Acidic Aqueous Solution Research Articles

The retention features of nitrogen-containing heterocyclic compounds in reversed-phase and hydrophilic HPLC-MS modes

Aromatic five- and six-membered nitrogen-containing heterocyclic compounds are biologically active substances and are widely used in biochemistry and medicine. In addition, such compounds are known as ecotoxicants formed during oxidation processes in industrial wastewater. High-performance liquid chromatography-mass spectrometry is widely used to determine nitrogen-containing heterocycles in various complex mixtures. Octadecyl silica gel is the main sorbent for chromatographic separation. However, octadecyl silica gel does not always enable satisfactory separation in the presence of highly polar isomeric molecules, and more selective chromatographic approaches are required. One of these is hydrophilic chromatography, which facilitates the separation of polar compounds. The aim of the study was to comparatively characterize the retention of a number of five- and six-membered nitrogen-containing heterocyclic compounds during reversed-phase and hydrophilic liquid chromatography with mass spectrometric detection. In addition, spectrophotometric detection at a wavelength of 210 nm was carried out. In the study, we used sorbents based on octadecyl silica gel and unmodified silica gel. High-resolution mass spectrometry was used in the electrospray ionization mode. We studied 19 nitrogen-containing heterocyclic compounds. We used aqueous acetonitrile mobile phases with added aqueous solutions of formic acid and diethylamine as acid-base modifiers. An ammonium formate solution was used as a modifier during hydrophilic chromatography. Reversed-phase chromatography showed that the introduction of 0.1% aqueous formic acid solution increased the ionization and the mass spectrometer signal intensity, but did not always result in a satisfactory separation of isomers upon elution from the octadecyl silica gel surface. The introduction of 0.01% diethylamine solution provided no significant improvement in the separation compared to the mobile phase without modifiers. The use of unmodified silica gel in hydrophilic chromatography mode allowed us to separate isomeric five-membered heterocycles, which was demonstrated by narrow symmetric peaks, but did not result in selective separation of isomeric diazines. Thus, we studied the retention of 19 nitrogen-containing heterocyclic compounds using reversed-phase and hydrophilic liquid chromatography with electrospray ionisation. It was determined that hydrophilic chromatography on unmodified silica gel could be used for satisfactory separation of isomeric five-membered heterocyclic compounds of different classes. For six-membered heterocycles, satisfactory separation was achieved by elution from the surface of octadecyl silica gel using aqueous acetonitrile mobile phase without modifiers.

Simultaneous estimation of rutin and donepezil through RP-HPLC: implication in pharmaceutical and biological samples.

Aim: AHPLC method was developed and validated for the novel combination of rutin (RN) and donepezil (DNP). Materials & methods: RN and DNP were simultaneously eluted through a C18 column (Ø 150×4.6mm) with a 60:40 v/v ratio of 0.1% formic acid aqueous solution to methanol at 0.5ml/min. Results: The purposed method was found linear, selective, reproducible, accurate and precise with percent RSD less than 2. The limit of quantification for RN and DNP was found 3.66 and 3.25μg/ml, respectively. Conclusion: Validated as per the ICH guidelines, the developed method efficiently quantified RN and DNP co-loaded in DQAsomes (121nm) estimating matrix effect, release profile, entrapment efficiency, loading efficiency and in vivo plasma kinetics.

Microfluidic Chip Coupled with MALDI-TOF MS for Multitarget Detection of Allergens in Crucian Carp (Carassius auratus).

The goal of the present study was to establish a rapid, simple method for simultaneous allergy testing of sera from multiple fish-allergic patients. Sera from fish-allergic patients were pooled and used for capturing allergens in fish muscle of crucian carp (Carassius auratus), which was studied as a fish model. Sarcoplasmic proteins of crucian carp (Carassius auratus) were extracted for the analysis of allergens. Anti-human IgE antibody-functionalized magnetic beads were utilized to collect IgE antibodies from human pooled sera. The isolation of allergenic proteins was immunomagnetically performed in microfluidic channels, and the elution of the captured allergenic proteins was done with 5% (v/v) acetic acid aqueous solution. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and peptide mass fingerprinting were used for the analysis of tryptic digests of eluted proteins. Ten potential allergenic proteins were identified from crucian carp (Carassius auratus). The present protocol provides a rapid, efficient, and simple method for simultaneous detection of multiple allergens, based on multitargeted antibodies from pooled sera of allergic patients. The constructed multiple antibody-modified MBs can be applied for the deallergenicity of food matrices. The efficiency of allergen detection can be greatly improved, with promising application in allergen discovery and filtration for other muscle-based foods.

