Formic Acid Solution Research Articles

1H and 13C NMR and FTIR Spectroscopic Analysis of Formic Acid Dissociation Dynamics in Water.

The formation and transport of ionic charges in formic acid-water (HCOOH-H2O) mixtures with initial water mole fractions ranging from XH2Oi = 0 to 1 were investigated using 13C and 1H NMR, FTIR spectroscopy, viscosity, conductivity, and pH measurements. The maximum molar concentration of ions (H3O+ and HCOO-), along with the relative differences between theoretical and experimental densities, spin-lattice relaxation times (T1), activation energies (Ea), viscosity (η), and conductivity (σ), were identified within the range of XH2Oi ≈ 0.5-0.7. These results indicate that pure formic acid (FA) solutions predominantly consist of cyclic dimers at room temperature. As the water mole fraction increases up to 0.6, a structural shift occurs from cyclic dimers to a mixture of linear and cyclic dimers, driven by the formation of strong hydrogen bonds. Beyond a water mole fraction of 0.6, the structure transitions to linear dimers, with FA molecules behaving as free entities in the water. Furthermore, the acidity was found to increase approximately 2-fold with every 0.1 increment in water mole fraction. These findings are critical for understanding the kinetics of formic acid anions in body fluids, the structure of the hydrogen bonding network, and ionization energies.

Electrospun gelatin/hyaluronic acid nanofibers as a platform for uric acid delivery to neural tissue.

Uric acid (UA) is an antioxidant that has been reported to be a neuroprotective compound for injuries and diseases, and specifically, diseases of the central nervous system. However, uric acid is highly insoluble in aqueous solutions, and high levels in the serum lead to gout, which limits its use in humans. Here, we develop a novel drug delivery platform that will release uric acid in a sustained manner for application to neural tissue. We demonstrate that one-step incorporation of UA into an electrospun gelatin/hyaluronic acid nanofiber mat results in controlled release of UA in culture medium. Taking a unique approach, we made solutions of 12% gelatin and 1% hyaluronic acid in a formic acid solvent and added UA for production of nanofiber mats. We then dehydrothermally crosslinked the mats and tested for release of UA into physiological cell culture medium. To test whether the mats have any detrimental effects on healthy nervous system tissue, we cultured spinal cord explants on the mats extended and assessed extensions from the explants. We observed that comparable numbers and lengths of dendrites are extended from the spinal cord tissue, regardless of the amount UA content in the mats. Our results suggest that electrospun gelatin/hyaluronic acid nanofibers can be used as a platform for sustained uric acid delivery to neural tissue without detrimental effects.

A novel, sensitive, and fast ultra-high-performance liquid chromatography tandem mass spectrometry method for TNG908 determination in dog plasma and pharmacokinetic study.

TNG908 is a potent and selective protein arginase methyltransferase 5 (PRMT5) inhibitor that is currently going through phase I/II clinical development for the treatment of non-small cell lung cancer. To facilitate pharmacokinetic and toxicokinetic studies of TNG908, here, we reported an ultra-high-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method for the detection of TNG908 in dogs. The dog plasma samples were precipitated by acetonitrile and analyzed using a Waters ACQUITY BEH C18 column combined with a Thermo triple quadrupole mass spectrometer. The mobile phase consisted of 0.1% formic acid solution and acetonitrile, at a flow rate of 0.3mL/min. TNG908 and internal standard were monitored by selective reaction monitoring (SRM) with m/z 410.2 > 150.1 and m/z 394.2 > 278.1, respectively. The method demonstrated excellent linearity over the concentration range of 1-1000 ng/mL, with a correlation coefficient greater than 0.995. Acetonitrile-mediated protein precipitation showed high extraction efficiency and a recovery above 80%. The validated assay was further applied to measure TNG908 in dog plasma after oral and intravenous administration and achieved success. The obtained pharmacokinetic parameters indicated low clearance of TNG908 (3.7 ± 0.8mL/min/kg) and moderate oral bioavailability (>36.4%).

