Negative Ion Research Articles

Nonlinear analysis of ion‐acoustic solitary waves in an unmagnetized highly relativistic quantum plasma

AbstractThe present paper explores the dynamics of ion‐acoustic solitary waves (IASWs) within an unmagnetized, highly relativistic quantum plasma containing positive and negative ions alongside electrons, employing the quantum hydrodynamic model. The treatment accounts for the inertial characteristics of negative and positive ions, considering electrons as inertialess. The nonlinear nature of quantum IASWs is investigated through the derivation of the Korteweg–de Vries equation using the reductive perturbation method. The investigation highlights how wave propagation characteristics, whether compressive or rarefactive, are substantially modulated by several parameters, such as the quantum diffraction parameter , relativistic effects , equilibrium density , and ion mass ratio . The analysis identifies the existence of both slow and fast wave modes, heavily influenced by the relativistic parameters involved. Our findings have significant implications for the understanding of both laboratory and space plasmas, especially in contexts where negative ions are present.

Laser Driven Wake Wave in Pair-ion Electron Plasma with Inclusion of Ion Dynamics

Abstract The generation of laser driven plasma wake wave has been investigated in hydrogen 
 pair-ion electron plasma. The consideration of 
 dynamics of the positive and negative ion pair have been adopted. Inclusion of the ion motion
 has the effect of modifying the electric field and density profiles of the wake wave.
 This has been demonstrated by observing the variation of the 
 electron density and electric field profiles with the change in positive ion/ negative ion concentration.
 High density spikes and sawtooth like electric field profiles (indication of wave breaking) are observed 
 to transform into sinusoidal electric field profile and low amplitude density profile 
 when the positive ion density in the plasma system is kept higher. Furthermore, we observe the variation of 
 the electric field amplitude of the wake wave with the laser pulse width. This feature is the indication of 
 the possibility of hybrid acceleration (Direct Laser Acceleration and wake field acceleration) 
 of accelerated beam. The results are quite relevant in the field Laser plasma interaction field 
 in experimental physics and also in planetary
 environment.

Persistent and Bioaccumulative Halogenated Natural Products in Various Tropical Reef Fish Species from the Seychelles, Western Indian Ocean.

Gas chromatography with electron capture negative ion mass spectrometry (GC/ECNI-MS) was used to quantify and compare halogenated natural products (HNPs) and selected anthropogenic persistent organic pollutants (POPs) in individual samples of 17 fish species from the Seychelles (Western Indian Ocean). The sum-HNP amounts (9.5-1100 ng/g lipid mass (lm)) were between 1 and 2 orders of magnitude higher than those of the sum of seven abundant polychlorinated biphenyl (PCB) congeners (0.2-15 ng/g lm) and dichlorodiphenyltrichloroethane-related compounds (DDTs) (<1.1-43 ng/g lm). Within the group of HNPs, the two tetrabrominated phenoxyanisoles (aka methoxylated diphenyl ethers, MeO-BDEs), 2'-MeO-BDE 68 ≫ 6-MeO-BDE 47, were predominant in most cases. Pearson correlation analysis showed that MeO-BDE levels were positively correlated with less abundant HNPs (2,2'-diMeO-BB 80, 2',6-diMeO-BDE 68, and Br6-DBP) (p < 0.01). Accordingly, HNPs, rather than PCBs and DDTs, were the predominant polyhalogenated contaminants in the current species.

Addressing a major interference in the quantification of psilocin in mouse plasma: Development of a validated liquid chromatography tandem mass spectrometry method

