Ion transfer and adsorption behavior of ionizable drugs affected by PAMAM dendrimers at the water|1,2- dichloroethane interface

Detection of perfluorooctane sulfonate by ion-transfer stripping voltammetry at an array of microinterfaces between two immiscible electrolyte solutions

Per- and polyfluoroalkyl substances (PFAS) are a category of persistent environmental contaminants that have been linked to health issues in humans. In this work, we investigate the detection of perfluorooctanesulfonate (PFOS-), one such PFAS, by ion-transfer voltammetry at an array of microinterfaces between two immiscible electrolyte solutions (μITIES). Cyclic voltammetry, differential pulse voltammetry and differential pulse stripping voltammetry (DPSV) indicated the ion-transfer behaviour and detection of PFOS-, with the latter enabling detection at picomolar concentrations. Using a 5 min preconcentration time, during which PFOS- was preconcentrated into the organic phase of the μITIES array, a limit of detection (LOD) of 0.03 nM (0.015 μg L-1) in aqueous electrolyte was achieved. This performance is attributed to the enhanced mass transport (radial diffusion) to the μITIES that occurs during preconcentration. To investigate the potentiality for applications of this analytical approach to environmental samples, measurements in a range of water matrices were investigated. Drinking water, laboratory tap water and seawater matrices were assessed by spiking with PFOS- over the 0.1-1 nM range. A matrix effect was observed, with changes in sensitivity and LOD relative to those in pure aqueous electrolyte solutions. Such matrix effects need to be considered in designing applications of these PFOS- measurements to environmental samples. The results presented here indicate that DPSV at a μITIES array can form the basis for a fast and sensitive screening method for PFOS- contamination that is suited to portable and on-site applications.

Novel Chemical Cross-Linked Ionogel Based on Acrylate Terminated Hyperbranched Polymer with Superior Ionic Conductivity for High Performance Lithium-Ion Batteries

A new family of chemical cross-linked ionogel is successfully synthesized by photopolymerization of hyperbranched aliphatic polyester with acrylate terminal groups in an ionic liquid of 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF₄). The microstructure, viscoelastic behavior, mechanical property thermal stability, and ionic conductivities of the ionogels are investigated systematically. The ionogels exhibit high mechanical strength (up to 1.6 MPa) and high mechanical stability even at temperatures up to 200 °C. It is found to be thermally stable up to 371.3 °C and electrochemically stable above 4.3 V. The obtained ionogels show superior ionic conductivity over a wide temperature range (from 1.2 × 10^-3 S cm^-1 at 20 °C up to 5.0 × 10^-2 S cm^-1 at 120 °C). Moreover, the Li/LiFePO₄ batteries based on ionogel electrolyte with LiBF₄ show a higher specific capacity of 153.1 mAhg^-1 and retain 98.1% after 100 cycles, exhibiting very stable charge/discharge behavior with good cycle performance. This work provides a new method for fabrication of novel advanced gel polymer electrolytes for applications in lithium-ion batteries.

Wide pH range enantioseparation of cyclodextrin silica-based hybrid spheres for high performance liquid chromatography

pH plays an important role in the enantiomeric separation process by changing the polarity of the mobile phase and the conformation and ionization state of the enantiomers. Herein, β-cyclodextrin-silica hybrid spheres with n-propyl groups as hydrophobic linkers and ethyl-silica as a support were prepared using a one-pot approach, and then the hydroxyl group was further modified with 3,5-dimethylphenyl isocyanate. The new β-cyclodextrin-silica hybrid chiral stationary phase (CD-HCSP) was prepared and characterized using techniques including scanning electron microscopy and transmission electron microscopy. The enantioseparation properties of CD-HCSP were evaluated with different solvents over a wide pH range (1-10) in reversed phase. 14 enantiomers were successfully resolved, and favorable chiral resolution and high stability was demonstrated for multiple types of enantiomer under different pH conditions. Compared with commercial columns, CD-HCSP showed better chiral resolution and, more importantly, could be used for chiral resolution over a wide pH range. This work combines the high pH tolerance of the hybrid material and excellent chiral recognition of cyclodextrin for enantioseparation of chiral drugs, which could lead to the development of a new type of chiral separation material.