Study on the influence characteristics of multi-working condition parameters on membrane electrode type CO2 electrolyzer

The electrochemical conversion of carbon dioxide (CO2) into basic chemicals or carbon-based fuels is a promising new strategy for carbon resource utilization. Within this domain, solid-electrolyte CO2 electrolyzer demonstrate significant potential for the continuous production of pure formic acid solutions. This study, leveraging a 4 cm2 visualization electrolyzer, explores the impact of three working condition parameters on performance: working voltage, gas flow rate, and the intermediate chamber water flow rate. It compares the variations in current density, formic acid concentration, and the distribution of liquid water on the cathode side under different working conditions. The results indicate that the working voltage, current density, and formic acid yield are all positively correlated; overly low gas flow rates can lead to CO2 deficiency and diminished electrolyzer performance; concentration control of the formic acid solution is effectively achieved by adjusting the intermediate chamber water flow rate; and during the electrolyzer reaction process, almost all of the liquid water is positioned at the bends downstream of the cathode flow channel.

Online restricted access molecularly imprinted solid phase extraction coupled with electrospray ionization-tandem mass spectrometry for determination of mebendazole and albendazole in milk samples

Multifunctional materials, such as restricted access molecularly imprinted polymers covered with bovine serum albumin (RAMIP-BSA), are effective alternatives for sample preparation techniques. This material selectively adsorbs analytes while excluding macromolecules, enhancing the analysis's efficiency. Among analytical techniques, ESI-MS/MS (Electrospray Ionization-Tandem Mass Spectrometry) has successfully identified and quantified various molecules, including trace-level drugs. Therefore, we proposed, for the first time, an integrated online extraction/analysis system that combines the benefits of RAMIP-BSA and ESI-MS/MS for analyzing mebendazole (MBZ) and albendazole (ABZ) in milk samples without the need for chromatographic separation. Initially, a RAMIP selective for MBZ was synthesized using the bulk method with methacrylic acid and glycidyl methacrylate. Then, the polymer was covered with bovine serum albumin. Subsequently, this adsorbent was packed in a small column and coupled with an ESI-MS/MS instrument in an online configuration. Milli-Q water was used as the loading and reconditioning mobile phases, and a solution of formic acid in methanol (1:100 v/v) was employed as the elution phase. The system enabled simultaneous extraction and determination of MBZ and ABZ in milk samples. The method exhibited linearity between 15.0 and 125.0 μg L−1 for MBZ and 10.0 and 125.0 μg L−1 for ABZ (with a correlation coefficient exceeding 0.99). The limits of quantification were 15.0 and 10.0 μg L−1 for MBZ and ABZ, respectively. Good precision and accuracy were achieved. The developed method was used to analyze MBZ and ABZ in real milk samples and proved to be a viable alternative to conventional sample preparation and chromatographic techniques.

Liquid chromatography-mass spectrometric method for the simultaneous analysis of branched-chain amino acids and their ketoacids from dried blood spot as secondary analytes for the detection of maple syrup urine disease

BackgroundMaple syrup urine disease (MSUD) is an aminoacidopathy caused by a defective branched-chain alpha-ketoacid dehydrogenase complex, leading to the accumulation of branched-chain amino acids (BCAAs) and their respective keto acids (BCKAs). A comprehensive test was developed to measure BCAAs and BCKAs using LC-MS from dried blood spot (DBS) samples for the diagnosis and prevention of MSUD in newborns and infants. MethodsAnalytes were extracted from DBS using a methanol:0.1 % v/v formic acid solution (75:25) containing internal standards and analyzed on a Luna PFP column (150 mm × 4.6 mm, 3 µm) at a flow rate of 0.3 mL/min. The method was validated for linearity, accuracy, precision, recovery, carry-over, matrix effect, hematocrit, blood volume, and punch position effects. Biomarker stability in the matrix and stock solution was assessed. Correlation with the plasma method was determined using Pearson’s correlation coefficient and Bland-Altman analysis. The method established reference ranges for the Udupi district population in South India. ResultsThe method demonstrated linearity (r2 > 0.99), with a lower limit of detection at 2 µM (BCAA) and 1 µM (BCKA), and acceptable recovery of QC samples. Hematocrit, blood volume, punch position, and storage condition effects were within acceptable limits. Correlation and Bland-Altman analysis showed strong interconvertibility between plasma and DBS assays. Reference ranges for leucine, isoleucine, valine, KIC, KIV, and KMV were established. ConclusionThe developed DBS method, requiring no derivatization and involving simple sample preparation with short run times, is a cost-effective and reliable approach for the confirmatory diagnosis of MSUD.

