Gradient Mode Research Articles

Highly sensitive ultra-high-performance liquid chromatography coupled with tandem mass spectrometry method for the multiplex analysis of levosimendan and its metabolites OR-1855 and OR-1896 in human plasma

Levosimendan is a positive inotrope and vasodilator used in patients with acute and chronic decompensated heart failure. It is metabolized into OR-1855 (inactive metabolite), which is further acetylated into OR-1896 (active metabolite having a prolonged half-life, hence a sustained effect). Levosimendan represents a valuable alternative to traditional inotropes with broad clinical applications in critically ill patients with cardiogenic shock, advanced heart failure and post-cardiac surgery. However, while levosimendan demonstrates dose-dependent hemodynamic effects, its pharmacokinetics has not yet been investigated in adult critically ill patients, a vulnerable population characterized by complex and unstable conditions that may significantly alter drug disposition. Therefore, pharmacokinetics studies of levosimendan and metabolites in critically ill patients require a reliable and sensitive quantification method.We developed and validated a highly sensitive method using ultra-high-performance liquid-chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS) for the quantification of levosimendan, OR-1855 and OR-1896 in human plasma. To achieve the required analytical sensitivity, plasma sample preparation included protein precipitation with acetonitrile, subsequent supernatant’s evaporation to dryness under nitrogen, and reconstitution of the solid residues with a solution of H2O:MeOH 4:1, followed by a 40 µL-aliquot injection into the LC column. Chromatographic separation of the three analytes was achieved in a 6-minute run in gradient mode, using an Acquity UPLC BEH C18 1.7µm, 2.1 ×150mm column. The method was extensively validated according to international bioanalytical assay guidelines, on a clinically relevant concentration range of 0.1 to 100ng/mL, for each analyte. Considering these very low concentrations, the assay showed excellent performances in terms of trueness (94.3-105.3%), repeatability (1.9-7.2%) and intermediate fidelity (2.3-9.7%).Of note, during our ex vivo studies on whole blood samples stability, acetylation of the metabolite OR-1855 into the active OR-1896 metabolite was observed in the presence of red blood cells.The UHPLC method is being applied for a prospective observational pharmacokinetics study of levosimendan in patients undergoing extracorporeal membrane oxygenation support. The benefit of levosimendan therapeutic drug monitoring in intensive care patients remains to be assessed.

Effect of ion temperature anisotropy on ITG mode in reversed-field-pinch plasmas

The Ion Temperature Gradient (ITG) mode instability in the Reversed-Field-Pinch (RFP) plasmas with anisotropies in ion temperature and its gradient, is studied for the first time using the gyrokinetic integral eigenmode equation. Detailed numerical results indicate that ITG instability is reduced by ion temperature anisotropy, specifically when the temperature is higher in the direction perpendicular to the magnetic field or sufficiently high in the direction parallel to the magnetic field, with Landau damping playing a significant role. Moreover, the driving force of the ion temperature gradient in the parallel direction for the ITG mode is stronger than that in the perpendicular direction, particularly when the parallel ion temperature is higher. In addition, the study provides detailed insights into the synergistic effects of ion temperature anisotropy with magnetic shear, poloidal wave number, safety factor, and density gradient on ITG mode. It also elucidates the threshold of the ion temperature gradient necessary for mode excitation.

Mechanical properties and multiscale structure evolution of cement mortars under temperature cycling and low-humidity coupled condition

The degradation of concrete induced by wide temperature differences and drying significantly impacts the durability of constructions in plateau regions. This study systematically investigated the mechanical properties, the structure evolution from nanoscale to macroscale, and the hydration product changes under temperature cycling with low relative humidity (5–60°C cycling, 30±5 % RH). Damage gradients were meticulously discussed based on the experimental measured thermal gradient and mechanical failure modes. Pore coarsening and microcracks which increased with w/c mainly occurred between 50 nm and 50 μm, becoming key factors contributing to the mechanical degradation. Nevertheless, the relatively small damages enable the mortar to maintain much stable mechanical properties than cement paste and concrete. The hydration and the small amount of decomposition had little effect on the structure. Overall, the strength increased until a certain time window followed by a decreasing trend because of two contradictory factors: enhancement led by the increase of capillary pressure and surface energy and degradation driven by the gradient damage.

