Cationic Substituents Research Articles

Structural design of anthraquinone bridges in direct electron transfer of fructose dehydrogenase

Multi-functional small molecules attached to an electrode surface can bind non-covalently to the redox enzyme fructose dehydrogenase (FDH) to ensure efficient electrochemical electron transfer (ET) and electrocatalysis of the enzyme in both mediated (MET) and direct (DET) ET modes. The present work investigates the potential of exploiting secondary, electrostatic and hydrophobic interactions between substituents on a small molecular bridge and the local FDH surfaces. Such interactions ensure alignment of the enzyme in an orientation favourable for both MET and DET. We have used a group of novel synthesized anthraquinones as the small molecule bridge, functionalised with electrostatically neutral, anionic, or cationic substituents. Particularly, we investigated the immobilisation of FDH on a nanoporous gold (NPG) electrode decorated with the novel synthesised anthraquinones using electrochemical methods. The best DET-capable fraction out of four anthraquinone derivatives tested is achieved for an anthraquinone functionalised with an anionic sulphonate group. Our study demonstrates, how the combination of chemical design and bioelectrochemistry can be brought to control alignment of enzymes in productive orientations on electrodes, a paradigm for thiol modified surfaces in biosensors and bioelectronics.

Cu+ → Mn2+ Energy Transfer in Cu, Mn Coalloyed Cs3ZnCl5 Colloidal Nanocrystals.

In this work, we report the hot-injection synthesis of Cs3ZnCl5 colloidal nanocrystals (NCs) with tunable amounts of Cu+ and Mn2+ substituent cations. All the samples had a rodlike morphology, with a diameter of ∼14 nm and a length of ∼30–100 nm. Alloying did not alter the crystal structure of the host Cs3ZnCl5 NCs, and Cu ions were mainly introduced in the oxidation state +1 according to X-ray photoelectron and electron paramagnetic resonance spectroscopies. The spectroscopic analysis of unalloyed, Cu-alloyed, Mn-alloyed, and Cu, Mn coalloyed NCs indicated that (i) the Cs3ZnCl5 NCs have a large band gap of ∼5.35 eV; (ii) Cu(I) aliovalent alloying leads to an absorption shoulder/peak at ∼4.8 eV and cyan photoluminescence (PL) peaked at 2.50 eV; (iii) Mn(II) isovalent alloying leads to weak Mn PL, which intensifies remarkably in the coalloyed samples, prompted by an energy transfer (ET) process between the Cu and Mn centers, favored by the overlap between the lowest (6A1 → 4T1) transition for tetrahedrally coordinated Mn2+ and the PL profile from Cu(I) species in the Cs3ZnCl5 NCs. The efficiency of this ET process reaches a value of 61% for the sample with the highest extent of Mn alloying. The PL quantum yield (QY) values in these Cu, Mn coalloyed NCs are lower at higher Mn contents. The analysis of the Mn PL dynamics in these samples indicates that this PL drop stems from inter-Mn exciton migration, which increases the likelihood of trapping in defect sites, in agreement with previous studies.

Sulfate ionic liquids promoted FeCl3-catalyzed dehydration of propargyl alcohols

Conjugated enynes are an important class of compounds that could be widely used in medicinal chemistry and organic synthesis. Herein, various sulfate ionic liquids with FeCl3 were used to catalyze the dehydration of propargyl alcohols to prepare conjugated enynes. Sulfate ionic liquids with different substituent chain lengths or cations exhibited high catalytic activity, affording the highest conjugated enyne yield of 96 % with selectivity of 97 %. At the same time, the by-product naphthofuran derivative was isolated and verified by the single crystal X-ray diffraction for the first time. Kinetic studies found that the addition of sulfate ionic liquids increased the rate of formation of desired product conjugated enyne and inhibited the production of by-product naphthofuran derivative. Deuterated kinetic isotope studies were carried out by using the deuterated substrate PhCC(CD3)2OH and PhCC(CH3)2OD. A large value of H/D kinetic isotope effects (KIE1 = 5.5) suggested that the βC—H bond cleavage was involved in the rate-determining step and the formation of desired conjugated enyne followed the E2 elimination mechanism. An inverse kinetic isotope effects (KIE3 = 0.66) suggested that the formation of by-product naphthofuran derivative followed the SN2 mechanism. Density functional theory (DFT) calculations were conducted to reveal the activation of sulfate anion on the methyl group of propargyl alcohol. Based on the crystal structure of by-product, kinetic studies, deuterated kinetic isotope studies and DFT calculations, a cooperative mechanism of dehydration of propargyl alcohol over sulfate ionic liquids and FeCl3 was proposed.

