A multifunctional quinoxaline-based chemosensor for colorimetric detection of Fe3+ and highly selective fluorescence turn-off response of Cu+2 and their practical application

A new dual responsive colorimetric and fluorescent turn-off sensor for Fe3+ and Cu2+ was designed and synthesized based on quinoxaline derivative by a simple procedure reaction. 2,3-bis(6-bromopyridin-2-yl)-6-methoxyquinoxaline (BMQ) was fabricated and characterized using ATR-IR, 13C and 1H NMR, and Mass spectroscopy. The interaction of BMQ with Fe3+ caused a significant color change from colorless to yellow. The sensing complex BMQ-Fe3+ with high selectivity was described to be 1:1 by the molar ratio plot. In this experiment, iron was detected by naked-eye using a recently synthesized ligand (BMQ). This color change was unexpectedly observed in iron-overloaded plasma, which had previously been admitted by AAS (Atomic Absorption Spectroscopy). Normal plasma, however, did not exhibit this color change. Interestingly, Cu2+ ions cause a quench at the local emission around 565 nm. On the other hand, receptor-binding selectivity for Cu2+ over a wide linear concentration range was observed through changes in the emission spectra. BMQ-Cu2+ was characterized to be 1:1 by the Job's plot. The emission intensity of BMQ-Cu2+ complex was balanced within only 1 min. various mineral water samples were analyzed for detecting Cu2+. The results show the great potential of the developed probe BMQ for the sensing of Cu2+ ions in mineral and drinking water samples.

Combination effect of cold atmospheric plasma with green synthesized zero-valent iron nanoparticles in the treatment of melanoma cancer model

Green synthesized zero-valent iron nanoparticles (nZVI) have high potential in cancer therapy. Cold atmospheric plasma (CAP) is also an emerging biomedical technique that has great potential to cure cancer. Therefore, the combined effect of CAP and nZVI might be promising in treatment of cancer. In this study, we evaluated the combined effect of CAP and nZVI on the metabolic activity of the surviving cells and induction of apoptosis in malignant melanoma in comparison with normal cells. Therefore, the effect of various time exposure of CAP radiation, different doses of nZVI, and the combined effect of CAP and nZVI were evaluated on the viability of malignant melanoma cells (B16-F10) and normal fibroblast cells (L929) at 24 h after treatment using MTT assay. Then, the effect of appropriate doses of each treatment on apoptosis was evaluated by fluorescence microscopy and flow cytometry with Annexin/PI staining. In addition, the expression of BAX, BCL2 and Caspase 3 (CASP3) was also assayed. The results showed although the combined effect of CAP and nZVI significantly showed cytotoxic effects and apoptotic activity on cancer cells, this treatment had no more effective compared to CAP or nZVI alone. In addition, evaluation of gene expression showed that combination therapy didn't improve expression of apoptotic genes in comparison with CAP or nZVI. In conclusion, combined treatment of CAP and nZVI does not seem to be able to improve the effect of monotherapy of CAP or nZVI. It may be due to the resistance of cancer cells to high ROS uptake or the accumulation of saturated ROS in cells, which prevents the intensification of apoptosis.

Investigation of the physicochemical, antioxidant, rheological, and sensory properties of ricotta cheese enriched with free and nano‐encapsulated broccoli sprout extract

This study aimed to produce the functional ricotta cheese using broccoli sprouts extract (BSE) and to evaluate its physicochemical, antioxidant, rheological, and sensory properties. The BSE nano‐liposome was nano‐encapsulated into basil seed gum (BSG) and was incorporated into the ricotta cheese formulation in two forms of free and nano‐capsules in two levels of 3% and 5% w/w. The measurements were conducted during a 15‐day storage period at 4–6°C. The results showed that the titratable acidity, hardness, and chewiness of cheeses were increased and the pH, moisture, total phenol content (TPC), and antioxidant activity were decreased (p < .05). With the addition of BSE concentration, the TPC and antioxidant activity increased significantly (p < .05) and applying the nano‐encapsulation method for BSE led to better preservation of bioactive compounds. Based on the rheological results, viscoelastic solid behavior and a weak gel were observed in all cheese samples. The results of sensory evaluation demonstrated that cheeses containing free extract had lower flavor and overall acceptability scores than other samples, which indicates that the nano‐encapsulation covered the undesirable flavor of the BSE. Generally, during the 15‐day cold storage period, the highest sensory acceptance and functional activity were related to the samples containing nano‐encapsulated BSE, especially at the 5% level.