Mechanistic Analysis of Ion Association between Dendrigraft Poly-l-lysine and 8-Anilino-1-naphthalenesulfonate at Liquid|Liquid Interfaces

Molecular association between biocompatible dendritic polymers, dendrigraft poly-l-lysines (DGLs), and an anionic fluorescent probe, 8-anilino-1-naphthalenesulfonate (ANS^-), was studied at the polarized water|1,2-dichloroethane (DCE) interface. The fluorescence intensity of ANS measured in aqueous solution was enhanced by the coexistence of DGLs over a wide pH range (2 < pH < 10), where ANS and DGL exist as a monoanionic form and a polycation, respectively. The voltammetric responses indicated that the positively charged DGLs were adsorbed at the water|DCE interface, whereas ANS^- was transferred across the interface accompanied by the adsorption process. The interfacial behavior of the DGL-ANS associates was analyzed by potential-modulated fluorescence (PMF) spectroscopy. The PMF results demonstrated that the ion association between DGLs and ANS at the water|DCE interface is strongly affected by the applied potential and the dendritic generation of DGL. By applying appropriate potentials, the ANS anion was dissociated from its ion associate with DGLs at the interface and transferred into the organic phase, whereas DGLs remained in the aqueous phase. The Gibbs free energy of ion association (Δ G_D···ANS) was estimated for the second-fourth generation DGLs (DGL-G2-G4) and the G4 polyamidoamine (PAMAM) dendrimer as a control. The highest stability of the DGL-G4-ANS associate manifested itself through Δ G_D···ANS: DGL-G4-ANS (>G4 PAMAM dendrimer-ANS) > DGL-G3-ANS > DGL-G2-ANS. The results elucidated the efficient anion-binding ability of higher generation DGLs and its potential dependence at the liquid|liquid interface.

Theoretical Treatment of Ion Transfers in Two Polarizable Interface Systems When the Analyte Has Access to Both Interfaces

A new theory is presented to tackle the study of transfer processes of hydrophilic ions in two polarizable interface systems when the analyte is initially present in both aqueous phases. The treatment is applied to macrointerfaces (linear diffusion) and microholes (highly convergent diffusion), obtaining analytical equations for the current response in any voltammetric technique. The novel equations predict two signals in the current-potential curves that are symmetric when the compositions of the aqueous phases are identical while asymmetries appear otherwise. The theoretical results show good agreement with the experimental behavior of the "double transfer voltammograms" reported by Dryfe et al. in cyclic voltammetry (CV) ( Anal. Chem. 2014 , 86 , 435 - 442 ) as well as with cyclic square wave voltammetry (cSWV) experiments performed in the current work. The theoretical treatment is also extended to the situation where the target ion is lipophilic and initially present in the organic phase. The theory predicts an opposite effect of the lipophilicity of the ion on the shape of the voltammograms, which is validated experimentally via both CV and cSWV. For the above two cases, simple and manageable expressions and diagnosis criteria are derived for the qualitative and quantitative study of ion lipophilicity. The ion-transfer potentials can be easily quantified from the separation between the two signals making use of explicit analytical equations.

Characterization of inclusion complexes of organic ions with hydrophilic hosts by ion transfer voltammetry with solvent polymeric membranes

The quantitative characterization of inclusion complexes formed in aqueous phase between organic ions and hydrophilic hosts by ion-transfer voltammetry with solvent polymeric membrane ion sensors is studied, both in a theoretical and experimental way. Simple analytical solutions are presented for the determination of the binding constant of the complex from the variation with the host concentration of the electrochemical signal. These solutions are valid for any voltammetric technique and for solvent polymeric membrane ion sensors comprising one polarisable interface (1PI) and also, for the first time, two polarisable interfaces (2PIs). Suitable experimental conditions and data analysis procedures are discussed and applied to the study of the interactions of a common ionic liquid cation (1-octyl-3-metyl-imidazolium) and an ionisable drug (clomipramine) with two hydrophilic cyclodextrins: α-cyclodextrin and 2-hydroxypropyl-β-cyclodextrin. The experimental study is performed via square wave voltammetry with 2PIs and 1PI solvent polymeric membranes and in both cases the electrochemical experiments enable the detection of inclusion complexes and the determination of the corresponding binding constant.