Development of an HPLC Method for Simultaneous Quantitation of Hyperin, Quercetin and Kaempferol in the Semen cuscutae

In this study, a method for the simultaneous quantification of hyperin, quercetin, and kaempferol in samples of Semen cuscutae was developed using high-performance liquid chromatography (HPLC). The chosen chromatographic conditions were a mobile phase of methanol – 0.1% formic acid in water, running in gradient mode, with a flow rate of 0.9 ml/min, and detection wavelengths of 354, 365, and 369 nm for hyperin, kaempferol, and quercetin, respectively. The results of the quantitative analysis of 5 samples of Semen cuscutae purchased from Phu Tho province showed hyperin content ranging from 0.950 to 1.218 mg/g; quercetin from 0.077 to 0.118 mg/g; and kaempferol from 1.051 to 1.190 mg/g based on the dry weight of the medicinal material. This research may be suitable for the quality control of Semen cuscutae in the market.

The role of ion-scale micro-turbulence in pedestal width of the DIII-D wide-pedestal QH mode

Abstract The low-edge rotation, intrinsically ELM-free, and improved confinement wide-pedestal quiescent H-mode (QH-mode), discovered in DIII-D tokamak, has pedestal widths exceeding the EPED-KBM model scaling typically by at least 25%. Ion-scale (k_y ρ_s<1) microturbulence and its role in setting the pedestal structure is investigated using the radially local δf gyrokinetic code CGYRO. The electromagnetic trapped electron mode (TEM) is unstable at the pedestal top, while plasma beta (β_e) is ~60% below the kinetic-ballooning mode (KBM) onset threshold and the electron temperature gradient (ETG) mode is found to be unstable in the peak gradient region. Nonlinear simulation reveals that the ion-scale turbulence could produce electron energy flux consistent with the flux inferred from power balance at the pedestal top, with a reasonable variation of the local E×B shearing rate; and the local neoclassical transport from NEO is dominant over the simulated turbulent transport in the ion energy flux channel. The simulated ion-scale turbulence produces much lower electron energy flux than inferred from experiment in the pedestal peak gradient region. A correction to the EPED-KBM pedestal width scaling is obtained based on the two-dimensional scan of pedestal top plasma beta (β_e) and normalized electron density and temperature scale lengths, a⁄L_(n_e ) , a⁄L_(T_e ) using CGYRO linear simulations. Mode transitions among TEM, micro-tearing mode (MTM), ion-temperature gradient (ITG) mode and KBM, are observed in the 2D scan at the pedestal top. A fixed normalized growth rate for these drift-type modes is taken to determine the pedestal width scaling, which shows good consistency with the QH experimental database on pedestal heights and widths. The onset of KBM instabilities and the local ExB shear suppression criterion set the lower and upper limit for the pedestal width of standard QH-mode, wide-pedestal QH-mode and type-I ELMy H mode. A potentially higher and wider pedestal is expected from the new scaling of pedestal width. This work presents an improved understanding of the ion-scale micro-turbulence of wide-pedestal QH-mode and sheds light on a promising scenario for future reactors, including ITER and beyond.