Naked Eye Chemosensor and In Vivo Chelating Activity of Iron (III) By Bromopyridine Quinoxaline (BPQ)

A wide variety of medical, biomedical, and industrial applications has been reported for quinoxalines derivatives. In this work, a novel quinoxaline derivative was designed and synthesized. Naked-eye and quantitative detection of Fe³⁺ among several cations were evaluated using UV-Vis spectroscopy. New chemosensor, 2,3-bis(6-bromopyridine-2-yl)-6-chloroquinoxaline named BPQ, showed a selective interaction for iron ion over other tested cations by changing color. Iron overloaded mice were prepared as a thalassemia model and then the effects of iron-chelating activities of BPQ were experienced. The job's plot methods determined the stoichiometric ratio of ligand to Fe³⁺ (1:1). The iron content in serum was evaluated by atomic absorption spectroscopy (AAS). Results showed significant differences (two-fold decrease in total iron and Fe³⁺) between the iron overloaded and BPQ (dose of 20 mgkg-1). The BPQ was identified as a ligand, which can be applied as a new chelator for decreasing the excess iron of blood.

Pyridine-2-yl Quinoxaline (2-CPQ) Derivative As a Novel Pink Fluorophore: Synthesis, and Chemiluminescence Characteristics

Quinoxaline derivatives are well-known N-heterocycles with pharmacological and fluorescence activities. Almost all quinoxaline derivatives with extensive π-conjugation have been introduced as fluorophores which emit blue and green light. For the first time, we designed and synthesized 6-chloro-2,3 di(Pyridine-2yl) quinoxaline (2-CPQ) as a pink fluorophore in acetonitrile medium by simple route at room temperature whitin 30 min. The synthesized quinoxaline was identified using ¹H, ¹³C NMR, MS, and FT-IR spectroscopy. Our results showed that the iodine-catalyzed method for both oxidation and cyclization during the synthesis of quinoxaline from pyridine 2-carbaldehyde was straightforward, efficient, and clean. All of the mentioned characterization devices confirmed the synthesis of 2-CPQ.Moreover, we studied the photophysical properties of the synthesized fluorophore in which The UV-Vis absorption spectrum of 2-CPQ in DMF were three peaks at 451, 518 and 556 nm. Based on photophysical properties investigation, 2-CPQ shows good fluorescence with maximum peaks 607 and 653 nm in DMF as solvent (ф_F = 0.21). Hence, the fluorophore was applied in the peroxyoxalate chemiluminescence system. The reaction of imidazole, H₂O_2, and bis (2,4,6-trichlorophenyl) oxalate (TCPO) can transfer energy to a 6-chloro-2,3 di(pyridine-2yl) quinoxaline. In this process, dioxetane was synthesized, which chemically initiated the electron exchange luminescence (CIEEL) mechanism and led to pink light emission. We anticipate our synthesized fluorophores 2-CPQ will have great potential applications in imaging and medical markers.

Food frequency questionnaire is a valid assessment tool of quercetin and kaempferol intake in Iranian breast cancer patients according to plasma biomarkers