Molecular Dynamic Simulation of the Interaction of a Deep Eutectic Solvent Based on Tetraethylammonium Bromide with La3+ in Acidic Media

In recent years, noticeable progress has been made in the development of alternative extraction systems characterized by greater sustainability. In this context, deep eutectic solvents (DESs) have emerged as a promising alternative to the conventional solvents commonly used in metal extraction. This work focuses on investigating the extraction of lanthanum in an aqueous solution of sulfuric acid using a deep eutectic solvent, employing molecular dynamics simulations (MD). The structural characteristics of the solvent and its interactions with the components of the aqueous solution are explored. In this study, tetraethylammonium bromide (TEABr) is combined with ethylene glycol (EG) to form a DES, in which sodium cyanide (NaCN) is subsequently solubilized. According to the results obtained from the MD simulation, the primary interactions in the DESs are established through hydrogen bonds between the bromine and the hydrogens of the methyl group of tetraethylammonium at 3.5 Å, as well as between the bromine and the hydrogens of the methylene group of ethylene glycol at 3.5 Å. Similarly, the main interactions between the binary DES and sodium cyanide occur through the hydrogens of the hydroxyl group of EG and the carbon of cyanide at 1.7 Å, and between the oxygen of the hydroxyl group of EG and the sodium at 2.5 Å. In the acidic solution, the primary interaction is highlighted between the lanthanum ion and the oxygen of the bisulfate at 2.8 Å. Additionally, it is observed that the interaction between the DES and the aqueous solution occurs between the lanthanum and the oxygen of the hydroxyl group of EG, as well as between the lanthanum and the carbon of cyanide at 4.4 Å. It is important to note that, when increasing the temperature from 25 to 80 °C, the interaction distance between the lanthanum and the carbon of cyanide decreases to 2.4 Å, suggesting a possible correlation with the increase in lanthanum extraction, as experimentally observed. Overall, this study underscores the importance of considering the fundamental structural interactions of the DES with the lanthanum acid solution, providing an essential theoretical basis for future experimental investigations.

Highly Compressible, Superabsorbent, and Biocompatible Hybrid Cryogel Constructs Comprising Functionalized Chitosan and St. John's Wort Extract.

Biobased porous hydrogels enriched with phytocompounds-rich herbal extracts have aroused great interest in recent years, especially in healthcare. In this study, new macroporous hybrid cryogel constructs comprising thiourea-containing chitosan (CSTU) derivative and a Hypericum perforatum L. extract (HYPE), commonly known as St John's wort, were prepared by a facile one-pot ice-templating strategy. Benefiting from the strong interactions between the functional groups of the CSTU matrix and those of polyphenols in HYPE, the hybrid cryogels possess excellent liquid absorption capacity, mechanical resilience, antioxidant performance, and a broad spectrum of antibacterial activity simultaneously. Thus, owing to their design, the hybrid constructs exhibit an interconnected porous architecture with the ability to absorb over 33 and 136 times their dry weight, respectively, when contacted with a phosphate buffer solution (pH 7.4) and an acidic aqueous solution (pH 2). These cryogel constructs have extremely high compressive strengths ranging from 839 to 1045 kPa and withstand elevated strains of over 70% without developing fractures. Moreover, the water-swollen hybrid cryogels with the highest HYPE content revealed a complete and instant shape recovery after uniaxial compression. The incorporation of HYPE into CSTU cryogels enabled substantial improvement in scavenging reactive oxygen species and an expanded antibacterial spectrum toward multiple pathogens, including Gram-positive bacteria (Staphylococcus aureus and Staphylococcus epidermidis), Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa), and fungi (Candida albicans). Cell viability experiments demonstrated the cytocompatibility of the 3D cryogel constructs, which did not induce changes in the fibroblast morphology. This work showcases a simple and effective strategy to immobilize HYPE extracts on CSTU 3D networks, allowing the development of novel multifunctional platforms with promising potential in hemostasis, wound dressing, and dermal regeneration scaffolds.