Psilocybin is a psychedelic compound found in some hallucinogenic “magic mushrooms”. Psilocin is the active metabolite of Psilocybin, and it is the subject of several studies for the treatment of psychological disorders, such as anxiety, depression, and post-traumatic stress disorder. As such, the pharmacokinetic properties of psilocin should be evaluated to ensure its safety and efficacy as part of the drug development process. Based on the previously published studies, reversed-phase liquid chromatography (LC) was tested for psilocin quantification. The analysis, however, showed a major interference in mouse plasma that was not, to the best of our knowledge, reported previously. We, therefore, aimed to identify and separate the interference, using various chromatographic columns, mobile phase conditions, and mass spectrometers (MS) instruments. Chromatographic separation was achieved on an ultra high performance liquid chromatography (UHPLC) system, and a quadrupole-linear ion trap equipped with an electrospray ionization (ESI) source was used in positive ion mode with multiple reaction monitoring (MRM). Several chromatographic conditions and column chemistries, including C-18 and Phenyl-hexyl were initially tested, and failed to separate the interference. Exact mass measurement and MS/MS analysis were used to determine the structure of the interfering compound, which was confirmed to be tryptophan. Using the identified structure of the interfering compound, a fast and reliable hydrophilic interaction liquid chromatography (HILIC)-MS/MS method was developed and validated, that was capable of separating psilocin from the interference while achieving a 0.5 ng/ml lower limit of quantification (LLOQ). The validated method was successfully applied to a pharmacokinetic study where psilocin was orally administered to C57BL/6 mouse subjects. Psilocin concentration in all the analyzed mouse plasma samples was successfully determined.

Cationization agent affects the stability of secondary ions in MeV-SIMS

The work presents studies of the cationization agent effect on the ionization efficiency, and on the stability of secondary molecules, which are desorbed from the surface as a result of bombardment by MeV primary ions. Different organic molecule standards were mixed with various trifluoroacetate (TFA) salts, namely AgTFA, LiTFA, NaTFA and KTFA, with Ag, Li, Na and K being common cationization agents of secondary ions besides hydrogen. Results show modest differences in ionization efficiency, and significant variation of secondary ions’ stability when different cationization agents are attached to the molecule. For all reference samples, lithium provided the most stable secondary ions with almost none detected fragmentations after the desorption, while secondary ions with attached potassium were measured as much less stable, and the ratio between neutrals (fragments) and normal positive ions is estimated to be more than 0.2. However, even potassium – ionized molecules were recognized as more stable than protonated molecules.

Hysteresis in radio frequency capacitively coupled CF4 plasmas

Abstract Based on experiments and simulations, various plasma parameters are found to undergo a hysteresis as a function of the driving voltage amplitude in capacitively coupled CF4 discharges. Phase Resolved Optical Emission Spectroscopy reveals that the discharge operates in a hybrid combination of the drift-ambipolar and α-mode at low voltage. In this mode, the electric field and mean electron energy are high in the electronegative plasma bulk region. As the cross section for electron attachment is appreciable only at high electron energies, this mode results in strong negative ion production and keeps the electron density low as well as the mode of plasma operation stable, when the voltage is increased moderately. Increasing the driving voltage amplitude further ultimately induces a mode transition into a pure α-mode, once the electron density increases strongly. Decreasing the voltage again results in a reverse mode transition at a lower voltage compared to the previous mode transition, because the electron density is now initially high in the bulk and, thus, the bulk electric field and mean electron energy are low resulting in inefficient generation of negative ions via electron attachment. This keeps the electron density high even at lower driving voltages. This effect leads to the emergence of two steady states of plasma operation within a certain voltage range. The different electron energy distribution functions in these two states result in markedly different generation and density profiles of F atoms, with higher values occurring in the increasing voltage branch of the hysteresis. The ion flux and mean energy at the electrodes also differ. The voltage range, where the hysteresis occurs, is affected by the ion induced secondary electron coefficient (γ). A larger value of γ results in a shift of the hysteresis voltage range towards lower values.

Investigating the Chemical Profile of Underexplored Parts of Dipteryx alata (Baru) Using the PS–MS Technique

The baru (Dipteryx alata Vog.), a fruit native to the Cerrado biome, is well-known for its almonds, which are extensively exploited and exported. Unfortunately, the remaining parts of this fruit are often discarded. This study investigates the fixed chemical constituents of the baru, including the bark, pulp, endocarp, and almonds, using the PS–MS technique in positive and negative ionization modes. Notably, this research presents the first chemical profile of baru almonds in both their raw and roasted states. The analysis identified 57 compounds reported for the first time in a baru and 24 common compounds. The majority of these compounds are classified as flavonoids. In both ionization modes, the peel exhibited a higher proportion of phenolic compounds, although the chemical compounds varied among the peel, pulp, almond, and endocarp. These findings highlight the perspective of bioeconomy and biotechnology. By staggering baru fruit production alongside extractivists, we can optimize the utilization of all parts of the fruit. Furthermore, given the knowledge of the biological properties of flavonoids and the baru composition, we recommend additional studies to analyze their potential in preventing chronic non-communicable diseases.