In epidemiological and clinical studies, the most common nutritional tool to assess dietary flavonol intake is the food frequency questionnaire (FFQ), which needs to contain a detailed list of plant-based foods and be previously validated. Our study aimed to assess the accuracy of dietary flavonol (quercetin, kaempferol, and isorhamnetin) intake from a food frequency questionnaire (FFQ) compared to fasting plasma flavonol concentrations, as biomarkers of exposure, in breast cancer patients. In a consecutive case series, newly diagnosed patients with breast cancer (n = 140) were recruited at Nour-Nejat Hospital, Tabriz, Iran. Flavonol intake was assessed using a validated FFQ. Plasma flavonol concentrations were measured using high-performance liquid chromatography-ultraviolet detection. The accuracy of dietary status was evaluated using a receiver operating characteristic (ROC) and area under the ROC curve (AUC). Dietary status was shown in dichotomous using ROC-cutoff point. The plasma concentrations of quercetin were moderately correlated with dietary intake of quercetin (Spearman's correlation coefficient (r_s) = 0.188, P < .05; r_partial= 0.330, P < .01) and plasma concentrations of isorhamnetin (r_s = 0.337, P < .001). A linear correlation between dietary levels and plasma concentrations of kaempferol was attained (r_partial = 0.240, P < .05). Using a ROC-cutoff of 61.9 nmol/L for plasma quercetin (test reference), we were able to differentiate between lower and higher consumers of quercetin with an AUC_{ROC-based reference} =0.65 (P < .01, sensitivity = 61.8%, and specificity = 60.0%). Using a plasma kaempferol concentration of 60.1 nmol/L (ROC-cutoff), it was possible to detect significant differences between higher and lower intakes of kaempferol (AUC_{ROC-based reference} = 0.64, P < .05). The correlations and diagnostic performance with plasma concentrations could present a significant accuracy rate (validity), which seems acceptable for a nutritional questionnaire (FFQ) to assess intakes intake levels of quercetin and kaempferol. An improvement in the accuracy of the flavonol exposure can provide more precise relationship with health outcomes, which may increase their clinical significance.

Biogenic Silver and Zero-Valent Iron Nanoparticles by Feijoa: Biosynthesis, Characterization, Cytotoxic, Antibacterial and Antioxidant Activities

Background: and Purpose:

Green nanotechnology is an interesting method for the synthesis of functional nanoparticles. Because of their wide application, they have set up great attention in recent years.

Objective:

The present research examines the green synthesis of Ag and zero-valent iron nanoparticles (AgNPs, ZVINPs) by Feijoa sellowiana fruit extract. In this synthesis, no stabilizers or surfactants were applied.

Methods:

Eco-friendly synthesis of Iron and biogenic synthesis of Ag nanoparticles were accomplished by controlling critical parameters such as concentration, incubation period and temperature. Scanning Electron Microscopy (SEM), Transmission Electron Microscope (TEM), Energy-Dispersive X-ray Spectroscopy (EDS), Fourier-Transform Infrared (FT-IR) spectroscopy, X-ray Diffraction analysis (XRD), Dynamic Light Scattering (DLS) and UV-Vis were applied to characterize NPs. The cytotoxicity of NPs was investigated in two cell lines, MCF-7 (breast cancer) and AGS (human gastric carcinoma). A high-performance liquid chromatography (HPLC) analysis was also performed for characterization of phenolic acids in the extract.

Results:

Both NPs displayed powerful anticancer activities against two tumor cell lines with little effect on BEAS-2B normal cells. Synthesized AgNPs and ZVINPs inhibited the growth of all selected bacteria. Pseudomonas aeruginosa, Proteus mirabilis, Klebsiella pneumonia, Staphylococcus aureus, Enterococcus faecalis, Acinetobacter baumannii and Escherichia coli have been studied in two stages. We initially examined the ATCCs followed by clinical strain isolation. Based on the results from resistant strains, we showed that nanoparticles were superior to conventional antibiotics. DPPH (diphenyl-1-picrylhydrazyl) free radical scavenging assay and iron chelating activity were used for the determination of antioxidant properties. Results showed a high antioxidant activity of scavenging free radicals for ZVINPs and powerful iron-chelating activity for AgNPs. Based on the HPLC data, catechin was the major phenolic compound in the extract.

Conclusion:

Our synthesized nanoparticles displayed potent cytotoxic, antibacterial and antioxidant activities.

Highly Concentrated Multifunctional Silver Nanoparticle Fabrication through Green Reduction of Silver Ions in Terms of Mechanics and Therapeutic Potentials

BACKGROUND

Green synthesis of silver nanoparticles (AgNPs) is limited to produce AgNPs with only relatively low concentrations, and is unsuitable for large-scale productions. The use of Myrtus communis (MC) leaf methanolic extract (rich in hydrolyzable tannins) has been recommended to resolve the issues related to the aggregation of nanoparticles at high concentrations of silver ions with added facet of antioxidant properties.