Methanol electrooxidation performance of nickel-modified polyaniline thin films for direct methanol fuel cells

A metal–organic composite thin film composed of polyaniline (PANI) and Ni was prepared and characterized for methanol electrooxidation reaction. First, PANI thin films were electrodeposited on a fluorine-doped tin oxide (FTO) coated glass support in an aqueous acidic solution. Subsequently, the polymer film was modified with Ni particles (FTO/PANI-Ni) by chronoamperometric (CA) technique. The composite film was characterized by structural, morphological and electrocatalytic analyses. X-ray diffraction (XRD) results confirmed the crystallization of Ni according to the cubic structure. Scanning electron microscopy (SEM) images showed that the Ni nanoparticles were uniformly dispersed on the PANI surface. The electrocatalytic performance of the FTO/PANI-Ni composite electrode for the methanol electrooxidation reaction was investigated in 0.5 M KOH solution containing methanol using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and chronoamperometry (CA) techniques. The effects of temperature and methanol concentration on the methanol electrooxidation performance were also studied. The modified composite catalyst exhibited an electrochemically active surface area of 0.5235 cm2. The presence of Ni nanoparticles on the polymer surface promoted the adsorption of methanol molecules and facilitated the oxidation process, leading to higher current densities and better overall performance. The maximum current density was 14 mA cm-2 and the electrode maintain 68 % of its initial activity even after 200 cycles, indicating that the FTO/PANI-Ni electrode exhibited good stability. The high methanol oxidation performance of the composite electrode was associated with large real surface area, a possible synergistic effect between the polymer moleucles and Ni particles as well as high intrinsic activity of Ni for this process.

Electromembrane Extraction of Ofloxacin from Human Plasma and Its Quantification by Capillary Electrophoresis

Background: Application of electromembrane extraction coupled with capillary electrophoresis was studied for ofloxacin extraction from plasma samples. Methods: Ofloxacin migrated from acidic plasma samples through a thin layer of 1-octanol immobilized in the pores of a porous hollow fiber wall into a 10 µL acidic aqueous acceptor solution located inside the lumen of the fiber. Results: Under optimum conditions influencing electromigration (i.e., 20 min of the operation time, stirring speed of 750 rpm, donor phase pH at 4.0, acceptor pH at 3.0, and applied voltage of 30 V across the supported liquid membrane), ofloxacin was extracted from plasma samples with an enrichment factor of 100-fold corresponding to extraction percent of 24%. The calibration curve showed acceptable linearity in the range of 0.2-7.0 µg.mL-1 (R=0.9993). The limits of detection and quantification of 0.05 and 0.2 µg.mL-1 were obtained, respectively. The inter- and intra-day precision and accuracy were obtained below 8.65%. Conclusion: The validated method was successfully processed for the ofloxacin determination in the plasma samples of patients under ofloxacin therapy. There were no interfering peaks which indicates the great selectivity of the developed method.

Formation of zinc carbonate phases on dissolving calcite, aragonite, and vaterite in acidic aqueous solutions

