Effects of Salicylic Acid on Carotenoids and Antioxidant Activity of Saffron (Crocus sativus L.)

Saffron (Crocus sativus L.), the most valuable medicinal food product, belongs to the Iridaceae family, which has been widely used as a coloring and flavoring agent. The stigmas contain three major compounds; crocins (carotenoid compound responsible for color), picrocrocin (responsible for taste) and safranal (responsible for odor). It has been used for medicinal purposes, as a spice and condiment for food and as a dye since ancient times. Numerous studies have shown crocins as main carotenoids of saffron to be capable of a variety of pharmacological effects, such as protection against cardiovascular diseases and inhibition of cancer cell development. Salicylic acid is a signaling molecule and a hormone-like substance that plays an important role in the plant physiological processes. Due to the importance of saffron as a valuable product, the aim of this study is to investigate the effect of salicylic acid application (0.01, 0.1 and 1 mM) on crocin and safranal content and antioxidant activity of stigmas. The results showed that salicylic acid application at 1 mM was the most effective treatment in increasing the crocin content and stronger antioxidant activity of stigmas, but it had a negative effect on safranal content; the highest quantity of this compound was observed in the control plants

Voltammetric and amperometric sensors for determination of epinephrine: A short review (2013-2017)

The present review focuses on voltammetric and amperometric methods applied for determination of epinephrine (EP) in last five years (2013-2017). Occurrence, role and biological importance of EP, as well as non-electrochemical methods for its assessment, are firstly reviewed. The electrochemical behavior of EP is then illustrated, followed by a description of the voltammetric and amperometric methods for EP content estimation in various media. Different methods for development of electrochemical sensors are reviewed, starting from unmodified electrodes to different composites incorporating carbon nanotubes, ionic liquids or various mediators. From this perspective, the interaction between functional groups of the sensor material and the analyte molecule is discussed, as it is essential for analytical characteristics obtained. The analytical performances of the voltammetric or amperometric chemical and biochemical sensors (linear range of analytical response, sensitivity, precision, stability, response time, etc.) are highlighted. Numerous applications of EP electrochemical sensors in fields like pharmaceutical or clinical analysis where EP represents a key analyte, are also presented

A novel dopamine electrochemical sensor based on La3+/ZnO nanoflower modified graphite screen printed electrode

Flower-like La3+/ZnO nanocomposite was facile synthesized. A simple and ultrasensitive sensor based on graphite screen printed electrode (SPE) modified by La3+/ZnO nanoflower was developed for the electrochemical determination of dopamine. The electrochemical behavior of dopamine was studied in 0.1 M phosphate buffer solution (PBS) using cyclic voltammetry (CV), chronoamperometry (CA) and differential pulse voltammetry (DPV). Compared with the unmodified graphite screen printed electrode, the modified electrode facilitates the electron transfer of dopamine, since it notably increases the oxidation peak current of dopamine. Also, according to CV results the maximum oxidation of dopamine on La3+/ZnO/SPE occurs at 150 mV which is about 140 mV more negative compared with unmodified SPE. Under optimized conditions, the modified electrode exhibited a linear response over the concentration range from 0.15 to 300.0 μM, with a detection limit of 0.08 μM (S/N = 3). The proposed sensor exhibited a high sensitivity, good stability and was successfully applied for dopamine determination in dopamine ampoule, with high recovery

Electrochemical determination of propranolol by using modified screen-printed electrodes

73-78A simple and sensitive method for the determination of propranolol using modified screen printed carbon electrode (MSPCE) has been presented. The electrochemical measurements of propranolol are studied using differential pulse voltammetry (DPV), cyclic voltammetry (CV) and chronoamperometry (CHA). The MSPCE exhibite excellent catalytic activity towards electrochemical oxidation of propranolol in phosphate buffer solution (PBS) of pH 7.0. The MSPCE facilitate the determination of propranolol in the concentration range 0.4 – 200.0 μM and a detection limit and sensitivity of 80 nM and 0.052 μA/μM has been achieved

A sensitive Cu(salophen) modified screen-printed electrode for simultaneous determination of dopamine and uric acid

This research applied a nanostructured electrochemical sensor with a screen-printed electrode (SPE) for examining the dopamine (DA) electrocatalytic oxidation when uric acid (UA) was present. Cu(salophen) nanostructured modified SPE (Cu(salophen)/SPE)was employed to investigate the electrochemical behavior of DA. At optimal pH (pH7.0), oxidation of DA at the modified electrode takes place at a potential around 100 mV less positive than at the unmodified SPE. Chronoamperometry was used to determine the diffusion coefficient of DA (D=1.96×10-5cm2s-1). Differential pulse voltammetry (DPV) showed linear response in the range between 0.2-450.0 μM for DA. The limit of detection (LOD) of DA was computed to be 0.05 μM. Moreover, Cu(salophen)/SPE was employed for determining DA in the presence of UA using DPV. The DPV results showed that at the modified electrode, two well-separated oxidation peaks of DA and UA could be obtained at potentials of 180 and 325 mV, respectively. This separation forms the basis for the co-detection of these two materials on the surface of Cu(salophen)/SPE. This sensor was then employed to determine DA and UA in real specimens