A systematic approach for estimating colloidal particle adsorption model parameters

The estimation of ion-exchange chromatography model parameters is crucial to enable efficient model-assisted biopharmaceutical downstream process development. Model calibration methods can be hindered by model limitations combined with parameter correlations, leading to time-consuming repeated parameter estimations. While Steric Mass Action isotherm estimation methods exist, there is a need for a systematic approach to estimate model parameters for an emerging Colloidal Particle Adsorption (CPA) model proposed by Briskot et al. This study presents a novel strategy that addresses this challenge, offering significant improvements.Through a parameter sensitivity analysis, we identified key levers for improved CPA parameter estimation, enabling the prediction of elution behavior for low and high load densities in gradient and step elution mode. This analysis also revealed the correlation structure of parameters, allowing the establishment of a minimalized experimental data set for parameter estimation, by using one breakthrough, a high load and three low load density gradient elution experiments. Our workflow leverages a surrogate-assisted global-optimization tool, minimizing computationally expensive function evaluations during parameter fitting. Furthermore, we employed a customized objective function, specifically adapted to the model structure and sensitivity results, to enhance the solver's performance.Our strategy was tested on three model proteins with molecular weights of approximately 50, 150 and 200 kDa using a strong cation exchange Poros 50 HS resin. Our final approach enabled high throughput CPA model calibration for single components. The resulting CPA models were able to describe non-binding protein-pulses, low and high-loaded gradient elution, break through, as well as isocratic elution experiments.

Comprehensive honey analysis: A novel HPLC-DAD method for hydroxymethylfurfural quantification and quality evaluation via diastase activity and sugar profile determination

Ensuring the authenticity and quality of honey is essential to safeguarding consumer health and combating food fraud. The primary analyses for honey quality involve determining diastase activity (DA), 5-hydroxymethylfurfural (HMF), and carbohydrate composition. A new high-performance liquid chromatography coupled with diode array detection (HPLC-DAD) method was developed, for the precise quantification of HMF, a key marker of honey quality and degradation. Utilizing a Phenomenex Kinetex RP-18 column (5 µm, 150 × 4.6 mm i.d.), with a mobile phase containing water and methanol (95:5, v/v) in gradient mode, at a flow rate of 1 mL/min, and UV detection at 284 nm, the method achieved rapid and efficient separation within 10 minutes, with a low detection limit of 0.03 mg L−1, and demonstrated good linearity, precision and recovery rates. The carbohydrate composition of honey, specifically glucose, fructose, saccharose, and maltose, was analysed using a HPLC with refractive index detection (HPLC-RI) method, using a Phenomenex Luna Omega Sugar column (3 µm, 250 ×4.6 mm i.d.), with a mobile phase composed of acetonitrile and water (85:15, v/v). This analytical protocol, incorporating the quantification of maltose, a critical yet often overlooked sugar, significantly bolsters the standard evaluation framework for honey authenticity. DA, a crucial enzymatic indicator, was assessed via the Schade method, providing additional insights into the enzymatic integrity and freshness of the honey samples. The methods were applied to analyse 65 commercial Spanish honey samples, revealing significant compliance with EU regulatory standards, yet also uncovering situations of potential adulteration. This research adds to the ongoing discussions on food safety by offering improved and dependable techniques for thoroughly assessing honey samples.

Performance prediction applying different reduced turbulence models to the SMART tokamak

Abstract The SMall Aspect Ratio Tokamak (SMART) is currently being commissioned at the University of Seville and will be able to compare the performance of positive and negative triangularity plasmas at low aspect ratio. Predictive simulations have been performed for different machine scenarios and heating schemes using the TRANSP code. The objectives of these simulations are to predict the parameters expected in positive triangularity plasmas, to guide diagnostic development, and to validate transport models. Several reduced turbulence models have been used to predict electron and ion temperatures for the operational phase 2. All models provide similar results from approximately mid-radius to the separatrix but important discrepancies are found in the core region. These positive triangularity results are compared with experiments from a similar size machine like GLOBUS-M2. The multi-mode model (MMM) shows the best agreement. Simulations with different boundary conditions have been performed and no strong differences have been observed between them. The impact of neutral beam injection (NBI) on the predicted profiles has also been addressed. Rotation reduces turbulence levels so higher temperatures are achieved when included in the simulations. Studying the different contributions to the thermal diffusivities, it is observed that electron temperature gradient (ETG) turbulence dominates at the plasma core while micro-tearing modes (MTM) dominate at the edge in the electron channel. In the ion channel, the neoclassical contribution is dominant at the core and at the very edge while the Weiland component, which includes ion temperature gradient mode (ITG), trapped electron mode (TEM), kinetic ballooning mode (KBM), peeling mode (PM) and collisionless and collision dominated magnetohydrodynamic (MHD) modes governs the mid-radius region. For phase 3, two plasmas with different electron densities have been studied. The case with lower density matches well a specific discharge of GLOBUS-M2. The higher density plasma shows high performance with β N ≈ 3.8 .

