a calibration response for Gd3+ ions over a wide concentration range of 1.0x10(-6)-1.0x10(-1) M with Nernstian slopes of 19.8+/-0.2 mV per decade and a detection limit as 5.8x10(-7) M. The sensor has a relatively fast response time of <10 s and can be used in the pH range 3.2-8.7 for at least 2 months without any significant divergence in potentials. The selectivity coefficients for mono-, di-, and trivalent cations indicate good selectivity for Gd(III) ions over a large number of interfering cations. The membrane sensor was used as an indicator electrode in the potentiometric titration of Gd(III) ions with EDTA. The proposed electrode was also applied to the determination of concentration of Gd(III) ions in soil and sediment samples and validation with CRMs.

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This study presents the development of an original electrode, employing 6-methy-4-{[1-(1H-pyrrol-2-yl)methylidene]amino}-3-thioxo-3,4dihydro-1,2,4-triazin-5(2H)-one (PMTO) as a suitable ionophore. Interestingly, the electrode performance provided a very good response for Yb(3+) in a wide concentration range (from 1.0x10(-6) to 1.0x10(-1)molL(-1)) with a detection limit of 4.6x10(-7)molL(-1) and a slope of 19.5+/-0.3mV per decade of Yb(3+) concentration. Furthermore, it possessed a fast response time of about 10s and it functioned in the pH range of 3.3-8.0 with a usage of at least 2 months without observing any deviations. Noticeably, the proposed electrode revealed an excellent selectivity for Yb(3+) over a broad variety of alkali, alkaline earth, transition and heavy metal ions. The practical applicability of the electrode was demonstrated by its utilization as an indicator electrode in the potentiometric titration of Yb(3+) ions with EDTA and in the determination of F(-) in mouth wash samples. Additionally, it was also applied for the determination of Yb(3+) ions in binary mixtures.

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A highly La(III) ion-selective PVC membrane sensor based on N'-(1-pyridin-2-ylmethylene)-2-furohydrazide (NPYFH) as an excellent sensing material was successfully developed. The electrode shows a good selectivity for La(III) ion with respect to most common cations including alkali, alkaline earth, transition and heavy metal ions. The proposed sensor exhibits a wide linear response with slope of 19.2 +/- 0.6 mV per decade over the concentration range of 1.0 x 10(-6) - 1.0 x 10(-1) M, and a detection limit of 7.0 x 10(-7) M of La(III) ions. The sensor response is independent of pH in the range of 3.5-10.0. The proposed electrode was applied as an indicator electrode in potentiometric titration of La(III) ion with EDTA.

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