Calcium carbonate (CaCO3) minerals serve as a major sink to retain metal ions through mineral-water interfacial reactions in which the capacity and long-term stability of contaminant uptake are influenced by coupled dissolution and precipitation reactions of both primary and secondary carbonate minerals (i.e., mineral replacement). Notably, recent studies of calcite reactivity in acidic solutions containing high levels of metal ions demonstrated complex behavior under conditions of sustained disequilibrium. We explored the reactivity of three CaCO3 polymorphs (calcite, aragonite, and vaterite) with acidic Zn2+-containing aqueous solutions using a suite of imaging techniques including optical and scanning electron microscopies, synchrotron-based micro X-ray fluorescence, and transmission X-ray microscopy. Zn uptake by calcite occurred through a two-step process: the formation of a thin layer of the zinc precipitate on the substrate surface followed by the growth of fibrous and radiating hydrozincite particles from the layer. In contrast, Zn uptake by aragonite occurred by mineral replacement where the secondary Zn carbonate phase preserved the external morphology of the original crystal (i.e., a pseudomorph). The replacement of vaterite by hydrozincite occurred within the confined space beneath the porous shell of vaterite, signifying that the primary mechanism driving Zn carbonate precipitation was chemical exchange through the pores. When multiple CaCO3 polymorphs coexisted, the replacement of aragonite and vaterite occurred preferentially over that of calcite. These results demonstrate the distinct morphological and mineralogical controls over the reactivities of calcium carbonate minerals with Zn2+ under acidic conditions.

CeO2-CuO composites prepared via supercritical antisolvent precipitation for photocatalytic hydrogen production from lactic acid aqueous solution

The global increase in energy demand requires a continuous search for renewable and clean alternative resources to fossil fuels. Hydrogen is emerging as a promising energy carrier for the future; its production via photocatalysis, driven by sunlight, can directly convert solar energy into a usable or storable energy resource. However, water splitting requires sacrificial agents or electron donors/hole scavengers, such as short-chain organic acids. This research explores the use of lactic acid as a source for photocatalytic hydrogen production, offering valuable alternatives for wastewater management and renewable energy production. This study employed the innovative supercritical antisolvent (SAS) technique to micronize the precursors of both the active phase (CeO2) and co-catalyst (CuO), ensuring rapid and complete solvent removal and size reduction of photocatalyst precursors. The prepared samples were characterized by field emission scanning electron microscopy (FESEM), Fourier transform infrared (FT-IR) spectroscopy, dynamic light scattering (DLS) analysis, Brunauer-Emmett-Teller (BET) analysis and thermogravimetric analysis (TGA). This study has shown that the micronization process resulted in a notable improvement in CeO2 photocatalytic activity, attributed to the reduction of the dimensions of the powders. Hydrogen production was equal to 3989 μmol L−1 for the SAS-produced photocatalyst while using a commercial CeO2 sample resulted in H2 production of 2519 μmol L−1. The enhanced photoactivity of CeO2-CuO composites was found to be related to the presence of CuO. The optimal CuO amount was equal to 0.5 wt%, determining a hydrogen production of 9313 μmol L−1 after 4 h of UV irradiation time. A photocatalytic test carried out with deuterated water (D2O) instead of distilled H2O demonstrated that hydrogen was preferentially produced from water splitting reaction, whereas lactic acid acted as a sacrificial agent being oxidized from positive holes photogenerated in the valence band of CuO.

Comparative analysis of multi-effect evaporators in an ammonium acetate concentration process for L-methionine production

The process of treating an acetic acid aqueous solution generated during L-methionine production with ammonia and recovering a highly concentrated ammonium acetate aqueous solution using a multi-effect evaporator process was studied. The electrolyte non-random two-liquid model was applied to calculate the activity in the electrolyte solution, and the Hayden-O’Connell model was used to consider the dimerization reaction of acetic acid in the vapor phase. The dissociation equilibrium constant of acetic acid was modeled based on experimental values, and all other thermodynamic property models and parameters were used as implemented in the Aspen Plus software. Economic evaluation was carried out with various sensitivity tests, considering the loss of acetic acid and ammonia, as well as the steam cost. Evaporator operation was found to be more economical when the molar ratio of acetic acid to ammonia was equal, feed concentration was high, feed flow rate was low, and evaporator temperature was low. These results were confirmed in actual plant operations, with significant correlations between the feed flow rate and evaporator temperature. Our findings have significant implications for the development of sustainable and economical L-methionine production methods that enable the recycling of ammonium acetate.

Pharmacokinetics of Anti-rheumatic Drugs Methotrexate and Tofacitinib with its Metabolite M9 in Rats by UPLC-MS/MS.