Development of a liquid chromatography method for the analysis of oil extract of artemisia cina

Introduction. The problem of development and implementation of own drugs in Kazakhstan today is acute and urgent. The solution to this problem is possible through the use of own resources – domestic medicinal plant raw materials. A promising medicinal raw material is Artemisia cina – an endemic medicinal plant of the of the Turkestan region of Kazakhstan.Aim. Designing a liquid chromatography methodology to analyze the oil extract obtained from Artemisia cina.Materials and methods. Standard sample (SS) of santonin, Artemisia cina’s oil extract. The substance was identified and quantitatively determined using an Agilent Technologies 1200 liquid chromatograph (USA) equipped with ChemStation software.Results and discussion. The main active substance of the oil extract was analyzed using high-performance liquid chromatography (HPLC) method. Choosing the separation conditions for the column involves determining the best composition of the mobile phase and the rate of elution. There were used a reversed-phase system with sorbent C18 and a mobile phase consisting of acetonitrile and a phosphate buffer with a pH of 6.8. Chromatographic studies of the substance were carried out in a gradient mode at an analytical wavelength of 237 nm. The retention time of the standard sample (SS) of santonin matched the retention time (tR) of santonin isolated from the oil extract of Artemisia cina and amounted to 14.3 minutes.Conclusion. A liquid chromatography method has been established for the identification and quantitative determination of the oil extract, focusing on the main active substance, santonin.

Ion temperature gradient mode mitigation by energetic particles, mediated by forced-driven zonal flows

Ion temperature gradient mode mitigation by energetic particles, mediated by forced-driven zonal flows

On how finite β and three-dimensional magnetic perturbations affect the instability of toroidal ion temperature gradient mode

Abstract The effects of finite β (the ratio of plasma kinetic pressure to magnetic pressure) and three-dimensional (3D) magnetic perturbations (MPs) on the instability of toroidal ion temperature gradient (ITG) mode are studied in this work. The expression of ion magnetic drift frequency ω_di modified by the effects from both finite β and 3D MPs is firstly derived based on the local 3D equilibrium model. Then, under the assumptions of adiabatic electrons and localized mode structure around the outboard mid-plane (ϑ_p=0), the dispersion equation of the long wavelength toroidal ITG mode with considering the parallel ion dynamics is derived and solved. The results show that the distribution of ω_di around the outboard mid-plane, including both ω_(di,0)=├ ω_di ┤|_(ϑ_p=0) and ω_(di,0)^''≡├ (d^2 ω_di \/dϑ_p^2 )┤|_(ϑ_p=0) (twist parameter quantifying the degree of concave or convex of ω_di), is the key for affecting the toroidal ITG mode instability. The diamagnetic effects from finite β and the effects from 3D MPs can suppress the instability by reducing |ω_(di,0) |. Via reducing |ω_(di,0)^'' | under the prerequisite of unchanged sign of ω_(di,0)^'', there also exist stabilization effects on the instability from 3D MPs and the modification of local magnetic shear by finite β effects. In addition, the stabilization effects induced by reducing |ω_(di,0)^'' | are closely associated with the global magnetic shear. The mechanisms for the effects of finite β and 3D MPs on the instability of toroidal ITG mode revealed in this work are helpful to the comprehensive understanding of the relationship between internal kink mode induced non-axisymmetric flux surface distortion and internal transport barrier physics in tokamak plasmas.