METHODS

The produced highly concentrated MC-AgNPs were characterized by using imaging and spectroscopic methods. Subsequently, antioxidant, anticancer and antifungal activities of the nanoparticles were evaluated.

RESULTS

The thermogravimetric analysis and energy dispersive spectroscopy quantitative results suggested that the nanoparticles are biphasic in nature (bio-molecule + Ag0) and layered in structure, suggesting the formation of nanoparticles through a different mechanism than those described in the literature. MC-AgNPs showed greater scavenging activity of nitric oxide and iron (II) chelating ability than the extract. It also showed good reducing power compared to the standard antioxidant. Remarkable anticancer activity of MC-AgNPs (IC50 = 5.99µg/mL) was found against HCT-116 (human colon carcinoma) cell lines after 24h exposure with a therapeutic index value 2-fold higher than the therapeutic index of standard doxorubicin. Furthermore, distinct antifungal activity (MIC = 4µg/mL) was found against Candida krusei.

CONCLUSION

The current method outperforms the existing methods because it produces a large amount of multifunctional nanoscale hybrid materials more efficiently using natural sources; thus, it may be used for diverse biomedical applications.

Monolithic mixed matrix membrane based on polyethersulfone/functionalized MWCNTs nanocomposite as an SPME fiber: Application to extract chlorophenols from human urine and serum samples followed by GC-ECD

A monolithic mixed matrix membrane of functionalized multi-walled carbon nanotubes-polyethersulfone (MWCNT/PES) was prepared in a non-covalent approach and employed as an SPME fiber for extraction of chlorophenols (CPs). The proposed extraction method was followed by GC-ECD to determine the analytes. The influencing factors on the extraction efficiency such as pH, ionic strength, extraction and desorption temperature and time were studied. Under the selected conditions, calibration curves were linear over a wide concentration range from 0.005 to 1000 µgL^-1 (r² > 0.9961) for target analytes. In addition, the limits of detection (LOD) of the method were obtained in the range of 0.3-30 ng L^-1. The relative standard deviation (RSD) for single fiber repeatability (n = 5) is from 1.4 to 4.6%. Fiber-to-fiber repeatability (n = 3) was also evaluated and the RSD is in the range of 1.3-6.3%. Applications of proposed fiber for extraction of CPs from the headspace of urine and serum samples were successfully investigated. The relative recovery in the biological samples spiked with different levels of CPs were in the range of 91.6-102.5%.

Functional and conformational properties of proteolytic enzyme-modified potato protein isolate

BACKGROUND

Potato protein hydrolysates (PPHs) were preparedwith Alcalase on intact potato protein isolates (PPI), with differenthydrolysis times (0.5-4 h), and functional and conformational properties of resultant hydrolysates were investigated.

RESULTS

The degree of hydrolysis changed during incubation. Peptide bond cleavage increased and hydrolysis progressed rapidly. Gel electrophoresis showed that, by increasing the hydrolysis time, peptides with an apparent molecular weight below 20 kDa increased. It also revealed that, among potato protein components, patatin was more sensitive to Alcalase® hydrolysis than protease inhibitors. Enzymatic hydrolysis significantly enhanced the solubility and foam capacity of PPHs, but impaired foam stability (P < 0.05). Limited enzymatic hydrolysates (0.5PPH) at the interface improved the emulsion activity and stability index. These emulsions also had the smallest z-average and polydispersity index and showed the highest zeta potential. Fourier-transform infrared spectrometry (FTIR) analysis indicated extensive disruption of hydrogen bonds in PPHs, besides augmentation of α-helices and β-turns, and a decline in the β-sheets in the secondary structure of the PPHs was shown.

CONCLUSION

Potato protein isolate, especially 0.5PPH, has good functional and conformational properties. Overall, our results provide new insights into the use of potato protein hydrolysates as a functional food component in the food industry. © 2019 Society of Chemical Industry.