Tofacitinib is an oral JAK inhibitor for the treatment of rheumatoid arthritis (RA). The clinical efficacy and safety of an administered tofacitinib, either monotherapy or in combination with conventional synthetic disease-modifying anti-rheumatic drugs, mainly methotrexate (MTX), have been evaluated. The high plasma concentration with delayed medicine clearance may affect the liver and/or kidney functions. In this study, an ultra-performance liquid chromatography-tandem mass spectrometry (UPLC- MS/MS) method for the quantitative analysis of methotrexate, tofacitinib, and metabolite M9 in plasma of Sprague Dawley (SD) rats was developed, and its effectiveness was validated as well. Methotrexate, tofacitinib, M9 and fedratinib (internal standard, IS) were separated by gradient elution. The chromatography was performed on an Acquity BEH C18 (2.1 mm × 50 mm, 1.7 μm) column with the mobile phases of acetonitrile and 0.1% formic acid aqueous solution with different proportions at the flow rate of 0.30 mL/min. In the positive ionization mode, the analyzes were detected using a Xevo TQ-S triple quadrupole tandem mass spectrometer, with the following mass transition pairs: m/z 313.12 → 148.97 for tofacitinib, m/z 329.10 → 165.00 for M9 and m/z 455.12 → 308.05 for methotrexate. The obtained results manifested good calibration linearity over the ranges of tofacitinib at 0.1-100 ng/mL, M9 at 0.05-100 ng/mL, and methotrexate at 0.05-100 ng/mL. The lower limit of quantifications (LLOQs) of methotrexate, tofacitinib and M9 were 0.05 ng/mL, 0.1 ng/mL and 0.05 ng/mL, respectively. Intra-day and inter-day accuracy values were confirmed with a range of -6.3% to 12.7%, while intra-day and inter-- day precision values were ≤14.4%. Additionally, recoveries were greater than 86.5% for each compound without significant matrix effects. The currently established analytical method exhibited great potential for the evaluation of plasma concentrations of methotrexate, tofacitinib and M9 simultaneously, greatly reducing the detection time, which would serve as a supplementary role in formulating dose decisions to achieve personalized treatment, identify drugs that cause adverse reactions and finally, to assess drug-drug interactions on clinical studies.

SYNTHESIS AND STUDY OF OPTICAL, ELECTRICAL PROPERTIES OF TIN DIOXIDE NANOWIRES IN A SiO<sub>2</sub>/Si TRACK TEMPLATE

This work presents a study of the structural, optical and electrical characteristics of tin dioxide (SnO2) nanowires obtained by chemical deposition (CD) into a SiO2/Si track template (template synthesis). Latent tracks in the SiO2 layer were created by irradiation with swift heavy ions (SHI) of Xe at an energy of 200 MeV with a fluence of Ф = 108 cm−2 and subsequent etching in a 4% aqueous solution of hydrofluoric acid (HF). The chosen CD method is widely used for the deposition of semiconductor oxide nanowires in SiO2 nanopores. The CD method is cost-effective because it does not require special equipment for deposition of nanowires. To carry out deposition, a solution of a coordination compound of a metal and a reducing agent is used. To analyze the filling of pores after the CD process, the surface morphology of the samples was studied using a Zeiss Crossbeam 540 scanning microscope. The crystallographic structure of SnO2/SiO2/Si nanostructures with SnO2 nanopore filling was studied by X-ray diffraction. X-ray diffraction analysis (XRD) is carried out on a Rigaku SmartLab X-ray diffractometer. As a result, a SnO2-NW/SiO2/Si nanoheterostructure with an orthorhombic crystal structure of SnO2 nanowires was obtained. Photoluminescence (PL) spectra were measured upon excitation with light at a wavelength of 240 nm using a CM2203 spectrofluorimeter (Solar). Gaussian decomposition of the photoluminescence spectrum of SnO2-NW/SiO2/Si structures showed that they have low intensity, which is mainly due to the presence of defects such as oxygen vacancies, interstitial tin or tin with damaged bonds. Electrical characterization studies were performed using a VersaStat 3 potentiostat (Ametek). Measurement of the current-voltage characteristic showed that the resulting SnO2-NW/SiO2/Si nanoheterostructure contains arrays of p-n junctions.