Features of Crystallization of Indoline Spiropyran with a Cationic Substituent

Features of Crystallization of Indoline Spiropyran with a Cationic Substituent

Uncovering Activity-Stability Relationships in Mixed Ir-Based Catalysts Toward Improved Water Electrolysis

The role of proton exchange membrane water electrolysers (PEMWE) in providing clean and reliable green hydrogen is undeniable in a fully decarbonized energy system. Indeed, the ambitious “Hydrogen Shot” initiative by the U.S. DoE seeks to decrease in a decade green hydrogen pricing down to 1$/Kg H2.(1) Such endeavour will require a mass-scale implementation of PEMWEs, which is currently bottlenecked by the use of scarce precious metal catalysts, particularly at the anode where loadings of the state-of-the-art iridium (Ir) catalyst typically range between 1-3mgIr cm-2.(2) Thus, recent strategies in the literature have aimed to reduce Ir loading with several approaches such as higher catalyst dispersion and preparation of mixed metal oxides (IrxM1-xOy). The latter is particularly promising if the cation substituent M is an earth-abundant metal highly active to the oxygen evolution reaction (OER), which could lead to drastic catalyst cost reductions retaining high activities. The activity-stability relationships of various Ir phases are well-reported,(3) but hardly studied for IrxM1-xOy where any preferential dissolution of M under OER operation could result in misleading conclusions.The work presented here aims to bridge this knowledge gap by online quantification of catalyst dissolution products with our electrochemical flow cell coupled to inductively-coupled plasma mass spectrometry setup. First, we evaluated these relationships in cationic-substituted IrxM1-xO2 (100) epitaxial thin films, model systems which will allow us to clearly uncover any cation-dependent trends. It was observed that the Ir stability in such model systems directly correlated with the OER enhancement effect of the cation substituent: higher OER activities induced by the cation yielded lower Ir stabilities and vice versa. In addition, the IrO2 matrix does not seem to affect the thermodynamic dissolution trends of the cation M. In conjunction with ex-situ XPS characterization, we successfully identified two promising cation substituents considering the experimental activity-stability trends: Mo and W. Next, we moved to the industrially-promising IrxRu1-xO2 nanoparticle (NP) systems, with different relative compositions and degrees of crystallinity. Although Ru generally presents high dissolution rates under OER potentials, preliminary studies on sputtered thin films revealed a drastic stabilization of the RuO2 matrix upon incorporation of less than 20 at. % Ir.(4) The one-step synthetic approach used here, flame spray pyrolysis, allowed to easily tune the NPs Ir:Ru ratio by the relative content of the metal precursors in the pyrolized solution. Additionally, a post-calcination step enabled to convert the NPs phase from hydrous to rutile-type oxide. Using as start-up/shut-down OER protocol, we observed at 1000-fold lower stability for hydrous vs. rutile-type IrxRu1-xO2 regardless of the composition after selective Ru leaching. For rutile-type IrxRu1-xO2 nanoparticles, the sequential on/off OER operation revealed a ca. 10-fold decrease in Ru dissolution upon Ir incorporation, as well as the key role of surface Ru in OER activity.(5) Minimal Ru losses (<1 at. %) led to the formation of an Ir-rich protective shell, which for Ir0.2Ru0.8O2 resulted in an OER performance shift equivalent to that of pristine Ir0.8Ru0.2O2. These results showcase, contrary to previous reports, that Ru-rich compositions can indeed be implemented in PEMWE devices.

DFT modeling of indoline spiropyrans with a cationic substituent in the gas phase

Isomeric forms of indoline spiropyrans show unusual behavior compared with similar compounds, according to experimental data. DFT modeling for gas phase was made to consider the simplest case without environmental effects, which revealed the intramolecular reasons for occurrence of ring opening reaction depending on the particular structure of the compound. The questions of charge redistributions, the changes of geometry and chemical bonds in the structures are also discussed.