The morphology and thermo-regulating properties of electrospun PVA/PEG/Ag nanofibers of water and formic acid solvents

The solvent utilized in the electrospinning solution significantly impacts the morphology and thermal properties of PVA/PEG/Ag nanofibers. To prevent leakage of PEG, solid-liquid phase change, a suitable encapsulation method involves utilizing a combined single-phase electrospinning that incorporates PEG and supporting polymer of PVA. This study aims to investigate the production of thermal-regulating nanofibers from a solution containing PEG 6000, PVA, and AgNO3 precursor using electrospinning method. The influence of water and formic acid as a solvent on the morphology of the nanofibers was examined using SEM. The selected nanofiber characteristics and thermal performance were evaluated through FE-SEM, FT-IR, XRD, DSC, PCM leakage, and DTG tests. SEM images revealed that the formic acid-based nanofibers, consisting of two polymers and two polymer/Ag NPs, exhibited a nanoporous membrane, possibly due to enhanced cross-linking compared to water-based nanofibers. The results of the DSC indicated that fusion and solidification enthalpies of the selected water-based nanofibers were measured as 70.09 and −85.43 J/g, respectively. Unexpectedly, the DSC results indicated higher enthalpies compared to unheated samples. SEM image after thermal cycles, leakage results, and DTG of water-based nanofibers demonstrated their production with thermal stability, reliability, and the potential for creating shape-stable, thermally regulating fabricated nanofibers for various applications.

Advanced reduction processes initiated by oxidative radicals for trichloroacetic acid degradation: Performance, radical generation, and mechanism

The degradation of haloacetic acids (HAAs) in aqueous environments poses a challenge due to their oxidative resistance. Given that HAAs are highly carcinogenic disinfection byproducts, it is imperative to develop effective degradation methods to reduce their potential health risk. In this study, we found that only 27.2% of 200 μM trichloroacetic acid (TCA) was removed in the UV-activated persulfate (PS) system after 2 h, while complete removal was achieved with the addition of 15 mM formic acid (FA). The main products of TCA degradation were dichloroacetic acid and monochloroacetic acid. Results from free radical quenching experiments and electron paramagnetic resonance spectroscopy analyses indicated that reductive carbon dioxide radical (CO2•−) was the main active species responsible for TCA reduction. Oxidative radicals (i.e., SO4•− and •OH) generated from PS activation reacted with FA to form CO2•−, efficiently degrading TCA. The effects of PS and FA concentrations, solution pH, anions (e.g., Cl−, SO42−, and HCO3−), and small organic molecules (e.g., methanol, ethanol, and acetic acid) on degradation efficiency were examined. Overall, this study proposes a simple and efficient method to improve the degradation efficiency of HAAs in the UV/PS system and provides new insights into the advanced reduction processes used for water treatments.

Chromatographic Separation of Hydrophilic Organophosphates on a Porous Graphitized Carbon Sorbent Hypercarb Using an Aqueous Solution of Formic Acid As a Mobile Phase

Chromatographic Separation of Hydrophilic Organophosphates on a Porous Graphitized Carbon Sorbent Hypercarb Using an Aqueous Solution of Formic Acid As a Mobile Phase

Molecular Engineering of Poly(Ionic Liquid) for Direct and Continuous Production of Pure Formic Acid from Flue Gas.

