Three-way Resolution of the Overlapping Ultrahigh-performance Liquid Spectrochromatograms for the Analysis of a Quaternary Mixture Using Parallel Factor Analysis

This paper presents a new application of three-way parallel factor analysis (3W-PARAFAC) model to the coeluting spectrochromatograms for the quantitative resolution of a quaternary mixture system consisting of paracetamol, propyphenazone, and caffeine with aspirin as an internal standard. Spectrochromatograms of calibration standards, validation sets, and unknown samples were recorded as a function of retention time and wavelength in the range of 0.0–2.5?min and 200–400?nm, respectively, using ultra-performance liquid chromatography with photodiode array detection (UPLC-PDA). Three-way UPLC-PDA data array X (retention time?×?wavelength?×?sample) was obtained from the data matrices of the spectrochromatograms. 3W-PARAFAC decomposition of three-way UPLC-PDA data array provided three loading matrices corresponding to chromatographic mode, spectral mode, and relative concentration mode. Quantitative estimation of paracetamol, propyphenazone, and caffeine in analyzed samples was accomplished using the relative concentration mode obtained by the deconvolution of the UPLC-PDA data set. The validity and ability of 3W-PARAFAC model were checked by analyzing independent test samples. It was observed from analyses that 3W-PARAFAC method has potential to uniquely resolve strongly overlapping peaks of analyzed compounds in a spectrochromatogram, which was obtained under experimental conditions consisting of the lower flow rate, short run time, and simple mobile phase composition. The proposed three-way chemometric approach was successfully applied to the simultaneous quantification of paracetamol, propyphenazone, and caffeine in tablets. Experiments showed that the determination results were in good agreement with label amount in commercial pharmaceutical preparation.     

Computational and experimental investigation of the effect of cation structure on the solubility of anionic flow battery active-materials

Recent advances in clean, sustainable energy sources such as wind and solar have enabled significant cost improvements, yet their inherent intermittency remains a considerable challenge for year-round reliability demanding the need for grid-scale energy storage. Nonaqueous redox flow batteries (NRFBs) have the potential to address this need, with attractive attributes such as flexibility to accommodate long- and short-duration storage, separately scalable energy and power ratings, and improved safety profile over integrated systems such as lithium-ion batteries. Currently, the low-solubility of NRFB electrolytes fundamentally limits their energy density. However, synthetically exploring the large chemical and parameter space of NRFB active materials is not only costly but also intractable. Here, we report a computational framework, coupled with experimental validation, designed to predict the solubility trends of electrolytes, incorporating both the lattice and solvation free energies. We reveal that lattice free energy, which has previously been neglected, has a significant role in tuning electrolyte solubility, and that solvation free energies alone is insufficient. The desymmetrization of the alkylammonium cation leading to short-chain, asymmetric cations demonstrated a modest increase in solubility, which can be further explored for NRFB electrolyte development and optimization. The resulting synergistic computational–experimental approach provides a cost-effective strategy in the development of high-solubility active materials for high energy density NRFB systems.

Active-material solubility is critical in determining NRFB energy density, yet a predictive model accounting for solid-state cohesion energy has remained elusive. Herein we present such, based on an empirically calibrated computational framework.     

A New Chemometric Strategy in Electrochemical Method Optimization for the Quantification of Cefdinir in Tablets,Effervescent Tablets and Suspension Samples

A new voltammetric method, based on the use of single‐use pencil graphite electrode, was developed for the quantitative determination of cefdinir by square wave voltammetry. Chemometric optimization strategy was used to select the suitable values for three experimental parameters (pH of the supporting electrolyte, frequency and square wave amplitude) by applying a 3³ full factorial design model. The optimal voltammetric conditions were found to be pH 5.0 for supporting electrolyte (Britton‐Robinson buffer), 43 mV for square wave amplitude and 108 Hz for frequency. Square wave voltammograms of calibration, validation and unknown samples were recorded between 0.0–1400 mV under the optimized voltammetric conditions. Linear regression equation was computed in the linear working range of 0.5–20 μg/mL by using the relationship between the concentration and peak current at 600 mV. The optimized voltammetric method was validated by assessing the analysis results of validation samples. Then the proposed method was applied for the quantitative determination of cefdinir in three different pharmaceutical preparations, namely film‐coated tablets, effervescent tablets and powder for oral suspension. It was concluded that the proposed voltammetric method was suitable for the quantitative analysis of commercial pharmaceutical preparations containing cefdinir.     