Interaction of 5-[4′-(N-Methyl-1,3-benzimidazol-2-yl)phenyl]-10,15,20-tri-(N-methyl-3′-pyridyl)porphyrin Triiodide with SARS-CoV-2 Spike Protein

The results of experimental studies of the interaction of the S-protein with a monohetaryl-substituted porphyrin containing a benzimidazole residue are presented. It has been revealed that the S-protein forms high-affinity complexes with the specified porphyrin. The porphyrin binding by the SARS-CoV-2 S-protein has proceeded stepwise; at the first stage, the driving force of the complexation is electrostatic interaction between the surface negatively charged regions of the protein and cationic substituents of the porphyrin. At the second stage, the target complex of the S-protein with the porphyrin is formed. It has been established that the introduction of 5-[4′-(N-methyl-1,3-benzimidazol-2-yl)phenyl]-10,15,20-tri-(N-methyl-3′-pyridyl)porphyrin triiodide into a solution of the S-protein complex with the angiotensin-converting enzyme leads to the replacement of the latter with the porphyrin. Displacement of the angiotensin-converting enzyme from the complex with the S-protein under the action of 5-[4′-(N-methyl-1,3-benzimidazol-2-yl)phenyl]-10,15,20-tri-(N-methyl-3′-pyridyl)porphyrin triiodide is the experimental evidence for the porphyrin binding at the receptor-binding domain of the S-protein.

Thermal and structural properties of sodium, potassium and carbonate doped strontium hydroxyfluorapatite

Ion-doping in hydroxyapatite bioceramics has attracted a lot of interest particularly for biomedical applications in repairing and replacing failure parts of musculoskeletal systems. Thus the multiple doping aims to mimic and resemble the chemical composition of the bone mineral component. Herein strontium hydroxyapatites bioceramics containing sodium Na+ and potassium K+ as cationic substituent and carbonate CO32− and fluoride as anionic substituent were synthesized and characterized by several analysis techniques. Therefore the chemical assays indicated that obtained compounds were less stoichiometric comparably to bone tissues. The X-ray diffraction diagrams and the infrared spectra revealed that pure phases of hydroxyfluorapatite containg the cited ions were obtained. The triple insertion of sodium, potassium and carbonate into the apatite structure leaded to the B-type carbonate apatite. The FE-SEM micrographs of the powders were formed by agglomerates. Moreover, the particles' morphology strongly depends on the ions nature and amount. The D-GTA curves indicated that the heating of the powders from the room temperature to 1000 °C didn't affect the structural and thermal stability of the materials apart from a partial decomposition of the apatite inducing the formation of the β-tristrontium phosphate phase and enhancing the biomaterial character of the materials.

Partitioning of Ti, Al, P, and Cr between olivine and a tholeiitic basaltic melt: Insights on olivine zoning patterns and cation substitution reactions under variable cooling rate conditions

The mechanism governing the kinetic growth of olivine in dynamic volcanic settings has been the subject of considerable attention in recent years. Under variable cooling rate (CR) and undercooling (−ΔT) regimes, the textual maturation of olivine proceeds from skeletal/dendritic crystals to polyhedral morphologies by infilling of the crystal framework. Owing to the establishment of a diffusion-controlled growth regime, a sharp diffusive boundary layer develops in the melt next to the advancing olivine surface. In this context, we have quantified the apparent partitioning of Ti, Al, P, and Cr between olivine and a Hawaiian tholeiitic basaltic melt at P = 1 atm, fO2 = QFM-2 buffer, and CR = 4, 20, and 60 °C/h over a constant -ΔT = 85 °C. Differences in charge and/or size between the substituent minor cations and the major species in the olivine crystallographic site dominate the energetics of homovalent and heterovalent cation substitutions. While the entry of Ti in the olivine lattice site accounts for the simple exchange [TSi4+] ↔ [TTi4+], more complex charge-balancing coupled-substitution mechanisms have been determined for the incorporation of Al, P, and Cr, i.e., [MMg2+, TSi4+] ↔ [MAl3+, TAl3+], [2 TSi4+] ↔ [TP5+, TAl3+], and [MMg2+, TSi4+] ↔ [MCr3+, TAl3+], respectively. In order to maintain charge balance, the disequilibrium uptake of minor cations in rapidly growing crystals is controlled by the same substitution mechanisms observed under equilibrium crystallization. This finding is consistent with the achievement of a local interface equilibrium at the olivine-melt interface independently of the diffusive boundary in the melt. A statistical approach based on multivariate analysis of olivine/melt compositional parameters confirms that the control of melt structure on the partitioning of Ti, Al, P, and Cr is almost entirely embodied in the olivine structure and chemistry via charge compensation reactions. Therefore, the magnitude of minor element partition coefficients is weakly dependent on diffusion kinetics in the melt but rather strongly governed by olivine zoning patterns resulting from fast crystal growth rates.

