Ammonium Formate Research Articles

DFT Simulations on the Nitrogen Reduction Reaction Activity of Transition Metal Nitride and Oxynitride

Transition metal nitride (TMN) is a promising material towards the energy related applications including catalysis and energy storage.1 The sluggish nitrogen reduction reaction (NRR) due to the high energy input to activate N2 remains a significant challenge for NRR electrocatalysts. The surface N of TMN can be a solution to this with initial N vacancy formation via hydrogenation steps and ammonia formation. In addition, with a small amount of surface oxygen present in the catalyst surface, the resulting oxynitride seems very interesting and active towards NRR.2 But the mechanism behind this is not yet understood.In this study, we first focused on the modelling of the structure of metal nitride (ZrN) and oxynitride (ZrOxNy/ZrN) surfaces. The structure of oxynitride is obtained by running molecular dynamics (MD) calculations at both room temperature and experimental deposition temperature (90°C and 750°C). NRR reaction is then studied via the Mars-Van Krevelen (MvK) mechanism with introducing surface N vacancy and subsequent N2 adsorption and N filling. With computing the reaction energy and activation barriers of key reaction steps on both ZrN and ZrOxNy/ZrN, we can find a clue on how surface N of TMN helps to activate N2 and the role of small amount of surface oxygen on activating N2. To study the origin of small amount of oxygen, reaction energies and full reaction pathway along the deposition process are computed and plotted. Finally, dopant effect will be modeled with transition metal dopants (e.g. Cu and Hf) at surface region to study any localized electronic effect on NRR.These results can be useful to design and deposit ZrN acting as effective NRR electrocatalysts.

Validation of Liquid Chromatography Coupled with Tandem Mass Spectrometry for the Determination of 12 Tyrosine Kinase Inhibitors (TKIs) and Their Application to Therapeutic Drug Monitoring in Adult and Pediatric Populations.

Tyrosine kinase inhibitors (TKIs) are used as targeted cancer therapies in adults and have an off-label pediatric application for the treatment of Langerhans cell histiocytosis. A multitarget LC-MS/MS method was developed and validated for the determination of alectinib, alectinib-M4, binimetinib, cobimetinib, crizotinib, dabrafenib, encorafenib, imatinib, lorlatinib, osimertinib, AZ5104, and trametinib. A total of 150 µL of internal standard methanolic solution was added to 50 µL of plasma sample to precipitate proteins. After centrifugation, 10 µL of the supernatant was injected into the chromatographic system. The chromatographic separation was conducted on a Kinetex C18 Polar column with a gradient of 2 mM ammonium formate in 0.1% formic acid and acetonitrile over 5 min. Limits of detection and quantification, linearity, accuracy, precision, selectivity, carryover, matrix effect, recovery, and stability were evaluated and satisfied EMA guidelines on bioanalytical methods. This method has been successfully applied to the therapeutic drug monitoring (TDM) of adults with melanoma and lung cancer, as well as children with histiocytosis, to improve the pharmacokinetic data for these drugs, with the aim of enhancing the therapeutic management and follow-up of patients. Blood concentrations of trametinib and binimetinib were different in the two groups, highlighting the age-related inter-individual variability of these molecules and the need for TDM.

Assessment of exhaust raw emissions and aftertreatment performance in a retrofitted heavy duty-spark ignition engine operating with liquefied petroleum gas