Electrochemical CO2 reduction reaction (CO2RR) offers a promising approach to close the carbon cycle and reduce reliance on fossil fuels. However, traditional decoupled CO2RR processes involve energy-intensive CO2 capture, conversion, and product separation, which increases operational costs. Here, we report the development of a bismuth-poly(ionic liquid) (Bi-PIL) hybrid catalyst that exhibits exceptional electrocatalytic performance for CO2 conversion to formate. The Bi-PIL catalyst achieves over 90% Faradaic efficiency for formate over a wide potential range, even at low 15% v/v CO2 concentrations typical of industrial flue gas. The biphenyl in PIL backbone affords hydrophobicity while maintaining high ionic conductivity, effectively mitigating the flooding issues. The PIL layer plays a crucial role as a CO2 concentrator and co-catalyst that accelerates the CO2RR kinetics. Furthermore, we demonstrate the potential of Bi-PIL catalysts in a solid-state electrolyte (SSE) electrolyzer for the continuous and direct production of pure formic acid solutions from flue gas. Techno-economic analysis suggests that this integrated process can produce formic acid at a significantly reduced cost compared to the traditional decoupled approaches. This work presents a promising strategy to overcome the challenges associated with low-concentration CO2 utilization and streamline the production of valuable liquid fuels and chemicals from CO2.

Application of newly developed and validated UPLC-MS/MS method for pharmacokinetic study of ROS1/NTRK inhibitor taletrectinib in beagle dog plasma

Taletrectinib is a potent selective ROS and pan-NTRK tyrosine kinase inhibitor (TKI) and has been developed to treat non-small cell lung cancer (NSCLC). To facilitate pharmacokinetic and toxicokinetic studies of taletrectinib, we developed a procedure for ultra-high-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) to detect the plasma level of taletrectinib in dogs. This assay procedure was validated in compliance with FDA guidance. The dog plasma samples were spiked with internal standard (IS), followed by protein precipitation, and analyzed using a Waters ACQUITY BEH C18 column coupled to a Thermo triple quadrupole mass spectrometer. Separation was executed using the acetonitrile-0.1 % formic acid solution with gradient elution, at a flow rate of 0.4 mL/min. Taletrectinib and IS were monitored by multiple reaction monitoring (MRM) with m/z 406.2 > 349.2 and m/z 441.2 > 138.1, respectively. The procedure demonstrated excellent linearity with a correlation coefficient greater than 0.999 within the concentration range of 0.2–200 ng/mL. The inter- and intra-day accuracy ranged from −5.25 % to 5.26 %, and the precision was below 6.39 %. Acetonitrile-mediated protein precipitation showed high extraction efficiency and a recovery above 85 %. The procedure was then applied to quantify taletrectinib in beagle dog plasma after oral and intravenous doses and achieved success. The obtained pharmacokinetic parameters indicated high bioavailability of taletrectinib (>85 %) and extensive tissue distribution (>40 L/kg).

Characterization of cyclotides Mra30 and cycloviolacin O17 derived from Viola dalatensis Gadnep.

Bacteria threaten human and animal health, and standard antibiotics no longer effective. Antibiotic-resistant microorganisms can make infection treatment challenging and perhaps fail. Investigating the attributes of cyclotide, a peptide with promising antibacterial properties that holds great potential in the field of antibiotic research. The structure of these cyclic peptides involves six conserved cysteine residues that form three disulfide bonds, resulting in a cyclic cystine knot (CCK). This feature guarantees their durability when exposed to changes in temperature, chemicals, and enzymatic degradation. The two cyclotides, cycloviolacin O17 and mra30, were obtained from Viola dalatensis Gadnep through a series of techniques including the use of a 50% acetonitrile/49% miliQ water/1% formic acid solution for extraction, ammonium salt precipitation, RP-HPLC purification and sequence identification by LC-MS/MS. These cyclotides exhibit antibacterial effects on specific strains of bacteria like Staphylococcus aureus, Bacillus subtilis, and Pseudomonas aeruginosa at a concentration of 0.2mg/mL, leading to inhibition zones ranging from 10 to 14mm. In addition, the disulfide bonds play a crucial role in the antibacterial function of cyclotides. Disrupting the disulfide bonds through ankylation reaction results in the loss of antibacterial properties in the cyclotides (cyO17 and mra30). The minimum inhibitory concentration (MIC) values of mra30 and cyO17 are significantly low, ranging from 0.1 to 0.6 µM. These values are approximately three times lower than the MIC values observed in salt precipitation samples.