A multifunctional strontium/silver-co-substituted hydroxyapatite derived from biogenic source as antibacterial biomaterial

The bioactive properties of hydroxyapatite (HAp) facilitate bone regeneration, however, its physico-chemical and bioactive properties can be further enhanced by ionic substitutions within the crystalline lattice. In this work, substitution with Sr2+ and Ag+ ions was investigated for the improvement of osseointegration and antibacterial activity in potential treatment of traumatic bone injuries. A series of single substituted HAp with Sr2+ or Ag+ ions and Ag/Sr-co-substituted HAp with different degrees of substitution (0, 1, 2.5, and 5 mol%) were obtained by wet precipitation from cuttlefish bone. Rietveld refinement indicated successful Ca2+ substitution by increasing cell parameters due to the larger ionic radii of Sr2+ and Ag+ compared to Ca2+, which was confirmed by elemental mapping showing uniform distribution of substituent cations. Characterization of the zeta-potential of Ag/Sr-co-substituted HAp showed negatively charged populations, at potentials not lower than −15 mV. Increasing the degree of substitution resulted in decreasing zeta-potential. The higher absorption capacity of bovine serum albumin was determined on Ag/Sr-co-substituted HAp powders as compared to non-substituted HAp. All Ag-substituted HAps have shown an antibacterial activity towards Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli, as determined by inhibition zone, viability analysis and scanning electron microscopy. In addition, non-cytotoxicity towards human cells was confirmed by in vitro tests with embryonic kidney 293 and mesenchymal stem cells.

Charged groups on pyropheophorbide-based photosensitizers dictate uptake by tumor cells and photodynamic therapy efficacy.

This study investigated the impact of anionic and cationic substituents of the pyropheophorbide-based photosensitizers (PS) on uptake and retention by tumor epithelial cells and photodynamic therapy (PDT). A series of PSs were generated that bear carboxylic acid functionalities, alkyl amines with variable length of carbon units or as a quaternary ammonium salt introduced at position 172 of 3-(1'-hexyloxy)ethyl-3-devinylpyropheophorbide-a (HPPH). The nature of the functionalities in the macrocycle made a significant difference in overall lipophilicity (log D values at pH7.4), and in binding to and retention by human and murine tumor cells. Depending on the presence of functional groups, the PSs showed a change in cellular uptake from diffusion to endocytosis and in the preference for subcellular localization to mitochondria/ER or lysosomes. Two and more carboxylic groups drastically reduced uptake by all cell types. In contrast, PSs with amine and quaternary amine salt showed higher cellular binding, uptake and in vitro PDT efficacy than HPPH. The enhanced cellular uptake of the cationic PSs was accompanied by a loss of tumor cell specificity and contributed to severe systemic toxicity in tumor-bearing mice intravenously injected with the PS and subjected to investigate their therapeutic potential.

Effect of chemical substituents attached to the zwitterion cation on dielectric constant.

Materials with high dielectric constant, εs, are desirable in a wide range of applications including energy storage and actuators. Recently, zwitterionic liquids have been reported to have the largest εs of any liquid and, thus, have the potential to replace inorganic fillers to modulate the material εs. Although the large εs for zwitterionic liquids is attributed to their large molecular dipole, the role of chemical substituents attached to the zwitterion cation on εs is not fully understood, which is necessary to enhance the performance of soft energy materials. Here, we report the impact of zwitterionic liquid cation chemical substituents on εs (50 < εs < 300 at room temperature). Dielectric relaxation spectroscopy reveals that molecular reorientation is the main contributor to the high εs. The low Kirkwood factor g calculated for zwitterionic liquids (e.g., 0.1-0.2) suggests the tendency for the antiparallel zwitterion dipole alignment expected from the strong electrostatic intermolecular interactions. With octyl cation substituents, the g is decreased due to the formation of hydrophobic-rich domains that restrict molecular reorientation under applied electric fields. In contrast, when zwitterion cations are functionalized with ethylene oxide (EO) segments, g increases due to the EO segments interacting with the cations, allowing more zwitterion rotation in response to the applied field. The reported results suggest that high εs zwitterionic liquids require a large molecular dipole, compositionally homogeneous liquids (e.g., no aggregation), a maximized zwitterion number density, and a high g, which is achievable by incorporating polar chemical substituents onto the zwitterion cations.