The electron affinity of rubidium: a state selective measurement

Abstract Negative ions, which are formed when an electron is attached to a neutral system, are unique quantum systems. The lack of a long-range Coulomb force causes the inter-electronic interactions to become relatively more important. As a consequence, the independent particle model, which adequately describes atomic structure under normal conditions, breaks down. The alkali negative ions, with a closed valence s-shell, are among the simplest anionic systems. Hence, they can favorably be used to benchmark atomic theory. In this work, we have determined the electron affinity of 85Rb by measuring the relative partial photodetachment cross section of the negative ion, leaving the residual atom in the 5p 2P3/2 excited state. Resonance ionization spectroscopy allows for state selectivity and the ability to measure the Wigner s-wave threshold onset of the photodetachment process. The electron affinity of 85Rb was determined to be 485.887(6) meV.&amp;#xD;

The detachment-induced mode in electronegative capacitively coupled radio-frequency plasmas

Abstract Insights into the spatio-temporally resolved electron power absorption dynamics in capacitively coupled radio-frequency plasmas are essential for understanding the fundamentals of their operation and as a basis for knowledge-based plasma process development. Similar to the γ-mode, an ionization maximum is observed at the sheath edge around the time of maximum sheath voltage in electronegative oxygen discharges at a pressure of 300 Pa. Based on Particle-in-Cell/Monte Carlo Collisions (PIC/MCC) simulations, we demonstrate that this maximum is not only caused by secondary electrons emitted at the electrode and collisionally multiplied inside the sheath. In fact, it also occurs in the complete absence of secondary electrons in the simulation, and is caused by the generation of O− ions by electron attachment close to the electrode during the local sheath collapse. These negative ions are accelerated towards the plasma bulk by the sheath electric field during sheath expansion. By electron detachment from these negative ions, electrons are generated inside the sheath and are accelerated towards the plasma bulk by the instantaneous sheath electric field - similarly to secondary electrons. Ionization is also observed in the plasma bulk and caused by electrons generated by detachment and accelerated by the high drift-and ambipolar electric fields. This detachment-induced electron power absorption is found to have significant effects on the discharge in the presence and absence of secondary electron emission. Its fundamentals are understood based on an analysis of the spatiotemporal electron and O− power absorption dynamics as well as the trajectory of selected O− ions close to the electrode.

Low energy electron scattering cross sections of cyanotriacetylene (HC7N) based on ab-initio R-matrix method

Abstract Cyanotriacetylene (HC7N) is a linear unsaturated molecule detected in various regions of space. In this present study, we explored the quantum dynamics of low-energy electron collisions with linear cyanopolyyne molecule (HC7N) to identify the locations and structural features of their metastable negative ions (also known as transient negative ions). We employed the R-matrix method for handling low-energy electron scattering studies. To uncover trends among cyanopolyynes molecules, we have also incorporated results from Cyanoacetylene (HC3N) and Cyanodiacetylene (HC5N). Notably, we observed that the number of π* resonances increases and shifts to lower energies as the number of triple bonds increases in higher-order molecules. Our theoretical calculations contain elastic, differential, and momentum cross-sections in the elastic part. Additionally, we calculated excitation and ionization cross-sections in the inelastic regime. This comprehensive theoretical data on electron scattering will be valuable for understanding the molecular chemistry involving this interesting molecule.&amp;#xD;

Ionization processes of negative corona discharge. Part 2. Theory. Comparison with experiment