RP-HPLC Method for Simultaneous Quantification of Withanolides in <i>Withania somnifera</i>

Background: Withanolides are the primary bioactive components of Withania somnifera (L.) Dunal. Among them, withanolide A, and 12-deoxy-withastramonolide are the herb’s most physiologically active ingredients. The steroidal lactones are isomers, which makes them difficult to separate. Aim: In the current research, a simple, precise, accurate, and decent RP-HPLC method has been developed, optimised and validated for simultaneous quantification and separation. Methods: Resolution was conducted on Gemini, Phenominex C18 (250mm X 4.6mm, 5 μ) column at 40oC utilising binary mobile phases of acetonitrile and ammonium acetate (10 mM) in gradient mode with 1.0 mL/min flow rate and observed at 230 nm. The total run time was twenty-five minutes. The procedure complied with ICH guidelines, covering the limit of detection, specificity, linearity, quantification, precision, accuracy, and robustness. Results: The standard curves of both relevant analytes displayed a linear pattern with regression values > 0.999 in the 1–10 μg/mL range. For both herbal markers, 1 μg/mL was the lowest limit of quantification. The method’s accuracy was 100.38-100.93 % and 99.13-100.75 % for with withanolide A, and 12-deoxy-withastramonolide respectively. The precision of within and between days was found in the tolerable limit of >2% for both herbal markers. Conclusion: The suggested method worked well for simultaneously analyzing the extracted samples and identifying withanolides.

Advanced surrogate model for electron-scale turbulence in tokamak pedestals

We derive an advanced surrogate model for predicting turbulent transport at the edge of tokamaks driven by electron temperature gradient (ETG) modes. Our derivation is based on a recently developed sensitivity-driven sparse grid interpolation approach for uncertainty quantification and sensitivity analysis at scale, which informs the set of parameters that define the surrogate model as a scaling law. Our model reveals that ETG-driven electron heat flux is influenced by the safety factor $q$ , electron beta $\beta _e$ and normalized electron Debye length $\lambda _D$ , in addition to well-established parameters such as the electron temperature and density gradients. To assess the trustworthiness of our model's predictions beyond training, we compute prediction intervals using bootstrapping. The surrogate model's predictive power is tested across a wide range of parameter values, including within-distribution testing parameters (to verify our model) as well as out-of-bounds and out-of-distribution testing (to validate the proposed model). Overall, validation efforts show that our model competes well with, or can even outperform, existing scaling laws in predicting ETG-driven transport.

A sustainable RP-HPLC method for concurrent estimation of capecitabine and celecoxib in liposomal formulation: Greenness and whiteness appraisal.

Liposomes have been reported for combination therapy due to their ability to carry both hydrophilic and lipophilic drugs together. The current investigation aims to develop a novel, eco-friendly, and sustainable reverse-phase high-performance liquid chromatography (RP-HPLC) method for the simultaneous quantification of capecitabine and celecoxib co-encapsulated in liposomes. The method reported herein uses a C18 column (4.6 × 250 mm2, 5 μm) and a mobile phase consisting of water, and acetonitrile/methanol in a ratio of 60:40, containing 0.1% formic acid in both the phases. The flow rate is maintained at 1 mL/min, with an injection volume of 10 μL in the gradient mode. Detection is set at λmax = 240 nm for capecitabine and 252 nm for celecoxib. The developed liposomes are mono-disperse with a surface potential of -6.93 mV. The average size of the liposomes is 142 nm. The percentage entrapment efficiency for capecitabine is 52.39 ± 0.94%, and for celecoxib, it is 77.13 ± 0.74%. The Analytical Greenness Metric of 0.61 and Analytical Eco-Scale Score of 75 signify the greenness of the developed method. Also, the Red-Green-Blue model shows excellent whiteness, with a score of 83.2. Thus, the developed method offers a reliable, accurate, precise, buffer-free, and environment-friendly RP-HPLC approach for the simultaneous analysis of capecitabine and celecoxib co-encapsulated in liposomes.