In English

The synthesis and characterization of heterostructure por-Ga2O3/GaAs represent a crucial advancement in nanomaterials, particularly in optoelectronic applications. Employing a two-stage electrochemical etching methodology, this research has elucidated the precise conditions required to fabricate such a heterostructure. The initial stage involves etching monocrystalline gallium arsenide (GaAs) using an aqueous nitric acid solution as the electrolyte. This process is governed by the redox reactions at the crystal-electrolyte interface, where GaAs are partially oxidized and selectively etched. The second stage introduces ethanol into the electrolytic solution. This chemical addition serves a dual purpose: Firstly, it modulates the electrochemical environment, allowing for controlling pore morphology in GaAs. Secondly, it facilitates the etching of the resultant oxide layer, which predominantly consists of gallium oxide (Ga2O3). The formation of this oxide layer can be attributed to the oxidation of GaAs, driven by the electrochemical potentials and resulting in the deposition of reaction by-products on the substrate surface. The fabricated nanocomposite was comprehensively characterized using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Analysis (EDX), and Raman Spectroscopy. SEM imaging revealed a range of agglomerated nanostructures dispersed across the surface, with dimensions ranging from 8–25 μm, 1–1.5 μm, and 70–100 nm. These observations suggest a hierarchical pore structure indicative of a complex etching mechanism modulated by the electrolyte composition. Raman spectroscopic analysis corroborated the presence of various phases in the heterostructure. Signals corresponding to bulk GaAs, serving as the substrate, were distinguishable. In addition, peaks indicative of porous GaAs and porous Ga2O3 were observed. A cubic phase in the Ga2O3 layer was particularly noteworthy, suggesting a higher degree of crystallinity. Notably, the absence of Raman-active modes associated with internal stresses implies that the fabricated heterostructure is of high quality.

The influence of dissolved molecular oxygen on the corrosion of metals in aqueous acid solutions. Review

The influence of dissolved molecular oxygen on the corrosion of metals in aqueous acid solutions. Review

Photocatalytic Reduction of Perrhenate and Pertechnetate in a Strongly Acidic Aqueous Solution.

Pertechnetate (99TcO4-), a physiologically toxic radioactive anion, is of great concern due to its high mobility in environmental contamination remediation. Although the soluble oxyanion can be photoreduced to sparingly soluble TcO2·nH2O, its effective removal from a strongly acidic aqueous solution remains a challenge. Here, we found that low-crystalline nitrogen-doped titanium oxide (N-TiO2, 0.6 g L-1) could effectively uptake perrhenate (ReO4-, 10 mg L-1, a nonradioactive surrogate for TcO4-) with 50.8% during 360 min under simulated sunlight irradiation at pH 1.0, but P25 and anatase could not. The nitrogen active center formed by trace nitrogen doping in N-TiO2 can promote the separation and transfer of photogenerated carriers. The positive valence band value of N-TiO2 is slightly higher than those of P25 and anatase, which means that the photogenerated holes have a stronger oxidizability. These holes are involved in the formation of strong reducing •CO2- radicals from formic acid oxidation. The active radicals convert ReO4- to Re(VI), which is subsequently disproportionated to Re(IV) and Re(VII). Effective photocatalytic reduction/removal of Re(VII)/Tc(VII) is performed on the material, which may be considered a potential and convenient strategy for technetium decontamination and extraction in a strongly acidic aqueous solution.

