Voltammetric Studies of Anion Transfer Reactions Across a Microhole Array-Water/PVC-NPOE Gel Interface

Voltammetric characterization of hydrophilic anion transfer processes across a 66 microhole array interface between the water and polyvinylchloride-2-nitrophenyloctylether gel layer is demonstrated. Since the transfer of hydrophilic anions including Br-, NO3-, I-, SCN- and ClO4- across the liquid/gel interface usually sets the potential window within a negative potential region, a highly hydrophobic organic electrolyte, tetraoctylammonium tetrakis(pentafluorophenyl)borate, providing a wider potential window was incorporated into the gel phase. The transfer reaction of perchlorate anions across the microhole-water/gel interface was first studied using cyclic voltammetry and differential pulse voltammetry. The full voltammetric response of perchlorate anion transfer was then used as a reference for evaluating the half-wave transfer potentials, the formal transfer potentials and the formal Gibbs transfer energies of more hydrophilic anions such as Br-, NO3-, I- and SCN-. The current response associated with the perchlorate anion transfer across the micro-water/gel interface versus the perchlorate concentration was also demonstrated for sensing applications

Voltammetric studies of hexachromic anion transfer reactions across micro-water/polyvinylchloride-2-nitrophenyloctylether gel interfaces for sensing applications

The transfer reactions of various anionic hexavalent chromium species across a polarized water/polyvinylchloride-2-nitrophenyloctylether (PVC-NPOE) interface featuring a 66 microhole array are described for the development of selective and sensitive Cr(VI) sensors. The transfer of hydrophilic hexachromic anions across a liquid/liquid interface typically involves setting the potential window in a negative region. Therefore, a highly hydrophobic tetraoctylammonium tetrakis(pentafluorophenyl)borate (TOATB) salt was synthesized and incorporated into the PVC-NPOE gel phase as an organic supporting electrolyte to provide a larger potential window at the negative end. The transfer of different hexachromic anions across the microhole array interface between the aqueous and PVC-NPOE gel phase containing TOATB was first characterized by voltammetric measurements. Since Cr(VI) ion species can hold different anionic forms such as Cr2O72-, HCrO4-, and CrO42- depending upon the pH and the Cr(VI) concentration, the effect of these two parameters on the cyclic voltammetry (CV) and differential pulse voltammetry (DPV) responses was also investigated. In order to utilize the ion transfer reaction across the microhole array interface for the selective and sensitive detection of Cr(VI) ions, the assisted transfer of HCrO4- anion by an Aliquat 336 ionophore incorporated into the PVC-NPOE gel phase was investigated using CV and differential pulse stripping voltammetry (DPSV). An excellent detection limit of 0.5 mu M (26 ppb) with a wide linear dynamic range extending from 0.5 mu M to 10 mu M was achieved. (c) 2012 Elsevier Ltd. All rights reserved

Ionic Liquids for Lignin Processing: Dissolution, Isolation, and Conversion

We present a review on the multifunctional use of ionic liquids with respect to lignin processing. In a biorefinery context, lignocellulosics could be used to provide sustainable sources of fuels such as bioethanol, and feedstock molecules for the chemical industry such as phenols and other aromatics. However, separation of lignin from cellulose and hemicellulose is a vital step. Ionic liquids can dissolve extensive quantities of biomass, and even be designed to be multifunctional solvents. We highlight the use of ionic liquids in selectively or non-selectively dissolving lignin, the depolymerization reactions that have been attempted on lignin in ionic liquids, and the effect ionic liquids have been observed to have on such processes. Finally, we present some of the challenges and issues that must be addressed before the informed and large-scale application of ionic liquids can be realized for lignin processing. </jats:p

Amperometric Detection of Parathion and Methyl Parathion with a Microhole-ITIES

An amperometric sensor featuring a microhole-liquid/gel interface for the detection of both parathion and methyl parathion is developed on the basis of their different kinetics behavior when interacting with the enzyme organophosphorus hydrolase (OPH). OPH hydrolyzes parathion and methyl parathion producing a common product of para-nitrophenol and either diethylthio- or dimethylthio- phosphoric acid, respectively, of which all can release protons depending upon their pKa values. The detection method for both organophosphate (OP) compounds is designed to measure the current associated with the transfer of protons released from the products of OPH hydrolysis across a polarized microhole-water/polyvinylchloride-nitrophenyloctylether (PVC-NOPE) gel interface. The selective transfer of protons across the interface is tailored by the use of a proton selective ligand, ETH 1778, in the gel layer. A disposable proton selective sensor that can quantitatively analyze the OP compounds is also fabricated using simple polydimethylsiloxane microfabrication. Cyclic voltammetry and differential pulse stripping voltammetry are first utilized to characterize the transfer of protons across the microhole-water/PVC-NPOE gel interface initiated by the OPH reaction with parathion and methyl parathion and to establish a detection limit for each OP compound. In order to sequentially detect parathion and methyl parathion using a single proton selective strip-sensor, a novel time-resolved detection methodology is developed based on the different catalytic kinetics of OPH with each OP analyte; the maximum peak current for the preconcentrated protons transferring back from the organic to water phase assisted by ETH 1778 increases proportionally to the concentration of each OP agent. Since the maximum peak currents for both OP analytes are observed at different reaction times it was possible to demonstrate the multiplexed analysis of both parathion and methyl parathion down to 0.5 mu M using a single sensor.X111817sciescopu

Pretreatment of Macadamia Nut Shells with Ionic Liquids Facilitates Both Mechanical Cracking and Enzymatic Hydrolysis

The effect of ionic liquids upon the mechanical and (bio)­chemical integrity of macadamia nut shells (from Macadamia integrifolia) has been investigated. Whole macadamia nuts-in-shell are notoriously difficult to crack, and the Australian macadamia nut shells used in this study required 2240 ± 430 N of force to crack. Ionic liquids were screened for their solubility values, with 1-ethyl-3-methylimidazolium acetate ([Emim]­[OAc]) able to dissolve 5.5 ± 0.5 wt % macadamia nut shell. Treatment with small quantities of [Emim]­[OAc] resulted in weakened whole nut-in-shells that could be cracked with only ca. 46% of the displacement (0.67 ± 0.16 mm), ca. 34% of the force (760 ± 240 N) and ca. 15% of the energy (0.25 ± 0.10 J per shell) relative to no treatment. Further treatment by dissolution and precipitation of macadamia nut shell, followed by enzymatic hydrolysis with cellulase, resulted in the release of 80 ± 15% of the expected glucose content, relative to 1.3 ± 1.0% before any pretreatment