The purpose of the research is a theoretical analysis of ionization processes in the air, which are initiated by a high-voltage field generated by the negative needle-flat electrode electrode system. Methods. Fe, Cu, Al electrodes are used. Calculations are carried out using the methods of quantum mechanics and mathematical physics. Results. The processes of cold and thermoelectron emission of electrons, enhanced by an external high-voltage field (Schottky emission), are analyzed. The conditions under which the generation of charges from the cathode surface due to plasma-chemical reactions and the capture of surface electrons by electronegative oxygen molecules are decisive are investigated. Based on the PE theory, a theory of injection of negative ions from the cathode into an electronegative gas is constructed and the theory is compared with experiment. It has been shown that at small radii of curvature of needle tips, when E ≥ 106 V/cm, the generation of charges is due to cold emission of electrons. In average fields E ≈ 105 V/cm, electron emission is due to the Schottky effect. In fields E ≈ 104 V/cm and below, injection is caused by electrochemical processes and PE capture. A theory has been developed for PEs that appear at electric field intensities on the electrode of the order of several tens of kV/cm, that is, on flat and slightly curved negative electrodes. The capture of PE by electron-withdrawing molecules causes an injection current and, as a consequence, the ignition of a corona discharge. Analytical expressions for the surface density as a function of the local electric field strength, as well as an expression for the injection current, are obtained. The agreement between theory and experiment is satisfactory. Conclusion. An analysis of the development of CR on negative needles is given. A theory of PE at the cathode in strong electric fields was developed. Based on the results of measuring dark negative current-voltage characteristics, it is possible to determine the patterns of surface processes involving electronic transitions, in particular, determine the concentration of PE and injection currents.

A simple and sensitive LC-MS/MS method for the determination of loganic acid in rat plasma and its pharmacokinetic analysis.

Loganic acid is an iridoid compound extracted from Gentianaceae plant Gentiana macrophylla Pall. It can effectively inhibit inflammation and tumor migration and has antioxidant activity. In this paper, we establish a simple, fast, sensitive and validated LC-MS method with the purpose of quantification of loganic acid in rat plasma with gliclazide as an internal standard (IS). Methanol was used to precipitate the protein in the plasma sample, and a C18 column (2.1 × 50 mm, 1.7μm) was used for the separation of the target compound. Meanwhile, 0.1% formic acid water-methanol was employed as the mobile phase. Multiple reaction monitoring detection mode was adopted in detection with m/z 375.1 > 213.2 for loganic acid and m/z 322.1 > 169.9 for the IS, respectively, in negative ion scan mode. The linear range of calibration curve was 5.77-11,540.00 ng/ml, and the lower limit of detedtion was 2.89 ng/ml. The inter-day and intra-day precision and accuracy were <15% for lower limit of quantitation, low, middle and high quality control samples. This method was successfully used for the pharmacokinetic study of loganic acid in rat plasma at a dose range of 50-150 mg/kg for oral administration and 2mg/kg for intravenous administration. The pharmacokinetic results showed that the oral bioavailability of loganic acid was low (2.71-5.58%).

Constituents of alexander’s celery (Smyrnium olusatrum) extracts and their antioxidant, enzyme inhibitory and anticancer effects based on in vitro, in silico and network pharmacology methods

