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The voltammetric characterisation and determination of insecticide flonicamid (N-cyanomethyl-4-(trifluoromethyl)nicotinamide) were performed for the first time using a simple electrochemical sensor, renewable silver-amalgam film electrode (Hg(Ag)FE). During the development of the direct cathodic square wave voltammetric method (SWV) for the determination of flonicamid, a voltammetric behaviour of a target analyte in aqueous Britton-Robinson buffer solution from pH 2.0 to pH 11.98 was examined. In the investigated pH range, the peak which appeared in the potential span between −0.86 V and −1.56 V vs. saturated calomel electrode depending on the applied pH value was chosen for analytical purposes. As optimal pH for the determination of flonicamid, pH 2.5 was selected. Cyclic voltammetric measurements at pH 2.5 confirmed that the electrode reaction mechanism is an irreversible reduction controlled by the diffusion of flonicamid at Hg(Ag)FE. The optimised Hg(Ag)FE-SWV method resulted in good linearity in the concentration range of 1.96–41.2 µg mL−1 while the relative standard deviation of the method was 0.30%. Flonicamid was successfully determined in commercial formulation Teppeki 500 WG® and spiked river water sample by the developed method using the standard addition procedure. The average value of flonicamid amount found in a commercial formulation based on three repetitions was 497.8 ± 0.9 g kg−1, which is in good agreement with the manufacturer's declaration (500 ± 25 g kg−1) and with comparative high-performance liquid chromatographic measurements with diode array detection where a found average value of flonicamid content was 497.5 ± 11.5 g kg−1. The obtained results also indicate that the developed SWV procedure using Hg(Ag)FE was appropriate for the determination of flonicamid in a spiked river water sample with the recovery of 92.86% and RSD of 6.19%. [ABSTRACT FROM AUTHOR]

In present work, the enzyme cholesterol oxidase (ChOx) was immobilized by Nafion® (Naf) on Pt,Ru–C nanocomposite and an ionic liquid (IL)–modified carbon paste electrode (CPE) in order to create cholesterol biosensor (Naf/ChOx/Pt,Ru–C/IL-CPE). The prepared working electrodes were characterized using scanning electron microscopy–energy-dispersive spectrometry, while their electrochemical performance was evaluated using electrochemical impedance spectroscopic, cyclic voltammetric, and amperometric techniques. Excellent synergism between IL 1-allyl-3-methylimidazolium dicyanamide ([AMIM][DCA]), Pt,Ru–C, and ChOx, as modifiers of CPE, offers the most pronounced analytical performance for improved cholesterol amperometric determination in phosphate buffer solution pH 7.50 at a working potential of 0.60 V. Under optimized experimental conditions, a linear relationship between oxidation current and cholesterol concentration was found for the range from 0.31 to 2.46 µM, with an estimated detection limit of 0.13 µM and relative standard deviation (RSD) below 5.5%. The optimized amperometric method in combination with the developed Naf/ChOx/Pt,Ru–C/IL-CPE biosensor showed good repeatability and high selectivity towards cholesterol biosensing. The proposed biosensor was successfully applied to determine free cholesterol in a human blood serum sample via its enzymatic reaction product hydrogen peroxide despite the presence of possible interferences. The percentage recovery ranged from 99.08 to 102.81%, while RSD was below 2.0% for the unspiked as well as the spiked human blood serum sample. The obtained results indicated excellent accuracy and precision of the method, concluding that the developed biosensor can be a promising alternative to existing commercial cholesterol tests used in medical practice. [ABSTRACT FROM AUTHOR]

• Graphitic carbon nitride and ionic liquid TBACl were used for modification of carbon paste electrode (CPE). • Voltammetric characterization of carbamazepine (CBZ) at TBACl- g -C 3 N 4 -CPE was performed. • Rapid and selective SWV method with LOD of 0.13 µmol L −1 CBZ was developed. • Determination of CBZ in human urine and pharmaceutical samples was performed. • SWV results were in good agreement with HPLC-DAD measurements. The development of a rapid and straightforward electrochemical approach for the quantification of the anticonvulsant drug carbamazepine (CBZ) is herein presented. Carbon paste electrode (CPE) was bulk modified with a type of two-dimensional conjugated polymer, i.e. , graphitic carbon nitride (g -C 3 N 4), and additionally with an ionic liquid tetrabutylammonium chloride (TBACl) to obtain advanced electrochemical sensor for CBZ. Synthesized g -C 3 N 4 material was structurally and morphologically characterized by Raman spectroscopic, FTIR, and SEM/EDX methods. CV experiments showed that the resulting electrode (TBACl- g -C 3 N 4 -CPE) has an improved electrochemical response compared to unmodified CPE and g -C 3 N 4 -CPE due to the synergistic effect of electrode modifiers, as well as that the CBZ oxidation process is irreversible and diffusion-controlled. After optimization steps concerning the amount of electrode modifiers and the selection of pH of the supporting electrolyte, the analytical performance of TBACl- g -C 3 N 4 -CPE was investigated by direct anodic square-wave voltammetry (SWV). The most intensive peak of the target analyte was obtained in Britton-Robinson buffer solution at pH 7.0, whereby the developed SWV method was characterized by a linear concentration range of CBZ from 0.42 to 9.31 µmoL L −1, limit of detection (LOD) of 0.13 µmoL L −1, and relative standard deviation lower than 3 %. The interference study showed that TBACl- g -C 3 N 4 -CPE exhibits adequate selectivity for CBZ in the presence of ions/compounds commonly present in the urine matrix. The developed sensor was utilized to determine CBZ in pharmaceuticals and spiked human urine sample with excellent recovery and reproducibility, indicating a good application capability of TBACl- g -C 3 N 4 -CPE for monitoring CBZ in different matrices. [Display omitted] [ABSTRACT FROM AUTHOR]