Engineered Silver Nanoparticles, A New Nanoweapon Against Cancer

New modifications in nanoparticles changed their applications obviously. Green synthesis of nanoparticles and their biomedical utilizations have been the focus of increasing attention in recent years. Silver nanoparticles (AgNPs) demonstrated surprising effects and many advantageous features for cancer therapy. Investigations indicated the anticancer activity of AgNPs in different ways, comprising cell cycle arrest, DNA damaging and apoptosis, alteration of P53 function, up/down regulation of some important cytokine genes and so on. But some key inquiries like the ability to control the accidental effects of AgNPs, or encompassing process for parcels, which reduces the toxicological profile of nanoparticles, still remained. "Green synthesis" of nanoparticles has been shown to be a kind of approach to resolve the toxicity amounts in a range of 10-18 times. Using distinctive properties of this approach, i.e. as green synthesized silver nanoparticles (G-AgNPs), in order to raise potential therapeutic efficacy, even up to two-fold higher than cis-platin, is going to play a crucial role in cancer treatment and could be considered as a new insight in this field. The current review focuses on the antioxidant activity of G-AgNPs and potential impacts on cancer cells.

High-efficiency purification of sulforaphane from the broccoli extract by nanostructured SBA-15 silica using solid-phase extraction method

Sulforaphane, a promising phytochemical, has received much attention in recent decades as a potential anticarcinogenic compound. In this research work, a novel, specific and affordable method has been developed for the separation and purification of natural sulforaphane from broccoli extract using SBA-15 mesoporous silica. SBA-15 was found to be the most efficient in the purification of sulforaphane compared to some of the conventionally used adsorbents and zeolites. The nanoparticles of SBA-15 mesoporous silica were synthesized using the hydrothermal method from natural amorphous silica extracted from rice husk ash with a silica purity of 96%. Structural and morphological analysis of the synthesized SBA-15 mesoporous silica were performed by the XRD, FT-IR, FE-SEM, and BET techniques. The method includes the primary immiscible solvent extraction of autolyzed broccoli sample with dichloromethane, followed by purification of the extract by SBA-15 mesoporous silica using solid-phase extraction (SPE) method. The recovery of the purified sulforaphane from broccoli extract was >98% using SBA-15 mesoporous silica, which is higher compared to that obtained using current purification methods. The highest purity of sulforaphane product was measured 94% based on the results of analytical HPLC chromatograms. Moreover, the effects of different parameters on the sulforaphane purification by using SBA-15 were studied and optimized.

Green synthesis of safe zero valent iron nanoparticles by Myrtus communis leaf extract as an effective agent for reducing excessive iron in iron-overloaded mice, a thalassemia model

Green synthesis of Myrtus communis-Zero Valent Iron Nanoparticles (MC-ZVINs) was carried out in an alkaline environment.

Fabrication of novel TiO2 nanoparticles/Mn(III) salen doped carbon paste electrode: application as electrochemical sensor for the determination of hydrazine in the presence of phenol

Hydrazine and phenol are two important environmental pollutants. In this work, an electrochemical sensor for the selective and sensitive detection of hydrazine in presence of phenol was developed by the bulk modification of carbon paste electrode (CPE) with TiO2 nanoparticles and Mn(III) salen. Large peak separation, good sensitivity, and stability allow this modified electrode to analyze hydrazine individually and simultaneously along with phenol. Applying square wave voltammetry (SWV), a linear dynamic range of 3 × 10(-8)-4.0 × 10(-4) M with detection limit of 10.0 nM was obtained for hydrazine. Finally, the proposed method was applied to the determination of hydrazine and phenol in some real samples.