This research delves into the medicinal significance of Smyrnium olusatrum by investigating ethyl acetate, ethanol, ethanol/water, and infusion extracts. The chemical composition analysed through LC-MS-qTOF metabolomic analysis, determine total phenolic and flavonoid contents, evaluate antioxidant potential using six in vitro tests (DPPH, ABTS, FRAP, CUPRAC, phosphomolybdenum assay (PBD), and metal chelating assay (MCA)), assess enzyme inhibition activity against acetylcholinesterase (AChE), butyrylcholinesterase (BChE), tyrosinase, α-amylase, and α-glucosidase, and explore their anticancer effects on HEp-2 cells. Additionally, qPCR analysis is conducted on HEp-2 larynx cancer cells to examine the impact of S. olusatrum on self-renewal and apoptosis pathways, along with the expression levels of key genes associated with these pathways. The findings indicated that the infusion extraction method demonstrated the highest levels, with a recorded TPC of 35.02 mg GAE/g and a TFC of 15.08 mg RE/g. All four extracts of S. olusatrum exhibited a total of 328 entities. The most significant metabolites, primarily comprising polyphenolics, flavonoids, non-structural carbohydrates, and amino acids in negative ionization mode, as well as sesquiterpene lactone and amino acids in positive ionization, were identified. Infusion exhibited the highest antioxidant effect among the extracts, with peak values ranged from 55.55 mg TE/g (DPPH) to 100.07 mg TE/g (ABTS). The extracts exhibited variable enzyme activities. Notably, ethyl acetate also demonstrated superior α-Amylase inhibition (0.69 mmol ACAE/g), while the ethanol extract exhibited higher α-Glucosidase inhibition (1.70 mmol ACAE/g). The HEp-2 cells demonstrated the quickest attainment of half maximal inhibitory concentration values with ethanol and ethanol/water extracts, yielding IC50 values of 250 µg/mL (24 h) and 125 µg/mL (24 h), respectively, among the applied extracts. The qPCR results revealed that S. olusatrum inhibited all self-renewal pathways and activated the apoptotic pathway. The ethanol and ethanol/water extracts of S. olusatrum significantly suppressed WNT1, APC, LEF1, and TCF7 genes. Furthermore, the downregulation of NOTCH1, SHH, and SMO gene expressions in all extracts suggests the activation of the Type 1 non-canonical hedgehog pathway in laryngeal cancer. The findings not only underscore the therapeutic potential of these extracts but also open the way for further exploration of their applications in combating oxidative stress, enzyme-related disorders, and potential anti-cancer effects through modulation of crucial cellular pathways.

The cervicovaginal metabolome in women with favorable induction cervix and those unfavorable for induction when delivering at term

BACKGROUNDCervical ripening is crucial for induction. However, its influencing factors, mechanistic understanding, and effective risk stratification are still challenging. Recent research suggested that microorganisms and their metabolites in vaginal spaces correlate to preterm birth. However, it remains unclear whether the cervicovaginal metabolome is related to the natural physiological process of cervical maturation. OBJECTIVEWe aimed to analyze the cervicovaginal metabolome in women with favorable induction cervix and those unfavorable for induction when delivering at term. STUDY DESIGNCervicovaginal swabs were collected between 40 and 41 weeks gestation from the following 2 different groups of patients: Ripe group (n=25) which was favorable for the induction cervix and Unripe group which was unfavorable for the induction cervix (n=25). Samples were tested using untargeted metabolomics analysis and analyzed by a bioinformatics platform. The correlation analysis between the metabolome and the previously acquired microbiome was also performed. RESULTSA total of 629 metabolites were identified in cervicovaginal fluid. The cervicovaginal metabolome was significantly different between the women with the ripe cervix and those with the unripe cervix, especially within each stratum of the same CST. Metabolites within the amino acid, carbohydrate, and dipeptide pathways may play a role in this distinction. Thirty-four metabolites were significantly upregulated, and the remaining fourteen were significantly downregulated in the Unripe group with an unripe cervix unfavorable for induction. Statistical modeling identified Arachidonic Acid and Nicotinate associated with the risk of cervical maturation disorder (AUC 0.87) in negative ion mode. A combination of Choline and D-Mannose identified a risk of cervical maturation disorder (AUC 0.80) in positive ion mode, improved by Lactobacillus relative abundance (AUC 0.89). CONCLUSIONThese data suggested that the cervicovaginal space was metabolically active during pregnancy and significantly altered among the women with the mature and immature cervix. Combining the genera-level phylotypes and metabolites could build better cervix maturity prediction models. By using cervicovaginal fluid samples, we demonstrated the potential of multi-data type integration for developing composite models toward understanding the contribution of the vaginal environment to the remodeling of cervix during term pregnancy.

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.