Glutathione detection at carbon paste electrode modified with ethyl 2-(4-ferrocenyl-[1,2,3]triazol-1-yl)acetate, ZnFe2O4nano-particles and ionic liquid

The purpose of the present study was to introduce a newly designed approach for deter-mination of glutathione using modified carbon paste electrode with ZnFe2O4nanoparticles, ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate) and ethyl-2-(4-ferrocenyl--[1,2,3]triazol-1-yl)acetate (EFTA/ZFO/IL/CPE). According to the results from the electro-chemical experiments, oxidation current of glutathione on the modified electrode surface was incremented and its oxidation potential was decreased compared to bare CPE. A linear response was observed for the electrode at different glutathioneconcentrations (0.2 to 300.0 μM)

Screen-Printed Graphite Electrode Modified with Graphene-Co3O4 Nanocomposite: Voltammetric Assay of Morphine in the Presence of Diclofenac in Pharmaceutical and Biological Samples

This work focuses on the development of a novel electrochemical sensor for the determination of morphine in the presence of diclofenac. The facile synthesis of graphene-Co3O4 nanocomposite was performed. The prepared material (graphene-Co3O4 nanocomposite) was analyzed by diverse microscopic and spectroscopic approaches for its crystallinity, composition, and morphology. Concerning the electrochemical determinations, after drop-casting the as-fabricated graphene-Co3O4 nanocomposite on the surface of a screen-printed graphite electrode (SPGE), their electrochemical performance was scrutinized towards the morphine detection. It was also found that an SPGE modified by a graphene-Co3O4 nanocomposite exhibited better electrocatalytic activity for morphine oxidation than unmodified electrode. Under optimal conditions, the differential pulse voltammetry (DPV) was employed to explore the present sensor (graphene-Co3O4/SPGE), the findings of which revealed a linear dynamic range as broad as 0.02–575.0 µM and a limit of detection (LOD) as narrow as 0.007 μM. The sensitivity was estimated to be 0.4 µM/(µA cm2). Furthermore, the graphene-Co3O4/SPGE sensor demonstrated good analytical efficiency for sensing morphine in the presence of diclofenac in well-spaced anodic peaks. According to the DPV results, this sensor displayed two distinct peaks for the oxidation of morphine and diclofenac with 350 mV potential difference. In addition, the graphene-Co3O4/SPGE was explored for voltammetric determination of diclofenac and morphine in pharmaceutical and biological specimens of morphine ampoule, diclofenac tablet, and urine, where recovery rates close to 100% were recorded for all of the samples

Application of Fe3O4@SiO2/GO nanocomposite for sensitive and selective electrochemical sensing of tryptophan

A simple strategy for determination of tryptophan (TRP) based on Fe3O4@SiO2/GO nano­composite modified graphite screen printed electrode (Fe3O4@SiO2/GO/SPE) is re­ported. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used to characterize the performance of the sensor. The Fe3O4@SiO2/GO/SPE displayed excellent electro­che­mical catalytic activities. The oxidation overpotentials of tryptophan decreased significantly and its oxidation peak current increased dramatically at Fe3O4@SiO2/GO/SPE. Under the optimized experimental conditions tryptophan showed linear response over the range of 1.0-400.0 μM. The lower detection limit was found to be 0.2 μM for tryptophan. The prac­tical application of the modified electrode was demonstrated by measuring the concen­tration of tryptophan in real samples

Electrochemical measurements of ascorbic acid based on graphite screen printed electrode modified with La3+/Co3O4 nanocubes transducer

Electrochemical characterization of ascorbic acid oxidation on a graphite screen printed electrode (SPE) modified with La3+/Co3O4nanocubes is performed by applying cyclic voltammetry (CV), chronoamperometry (CHA), and differential pulse voltammetry (DPV) techniques. Synthesized La3+/Co3O4nanocubes for SPE modification, La3+/Co3O4/SPE, enhance the ascorbic acid electrooxidation kinetics by reducing the anodic overpotential. Excellent La3+/Co3O4/SPE electrochemical properties provide sensitive ascorbic acid voltammetric determination with low detection limit, good stability and quick response towards electrooxidation of ascorbic acid as compared to bare SPE. Under optimized conditions, DPV current demonstrates a linear response for ascorbic acid over a concentration range of 1.0 to 900.0 mM with a correlation coefficient of 0.9997, and detection limit (LOD) (S/N = 3) = 0.3 mM. The proposed procedure offers a potential application for producing the sensor with good repeatability. Also, fast response of fabricated sensor can allow a real-time analysis of real samples

MECANISMO DE DESEMPENHO ELETROANALÍTICO DA 2,7-BIS(FERROCENIL-ETINIL)-FLUORENO-9- ONA PARA ELETRODETECÇÃO DA HIDRAZINA E SUA DESCRIÇÃO MATEMÁTICA

Para o processo da eletrooxidação da hidrazina sobre a camada do composto carbonílico derivado de ferroceno, foi sugerido o mecanismo do desempenhoeletroanalítico. Para ele, também foi desenvolvido e analisado (por meio da teoria de estabilidadelineal e análise de bifurcações) o modelo matemático, capaz de descrever os processos no sistema. Os resultados da modelagem foram comparados com os experimentais, bem como com os teóricos, observados para sistemas análogos