Leaching of liquation-feeding furnace dross as a first step for germanium recovery

ObjectiveGermanium, an important component of electronics, is considered by many global economies as a critical raw material. Therefore, investigating its potential new sources is crucial for prospective technology development. This paper presents the investigation results on the leaching of liquation-feeding furnace dross using sulfuric and oxalic acid solutions.ResultsThe dross contained mostly zinc (68.0% wt.) but also elevated germanium concentration (0.68% wt.). The influence of temperature, time, initial acid concentration, and liquid-to-solid phase ratio (L:S) was examined. It was found that germanium availability via leaching is limited—maximum leaching yields using aqueous solutions of sulfuric and oxalic acids were 60% (80 °C, 2 h, 15% wt. H2SO4, L:S 25:1) and 57% (80 °C, 3 h, 12.5% wt. H2C2O4, L:S 10:1), respectively.

Uptake and coordination behaviour of uranyl on functionalised silica

The safe decommissioning of nuclear reactors is a complex process, requiring a range of technological options for it to be done effectively. It has become more important in recent years, with the substantial number of reactors entering the decommissioning phase. This paper details the use of functionalised silica for the recovery of uranium from aqueous hydrochloric acid solutions, a potential agent for the treatment of steel reactor components during nuclear reactor decommissioning. Silica functionalised with either phosphonic acid, bistriazine, or bistriazinylbipyridine ligands was shown to extract uranium, with the commercially available phosphonic acid functionality being the most effective. Extractions of 100 % were observed at [H+] ≤ 0.24 M, further the phosphonic acid functionality also had the highest loading capacity. Increasing [H+] has a suppressive effect on uranyl recovery, which was more pronounced for the in-house synthesized silica, and was attributed to protonation of the extracting moiety. Extended x-ray absorption fine structure spectroscopy was also used to determine the uranium coordination environments on the functionalised silica, and gain insights into the extraction mechanism. The uranyl cation was bound by two phosphonic acid groups, two bis-triazine groups, and one bistriazinylbipyridine group, respectively on each respective extractant. Uranyl was found to be penta-coordinate in the equatorial plane for all systems, with oxygen and/or chloride always present in the first coordination sphere. Evaluation of the mechanism indicated that uranyl must be loading onto the phosphonic acid functionality via multiple mechanisms, to both the phosphonic acid and silica related surface groups, although preferential binding of uranyl to the phosphonic acid groups was observed.

Environmental analysis of nitrobenzene using newly synthesized anisotropic gold nanostructures: Reaction kinetics and electrocatalytic activity

In this article, we established to produce anisotropic, colloidally stable gold nanostructures (AuNS) by rapidly mixing aqueous solutions of gold(III) chloride trihydrate (HAuCl4) and citric acid (CA) as dual reducing and capping agents at room temperature without the aid of a templating agent. Furthermore, the impact of various anions and shape-directing agents on the morphology and reaction kinetics of citric acid-capped gold nanostructures (CA-AuNS) was investigated. Additionally, the electrocatalytic activity of AuNS towards nitrobenzene (NB) was examined using a CA-AuNS modified glassy carbon (GC) electrode. The rate of reaction for the formation of CA-AuNS increased rapidly with higher concentrations of CA, indicating a strong dependence on the reductant’s concentration. This process followed first-order kinetics, suggesting that the reaction rate is directly proportional to the citric acid concentration. Consequently, optimizing CA levels can effectively control the synthesis rate and yield of CA-AuNS. The presence of nitrite ions led to rapid aggregation of gold nanostructures (AuNS) and a quick reaction time. Chloride ions increased the size of the AuNS. As bromide ion concentration increased, the reaction time slowed significantly, resulting in spherical gold nanoparticles. Both acetate ions and polyvinylpyrrolidone (PVP) inhibited the growth of AuNS. High-resolution transmission electron microscopy (HR-TEM) images showed the formation of various shapes, including spherical, hexagonal, pentagonal, and boat-like structures. In the presence of cetyltrimethylammonium bromide (CTAB), both complex formation between CTAB and HAuCl4 and the formation of spherical gold nanoparticles occurred. Upon addition of silver nitrate (AgNO3) to the colloidal solution, the color shifted to pale violet, and the morphology transitioned from anisotropic to irregular. However, when ascorbic acid (AA) was utilized, it proved ideal for maintaining the morphology of gold nanostructures (AuNS). The analysis of X-ray diffraction spectroscopy (XRD), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and Fourier transform infrared spectroscopy (FT-IR) further confirmed the synthesized CA-AuNS. The FT-IR spectra of CA before and after the formation of AuNS indicated the participation of carboxylic acid (–COOH) and hydroxyl (–OH) groups in the reduction process of Au3+ metal ions. The GC/CA-AuNS electrode exhibits a larger electroactive surface area due to the coating of AuNS onto the electrode surface, enhancing the electrode’s electrical conductivity by providing additional active sites for electron transfer. In addition, the electrocatalytic activity of NB was investigated in this study. The GC/CA-AuNS electrode had better electrocatalytic activity than the unmodified GC electrode. As a result, with a LOD of 28.2 nM (S/N = 3), this electrode was chosen for sensitive NB determination.