LC-MS/MS Bioanalytical Procedure for Atrasentan in Human Plasma: Method Development and Validation

11ABSTRACTObjectives: The objective of this work is to establish a bioanalytical technique for the quantification of atrasentan. The employed methodology for the detection and quantification of atrasentan in human plasma has a high degree of specificity, sensitivity, and simplicity. Methods: Shimadzu pumps were utilized in conjunction with an Autosampler Agilent Zorbax XDB C18 2.1 × 50 mm, 5 μm column employed as a stationary phase to achieve the chromatographic separation. Acetonitrile (0.1% formic acid) and 5 mM ammonium formate made up the mobile phase, which was optimized to have a 70:30% v/v ratio. Isocratic elution was employed in the experiment, with a flow rate of 0.150 mL/min. The entire cycle took 3.0 minutes, using a 10 μL injection volume. Results: The detection procedure is executed utilizing positive ion mode electrospray ionization (ESI) mass spectrometry under atmospheric pressure. For atrasentan, the precursor to product ion transitions used for quantification was m/z 511.623 to 354.15 and for the internal standard, verapamil, m/z 455.22 to 165. 02. The retention times for atrasentan and verapamil were found to be 1.68 and 0.96 minutes, respectively.Conclusion: In accordance with the recommendations of the United States Food and Drug Administration (USFDA) and EMA, it was ascertained that the remaining validation parameters remained within the specified range.

Bio-analytical Methodology for Exploring Ripretinib’s Pharmacokinetic Profile in Rat Plasma Employing Bosutinib as an Internal Standard Utilizing LC-MS/MS

A robust, consistent, straightforward, swift, and precise liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was tailored for the bioanalytical analysis of ripretinib, with bosutinib serving as the comparative standard. This article provides a synopsis of recent developments in bioanalytical LC-MS/MS techniques utilizing a phenyl column (150x4.6 mm, 3.5 μ) and an eluting agent composed of ammonium formate at a pH of 2.5, which was altered in a 50:50 ratio with formic acid and acetonitrile. The chromatogram was utilized to analyse ripretinib, and the MS detector was equipped with electrospray ionization (ESI) method functioning in positive ionization conditions with multiple reactions monitoring (MRM). This allowed for the recording of transition m/z values of 531.4465→170.9638 for ripretinib and 511.4230 → 160.7133 for BTB. In the chromatographic analysis, ripretinib was retained for approximately 2.433 minutes, whereas BTB was retained for around 3.608 minutes. The validity of the approach extends across a linearity scale of 5 to 100 ng/mL for ripretinib, boasting a correlation index of 0.9999. In the realm of biological matrices, the extraction procedure employing the protein precipitation technique yields recovery rates of 99.6, 99.2, and 98% at the lower, middle, and higher quality control levels, respectively. The obtained results for accuracy, precision, matrix effect, and stability were determined to be within the acceptable range. To observe the investigated analyte in bodily fluids, pharmacokinetic studies yielded key parameters, including a half-life of 10 hours and a time to reach a maximum drug level of 4 hours. This thorough assessment affirms that the method satisfies rigorous criteria for system suitability and specificity well within predefined acceptance limits. Such performance positions it as an indispensable asset in the realm of bioanalysis, significantly broadening its clinical applicability.

High Throughput LC-MS/MS Method for the Quantitation of Mefenamic Acid in Rat Plasma by Protein Precipitation Technique Using 96 Well Plate Format

An advanced and validated high-throughput liquid chromatography-tandem mass spectrometry (LC-MS/MS) approach has been established to accurately determine the concentration of mefenamic acid in rat plasma. This method utilizes mefenamic acid D4 as the internal standard (ISTD). The analyte and ISTD underwent protein precipitation in a 96-well plate format and were then separated on a BDS Hypersil C8 column (3 μm, 100 x 4.6 mm) using a precise isocratic mobile phase of 2 mM ammonium formate by 0.1% formic acid and acetonitrile (30:70 v/v). The detection was performed on a triple quadrupole mass spectrometer utilizing positive ionization consideration. The approach demonstrated a concentration range of 20.659 to 20067.772 ng/mL, thru relative regaining reaching from 69.1 to 74.3%. The inter-batch precision was excellent, with a coefficient of variation (%CV) of ≤ 7.8%. Additionally, the inter-batch accuracy at four different quality control-points ranged from 97.0 to 100.4%, demonstrating high levels of accuracy. This method has been thoroughly validated and is extremely specific, accurate, and precise. It is perfectly suited for high-throughput investigation of mefenamic acid in rat plasma, making it ideal for routine analysis.