Origin of Relaxor Behavior in Barium‐Titanate‐Based Lead‐Free Perovskites

AbstractIt is well known that disordered relaxor ferroelectrics exhibit local polar correlations. The origin of localized fields that disrupt long‐range polar order for different substitution types, however, is unclear. Currently, it is known that substituents of the same valence as Ti4+ at the B‐site of barium titanate lattice produce random disruption of TiOTi chains that induces relaxor behavior. On the other hand, investigating lattice disruption and relaxor behavior resulting from substituents of different valence at the B‐site is more complex due to the simultaneous occurrence of charge imbalances and displacements of the substituent cation. The existence of an effective charge mediated mechanism for relaxor behavior appearing at low (&lt;10%) substituent contents in heterovalent modified barium titanate ceramics is presented in this work. These results will add credits to the current understanding of relaxor behavior in chemically modified ferroelectric materials and also acknowledge the critical role of defects (such as cation vacancies) in lattice disruption, paving the way for chemistry‐based materials design in the field of dielectric and energy storage applications.

Oxidative Thermal Conversion of Hydrothermal Derived Precursors toward the Mixed-Metal Cobaltite Spinel Oxides (ZnCo2O4 and NiCo2O4): In-Situ Investigation by Synchrotron-Radiation XRD and XAS Techniques

In-situ investigations of structural transitions during the thermal-oxidative event of mixed-metal spinel oxide precursors, the so-called nickel- (NCO) and zinc-containing (ZCO) cobaltite spinel precursors, were investigated to understand the formations of the derived NiCo2O4 and ZnCo2O4 spinel oxides, respectively. In-situ XRD investigation revealed that emerged temperatures for spinel oxide phase were between 325 and 400 °C, depending on the cationic substituent. It indicated that the emerged temperature correlated with the absolute octahedral site preference energy (OSPE) of those cations that participated in the development of the spinel framework. Moreover, the incorporated nickel and zinc in the precursors was beneficial for inhibiting the occurrence of the undesired CoO phase. Time-resolved X-ray absorption spectroscopic (TRXAS) data suggested the local structure rearrangement of nickel and zinc throughout the calcination process, which differed from the behavior of single-metal cobalt system. The essential information reported herein provides a benefit to control the cationic distribution within spinel materials, leading to the tunable physical and chemical properties.

Thermal stability of ionic liquids in nitrogen and air environments

Ionic liquids (ILs) are being developed and studied for a variety of high-temperature applications, including as solvents for separations (where thermal regeneration is used) and as heat transfer fluids. Dynamic decomposition information has been reported for numerous ILs in the literature at various ramp rates. Although this information is useful for assessing how different characteristics, such as cation substituent groups or choice of anion, affect the decomposition of the ILs, dynamic decomposition temperature may overestimate the thermal stability of these compounds. Isothermal decomposition data is necessary when developing ILs in order to truly evaluate their thermal stability for high-temperature applications. However, this information is lacking for many ILs. In this study, we provide both fast (10 K/min) and slow (2 K/min) dynamic decomposition data, as well as isothermal decomposition data at five temperatures from 513.15 to 593.15 K for a selection of seventeen imidazolium, pyridinium, and tetraalkylammonium ILs and from 373.15 to 473.15 K for eight tetraalkylphosphonium ILs. There is significant mass loss after 16 h for most ILs even at 100 K below the decomposition temperature determined from dynamic measurements. Most ILs with the bis(trifluoromethylsulfonyl)imide anion ([Tf2N]−) show zero order mass loss, indicating that the mass loss is actually by evaporation rather than decomposition. Aminopyridinium ILs with [Tf2N]− are particularly thermally stable. We also compare isothermal decomposition rates for ILs under inert (N2) versus oxidative (air) gaseous environments. The mass loss activation energies are lower in air, suggesting more decomposition (vs. evaporation) in air. Mass spectrometry confirms that nucleophilic substitution is the main decomposition mechanism for most ILs in N2, but β-elimination also occurs for the tetra-alkylphosphonium ILs.