A green HPLC method for determination of mirtazapine in pharmaceutical products: Development, validation, and greenness assessment

AbstractMirtazapine is an antidepressant medication used to treat the major depressive disorder in adults. In this study, two different chromatographic methods were developed for the determination of mirtazapine in pharmaceutical products. In the first method, An Extend C18 column (250 × 4.6 mm, 5 μm) was used and the temperature was kept constant at 25 °C. The mobile phase was determined as 0.1% formic acid solution and acetonitrile (80/20, v/v), and isocratic elution was applied. The flow rate of the mobile phase was determined as 1.0 mL min−1 and the injection volume was 20 µL. Detection was performed at 291 nm. using a UV detector. In the second method, ethanol was used as the organic modifier. The only difference between these methods was the organic modifier. All other conditions of the methods were the same. Both chromatographic methods were validated by ICH guidelines for various parameters such as selectivity, linearity, accuracy, precision, detection and quantification limit, and robustness. The determination coefficients of chromatographic methods were greater than 0.999 in the concentration range of 5–30 µg mL−1. of mirtazapine. Later, these chromatographic methods were applied to pharmaceutical formulations. Comparison of the obtained results in terms of means was made using Student's (t) test, and comparisons in terms of standard deviations were made using the Fischer (F) test. It was observed that there was no significant difference between these methods. These two methods were then evaluated using the AGREE-Analytical GREEnness metric software. The chromatographic method using ethanol as an organic modifier has been proposed as an excellent eco-friendly and analyst-friendly alternative for the determination of mirtazapine in pharmaceutical formulations.

Ultra-performance liquid chromatography-mass spectrometry methods for the determination of the residual quantities of ramipril and hydrochlorothiazide for controlling the cleaning of equipment

Monitoring the completeness of equipment cleaning is essential to prevent cross-contamination of medicinal products. Therefore, it is necessary to develop fast and sensitive methods for studying residual quantities of active ingredients on the surfaces of technological equipment. The aim of the work was to develop and validate analytical methods for the determination of ramipril and hydrochlorothiazide in wash waters by ultra-performance liquid chromatography–mass spectrometry method. Materials and methods. In the study, standard samples of ramipril (USP RS) and hydrochlorothiazide (USP RS), as well as class A reagents, were used. Samples were analysed on a liquid chromatograph with an MS detector (Agilent 6420 and Waters Xevo TQD ACQUITY). We used the Kinetex C18 column (2.1 mm × 30 mm × 1.7 μm); mobile phase – 0.1% formic acid solution in deionised water – Acetonitrile (ratio 73:27 for the determination of ramipril and 91.5:8.5 for the determination of hydrochlorothiazide); mobile phase rate of 0.4 mL/min for the determination of ramipril and 0.35 mL/min for the determination of hydrochlorothiazide; column temperature 45 °C for the determination of ramipril and 40 °C for the determination of hydrochlorothiazide, ionisation mode - electric spray in positive mode; The detection parameters are the mode of registration of the daughter ion 417 → 234 m/z for the determination of ramipril and 298 → 281 m/z for the determination of hydrochlorothiazide. Results and discussion. Methods for the determination of ramipril and hydrochlorothiazide in wash waters by ultra-performance liquid chromatography–mass spectrometry have been developed. The developed methods have sufficient linearity, correctness and precision. The sensitivity of the techniques was confirmed at the level of 0.0026 μg/ml. The techniques can be used in the concentration range of 0.0026 – 0.0255 μg/ml Conclusions. Analytical methods for determining ramipril and hydrochlorothiazide in wash waters have been developed and validated.