The rapid and sensitive voltammetric determination of organic UV filters benzophenone-3 (BP-3) and avobenzone (AVO) was performed by an ionic liquid carbon paste electrode (IL-CPE). Namely, the synthesized pyridinium-based ILs, 1-butyl-3-methylpyridinium chloride ([ N –C 4 –3C 1 Py]Cl) and 1-ethoxyethyl-3-methylpyridinium chloride ([ N –C 2 OC 2 –3C 1 Py]Cl) were compared as bulk CPE modifiers for BP-3 determination. [ N –C 4 –3C 1 Py]Cl-CPE showed more favorable interactions with the target analyte, and it was tested for AVO determination, too. Cyclic voltammetric (CV) studies suggested that the irreversible electrode reaction is adsorption controlled in the case of both UV filters. Also, the square-wave adsorptive stripping voltammetric (SW-AdSV) method was optimized for quantifying selected UV filters. In the model solutions, the linear calibration curve was obtained by the SW-AdSV method in the concentration range from 0.05 to 0.89 μg mL−1 at pH 3.0 for BP-3 (E acc = −0.7 V, t acc = 100 s), and from 0.05 to 1.77 μg mL−1 at pH 11.98 for AVO (E acc = 0.2 V, t acc = 100 s). The evaluated limit of detection (LOD) was 0.015 μg mL−1 in both cases, while the relative standard deviation (RSD) was lower than 1.5%. The affordable IL-based voltammetric sensor fulfills the main requirements for application in real samples due to an adequate selectivity towards selected analytes in the presence of interferents usually found in swimming pool water. Therefore, the BP-3 and AVO were quantified in a swimming pool water matrix with good repeatability and recovery. The obtained results demonstrate an excellent potential of the IL-CPEs, especially of the [ N –C 4 –3C 1 Py]Cl-CPE, for determining selected UV filters in various real samples. [Display omitted] • Pyridinium-based ionic liquids were used for carbon paste electrode modification. • Simple and reliable SW-AdSV method for selected UV filters sensing was developed. • Achieved LOD for benzophenone-3 (BP-3) and avobenzone (AVO) was 0.015 μg mL−1. • [ N –C 4 –3C 1 Py]Cl-CPE enables determination of BP-3 and AVO in swimming pool water sample. • Good repeatability and high selectivity towards UV filters sensing were obtained. [ABSTRACT FROM AUTHOR]

A photoactive complex [Ir(3m-ppy)2(dppm)Cl] (1; dppm = bis(diphenylphosphino)methane, 3 m-Hppy = 3-methyl-2-phenylpyridine), which shows a green luminescence band at 517 nm in DMSO was synthesized from reaction of the dimeric [Ir2(3m-ppy)4Cl2] with dppm under an inert atmosphere. Complex 1 was characterized by 1H NMR, FT-IR, ESI-MS spectroscopies and CHN analysis. Single-crystal X-ray analysis of 1 revealed a distorted octahedral geometry comprising an IrIII center with monodentate dppm, bidentate-C,N 3 m-ppy and chlorido ligands. The electrochemistry of 1 was studied by cyclic voltammetry in 0.1 M NaClO4 in acetonitrile on a glassy carbon working electrode, displaying an oxidation peak of IrIII/IV at 1.2 V. Complex 1 showed anticancer activity against MDA-MB-231, MCF-7 and HCC1937 cell lines of human breast cancer; the respective cytotoxicity factors of 160, 32 and 25 were significantly greater than the cytotoxicity factors obtained with cisplatin. [ABSTRACT FROM AUTHOR]