In situ Single-Pass Perfused Rabbit Intestinal Study sample Analysis of Ractopamine by UPLC

In recent years, the prediction of oral drug absorption in humans has been a challenge for researchers and many techniques for permeability studies have been developed for several purposes, including biowaiver processes. The Single-Pass Intestinal Perfusion (SPIP) method performed in rats can provide permeability results closest to in vivo condition. he use of SPIP in rats and calculations for absorption prediction in humans may indicate the transport mechanisms and/or pre-systemic metabolism involved on permeation processes of drugs, since this model is the closest to in vivo conditions. Ractopamine hydrochloride is a commercial beta-adrenergic agonist commonly used as a dietary supplement in cattle production for improved feed efficiency and growth promotion. Currently, regulatory target tissues (as approved in the New Animal Drug Application with Food and Drug Administration) for ractopamine residue testing are muscle and liver. The aim of the study is to develop and validate an UPLC assay method to determine whether detectable and quantifiable levels of perfused ractopamine in small intestine of cattle or not. The separation is carried on Acquity UPLC BEH C18 (150mm x 2.1mm, 1.7 µm) reversed phase column using acetonitrile and 0.01M ammonium formate as the mobile phase in gradient mode at flow rate of 0.5mL/min. The precision, accuracy, extraction recovery, matrix effect, and stability meet the requirements of the guiding principles. In order to verify the sensitivity and selectivity of the method in a real-time situation, the developed method is successfully applied to a perfusion study in small intestine of rabbit and the samples were analyzed by Empower software.

Reversed‐Phase Analytical Method for Enantioselective Analysis of Ormeloxifene Hydrochloride: Application to Bulk Drug and Quality Control Analysis

ABSTRACTThe article reports simple, rapid, and novel enantioselective reversed‐phase high‐performance liquid chromatography (RP‐HPLC) for separation of (−)‐(3R, 4R)‐ormeloxifene hydrochloride (d‐ORM) and (+)‐(3S, 4S)‐ormeloxifene hydrochloride (l‐ORM) (ORM, centchroman) using chiral stationary phase (Chiral‐AGP, Chiracel OJ‐RH, and ChiraDEX HR). The best enantiomeric separation was obtained on the ChiraDEX HR (α = 0.89, Rs = 1.9) column with a gradient mode elution using a combination of ammonium acetate (10 mM, pH 4.0) and methanol as a mobile phase. The flow rate and column oven temperature were 0.7 mL/min and 30°C, respectively. The detection limits (λmax 280 nm) for d‐ORM and l‐ORM were 0.170 and 0.169 µg/mL, whereas quantification limits were 0.516 and 0.512 µg/mL. The method was validated according to the International Council on Harmonization (ICH) regulatory Guidelines Q2 (R1) in terms of its accuracy, precision, sensitivity, linearity, specificity, robustness, and solution stability. The designed analytical method could be extended as a quality control tool for pharmaceutical quality assessments as well as isomeric quantification of ORM in industrial bulk manufacturing.

Ion temperature gradient modes modulational stability with kappa-distribution

We investigated the modulational stability and instability of the ion temperature gradient (ITG) mode in electron-ion plasma. Ions are dynamic species, whereas electrons follow a Kappa distribution. We used the reduction perturbation approach to determine the linear dispersion relation for the fluid under consideration. The nonlinear Schrodinger equation describes nonlinear features such as nonlinear modulational stability or instability in the ITG mode. The product of dissipation and nonlinear coefficients, known as LM, contains both modulational stability and instability in the ion temperature gradient mode. Theoretical results are expanded numerically, showing the influence of various plasma parameters on modulational stability and instability, particularly the superthermality coefficient κ e . The current observations may be extended to space and laboratory plasma for modification.