This study investigates the effects of varying Liquefied Petroleum Gas compositions on pollutant emissions and three-way catalyst performance in retrofitted heavy-duty spark-ignition engines. It focuses on fuels with varying propane and butane ratios, providing new insights into the influence of the composition of Liquefied Petroleum Gas on catalyst activity and tailpipe emissions. Representative conditions from the world Harmonized Transient Cycle were selected to comprehensively assess engine emissions and catalyst performance. Experiments under constant and variable λ conditions tested the catalyst's response concerning raw emissions, exhaust temperature, and space velocity, all variables affected by engine operation. Key findings indicate that catalyst performance is not significantly affected by Liquefied Petroleum Gas composition. Under constant λ conditions, the catalyst achieved high conversion efficiency of carbon monoxide, unburned hydrocarbons, and nitrogen oxides, especially under rich conditions (λ = 0.990). However, rich conditions can lead to elevated ammonia levels, although nitrous oxide generation remains low in all circumstances. Implementing λ pulse strategies reduced ammonia formation to around 25 mg/kWh, ensuring high catalyst conversion efficiency for all pollutant species after optimizing the amplitude and frequency of the pulses to establish the balance of reducing-oxidizing species and oxygen storage for each operation mode. Crucially, Liquefied Petroleum Gas composition was determined to be non-critical for the catalyst in these engines, promoting the use of this fuel in retrofitted engines and promoting for a shift towards cleaner transportation.

ω-(5-Phenyl-2H-tetrazol-2-yl)alkyl-substituted glycine amides and related compounds as inhibitors of the amine oxidase vascular adhesion protein-1 (VAP-1)

Vascular adhesion protein-1 (VAP-1), also known as plasma amine oxidase or semicarbazide-sensitive amine oxidase, is an enzyme that degrades primary amines to aldehydes with the formation of hydrogen peroxide and ammonia. Among others, it plays a role in inflammatory processes as it can mediate the migration of leukocytes from the blood to the inflamed tissue. We prepared a series of ω-(5-phenyl-2H-tetrazol-2-yl)alkyl-substituted glycine amides and related compounds and tested them for inhibition of purified bovine plasma VAP-1. Compounds with submicromolar activity were obtained. Studies on the mechanism of action revealed that the glycine amides are substrate inhibitors, i.e., they are also converted to an aldehyde derivative. However, the reaction proceeds much more slowly than that of the substrate used in the assay, whose conversion is thus blocked. Examination of the selectivity of the synthesized glycine amides with respect to other amine oxidases showed that they inhibited diamine oxidase, which is structurally related to VAP-1, but only to a much lesser extent. In contrast, the activity of monoamine oxidase A and B was not affected. Selected compounds also inhibited VAP-1 in human plasma. The IC50 values measured were higher than those determined with the bovine enzyme. However, the structure–activity relationships obtained with the glycine amides were similar for both enzymes.

EFFECT OF MAGNETITE AND CHITOSAN-MAGNETITE ADDITION ON BACTERIAL LEVELS AND NH3-N (FREE-LIVING N2-FIXING BACTERIA CULTURE)

Free-living N2-fixing bacteria are essential in the soil because they provide a source of nitrogen in the form of ammonium needed by plants to be used in building protein blocks. The fixation of free N2 needs to be increased by adding nanomaterials such as magnetite (Fe3O4), which has an active group and can be a source of nitrogenase enzyme cofactor. In this study, increased N2 fixation used N2-fixing bacteria in Burks medium. This increase was determined by measuring NH3 levels using the Phenate method formed after Burks medium was treated with Fe3O4 and chitosan-magnetite (CS-Fe3O4). The study found that the number of bacteria can be well decreased. This research showed that using Fe3O4 and CS-Fe3O4 increased NH3-N levels in cultures of free-living nitrogen-fixing bacteria by 15.40% and 75.54%. For future development, it can be in the form of optimization, the effect of adding the same material to plant secondary metabolites, and the mechanism of bacteria in using the material.

Determination of 45 Pesticides in Avocado Varieties by the QuEChERS Method and Gas Chromatography-Tandem Mass Spectrometry.