An Electrochemical Biosensor Platform for Testing of Dehydroepiandrosterone 3‐Sulfate (DHEA−S) as a Model for Doping Materials

Endogenous steroids such as dehydroepiandrosterone (DHEA) and dehydroepiandrosterone 3‐sulfate (DHEA?S) have commonly used as doping materials by athletes and to date novel techniques are needed for detection of these molecules. In this study, antibody‐based electrochemical biosensor has developed for testing level of the DHEA?S. For this aim, gold surfaces were initially modified with cysteamine (Cys) and then, DHEA?S antibody was immobilized on the surface via glutaraldehyde (GA) as a crosslinking agent. The stepwise modification of electrode surface was monitored by using various electrochemical techniques such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Linear range was determined as 2.5–100 ng/mL DHEA?S using differential pulse voltammetry (DPV) technique, as well. Moreover, repeatability (±S.D.), coefficient of variation (%) and limit of detection (LOD) values were calculated as 0.033, 1.030 and 3.971, respectively. Also, DHEA?S in synthetic serum and urine samples were successfully determined with standard addition method and confirmation analysis were performed with liquid chromatography quadrupole‐time of flight mass spectrometry (LC‐QTOF/MS) system. The selectivity was studied with the addition of some interfering molecules (testosterone, bovine serum albumin (BSA), cholesterol, uric acid, lactic acid, codein (COD), ascorbic acid, DHEA). Consequently, this work is proposed as practical, innovative and cost‐effective technique that can be easily adapted for the miniaturized form for the analysis of other doping substances as well as DHEA?S for the future works.     

in vitro Selection of Aptamer for Imidacloprid Recognition as Model Analyte and Construction of a Water Analysis Platform

Pesticide use in agriculture is one of the threats to water safety. Therefore, detection of pesticide residues is crucial for human health. Compared to conventional chromatographic methods, aptasensors are promising tools for fast, cheap and sensitive detection of environmental contaminants. To the best of our knowledge, such an aptasensor has not been reported for imidacloprid (Imi) which is one of the most widely used pesticides. In order to meet this demand, we initially selected two novel aptamers designated as ‘Apta‐1’ and ‘Apta‐2’ by graphene oxide‐SELEX (GO‐SELEX) method. Then, these aptamers were used to fabricate the gold electrode‐based aptasensor platforms and characterized by using electrochemical methods such as cyclic voltammetry, and electrochemical impedance spectroscopy as well as X‐Ray photoelectron spectroscopy. It was found that the limit of detection value of Apta‐1 based sensor for the Imi was found better than Apta‐2 based system, although linear ranges were similar. Based on that finding, Apta‐1 based system was further tested against possible interference molecules. The proposed platform was successfully used for detection of very low concentrations of Imi in the range of ng/mL. Thus, it eliminates the need for sample pre‐treatment and enables a practical analysis in real wastewater samples.     

Carbon Dots as a Promising Green Photocatalyst for Free Radical and ATRP‐Based Radical Photopolymerization with Blue LEDs

Carbon dots (CDs) have been used for the first time as a sensitizer to initiate and activate free radical and controlled radical polymerization, respectively, based on an ATRP protocol with blue LEDs. Consideration of diverse heteroatom‐doped CDs indicated that N‐doped CDs could serve as an effective photocatalyst and photosensitizer in combination with LEDs emitting either at 405 nm or 470 nm. Free radical polymerization was initiated by combining the CDs with an iodonium or sulfonium salt in tri(propylene glycol) diacrylate. Polymerization of methyl methacrylate (MMA) by photo‐induced ATRP was achieved with CDs and ethyl α‐bromophenylacetate using Cu^II as catalyst in the ppm range. The polymers obtained showed temporal control, narrower dispersity ?1.5, and chain‐end fidelity. The first‐order kinetics and ON/OFF experiments additionally gave evidence of the constant concentration of polymer radicals. No remarkable cytotoxic activity was observed for the CDs, underlining their biocompatibility.     

The impact of an out‐of‐school STEM education program on students’ attitudes toward STEM and STEM careers

There is an increasing awareness of out‐of‐school program value in enhancing student interest and understanding of science, technology, engineering, and mathematics (STEM). This study examined the impact of an out‐of‐school STEM education program on student attitudes toward STEM disciplines and STEM careers. A STEM education program implemented at a public research university was designed to integrate STEM disciplines with hands‐on problem‐based activities. Design features included authentic learning contexts, engineering design processes, and content integration. Data sources included an attitude survey and interviews conducted with forty sixth grade middle school student participants. The analysis revealed significant differences between pre and posttests on student attitudes toward personal and social implications of STEM, science and engineering learning, and their relationship to STEM. Findings showed that the program contributed to students’ developing interest in STEM fields, and helped them make connections between schoolwork and daily lives. Recommendations for future research on out‐of‐school STEM education programs were discussed.     

Amperometric Lactate Biosensor Based on Carbon Paste Electrode Modified with Benzo[c]cinnoline and Multiwalled Carbon Nanotubes

Amperometric lactate biosensor based on a carbon paste electrode modified with benzo[c]cinnoline and multiwalled carbon nanotubes is reported. Incorporation of benzo[c]cinnoline acting as a mediator and multiwalled carbon nanotubes providing a conduction pathway to accelerate electron transfer due to their excellent conductivity into carbon paste matrix resulted in a high performance lactate biosensor. The resulting biosensor exhibited a fast response, high selectivity, good repeatability and storage stability. Under the optimal conditions, the enzyme electrode showed the detection limit of 7.0×10^?8 M with a linear range of 2.0×10^?7 M–1.1×10^?4 M. The usefulness of the biosensor was demonstrated in serum samples.