Silver nanoparticles enhanced a novel TCPO-H₂O₂-safranin O chemiluminescence system for determination of 6-mercaptopurine

The present study deals with first attempt to introduce safranin O as the fluorophore for peroxyoxalate chemiluminescence system. The reaction of bis-(2,4,6-trichlorophenyl) oxalate (TCPO) with H2O2 catalyzed by silver nanoparticles can transfer energy to safranin O via the formation of dioxetanedione intermediate and emits orange-red light. The relationship between CL intensity and the concentration of TCPO, fluorophore, hydrogen peroxide and nanocatalyst was investigated. The Ag nanoparticles were synthesized by chemical reduction method and characterized using scanning electron microscopy, particle size analyzer and UV-spectroscopy. Moreover, the system was applied successfully to detect a drug, 6-mercaptopurine (6-MP) in pharmaceuticals. Under optimum conditions, a linear working range for 6-MP concentrations from 5.5 × 10(-7) to 5.5 × 10(-5)mol L(-1) (r>0.9831, n=6) was obtained with a detection limit of 1.6 × 10(-7)mol L(-1). The relative standard deviation for 6 repetitive determinations was less than 3.8% and recoveries of 98% and 103% were obtained.

Visible light photo-degradation of methylene blue over Fe or Cu promoted ZnO nanoparticles

CuxZn(1-x)O, FexZn(1-x)O (x=0.01) and ZnO nanoparticles were and were characterized by X-ray diffraction, ultraviolet and visible spectroscopy, FTIR spectroscopy and SEM. The photodegradation of an aqueous solution of methylene blue (as an organic pollutant) by nanoparticles with H2O2 (30%) under visible light and the progress of the reaction were monitored by UV-Vis spectroscopy absorption. The photocatalytic oxidation efficiency of all nanoparticles was 100% at the appropriate time. The degradation time was 90 min for FeZnO, 120 min for CuZnO and 210 min for ZnO. This indicates that the photocatalytic activity of the doped nanoparticles was better than that of ZnO alone. ZnO doped with a small amount of Fe or Cu decreased the size of the nanoparticles and the band gap and increased photocatalytic efficiency.

In vitro study of the binding between chlorpyrfos and sex hormones using headspace solid-phase microextraction combined with high-performance liquid chromatography: A new aspect of pesticides and breast cancer risk

Endocrine-disrupting chemicals are compounds that alter the normal functioning of the endocrine system. Organophosphorus insecticides, as chlorpyrifos (CPS), receive an increasing consideration as potential endocrine disrupters. Physiological estrogens, including estrone (E1), 17β-estradiol (E2), and diethylstilbestrol (DES) fluctuate with life stage, suggesting specific roles for them in biological and disease processes. There has been great interest in whether certain organophosphorus pesticides can affect the risk of breast cancer. An understanding of the interaction processes is the key to describe the fate of CPS in biological media. The objectives of this study were to evaluate total, bound, and freely dissolved amount of CPS in the presence of three estrogenic sex hormones (ESHs). In vitro experiments were conducted utilizing a headspace solid phase microextraction (HS-SPME) combined with high-performance liquid chromatography (HPLC) method. The obtained Scatchard plot based on the proposed SPME-HPLC method was employed to determine CPS-ESHs binding constant and the number of binding sites as well as binding percentage of each hormone to CPS. The number of binding sites per studied hormone molecule was 1.10, 1, and 0.81 for E1, E2, and DES, respectively. The obtained results confirmed that CPS bound to one class of binding sites on sex hormones.

Palladium nanoparticles supported on natural nanozeolite clinoptilolite as a catalyst for ligand and copper-free C–C and C–O cross coupling reactions in aqueous medium

Pd⁰-nanoparticles supported on natural nanozeolite were synthesized and applied as a catalyst for the Sonogashira and Ullmann condensation coupling reactions.

Environmental monitoring of complex hydrocarbon mixtures in water and soil samples after solid phase microextraction using PVC/MWCNTs nanocomposite fiber

A novel nanocomposite based on incorporation of multiwalled carbon nanotubes (MWCNTs) in polyvinyl chloride (PVC) was prepared. Proposed nanocomposite was coated on stainless steel wire by deep coating. Composition of nanocomposite was optimized based on results of morphological studies using scanning electron microscopy. The best composition (83% MWCNTs:17% PVC) was applied as a solid phase microextraction fiber. Complex mixture of aromatic (BTEX) and aliphatic hydrocarbons (C5-C34) were selected as model analytes, and performance of proposed fiber in extraction of the studied compounds from water and soil samples was evaluated. Analytical merits of the method for water samples (LODs=0.10-1.10 ng L(-1), r(2)=0.9940-0.9994) and for soil samples (LODs=0.10-0.77 ng kg(-1), r(2)=0.9946-0.9994) showed excellent characteristics of it in ultra trace determination of petroleum type environmental pollutants. Finally, the method was used for determination of target analytes in river water, industrial effluent and soil samples.