Development and validation of the method of quantification of 5-[5-(trifluoromethyl)-1,2-oxazole-3-yl]-furan-2-sulfonamide and its metabolites in laboratory animal plasma

Introduction. The study of the systemic exposure of a new original drug is an essential part of its preclinical study. 5-[5-(trifluoromethyl)-1,2-oxazole-3-yl]-furan-2-sulfonamide is a new selective carbonic anhydrase II inhibitor for the treatment of open-angle glaucoma. Methods for the quantitative determination of this compound and its N-hydroxy- and N-acetyl metabolites in the plasma of laboratory animals have not been previously developed.Aim. Development and validation of a method of quantitative determination of 5-[5-(trifluoromethyl)-1,2-oxazole-3-yl]-furan-2-sulfonamide and its metabolites N-hydroxy-5-[5-(trifluoromethyl)-1,2-oxazole-3-yl]-furan-2-sulfonamide (M1) and N-acetyl-5-[5-(trifluoromethyl)-1,2-oxazole-3-yl]-furan-2-sulfonamide (M2) in rat and rabbit blood plasma by HPLC-MS/MS.Materials and methods. Protein precipitation by methanol was applied for sample preparation. 5-[2-(morpholine-4-carbonyl)-1,3-oxazole-5-yl]-thiophene-2-sulfonamide was used as an internal standard. A 5 % aqueous solution of ascorbic acid was added to the plasma samples at volume ratio 1 : 2 to prevent decomposition of N-hydroxy-5-[5-(trifluoromethyl)-1,2-oxazole-3-yl]-furan-2-sulfonamide. The combination of sodium fluoride and potassium oxalate was selected as an anticoagulant. Chromatographic separation was performed on Zorbax Eclipse Plus C18 column (150 × 3.0 mm, 3.5 µm) with Zorbax Eclipse Plus C18 pre-column (12.5 × 2.1 mm, 5.0 µm) using a mobile phase based on a 0.1 % aqueous solution of formic acid and methanol. Mass spectrometric detection was carried out in the MRM mode using electrospray ionization in negative polarity. The method was tested during a pharmacokinetic study of a 1 % ocular suspension of 5-[5-(trifluoromethyl)-1,2-oxazole-3-yl]-furan-2-sulfonamide on 6 Wistar rats. Blood samples were collected before administration, as well as 30 min, 1 h, 1 h 30 min, 2 h, 3 h, 4 h, 6 h, 8 h, 12 h, 24 h, 48 h, 72 h, 144 h, 216 h after administration. The non-compartment approach was used for calculation pharmacokinetic parameters.Results and discussion. The developed method has been validated in parameters of selectivity, calibration curve, accuracy and precision, matrix effect, dilution integrity, carry over, reinjection reproducibility, stability. The analytical range of determination of 5-[5-(trifluoromethyl)-1,2-oxazole-3-yl]-furan-2-sulfonamide in plasma was 10–4000 ng/ml, M1 – 1.0–400.0 ng/ml, M2 – 0.1–40.0 ng/ml. The selected combination of anticoagulant and stabilizer solution allows storage of plasma samples in freezing chamber for 28 days.Conclusion. The developed method has been fully validated and confirmed its suitability for quantitative determination of 5-[5-(trifluoromethyl)-1,2-oxazole-3-yl]-furan-2-sulfonamide and its metabolites in the blood plasma of laboratory animals. The method has been successfully used for pharmacokinetic study of 1 % ocular suspension of the drug.

Continuous production of pure formic acid solution from CO2 hydrogenation at room temperature via amine-functionalized PdMn nano-alloy

CO2 hydrogenation into formic acid is of great significance to mitigate CO2 emission. However, conventional routes typically require the addition of unrecyclable bases to shift the reaction equilibrium by the formation of formate, which leads to complex subsequent separation and difficulty in continuous production of pure formic acid solution. Here we report a secondary amine-modified PdMn nanocatalyst for the continuous production of pure formic acid solution in fixed-bed reactors via CO2 hydrogenation. By optimizing fine structure of PdMn nano-alloy, the optimal TOF of up to 26.5 h−1 is obtained under mild reaction conditions (25 ℃, 3.0 MPa). This is one of the highest levels reported for a heterogeneous catalyst without alkali additives under similar conditions. The characterization shows that the two-component alloying effect of PdMn and the synergistic effect between PdMn NPs and secondary amine group (NH) are the key to obtaining superior reactivity. These findings in this work may pave an avenue for conversion of CO2 in a more environmentally friendly way.

