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A simple and sensitive suspended droplet solvent microextraction (SDSME) method is proposed for the preconcentration and determination of copper by flame atomic absorption spectrometry (FAAS). The analytical procedure is based upon the formation of a complex between Cu(II) and 1-phenyl-1,2-propandione-2-oxime- thiosemicarbazone (PPDOT) as a complexing agent. After extraction of the complex by 1-octanol, copper concentration in the solvent drop was determined by FAAS. The effect of different parameters such as pH, PPDOT concentration, kind of buffer, kind and volume of organic solvent, volume of aqueous phase, extraction time, stirring rate of sample solution, temperature, and ionic strength were investigated. The effect of foreign ions on the determination was also studied. Under the optimized chemical and instrumental conditions, a linear calibration curve was achieved in the range of 0.0050-0.26 mg/L, with the limit of detection of 3 µg/L and the enrichment factor of 52.6. This method can be applied successfully to the determination of copper in water samples. Keywords: copper, 1-phenyl-1,2-propandione-2-oxime-thiosemicarbazone, suspended droplet solvent microextraction, flame atomic absorption spectrometry DOI: 10.1134/S1061934814110057, Determination of heavy metals in real samples, especially natural waters, is a task for analytical chemists frequently asked by environmentalists for the evaluation and phenomenon interpretation of aquatic systems. However, [...]

The novel severe acute respiratory syndrome coronavirus (SARS CoV-2) was introduced as an epidemic in 2019 and had millions of deaths worldwide. Given the importance of this disease, the recommendation and design of new active compounds are crucial. 3-chymotrypsin-like protease (3 CLpro) inhibitors have been identified as potent compounds for treating SARS-CoV-2 disease. So, the design of new 3 CLpro inhibitors was proposed using a quantitative structure-activity relationship (QSAR) study. In this context, a powerful adaptive least absolute shrinkage and selection operator (ALASSO) penalized variable selection method with inherent advantages coupled with a nonlinear artificial neural network (ANN) modelling method were used to provide a QSAR model with high interpretability and predictability. After evaluating the accuracy and validity of the developed ALASSO-ANN model, new compounds were proposed using effective descriptors, and the biological activity of the new compounds was predicted. Ligand-receptor (LR) interactions were also performed to confirm the interaction strength of the compounds using molecular docking (MD) study. The pharmacokinetics properties and calculated Lipinski's rule of five were applied to all proposed compounds. Due to the ease of synthesis of these suggested new compounds, it is expected that they have acceptable pharmacological properties. [ABSTRACT FROM AUTHOR]

The performance of glassy carbon electrodes (GCE) coated with multi-walled carbon nanotube poly(pyrocatechol violet) composite and bismuth film was investigated as an electrochemical sensor in the simultaneous determination of Cd 2+ and Pb 2+ ions in a 0.1 M acetate buffer solution at pH = 5.0. The presence of the bismuth film improves the analyte accumulation due to its ability to form a fused alloy with cadmium and lead. It was found that the Bi-film modified electrode shows a better performance than the bare GCE, GCE-MWCNT and GCE-MWCNT/poly(PCV) electrodes. The parameters affecting the stripping current response were investigated and optimized. Under optimal conditions, the electrode showed a good linear response to Cd 2+ and Pb 2+ in the concentration range of 1.0–300.0 μg L −1 and 1.0–200.0 μg L −1 , respectively. The detection limits were 0.20 μg L −1 and 0.40 μg L −1 for Cd 2+ and Pb 2+ , respectively. It was found that the sensor has least interference from most of the common ions due to specific and selective interaction of the modifier functionalities with lead and cadmium ions. The response of the electrode remained constant for at least 3 weeks of successive operation. The proposed method was applied for simultaneous determining Cd 2+ and Pb 2+ contents in water samples. [ABSTRACT FROM AUTHOR]

A sensitive and selective method is presented for the voltammetric determination of verapamil using a glassy carbon electrode modified with multi-walled carbon nanotubes (MWCNTs/GCE). The oxidation peak current of verapamil at 1.02 V (vs. Ag/AgCl) is remarkably increased on the MWCNTs/GCE. Scanning electron microscopy (SEM) was used for characterization of the modified electrode surface. The electrochemical oxidation of verapamil using the MWCNTs/GCE was investigated by cyclic voltammetry. The experimental parameters including chemical and instrumental variables were investigated and optimized for verapamil determination. Under the optimum conditions voltammetric peak currents showed a linear response for verapamil concentration in the range of 2.5–70.0 μM, for both CV and DPV with detection limits of 2.0 μM and 1.6 μM, respectively. The relative standard deviation of five replicates determinations of 15.0 μM verapamil was 3.92%. The interference effects of frequently encountered excipients, additives and common species on the determination of verapamil were also studied. The sensor was successfully applied for verapamil determination in pharmaceutical and spiked human serum samples. [ABSTRACT FROM AUTHOR]