Gas chromatography (GC) tandem mass spectrometry (MS/MS) stands as a preeminent analytical instrument extensively employed for the surveillance of pesticide residues in food. Nevertheless, these methods are vulnerable to matrix effects (MEs), which can potentially affect accurate quantification depending on the specific combination of analyte and matrix. Among the various strategies to mitigate MEs, matrix-matched calibration represents the prevailing approach in pesticide residue applications due to its cost-effectiveness and straightforward implementation. In this study, a total of 45 representative pesticides were analyzed in three different varieties of avocado (i.e., Criollo, Hass, and Lorena) using the Quick-Easy-Cheap-Effective-Rugged-Safe (QuEChERS) method with ammonium formate and GC-MS/MS. For this purpose, 5 g of the avocado sample was extracted with 10 mL of acetonitrile, and then 2.5 g of ammonium formate was added to induce phase separation. Subsequently, the supernatant underwent a cleanup process via dispersive solid-phase extraction employing 150 mg of anhydrous MgSO4, 50 mg of primary-secondary amine, 50 mg of octadecylsilane, 10 mg of graphitized carbon black, and 60 mg of a zirconium oxide-based sorbent (Z-Sep+). The GC-MS/MS analysis was successfully performed in less than 25 min. Rigorous validation experiments were carried out to assess the performance of the method. The examination of a matrix-matched calibration curve for each variety of avocado revealed that the ME remained relatively consistent and less than 20% (considered as a soft ME) for most pesticide/variety combinations. Furthermore, the method´s limits of quantification were lower than 5 µg/kg for all three varieties. Finally, the recovery values for most pesticides fell within the acceptable range of 70-120%, with relative standard deviation values below 20%.

New validated liquid chromatography‐tandem mass spectrometry method for the determination of Dacomitinib in human plasma and its application to a pharmacokinetic study

AbstractDacomitinib, a quinazoline compound, exhibits antineoplastic activity against brain metastasis activities in non‐small cell lung cancer and the central nervous system. In this study, the liquid–liquid extraction method with high‐performance liquid chromatography and tandem mass spectrometry detection method was established and validated for the determination of Dacomitinib in human plasma. Plasma samples were prepared and chromatographic separation was achieved on analytical column Discovery C18 (10 cm × 4.6 mm, 5 μm) with gradient elutes at a flow rate of 0.8 mL/min, using a mobile phase consisting of acetonitrile and ammonium formate. Dacomitinib and dacomitinib D10 (internal standard) were detected by multiple reactions. The method was fully validated according to the United States Food and Drug Administration guidelines. The calibration curve was linear with an excellent correlation coefficient (r2 ˂ 0.99). The method validation steps such as carry‐over, matrix effect, extraction recovery, dilution effect, intra‐inter accuracy, and precision were found within acceptable limits. The method was then applied to a pharmacokinetic study in human plasma. After oral administration, the plasma concentration in different volunteers reached 0.5–250.01 ng/mL. The result established can be applied to the estimation of drugs in human plasma.

Electrochemical nitrate reduction in acid enables high-efficiency ammonia synthesis and high-voltage pollutes-based fuel cells

Most current research is devoted to electrochemical nitrate reduction reaction for ammonia synthesis under alkaline/neutral media while the investigation of nitrate reduction under acidic conditions is rarely reported. In this work, we demonstrate the potential of TiO2 nanosheet with intrinsically poor hydrogen-evolution activity for selective and rapid nitrate reduction to ammonia under acidic conditions. Hybridized with iron phthalocyanine, the resulting catalyst displays remarkably improved efficiency toward ammonia formation owing to the enhanced nitrate adsorption, suppressed hydrogen evolution and lowered energy barrier for the rate-determining step. Then, an alkaline-acid hybrid Zn-nitrate battery was developed with high open-circuit voltage of 1.99 V and power density of 91.4 mW cm–2. Further, the environmental sulfur recovery can be powered by above hybrid battery and the hydrazine-nitrate fuel cell can be developed for simultaneously hydrazine/nitrate conversion and electricity generation. This work demonstrates the attractive potential of acidic nitrate reduction for ammonia electrosynthesis and broadens the field of energy conversion.