Quantification and analyses of seven tyrosine kinase inhibitors targeting hepatocellular carcinoma in human plasma by QuEChERS and UPLC-MS/MS

Tyrosine kinase inhibitors (TKIs) are commonly used to treat various cancers. Literature suggests that the blood concentration of TKIs strongly correlates with their efficacy and adverse effects. Therefore, establishing a Therapeutic Drug Monitoring (TDM) methodology for TKI drugs is crucial to improving their clinical efficacy and minimizing the treatment-related adverse effects. However, quantifying their concentrations in the plasma using existing methods to avoid potential toxicity is challenging. Herein, seven TKIs, namely sorafenib tosylate, axitinib, erlotinib, cediranib, brivanib, linifanib, and golvatinib, were successfully analyzed in human plasma by following a quick, easy, cheap, effective, rugged, and safe (QuEChERS) pretreatment method combined with ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Briefly, biological samples were extracted using 1 mL of methanol, followed by the sequential addition of 250 mg of anhydrous magnesium sulfate and 25 mg of N-propylethylenediamine (PSA) for salinization and purification by adsorption, respectively. In this study, dovitinib was used as the internal standard. The seven TKIs were detected by the gradient elution method for 4 min in the positive ion electrospray mode. The mobile phase comprised methanol (phase A) and 0.1 % aqueous formic acid solution (phase B) on the Agilent Zorbax RRHD Stablebond Aq, (2.1 × 50 mm; 1.8 μm). Brivanib, linifanib, axitinib, sorafenib tosylate, and golvatinib exhibited good linearity in the range of 5–500 ng/mL, and erlotinib and cediranib exhibited good linearity in the range of 10–1000 ng/mL, with linear correlation coefficients (R2) ≥ 0.99. The limits of detection and quantification were 0.60–0.18 ng/mL and 5–10 ng/mL, respectively. The intraday and interday accuracy values ranged from −6.12 % to 7.31 %, with a precision (RSD) of ≤ 10.57 %. The method was rapid, accurate, specific, simple, reproducible, and suitable for the quantitative determination of the seven TKIs in human plasma.

Laser‐Induced Nucleation of Acetaminophen through the Addition of Insoluble Impurities and Acidic Polymers

AbstractThis study investigates the crystallization of acetaminophen (ACET) in ultrapure water and a 10 wt.% aqueous polyacrylic acid (PAA) solution using non‐photochemical laser‐induced nucleation (NPLIN) for the first time. Using a 532 nm nanosecond laser, two distinct crystal morphologies—rhombic and tetragonal plate‐like—are formed in both solvents after adding impurities. Notably, the PAA solution showed a reduced number of crystals and slower growth rates compared to ultrapure water, suggesting that the acidic polymer modulates crystal growth. Interestingly, crystals are not induced by the laser without impurities. However, impurities like copper phthalocyanine (CuPc) or boron carbide (CB4) enabled successful NPLIN, with CB4 showing higher nucleation efficiency than CuPc. The study also explores how laser power affects nucleation probability and identifies potential laser energy thresholds. Experimental data on ACET crystal sizes over time are fitted to derived equations, which accurately represented trends and predicted results. The nanoparticle heating mechanism and the role of acidic polymers in affecting nucleation probability and growth rate are discussed, along with potential mechanisms for changes in crystal morphology.