Plasmonic Imaging of the Interfacial Potential Distribution on Bipolar Electrodes.

Bipolar electrochemistry is based on the gradient distribution of free-electron density along an electrically isolated electrode, which causes a positive electrode potential at one end and a negative potential at the other, allowing for wide applications in analytical chemistry and materials science. To take full advantage of its wireless and high-throughput features, various types of optical probes, such as pH indicators and fluorescence and electrochemiluminescence reagents, have often been used to indirectly monitor the interfacial electron transfer through chromogenic or fluorogenic reactions. Herein, we report the first probe-free imaging approach that can directly visualize the distribution of the interfacial potential in bipolar electrodes, providing essential information for the validation and development of the theory and applications of bipolar electrochemistry. This approach is based on the sensitive dependence of surface plasmon resonance imaging on the local electron density in the electrode, which enables the direct mapping of potential with a spatial resolution close to the optical diffraction limit, a temporal resolution of 50 ms, and a sensitivity of 10 mV. In addition, in contrast to previous optical readouts that relied on faradaic reactions, the present work achieved the impedance-based measurements under non-faradaic conditions. It is anticipated that this technique will greatly expand the application of bipolar electrochemistry as a platform for chemical and biosensing.

Computer-assisted design and synthesis of a highly selective smart adsorbent for extraction of clonazepam from human serum.

A computational approach was applied to screen functional monomers and polymerization solvents for rational design of molecular imprinted polymers (MIPs) as smart adsorbents for solid-phase extraction of clonazepam (CLO) form human serum. The comparison of the computed binding energies of the complexes formed between the template and functional monomers was conducted. The primary computational results were corrected by taking into calculation both the basis set superposition error (BSSE) and the effect of the polymerization solvent using the counterpoise (CP) correction and the polarizable continuum model, respectively. Based on the theoretical calculations, trifluoromethyl acrylic acid (TFMAA) and acrylonitrile (ACN) were found as the best and the worst functional monomers, correspondingly. To test the accuracy of the computational results, three MIPs were synthesized by different functional monomers and their Langmuir-Freundlich (LF) isotherms were studied. The experimental results obtained confirmed the computational results and indicated that the MIP synthesized using TFMAA had the highest affinity for CLO in human serum despite the presence of a vast spectrum of ions.

Computational design and synthesis of molecular imprinted polymers for selective extraction of allopurinol from human plasma.

The present study was focused on the rational development of polymers for selective extraction of allopurinol (ALP) from human plasma. Therefore, a computational modeling approach was combined with the molecular imprinting technology to obtain the polymers. The computational approach was used in order to screen the functional monomers as well as the polymerization solvents for rational design of molecular imprinted polymers (MIPs). It was based on the comparison of the binding energy (ΔE) of the formed complexes between the template molecule and different functional monomers. In the design, the effect of the polymerization solvent was also included using the polarizable continuum model. The theoretical calculation results showed that among virtual solvents tested, acrylamide (AAM) gave the largest ΔE while acrylonitrile (ACN) gave the smallest ΔE in acetone. Therefore, the MIP prepared using AAM as functional monomer in acetone was desired. To examine the validity of this approach, three MIPs were synthesized with different functional monomers i.e. AAM, acrylic acid (AA), and ACN, and then evaluated using Langmuir-Freundlich (LF) isotherm. The results obtained from this experiment confirmed the computational results that the MIP prepared by AAM was the most appropriate adsorbent. Subsequently, the MIP was used to develop a molecular imprinted solid-phase extraction (MISPE) procedure. Finally, the MISPE procedure followed by HPLC was developed for selective extraction and determination of allopurinol in human plasma. For the proposed MISPE method, the linearity between peak area and concentration was found in the range of 0.100-25.000 µM with a linear regression coefficient (R²) of 0.995. The limit of detection (LOD) and quantification (LOQ) in plasma were 0.028 and 0.093 µM, respectively. The results of this study indicated the possibility of using computer aided design for rational selection of functional monomers and solvents for preparation of the MIPs capable of extracting allopurinol from human plasma.

High quality potassium phosphate production through step-by-step glycerol purification: a strategy to economize biodiesel production.

The cost of biodiesel production can be reduced by a number of strategies such as utilization of waste cooking oils and non-edible plant oils as well as implementation of improved separation technologies. In addition, processes dealing with the glycerol by-product can have economic benefits. In the present study, acidification of crude glycerol with phosphoric acid to pH 9.67 followed by acidification to 4.67 was implemented to produce high quality potassium phosphate during glycerol purification. KH(2)PO(4), K(2)HPO(4), glycerol and free fatty acids (FFAs) with a purity of 98%, 98.05%, 96.08% and 99.58% were obtained, respectively.

Upstream and downstream strategies to economize biodiesel production.

In recent years biodiesel has drawn considerable amount of attention as a clean and renewable fuel. Biodiesel is produced from renewable sources such as vegetable oils and animal fat mainly through catalytic or non-catalytic transesterification method as well as supercritical method. However, as a consequence of disadvantages of these methods, the production cost increases dramatically. This article summarizes different biodiesel production methods with a focus on their advantages and disadvantages. The downstream and upstream strategies such as using waste cooking oils, application of non-edible plant oils, plant genetic engineering, using membrane separation technology for biodiesel production, separation and purification, application of crude glycerin as an energy supplement for ruminants, glycerin ultra-purification and their consequent roles in economizing the production process are fully discussed in this article.