LC-MS/MS Bioanalytical Approach for the Quantitative Analysis of Dabigatran in Biological Fluids

A novel bioanalytical methodology has been developed to establish a rapid and sensitive procedure for the detection of dabigatran in biological fluid, specifically human plasma. In this study, dabigatran 13C6 was utilized as an internal standard (IS). The solid phase extraction method was employed to extract dabigatran and internal standard (IS) from a plasma sample. The separated components are determined by utilizing a eluting mixture composed of 2 mM ammonium formate:methanol:acetonitrile (20:40:40 v/v/v). The procedure utilized a GL Sciences Ace C18 stationary phase with dimensions of 150 mm × 4.6 mm; 5 µm. The identification of dabigatran and IS was carried out using the MRM mode, which was chosen to minimize interference from the surrounding matrix. The measured m/z of the protonated precursor ion of dabigatran was 472.20, while the corresponding product ion has a m/z value of 289.10. The precursor ion with a m/z of 478.20 and the product ion with a m/z of 295.20 were generated by the internal standard (IS). Linearity was observed within the range of 1.016-304.025 ng/mL; r2 of 0.9956 and a sample size (n) of 5. The stability of the drug in plasma was evaluated through a series of tests. These tests included a 17 h period on a laboratory bench, 24 h in an injector, six cycles of freeze-thaw and a storage period of 7 days and 22 h at -20 ± 5 ºC. The results of these stability studies indicated that the drug remained stable in plasma. The method was subjected to validation and was determined to be qualified. The proposed analytical approach demonstrates potential for the routine analysis and pharmacokinetic study of dabigatran in biological fluids.

Development of Liquid Chromatography-Tandem Mass Spectrometry Analytical Methods for the Study of Whole-Body, Head, and Trunk Uptake and Elimination of Methamphetamine in 5-Day Postfertilization Zebrafish Larvae Using the Quick, Easy, Cheap, Effective, Rugged, and Safe Technique.

Synthetic cathinones are drugs of abuse substituted for amphetamine-like stimulant drugs such as methamphetamine. In this study, methamphetamine was studied as a prototypical amphetamine-like drug as a first step toward establishing methods to study this entire drug class. The internal concentration of methamphetamine in zebrafish larvae was determined using matrix-matched calibration along with extraction and purification of samples using the quick, easy, cheap, effective, rugged, and safe technique in liquid chromatography-tandem mass spectrometry. Whole-body and head/trunk uptake and elimination in 5-day postfertilization zebrafish larvae were determined. A gradient method was developed using 5 mM ammonium formate with 0.1% formic acid and methanol with 0.1% formic acid as mobile phases, 10 min of total run time, and a 0.3 mL/min flow rate. The limit of quantification was 60 ng/mL, linearity with r2 = 0.9991, and recovery values from 92% to 120%. The internal concentration of methamphetamine was quantifiable in whole-body homogenates within 15 min of uptake analysis. The internal concentration increased with time, whereas a biphasic elimination pattern was shown. With increasing length of exposure, a higher accumulation of drugs was found in the head than in the trunk.

Uranium Stripping with Ammonium Acetate and Formate

Uranium Stripping with Ammonium Acetate and Formate

Degradation kinetics of β-nicotinamide mononucleotide based on reliable HPLC quantitative method

To explore the stability characteristics of β-nicotinamide mononucleotide(NMN) and provide data support for NMN production, preparation, and related product development, this study established a simple HPLC content determination method for NMN in simple substrate and investigated the degradation behavior, degradation products, and degradation kinetics of NMN under various chemical, physical, and biological conditions. The HPLC method employed a Welch Xtimate AQ-C_(18) column(4.6 mm×250 mm, 5 μm), a detection wavelength of 266 nm, a column temperature of 30 ℃, a flow rate of 1.0 mL·min~(-1), an injection volume of 5 μL, and a mobile phase consisting of methanol(A) and a 10 mmol·L~(-1) ammonium formate aqueous solution(B) with a gradient elution(0-6.7 min, 0-4% A; 6.7-13 min, 4%-18% A; 13-14.2 min, 18% A; 14.2-15 min, 18%-0 A; 15-22 min, 0 A). This method provided good separation between NMN and potential impurities and degradation products, and had a wide linear range, short analysis time, good durability, high accuracy, an average sample recovery rate of 98.71%, and an RSD of 1.2%. The instrument precision had an RSD of 0.26%, and the linearity within the examined range was excellent(R~2≥0.999 9). This method can be applied for NMN content determination in simple substrate. The degradation process of NMN in aqueous solution followed apparent first-order kinetics, with the degradation rate primarily influenced by high temperature and pH. NMN was more stable in low-temperature, neutral, or weakly acidic/alkaline environments. Strong acids or strong alkalis could accelerate its degradation, and its degradation rate was less affected by pepsin and trypsin. In an aqueous solution at room temperature, it followed the kinetic equation lg C_t=0.005 7t + 4.817 2, with t_(0.9) and t_(1/2) values of 95.58, 860.26 h, respectively. The results suggest that pH and temperature are the main factors affecting the stability of NMN in aqueous solution, and low temperature, moisture protection, and a weakly acidic environment are more conducive to the storage and application of NMN and its products.

