Iranian Journal of Analytical Chemistry
Volume:9 Issue: 1, Winter and Spring 2022

For the first time, an analytical methodology based ondifferential pulse voltammetry (DPV) at a glassy carbon electrode (GCE) assisted by two multivariate calibration (MVC) models including back propagation-artificial neural network (BP-ANN), non-linear class, and partial least squares-1 (PLS-1), classical class, thatthey have been constructed on the basis of non-bilinear first order differential pulse voltammetry (DPV) data,was developed and validated for the simultaneous determination of Ascorbic acid, Uric acid, Acetaminophen, and Noradrenalinto identify which approach offers the best predictions.The baselines of the DPV signals were corrected by asymmetric least square spline regression (AsLSSR) algorithm. Before applying the PLS-1,lack of bi-linearity was tackled by potential shift correction using correlation optimised warping (COW) algorithm. The multivariate calibration (MVC) model was developed as a quaternary calibration modelin a blank human serum sample (drug-free) provided by a healthy volunteer to regard the presence of a strong matrix effect which may be caused by the possible interferents present in the serum, and it was validated and tested with two independent sets of analytes mixtures in the blank and actual human serum samples, respectively.According to the obtained results, the PLS-1 was recommended for simultaneous determination of AA, UA, AC, and NA in both blank and actual human serum samples .

Chelation therapy has been used to remove toxic metals from the body for a long time. Flavonoids such as quercetin (QUR), a well-known protective antioxidant and free radical scavenger, can bind to metal cations and protect our bodies from toxic metals. In the current study, we used UV–Vis, 1HNMR, IR, and fluorescence spectroscopic techniques as well as viscosity measurements to investigate the synthesis, characterization, and interaction between Bi(III)-QUR complex and calf thymus DNA (ctDNA) in physiological buffer. The antioxidant activity of the complex was assessed utilizing DPPH and ABTS free radical scavenging, and ferric reducing potential. After chelation of the Bi(III) cation, the antioxidant potential of QUR was reduced. In the presence of ctDNA, the absorption spectrum of Bi(III)-QUR complex was raised, and the fluorescence intensity of Bi(III)-QUR complex was increased. With the addition of the Bi(III)-QUR complex, the relative viscosity of ctDNA rose. These findings indicate that the Bi(III)-QUR complex interacts with ctDNA in a groove-binding mode. The thermodynamic parameters (ΔH, ΔS, and ΔG) of the Bi(III)-QUR complex with ctDNA, as well as well as association constant, Ka, and number of binding sites (n), were assessed from the fluorescence data, indicating that the binding of Bi(III)-QUR complex to ctDNA was primarily driven by hydrophobic interactions.

In this study, curcuma zedoaria extract was investigated as a mild steel (MS) corrosion inhibitor in 0.5 M H2SO4 solution by conventional methods of weight loss (WL), electrochemical impedance spectroscopy (EIS) and polarization at 25 °C. The highest percentage of inhibition was obtained for the concentration of 0.5 g/l of curcuma zedoaria extract. The results of polarization method showed that curcuma zedoaria extract acts as a mixed inhibitor. Examination of MS immersion time by weight loss method showed that with increasing immersion time, the inhibitory effect decreases in low concentrations of curcuma zedoaria extract but in higher concentrations of curcuma zedoaria extract (concentration 1.0 g/L), the inhibitory effect remains almost constant over time. The effect of temperature on the performance of curcuma zedoaria extract by electrochemical polarization method in the temperature range of 35-65 °C shows a decrease in inhibition percentage with increasing temperature. Adsorption of curcuma zedoaria extract molecules on the surface of MS at all studied temperatures follows the Langmuir adsorption isotherm. Using the results of kinetic and thermodynamic calculations, the adsorption of molecules of curcuma zedoaria extract on the surface of MS physical adsorption type was observed.