Mass spectrometric characterization of aminophospholipids containing N-(2-hydroxyethyl)glycine in kombu algae extracts.

1,2-Diacyl-sn-glycero-3-phospho-O-[N-(2-hydroxyethyl)glycines] (PHEGs) are a class of rare aminophospholipids found specifically in brown algae, including kombu seaweed. Despite their potential importance in algal physiology, a comprehensive mass spectrometry (MS) characterization, useful to understand their biological behaviour, is still lacking. To establish the structural regiochemical features of PHEGs, we employed hydrophilic interaction liquid chromatography (HILIC). Following separation, the isolated band of PHEGs was analyzed using MS techniques. This included multistage tandem MS experiments, performed in both positive and negative electrospray ionization modes at low and high resolution. By comparing MS/MS and MS3 spectra acquired in negative ion mode, the regiochemical rules for PHEG identification were established. The most abundant PHEG species in kombu seaweed, from both Laminaria ochroleuca (European Atlantic) and Laminaria longissima (Japan), was identified as PHEG 20:4/20:4. Less abundant species included PHEG 20:4/20:5 and hydroxylated forms of both PHEG 20:4/20:4 (i.e. 40:8;O) and 20:4/20:5 (40:9;O). The presence of a lyso PHEG 20:4 was consistently detected but at very low levels. This study employed MS analysis to elucidate the regiochemical patterns of PHEGs in kombu seaweed. We identified PHEG 20:4/20:4 as the dominant species, along with several less abundant variants, including hydroxylated forms. These findings provide valuable insights into the potential roles and metabolism of PHEGs in brown algae, paving the way for further investigation into their biological functions.

Benzylic rearrangement for urinary analysis of guanidino and ureido compounds in cardiac surgery-associated acute kidney injury using high-performance liquid chromatography-tandem mass spectrometry.

RationaleBecause acute kidney injury (AKI) is closely related to poor prognosis in critically ill patients, developing biomarkers for its prediction and early diagnosis is particularly important. Endogenous guanidino compounds (GCs) and ureido compounds (UCs) can participate in various biochemical processes because of their important physiological activities. The aim of this study was to investigate the alteration profiles of urinary GCs/UCs as potential biomarkers in patients with cardiac surgery–associated acute kidney injury (CSA‐AKI) at different stages.MethodsGCs/UCs were reacted with benzil via benzylic rearrangement, and their derivatives were used to investigate fragmentation mechanisms using tandem mass spectrometry (MS/MS) in positive ion mode. Furthermore, a high‐performance liquid chromatography (HPLC)–MS/MS method was developed to measure the concentrations of GCs/UCs in urine samples taken from patients with CSA‐AKI at different time points.ResultsMS/MS analysis in positive ion mode showed that benzylic GCs/UCs exhibited similar fragmentation processes, which could produce the characteristic ion (C13H12N+) at m/z 182.0. Furthermore, an obviously different fragmentation pattern of benzylic UCs in the positive ion mode might be due to the neutral loss of the H2CO2 group under low collision energy. Of the eight selected GCs/UCs, methylguanidine exhibited significantly increased concentrations in urine when CSA‐AKI occurred, whereas guanidinoethyl sulfonate (GDS), homoarginine (HArg) and homocitrulline (HCit) exhibited decreased concentrations. After recovery from AKI, the urinary concentrations of the aforementioned GCs/UCs returned to normal. Some of the aforementioned metabolites with significant changes (GDS, HArg and HCit) had large areas under the curve in the receiver operating characteristic curve for distinguishing AKI stages on the third day after surgery.ConclusionsIn patients with CSA‐AKI, urinary GCs/UCs were significantly disrupted due to injured kidney, and some GC/UC metabolites exhibited a good ability to become potential biomarkers for AKI stages. The present study provides essential resources and new therapeutic targets for further research on CSA‐AKI.