Structurally tunable characteristics of ionic liquids for optimizing lithium plating/stripping via electrolyte engineering

Electrolyte chemistry offers the opportunity to regulate the solid electrolyte interphase (SEI) and Li+ solvation, which is considered to be crucial to the growth of lithium crystals for safe lithium metal batteries (LMBs). Structurally tunable characteristics of ionic liquids (ILs) from anion type, cationic substituent chain length and cationic substituents, will contribute this field. Here, we explore the influence mechanism of imidazole-based ILs as electrolyte additives on Li+ solvation and the formation of SEI. ILs can participate into the formation of efficient SEI, together with cathode electrolyte interphase (CEI). Moreover, ILs can also regulate the sheath structure of Li+ solvation, to fasten the kinetics of Li. Furthermore, the imidazole-based cations with long alkyl chain can form an electrostatic shield around newly formed Li nucleus, and suppress further Li plating at this site. Under the optimized condition, the 1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([OMIm]TFSI) additive shows the best ability to enhance the electrochemical performance, endowing the Li||Li symmetric cell with a stable life (over 800 h) at 0.5 mA cm−2 and the Li||LiNi0.6Mn0.2Co0.2O2 (NMC622) full cell with a high capacity of 141.7 mAh g−1 after 200 cycles at 0.5 C.

Salinity durable self-healing hydrogels as functional biomimetic systems based on the intercalation of polymer ions into mica

Self-healing hydrogels were prepared in water via the intercalation of cationic substituents of polymer chains into the interlayers of mica, a layered inorganic compound. The obtained materials showed high tolerance to various environmental conditions, whereas their self-healing properties were not affected even under high salinity conditions. Since the human body contains high salt concentrations, the enhanced mechanical strength and durability of the prepared self-healing hydrogels under these conditions can be exploited for their application as artificial biomaterials, including skins, muscles, and cartilages, to heal injuries similarly as the human body.

Supramolecular exfoliation of layer silicate clay by novel cationic pillar[5]arene intercalants

Clays are multi-layered inorganic materials that can be used to prepare nanocomposite fillers. Because the multi-layered structure is thermodynamically stable, it is difficult to change a multi-layered material into single layers to improve its dispersity. Previously, clays were modified with dodecylammonium cations to promote complexation with nylon 6, nylon 66, polypropylene, polyethylene, polystyrene, and polycaprolactone to increase the mechanical strength (and/or thermal stability) of the composite material; however, complete exfoliation could not be achieved in these composites. In this study, pillar[5]arenes are synthesized and functionalized with ten cationic substituents as novel intercalants for modifying bentonite clay, which is a multi-layered metal-cation-containing silicate. The pillar[5]arenes exfoliate the clay by forming polyrotaxanes with poly(ethylene glycol) through host–guest interactions.

Control of retention mechanisms on an octadecyl-bonded silica column using ionic liquid-based mobile phase in analysis of cytostatic drugs by liquid chromatography

This study assesses the potential of using ionic liquids (ILs) as mobile phase additives to control the retention mechanism of four cytostatic drugs: doxorubicin hydrochloride (DOX), epirubicin hydrochloride (EPI), daunorubicin hydrochloride (DAU) and idarubicin hydrochloride (IDA). Chromatographic separations were performed on a C18 analytical column (Discovery C18 150 × 4.6 mm, 5 µm) using six IL anions and four methyl-substituted IL cations with different alkyl chain lengths (alone or with the additional methyl group on the aromatic ring), or with an allyl group added as a cationic substituent. Thus, a total of 17 different ILs were assessed. The aqueous formic acid solution and phosphate buffer were used to compare how mobile phase composition affected the behavior of the analyzed cytostatic agents in the presence of ILs. In addition, the impacts of IL concentration, phosphate buffer concentration, and phosphate buffer pH on the final results were also considered. The ability to change analyte retention without negatively impacting peak shape or analytical efficiency was also controlled via the tailing factor and number of theoretical plates. Based on the results, the tested ILs were classified as either effective or ineffective mobile phase additives for separation of anthracyclines and identification by LC-FL technique.

The Carbonate and Sodium Environments in Precipitated and Biomimetic Calcium Hydroxy-Carbonate Apatite Contrasted with Bone Mineral: Structural Insights from Solid-State NMR

Bone mineral consists of calcium hydroxy-carbonate apatite (HCA) that incorporates other minor cation substituents, primarily Na+ (0.5–0.8 wt %). We examine the carbonate species in various HCA spe...