The inhibitory activities (pIC50) of N2 and O6 substituted guanine derivatives as cyclin-dependent kinase 2 (CDK2) inhibitors have been successfully modeled using calculated molecular descriptors. Two linear (MLR) and nonlinear (ANN) methods were utilized for construction ofmodels to predict the pIC50 activities of those compounds.The QSARmodels were validated by cross-validation (leave-one-out) as well as application of the models for prediction of pIC50 of external set compounds. Also, the models were validated by calculation of statistical parameters and Y-randomization test. Two methods provided accurate predictions, although more accurate results were obtained by ANNmodel.Themean-squared errors (MSEs) for validation and test sets ofMLR are 0.065, 0.069 and of ANN are 0.017 and 0.063, respectively. [ABSTRACT FROM AUTHOR]

A flow injection (FI) system is described for the sequential determination of periodate and iodate based on their reaction with iodide at pH 3.5. Two sample plugs were injected into the same carrier stream sequentially. One injection is for the iodate determination and the other for the sum of iodate and periodate determination. For iodate determination, molybdate solution buffered at pH of 3.5 was used for selective masking of periodate. The influences of reagent concentrations were studied by a univariable method and the influence of FI manifolds was studied using univariable and simplex method. Periodate and iodate can be determined in the range of 0.050–5.0 and 0.050–10 μg/ml, respectively. The 3σ limit of detection was 0.030 and 0.050 μg/ml for periodate and iodate, respectively. The proposed method has been applied for the sequential determinations of periodate and iodate in water samples. [Copyright &y& Elsevier]

A simple and efficient flow-injection method was used with good results to determine periodate and iodate in water. The method is based on the reaction of periodate or iodate with pyrogallol red in sulfuric acid media. The reaction was monitored spectrophotometrically by measuring the decrease in absorbance of pyrogallol red at 470 nm. The chemical and FIA variables were established using the univariate and simplex optimization methods. The calibration curve was linear over the concentration ranges of 0.8–73.0 and 2.0–100.0 μM for IO4− and IO3−, respectively. The detection limits were 0.7 and 1.0 μM for IO4− and IO3−, respectively. The sample throughput was 20±5 h−1. The influence of potential interfering ions in the determination of the anions was tested. The relative standard deviations for 4.20 and 5.73 μM periodate and iodate were 1.8 and 2.2%, respectively. [ABSTRACT FROM AUTHOR]

A simple, sensitive, and rapid dispersive liquid-liquid microextraction (DLLME) method is developed for the preconcentration of silver ions prior to determination by flame atomic absorption spectrometry (FAAS). In this work, 1-phenyl-1,2-propanedione-2-oximethiosemicarbazone (PPDOT), chloroform, and methanol are used as the complexing agent, extraction solvent, and disperser solvent, respectively. The effects of different analytical parameters on the complex formation and the extraction efficiency are investigated and optimized. The effects of interfering ions on the determination of silver(I) are also examined. Under the optimized conditions, a linear calibration curve was achieved in the range of 0.60-120.0 µg L-1, with the detection limit of 0.61 µg L-1. The pre-concentration factor calculated as the ratio of the slopes of the calibration graphs with and without the pre-concentration was 35.5. The relative standard deviations (RSDs) for the silver(I) determinations were below 3 %. The proposed separation procedure was successfully applied to the determination of silver(I) in natural water and photographic film samples with satisfactory results (recoveries > 95 %). [ABSTRACT FROM AUTHOR]

The novel severe acute respiratory syndrome coronavirus (SARS CoV-2) was introduced as an epidemic in 2019 and had millions of deaths worldwide. Given the importance of this disease, the recommendation and design of new active compounds are crucial. 3-chymotrypsin-like protease (3 CL pro ) inhibitors have been identified as potent compounds for treating SARS-CoV-2 disease. So, the design of new 3 CL pro inhibitors was proposed using a quantitative structure-activity relationship (QSAR) study. In this context, a powerful adaptive least absolute shrinkage and selection operator (ALASSO) penalized variable selection method with inherent advantages coupled with a nonlinear artificial neural network (ANN) modelling method were used to provide a QSAR model with high interpretability and predictability. After evaluating the accuracy and validity of the developed ALASSO-ANN model, new compounds were proposed using effective descriptors, and the biological activity of the new compounds was predicted. Ligand-receptor (LR) interactions were also performed to confirm the interaction strength of the compounds using molecular docking (MD) study. The pharmacokinetics properties and calculated Lipinski's rule of five were applied to all proposed compounds. Due to the ease of synthesis of these suggested new compounds, it is expected that they have acceptable pharmacological properties.

A simple, selective, and sensitive kinetic spectrophotometric method is described for the determination of trace amounts of phenylhydrazine, which is based on its inhibition effect on the reaction between meta cresol purple (MCP) and periodate in the presence of bromide ions. The reaction was monitored spectrophotometrically by measuring the change in absorbance of MCP at 525 nm. The calibration graph was linear in the range of 1.0-10.0 microM. The detection limit (3 sigma) was 0.020 microM. The relative standard deviations for 10 replicate measurements of 3.0, 5.0 and 7.0 microM of phenylhydrazine were 2.0%, 1.4%, and 0.90%, respectively. The potential interfering substances were studied in the presence of phenylhydrazine. The proposed method was applied to the analysis of water samples.