Optimization and validation of a micro–QuEChERS method for phthalates detection in small samples of cetacean blubber

In this study, an innovative method was developed to detect and quantify phthalates in fresh cetacean blubber. An adaptation of the ammonium formate QuEChERS method was used and adapted as a micro-extraction for small quantities of samples. Significantly, this technique utilized minimal quantities of reagents and salts, with the additional implementation of rigorous Quality Assurance/Quality Control protocols to further reduce background contamination. To ensure the reliability of this method, comprehensive validation procedures were conducted, with a specific focus on two widely studied cetacean species: the common bottlenose dolphin (Tursiops truncatus) and the short-finned pilot whale (Globicephala macrorhynchus). Determination coefficients (R2) for matrix-matched calibration were >0.93 with limits of quantifications (LOQ) of the method in the range of 5–10 ng/g. Mean recovery values were between 40 and 100 %. This novel methodology holds particular relevance for environmental research studies, offering the capability to detect emerging contaminants with minimal sample requirements. This aspect is particularly valuable in investigations that involve free-ranging animals and rely on biopsy sampling. It allows for the assessment of contaminant levels in healthy individuals within wild populations, enhancing our understanding of ecological impacts and potential conservation measures.•A micro-extraction adaptation of the ammonium formate QuEChERS method was developed and applied to a small quantity of fresh cetacean blubber to detect phthalates.•Small quantities of reagents and salts were used, and additional Quality Assurance/ Quality Control procedures were taken to further minimize background contamination.•Method validation was carried out for two cosmopolitan and extensively studied cetacean species: the common bottlenose dolphin (Tursiops truncatus) and the short-finned pilot whale (Globicephala macrorhynchus).

Integration of TiO2 QDs with brown TiO2: S-scheme photocatalysts with boosted activity for simulated sunlight-driven N2 fixation without hole quencher

An alternative strategy to solve the energy consumption and pollution problems caused by traditional ammonia production is photocatalytic N2 fixation. Therefore, the rational design and facile synthesis of photocatalysts for the efficacious ammonia production is an active research hotspot. In this research, TiO2 QDs (TQDs) and brown TiO2 (BTO) nanoparticles were combined through a facile hydrothermal method. The optimal homojunction TQDs/BTO (1:1) photocatalyst with QDs size of about 4.5 nm was utilized for ammonia production, for the first time, with the activity of 11844 µmol L−1 g−1, which was almost 14.5, 4.46, and 3.07-folds as large as TiO2 (P25), TQDs, and BTO materials, respectively. In addition, the presence of hydrazine intermediate in the ammonium formation pathway and the impact of hydrogen-free solvents, electron quencher, and acidic and basic solutions on ammonia production were investigated. The electrochemical and spectroscopic characterizations confirmed that the boosted ability of photocatalyst is related to the boosted adsorption of N2 molecules and effective segregation/transfer of charge carriers. Consequently, the S-scheme TQDs/BTO (1:1) homojunction photocatalyst could be a suitable photocatalyst in N2 fixation technology, with high stability for repeated use and a facile synthesis route.