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.

In situ photodeposition of ultra-small palladium particles on TiO2.

In situ and operando investigation of photocatalysts plays a fundamental role inunderstanding the processes of active phase formation and the mechanisms ofcatalytic reactions, which is crucial for the rational design of more efficient materials. Using a custom-made operando photocatalytic cell, an in situ procedure to follow the formation steps of Pd/TiO2 photocatalyst by synchrotron-based X-ray absorption spectroscopy (XAS) is proposed. The procedure resulted in the formation of ∼1 nm Pd particles with a much narrower size distribution and homogeneous spreading over TiO2 support compared with the samples generated in a conventional batch reactor. The combination of in situ XAS spectroscopy with high-angle annular dark-field scanning transmission electron microscopy demonstrated the formation of single-atom Pd(0) sites on TiO2 as the initial step of the photodeposition process. Palladium hydride particles were observed for all investigated samples upon exposure to formic acid solutions.

Dehydration of pentose to furfural catalyzed by formic acid – Kinetics and application to real biomass hydrolysates

This paper investigates the kinetics of xylose and real biomass hydrolysate conversion into furfural catalyzed by formic acid through batch experiments. The kinetic experiments were conducted across temperatures ranging from 140 °C to 200 °C using various concentrations of formic acid solution (5–20 wt%) and xylose concentrations varying from 0.062 mol/L to 0.2 mol/L. Three common reaction mechanisms were examined, and their results were compared with previous studies. Among these mechanisms, the model 3 which incorporated the formation of an intermediate followed by its cross-polymerization with furfural, exhibited the most favorable performance, with coefficient of determination values surpassing 95 %. Furthermore, the study demonstrated the reliability of kinetic modeling for raw biomass hydrolysate, with minimal deviation between experimental and predicted values. Optimal conditions resulted in the highest furfural yield of 58 % with a xylose concentration of 0.062 mol/L. Similarly, under identical conditions, birchwood and oat spelts xylans yielded maximum furfural yields of 63 % and 51 %, respectively. Moreover, hydrolysates from oil palm empty fruit bunch and fir wood exhibited the best furfural yields of 62 % and 57 %, respectively, along with an equal 5-HMF yield of 32 %. The results indicated that the developed model exhibited a high level of accuracy in predicting maximum yields with a relative deviation of less than 10 %.

Comparative pharmacokinetics of five primary constituents in Huai-hua powder: a study on normal rats and rats with ulcerative colitis.

The goal of this research was to develop a fast, reliable, and sensitive method to simultaneously quantify five key components of Huai-hua Powder (HHP) in rat plasma with genistein served as the internal standard. Furthermore, the established method was used to perform a comparative evaluation of the pharmacokinetic properties of HHP in normal rats and rats with ulcerative colitis (UC). Chromatographic separation was conducted using an ACQUITY HSS T3 column held at a constant temperature of 35°C, with acetonitrile and a 0.1% formic acid solution in water employed as the mobile phases. Multiple-reaction monitoring facilitated MS operation in positive-negative-ion-switching mode. The method's validation demonstrated exceptional linearity (with a correlation coefficient of r ≥ 0.9970), and the validation tests, encompassing precision within and between days, accuracy, recovery, matrix effect, and stability; all met the predefined acceptable criteria. The results revealed significant variations in the pharmacokinetic characteristics of the five components between normal and UC rats, suggesting altered drug metabolism rates and extents in the latter group. These findings offer crucial scientific insights into the potential clinical application of HHP, particularly in the context of treating UC.