A novel modified carbon paste electrode based on NiO/CNTs nanocomposite and (9, 10-dihydro-9, 10-ethanoanthracene-11, 12-dicarboximido)-4-ethylbenzene-1, 2-diol as a mediator for simultaneous determination of cysteamine, nicotinamide adenine dinucleotide and folic acid

A carbon paste electrode (CPE) modified with (9, 10-dihydro-9, 10-ethanoanthracene-11, 12-dicarboximido)-4-ethylbenzene-1, 2-diol (DEDE) and NiO/CNTs nanocomposite was used for the sensitive voltammetric determination of cysteamine (CA), nicotinamide adenine dinucleotide (NADH) and folic acid (FA) for the first time. The synthesized materials were characterized with different methods such as XRD, cyclic voltammetry, electrochemical impedance spectroscopy (EIS) and square wave voltammetry (SWV). The modified electrode exhibited a potent and persistent electron mediating behavior followed by well-separated oxidation peaks of CA, NADH and FA. The peak currents were linearly dependent on CA, NADH and FA concentrations using square wave voltammetry (SWV) method in the ranges of 0.01-250, 1.0-500, and 3.0-550 µmol L⁻¹, with detection limits of 0.007, 0.6, and 0.9 µmol L⁻¹, respectively. The modified electrode was used for the determination of CA, NADH and FA in biological and pharmaceutical samples.

Application of experimental design for extraction of BHA and BHT from edible vegetable oil and their determination using HPLC

The optimal conditions of liquid–liquid extraction of two synthetic phenolic antioxidants, BHA and BHT were investigated in five Iranian edible vegetable oil samples using the central composite design. Stepwise multiple linear regression method was used for construction of different models based on the experimental data. Optimum conditions for BHA and BHT were achieved using 3 ml of ethanolic solution containing (0.25% v/v) of glacial acetic acid, three extractions and a mixing time of 10 minutes. Analytes were separated using HPLC with a C 18 column using methanol:water:glacial acetic acid (75:24:1, v/v/v) as the mobile phase. The limit of detections, linear ranges and relative standard deviation ( n = 7 ) were 0.04 μg/g−1 , 0.5– 200 μg/g−1 and 2.6% for BHA and 0.30 μg/g−1 , 1.0– 200 μg/g−1 and 4.20% for BHT, ( r 2 > 0 . 9 9 ), respectively. Amounts of BHA and BHT in analyzed oil samples were in the ranges of 29.8– 54.5 μg/g−1 and 0.0– 6.8 μg/g−1 respectively.

Voltammetric determination of homocysteine using multiwall carbon nanotube paste electrode in the presence of chlorpromazine as a mediator

We propose chlorpromazine (CHP) as a new mediator for the rapid, sensitive, and highly selective voltammetric determination of homocysteine (Hcy) using multiwall carbon nanotube paste electrode (MWCNTPE). The experimental results showed that the carbon nanotube paste electrode has a highly electrocatalytic activity for the oxidation of Hcy in the presence of CHP as a mediator. Cyclic voltammetry, double potential step chronoamperometry, and square wave voltammetry (SWV) are used to investigate the suitability of CHP at the surface of MWCNTPE as a mediator for the electrocatalytic oxidation of Hcy in aqueous solutions. The kinetic parameters of the system, including electron transfer coefficient, and catalytic rate constant were also determined using the electrochemical approaches. In addition, SWV was used for quantitative analysis. SWV showed wide linear dynamic range (0.1-210.0 μM Hcy) with a detection limit of 0.08 μM Hcy. Finally, this method was also examined as a selective, simple, and precise electrochemical sensor for the determination of Hcy in real samples.