Construct electron transport path through NH2-MIL-125 modified Fe-doped W18O49 nanowires to enhance photocatalytic nitrogen fixation performance

Ammonia has important application value in agriculture and industry as a raw material for producing nitrogen fertilizers and organic chemicals. The Haber-Bosch method is generally utilized to synthesize ammonia through N2 and H2 as raw materials in industry, but the process generates serious energy consumption and pollution. In the paper, a heterojunction catalyst is constructed that adopts NH2-MIL-125 and Fe-doped W18O49 (Fe-W18O49) for photocatalytic nitrogen fixation. Fe-W18O49 is a nanowire containing oxygen vacancies (OVs). OVs can provide active sites for the adsorption and activation of nitrogen gas. The 3D plate-like morphology of NH2-MIL-125 can observably reduce the occurrence of nanowires aggregation. This phenomenon can be attributed to NH2-MIL-125 playing a supporting role in the fixation of nanowires. New mesoporous are formed between NH2-MIL-125 and Fe-W18O49 in the constructed compound catalyst, which can realize efficient mass transfer between the inside and outside of the catalyst. EPR characterization discovers that Fe-W18O49/NH2-MIL-125 cannot produce •O2˗ and •OH radicals. The type II heterojunction forms between Fe-W18O49 and NH2-MIL-125. The heterojunction improves the carrier migration path, and the photocurrent intensity is significantly increased. Under simulated sunlight, Fe-W18O49/NH2-MIL-125–2 emerges the best catalytic performance with an ammonia formation rate of 128.2 µmol g−1 h−1. The yield of ammonia is boosted in comparing with NH2-MIL-125 (13 times) and Fe-W18O49 (1.7 times). After several cycles, Fe-W18O49/NH2-MIL-125 remain maintains good stability during the catalytic process. This paper provides a possibility for constructing low-cost heterojunction catalysts in the territory of photocatalytic nitrogen fixation.

Stability Indicating RP-HPLC Method Development and Validation for Simultaneous Estimation of Dapagliflozin Propanediol Monohydrate and Teneligliptin Hydrobromide Hydrate in Synthetic Mixture

For the quantitative measurement of Dapagliflozin propanediol monohydrate and Teneligliptin hydrobromide hydrate in synthetic mixture form in the presence of its degradants, precise, accurate, robust, cost-effective, and isocratic stability indicating RP-HPLC method was developed and validated. The mobile phase comprises [Methanol: 20 mM Ammonium formate (70:30 v/v)] at a flow rate of 1.0 ml/min, injection volume of 20 µl, and UV detection at 225 nm. Separation was accomplished using Gemini, C18 column. Teneligliptin hydrobromide hydrate and Dapagliflozin propanediol monohydrate were eluted with retention times of 6.65 minutes and 4.20 minutes, respectively. This procedure was approved following ICH guideline Q2 (R1). The calibration plots for Dapagliflozin propanediol monohydrate and Teneligliptin hydrobromide hydrate have correlation coefficients of 0.9995 and 0.9996 over the concentration ranges of 5-100 µg/ml and 10-200 µg/ml respectively. For Dapagliflozin propanediol monohydrate and Teneligliptin hydrobromide hydrate, accuracy ranged from 99.81-100.78% and 99.13-100.69%, respectively. For Dapagliflozin propanediol monohydrate and Teneligliptin hydrobromide hydrate, the LOD was found to be 0.947 µg/ml and 1.355 µg/ml. In contrast, the LOQ was 2.869 µg/ml and 4.107 µg/ml, respectively. The findings demonstrated the applicability of the devised approach for routine analysis of Teneligliptin hydrobromide hydrate and Dapagliflozin propanediol monohydrate in a synthetic mixture form with its degradants.