In this study, the acid dissociation constants (pKa) of three indicators, bromocresol green, phenolphthalein and methyl orange, were determined by scanning the solution of indicators and deposited pH paper in these solutions (in each step of color-changing solution) and then chemometrics method. These methods are simple, fast, and inexpensive. For this reason, first, the vessels containing the indicator solution and pH paper (in each step of color-changing solution) were scanned by the scanner, and then the images of sample solutions and pH papers were transferred to a computer using Microsoft Photo Editor (Microsoft XP). RGB values were measured, in each pixel, with the image processing tool box of MATLAB. In MATLAB (2013) software, a novel program was written based on RGB values, for calculating pKa indicators. The agreement between obtained pKa by this method and values reported in the literature demonstrates the utility of the method here used.

Fuel cells can directly convert chemical energy into electric energy with high conversion efficiency and no pollution. Among many factors affecting the chemical-electrical energy conversion, oxygen reduction reaction (ORR) on cathode is the pivot in fuel cell. This reaction is a kinetically slow process, which dominates the overall performance of a fuel cell. The ORR can proceed through two ways. One is a direct four-electron pathway, in which O2 is reduced directly to water without involvement of hydrogen peroxide. The other is a less efficient two-step two-electron pathway in which hydrogen peroxide is formed as an intermediate. To achieve a high efficiency fuel cell, the four-electron pathway is expected to occur. Because the ORR process is very slow in nature, catalysts must be used to facilitate the four-electron pathway to boost the efficiency of fuel cells. Traditionally, such electro catalysts are platinum and its alloys, but they are expensive and susceptible to time-dependent drift and CO poisoning, which limits large-scale application of the fuel cell. There have been intensive research efforts to reduce or replace Pt and Pt based alloys electrodes in fuel cell. In this work using calculated NMR and NQR parameters in some nitrogen-containing graphene sheets (with one or two nitrogen), the effect of nitrogen atom on charge density of carbon atoms was studied. The results showed that in the presence of nitrogen, charge density of some carbon atoms decreased and these atoms are better candidate as catalyst active site than pure graphene.

In the present work, switchable hydrophilic solvent-based extraction (SHSE) followed by high performance liquid chromatography with UV detection (HPLC-UV) was used to determine free amino acids in fertilizer samples. During the phase transformation of SHSE, the organic phase appeared to effectively capture the target analytes. In this extraction technique, 200 μL of a water-immiscible solvent (dipropylamine) is used, which can be solubilized in the acidic aqueous phase. Phase separation is then brought about by the addition of sodium hydroxide. The variables affecting this method were optimized to achieve the best extraction efficiency. The optimized conditions included: volume of sample 25 mL, volume of extraction solvent 200 μL, and extraction time 2 min. Under the optimal experimental conditions, good detection limits (0.0006-0.0021 µmol ml-1), linearities (R2 > 0.997), and precision (relative standard deviation less than 5.0%) were obtained. Finally, the developed method was successfully applied to the determination of target analytes in different types of fertilizer samples and acceptable recoveries (> 97.2%) were obtained.

In this study, an electrochemical sensor for simultaneous measurement of morphine and fentanyl based on a modified pencil graphite electrode with a semiconductor nanocrystalline structure was developed.The first layer of the sensor has a core of thioglycolic acid-bonded cadmium selenidequantum dot (TGA-CdSe), surrounded by a second layer, zinc sulfide quantum dot (ZnS). Functionalized carbon nanotubes (FCNT) have also been used to reinforce the sensor structure (TGA-CdSe/ZnS@FCNT). Measurements were performed by differential pulse voltammetry (DPV) and cyclic voltammetry (CV).The synthesis of nanostructures was confirmed by FTIR, EDX, SEM and XRD. In order to optimize the effective factors in the performance of this sensor, the Taguchi orthogonal array (OA16) design has been utilized. TheCV voltammograms showed irreversible oxidation peaks at potentials of 0.9 V and 0.38 V for fentanyl and morphine respectively. The transfer coefficients (α) of 0.96for morphine and 0.95 for fentanyl obtained. The diffusion coefficients gained on the electrode surface by chronoamperometrywere 3.84×10-6cm2 s-1and1.615×10-6cm2s-1 for morphine and fentanyl, respectively. Under optimal conditions, the linear concentration range and detection limit for morphine were 0.08-100 μM, and 0.024 μM. For fentanyl two linear ranges of 0.02-8μM, 8-100 μM and 0.006 μM were obtained. The fabricated sensor can be well used for the simultaneous measurement of morphine and fentanyl in biological samples with acceptable relative recoveries in the range of 98.3-102.