[Display omitted] • [Ir(3m-ppy) 2 (dppm)Cl] was used for modification of carbon paste electrode (CPE). • Ir based spherical particles were self-assembled on CPE surface as proved by SEM. • After electrochemical activation, modified electrode was tested for amperometric determination of H 2 O 2. • For practical applicability, H 2 O 2 content in color cream developers was determined. • Proposed method allows rapid, sensitive and reliable sensing of H 2 O 2. In this work, a simple strategy of carbon paste electrode (CPE) modification with previously synthesized iridium(III) complex i.e. [Ir(3m-ppy) 2 (dppm)Cl] (3m-ppy = 3-methyl-2-phenylpyridine, dppm = bis(diphenylphosphino)methane) was elaborated together with first application of [Ir(3m-ppy) 2 (dppm)Cl] as working electrode component for H 2 O 2 amperometric determination. The electrode with iridium(III) complex (Ir/CPE) was prepared in one step using optimized drop coating procedure. The characterization of Ir/CPE by scanning electron microscopy in combination with energy dispersive spectrometry confirmed the presence of densely populated Ir(III) complex based microspherical particles self-assembled on the electrode surface. Comparative cyclic voltammetric responses of the Ir/CPE and pristine CPE in phosphate (pH 7.50) and acetate (pH 4.50) buffer solution proved that in both supporting electrolytes in the case of the modified electrode one irreversible oxidation peak is present with maximum close to 1.2 V vs. SCE. Comparative measurements were performed with both electrodes in the presence of H 2 O 2 target analyte, and it was found that after appropriate electrochemical activation at 1.20 V, during 60 min, the Ir complex containing electrode is a promising sensor for analytical purposes offering the possibility for the analysis of H 2 O 2 at working potentials in anodic range from 0.30 to 0.60 V and in cathodic range from −0.05 to −0.30 V in phosphate buffer pH 7.50 (0.1 M) as supporting electrolyte. The optimized amperometric protocol which included stirred solution, electrochemical activation of the electrode and working potential as 0.60 V vs. SCE showed acceptable linearity of the calibration curve for the investigated H 2 O 2 concentration range from 51.5 to 508.2 µM, and with evaluated LOQ as 8.8 µM. Additionally, this electrode exhibited good stability and reproducibility with relative standard deviation lower than 3%. The optimized and simple amperometric method was successfully applied for determination of H 2 O 2 content in commercially available color cream developers and obtained results were in a good agreement with declared values by the producers indicating the reliability of prepared H 2 O 2 sensor. [ABSTRACT FROM AUTHOR]

[Display omitted] • The electrochemical behaviour of SOL was studied using different solid working electrodes. • The electrochemical stability of SOL was tested by cycling and using an Au electrode. • The BDDE enables the determination of SOL as the standard and in a spiked human urine sample. • A rapid and selective DPV method with LOD of 0.012 µM SOL was developed. • The proposed voltammetric method was proven to be simple, reliable and very sensitive. The anticholinergic drug, solifenacin, is frequently used for the treatment of the urological tract for urinary incontinence, and urinary frequency. The development of reliable and effective solifenacin electrochemical sensors is of great importance for the pharmaceutical industry and clinical practice. In this work, the electrochemical behavior of solifenacin succinate (SOL) was studied using three different working electrodes: gold (Au), glassy carbon (GCE) and boron-doped diamond electrode (BDDE). The cyclic voltammetric (CV) measurements performed in 0.05 M NaHCO 3 indicated that the SOL oxidation process is irreversible and diffusion-controlled at all investigated working electrodes. Afterwards, the testing of SOL electrochemical stability and the possibility of its electrochemical degradation was performed at the Au electrode by the cycling of the potential during 3 h and continuously to 6 h. It was shown that the SOL was electrochemically transformed into another electroactive species and its degradation was excluded. For electroanalytical application, the anodically pretreated BDDE (+2.0 V; 30 s) was selected. Various experimental parameters were optimized, including the pH of the aqueous Britton-Robinson (B-R) buffer as a supporting electrolyte (from pH 2.0 to 11.98) and the most intensive peak of the target analyte was at pH 11.0, so this pH value was chosen as the optimum for further measurements. Based on the correlation of the SOL peak intensity and different concentrations, the developed differential pulse voltammetric (DPV) method was characterized by a linear concentration range from 0.041 to 2.50 µM, with a correlation coefficient of 0.999, and a relative standard deviation of 0.3 %. Taking into account the sensitivity of the developed DPV method towards the electrochemical oxidation of SOL, a very low detection limit of 0.012 µM in the model system was achieved. The BDDE showed adequate selectivity for SOL in the presence of the investigated interferents. The obtained results indicate that the BDDE with an optimized DPV method could be applied for the trace-level electroanalytical determination of SOL in human urine sample with excellent recovery and reproducibility. [ABSTRACT FROM AUTHOR]