EXTH-48. PROTOPORPHYRIN IX LEVELS IN PATIENTS’ PLASMA, BLOOD, AND BRAIN TUMOR BY A VALIDATED LC-MS/MS METHOD

Abstract BACKGROUND Protoporphyrin IX (PPIX) is an intermediate molecule in the heme biosynthesis pathway. Cancer cells, having a higher metabolic rate than normal cells, accumulate PPIX when an exogenous dose of its precursor, 5-aminolevulinic acid (5-ALA), is administered. 5-ALA is currently approved by the U.S. FDA for the visualization of high-grade gliomas (HGG) and fluorescence guided surgery. 5-ALA and PPIX are also central to experimental treatments of photodynamic and sonodynamic therapy for HGG patients. Accurate quantitation of PPIX in brain tumor, plasma, and blood is necessary to evaluate its pharmacokinetics and hence optimize its therapeutic benefit in the context of experimental therapies and tumor visualization. METHODS Plasma was used as a matrix for PPIX quantitation in plasma and brain homogenate. Brain homogenates (1:7) were prepared in 5 mM ammonium formate containing 0.2% formic acid. A separate plasma curve was used for blood quantitation. Before protein precipitation, blood and corresponding calibrators were diluted five times with water. PPIX was extracted from human plasma, blood, and brain homogenate samples using methanol containing PPIX-d6 (internal standard). Sample preparation was performed under low light conditions (< 5 lux). Chromatographic separation of the analyte was achieved isocratically on Phenomenex Kinetex™ EVO C18 column, with a total run time of 3.5 min. Analyte detection was performed on Sciex QTRAP 6500+ MS/MS detector. RESULTS The method was validated for 1-2000 nmol/L range. Using plasma as a surrogate matrix, the maximum coefficient of variation for intra- and inter-day precision and accuracy were within acceptable ranges for all matrices. CONCLUSIONS A new rapid and sensitive LC-MS/MS method was successfully validated for the PPIX quantitation in human plasma, blood, and brain. It is currently used in a sonodynamic therapy clinical trial (NCT04559685) to evaluate PPIX pharmacokinetic profile in plasma and blood, and to determine levels in brain tumors of HGG patients.

Comprehensive UHPLC–MS screening methods for the analysis of triazolopyrazine precursor and its genotoxic nitroso-derivative in sitagliptin pharmaceutical formulation

A case study on Sitagliptin drug products and Sitagliptin/Metformin drug products concerning contamination with N-nitrosamines was performed using two newly developed analytical methods for determination of N-nitroso-triazolopyrazine (NTTP; 7-nitroso-3-(trifluoromethyl)–5,6,7,8-tetrahydro-[1,2,4]triazolo[4,3-a]pyrazine) and its precursor triazolopyrazine (3-(trifluoromethyl)–5,6,7,8-tetrahydro-[1,2,4]triazolo[4,3-a]pyrazine). The method for determination of triazolopyrazine was previously unpublished, the method for determination of NTTP was published only for analysis of active pharmaceutical ingredient Sitagliptin and not the drug forms. Solving the N-nitrosamine contamination is requested by regulatory authorities all over the world and thus is vital for all pharmaceutical companies. The solution always requires a sensitive analytical method. Both newly developed methods use liquid chromatography coupled with mass spectrometry (single quadrupole analyzer in case of triazolopyrazine and triple quadrupole analyzer in case of NTTP). Separation of triazolopyrazine was achieved on a column Acquity CSH C18 using a mobile phase consisting of aqueous ammonium formate buffered at pH 4.2 and acetonitrile. Detection was performed using positive electrospray and selected ion monitoring at m/z 193. Separation of NTTP was achieved on a column Acquity HSS T3 using a mobile phase consisting of 0.1 % formic acid in water and methanol. Detection was performed using positive electrospray and multiple reaction monitoring at transitions m/z 222.15→42.05 (collision energy 17 eV) and m/z 222.15→192.15 (collision energy 11 eV). Two issues specific to NTTP and triazolopyrazine previously not described in scientific literature were successfully troubleshooted. Spontaneous degradation of Sitagliptin to triazolopyrazine and methyl (R)–3-amino-4-(2,4,5-trifluorophenyl)butanoate was solved by using N,N-dimethylformamide as sample solvent during development of the method for quantitation of triazolopyrazine. A bad peak shape of NTTP due to the presence of rotamers of NTTP was successfully troubleshooted by increasing column temperature. Both methods were used during an optimization study of manufacturing of Sitagliptin and Sitagliptin/Metformin drug products. The goal of the study was to decrease NTTP content in the final drug product under the strict legislative limit set by Federal Drug Agency. The efficacy of several solutions was proven, but could not be fully disclosed due to Intellectual Property Protection policy of Zentiva. Instead, a brief review of recently published strategies to cope with N-nitrosamine contamination is presented.