In this research, a novel modified glassy carbon electrode (GCE) was successfully fabricated with a tri-component nanocomposite consisting of 5-(3,4-dihydroxyphenyl)8,8-dimethyl-2-(methyl thio)-7,8,9,10-tetrahydropyrimido [4,5-b]quinolone-4,6(3H,5H)-dione (PQ23) and Nitrogen-doped reduced graphene oxide aerogel/molybdenum oxide nanorods (PQ23/N-doped-rGO/MoO2 /GCE) as sensing platform toward hydrazine (HDZ). The nanocomposite is characterized by MAP analysis, X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). Through electrochemical investigations, the electron transfer coefficient between PQ23 and the N-doped-rGO/MoO2 /GCE (glassy carbon electrode which was modified with reduce graphene oxide decorated by molybdenum oxide nanorods) and the apparent charge transfer rate constant, ks, and diffusion coefficient (D) were calculated. Electrochemical behavior and electrocatalytic activity of the nanocomposite modified GCE were studied by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and differential pulse voltammetry (DPV). Under the optimum experimental condition, the designed sensor exhibited high sensitivity and suitable selectivity for hydrazine oxidation, enabling the detection of hydrazine with a linear range of 25.0-1000.0 µM and a good detection limit (3σ) was 4.2 µM. The designed electrochemical sensor shows good repeatability, reproducibility, and acceptable stability with an RSD less than 3.2%.

In this study, a new Zeolite Al/Na (ZAN) was synthesized and characterized and then a new modified Carbon Paste Electrode with ZAN was made to determine Acetaminophen. Electrochemical studies using Linear Sweep Voltammetry and differential pulse voltammetry were used to determine electrochemical  Acetaminophen . In the presence of Acetaminophen , modified electrode with ZAN shows a specific anodic peak at ~ 0.59 volts which is the result of using electrocatalytic oxidation of  Acetaminophen . The determination limit of this method to measure  Acetaminophen was 5.8 µM, the relative standard deviation for 7 repeated measurements was 1.1 % and linear range of the calibration to measure  Acetaminophen was 10 up to 115 µM . for the characterization of ZAN nanostructures we used SEM (Scanning Electron Microscopy), DLS (Dynamic Light Scattering) and FT-IR (Fourier-Transform Infrared spectroscopy).

One of the effective and important steps of the production of Zn in zinc factories is the purification step to remove the general impurities such as cobalt, nickel, and cadmium that can cause the creation of problems in the electrowinning process. In Iran's zinc factories, firstly, at the hot purification step cobalt using the manganometry method, and then at the cold purification step nickel & cadmium using the cementation method with the help of Zn powder removed. In the aim of this study is evaluated the usability of the cementation method instead of the manganometry method. In this paper, important and effective parameters such as temperature, Zn powder dosage, mixing time, amount of trioxide antimony, copper sulfate effect, particle size, zinc ions concentration, mixing speed, and pH of zinc sulfate solution were studied and optimized. The Optimal state is obtained at 85 °C, pH= 4.5, 20 mg/L Sb2O3 concentration, 8 g/L zinc dust, 600 rpm mixing speed in 75 minutes. Decreasing the particle size of zinc dust increased the removal efficiency, but increasing the amounts of copper sulfate and zinc ions caused decreasing in efficiency. Results showed that cobalt, nickel, and cadmium removal efficiencies for the manganomery method were 99%, 0%, and 20% and for the cementation method were 99.5%, 99.7%, and 99.9%, respectively. Also, results indicated that the cementation method due to the increase of soluble zinc concentration; not being removes of manganese ions; simultaneous removal of impurities such as cobalt, nickel, and cadmium in a single step; and saving time and cost, has a higher performance rather than to manganometry method.