BIOLOGICAL NITROGEN FIXATION AS A WAY OF INCREASE YIELD OF SOY

The article highlights the importance of soybeans as one of the main agricultural crops for the life support of society with food. It is well known that soybeans have been the main high-margin crop for many global farmers, including Ukraine, in recent years. The interest in this crop continues to grow as new opportunities for its sale abroad open up, especially in such a giant country as China, the world's largest soybean importer. The right variety accounts for more than 50% of production success. It is important to identify and create optimal conditions for realising the potential nitrogen-fixing activity of soybeans of each variety in specific soil and climatic conditions. Scientists have pointed out that the main reasons that significantly limit symbiotic fixation in our conditions are relatively drier soybean cultivation conditions, especially in the face of abrupt climate change. However, it is also noted that the starting rates of nitrogen fertilisers + symbiotically fixed nitrogen can only offset part of the soybean plants' need for a yield of 4.0 t/ha. The air contains about 76% of nitrogen in the form of N2 gas, which is not available for plant nutrition. However, thanks to the unique ability of legumes to form symbiotic relationships with bacteria of the Bradyrhizobium and Rhizobium genera, N2 gas is converted into an ammonium form of nitrogen suitable for plant use. This interaction takes place in the nodules, which contain the respective bacteria. According to established data, up to 70% of the total nitrogen consumption of soybeans is obtained through biological fixation of nitrogen from the air through symbiosis with nodule bacteria. Based on the analysis of scientific publications on the symbiotic productivity of soybean crops in Ukraine and the world, the indicators of biological fixation by soybean crops in the context of the main soybean producing countries are presented and the importance of soybean cultivation in Ukraine is proved. It is confirmed that soybeans are an important strategic crop in Ukraine, which contributes to the stabilisation of agriculture, increase of soil fertility and nitrogen reserves, eliminates protein deficiency and helps to solve the food problem. The increase in gross soybean harvest is not only due to the expansion of sown areas, but also due to higher yields. To increase the efficiency of soybean production, it is proposed to introduce a set of innovative solutions at different stages of production, as well as to use new, productive varieties. In many publications, the authors emphasise that 30-35% of success in soybean cultivation depends on the right choice of variety and optimally selected technological methods of growing this crop.

Validated extended multiplexed LC-MS/MS assay for the quantification of adagrasib and sotorasib in human plasma, together with four additional SMIs

Recently, two small molecular inhibitors (SMIs) –adagrasib and sotorasib– have been introduced for targeting Kirsten rat sarcoma (KRAS) p.G12C mutations in patients with non-small cell lung cancer (NSCLC). In order to support pharmacokinetic research as well as clinical decision making, we developed and validated a simple and accurate liquid chromatography-tandem mass spectrometry method for the multiplexed quantification of adagrasib and sotorasib. This assay was co-validated with the quantification for brigatinib, lorlatinib, pralsetinib and selpercatinib.Methanol was used for single-step protein precipitation. Chromatographic separation was performed using an Acquity® HSS C18 UPLC column, with an elution gradient of ammonium formate 0.1 % v/v in water and acetonitrile. In K2-EDTA plasma, adagrasib was found to be stable for at least seven days at room temperature and 4 °C, and at least 3 months at −80 °C. Sotorasib was found to be stable for at least three days at room temperature, seven days at 4 °C and at least 3 months at −80 °C. The method was validated over a linear range of 80–4000 ng/mL for adagrasib and 25–2500 ng/mL for sotorasib. The assay is therefore well-equipped for determining plasma concentrations in clinical practice.