First results of turbulence investigation on Globus-M2 using radial correlation Doppler reflectometry

The first results of investigation of the turbulence structure using Doppler backscattering (DBS) on the Globus-M2 tokamak are presented. A one-channel DBS system with a variable probing frequency within the 18–26 GHz range was installed to investigate the edge plasma at normalized minor radii 0.9–1.1. Radial correlation Doppler reflectometry was used to study the changes in turbulence eddies after the LH transition. Correlation analysis was applied to the phase derivative of complex in-phase and quadrature (IQ) signals of the DBS diagnostic as it contains information about the poloidal plasma rotation velocity. In L-mode, the radial correlation length L r is estimated to be 3 cm and after transition to H-mode reduces to approximately 2 cm. Gyrokinetic modelling in a linear local approximation using code GENE indicates that the instability with positive growth rate at the normalized minor radius 0.75 in L-mode and H-mode on Globus-M2 was the ion temperature gradient (ITG) mode.

Hybrid organic monolithic column containing MIL-68(Al) for the separation of small molecules by capillary HPLC

A hybrid organic monolithic column made of poly(lauryl methacrylate-co-1,6-hexanediol dimethacrylate) and the metal-organic framework MIL-68(Al) was prepared for the first time. The column was used in capillary liquid chromatography, both in isocratic and gradient elution modes. Separation performance towards small molecules of different chemical nature (polycyclic aromatic hydrocarbons, alkylbenzenes, phenols, etc.) was studied. Monte Carlo simulations were made to both select the proper precursors to obtain empty metal-organic framework micropores in the monolithic polymer and also, to analyze the potential free access of the studied analytes into the micropores (necessary to improve mass transfer and column efficiency). The hereby synthesized metal-organic framework microcrystals allowed obtaining homogeneous hybrid monolithic columns. Adding of MIL-68(Al) (1030 m2 g-1 BET specific surface area) increased the surface area from 3.9 m2 g-1 for the parent monolith to 18.2 m2 g-1 for the hybrid column containing 8 mg mL-1 of the microcrystals. Chromatographic performance of this new column was evaluated by studying retention factors, resolution, and plate counts at room temperature. Different compounds, not completely resolved in the parent monolith, were partially or completely separated after metal-organic framework addition. Using the monolithic column with only 2 mg mL-1 of MIL-68(Al), five alkylbenzenes were completely separated with very symmetrical peak shapes, resolution factors up to 3.60 and plate counts of 4300 plates m-1 for n-hexylbenzene. This value is higher than those obtained by other authors who used organic monolithic columns with embedded metal-organic frameworks to perform separations at room temperature. Additionally, nine polycyclic aromatic hydrocarbons were partially or completely resolved in gradient elution mode. The hybrid monolithic columns exhibited very good intra-day (%RSD=1.9), inter-day (%RSD=2.6), and column-to-column (%RSD=4.3) reproducibility values. Easy and fast column preparation, and versatility to efficiently separate several compounds of different chemical nature in isocratic and gradient mode, makes this new hybrid column a very good option for the analysis of small molecules in capillary (or nano) HPLC.

Magnetic shaping effects on turbulence in ADITYA-U tokamak

The work reported in this paper addresses two aspects. In the first part, numerical simulations are conducted to examine the impact of magnetic equilibrium shaping (elongation and triangularity), on both conventional Ion Temperature Gradient (ITG) modes and Short Wavelength ITG modes. This analysis is performed considering the experimental profiles and parameters of the ADITYA-U tokamak, employing the nonlinear global gyrokinetic Particle-in-Cell code ORB5. The linear and nonlinear collisionless electrostatic simulation of these modes are carried out with kinetic ions and adiabatic electrons. From the linear results, it has been observed that the magnetic equilibrium shaping slighty reduced the growth rates and widened the spectrum, and the maxima of growth rate curve is shifted to higher toroidal wave number. We find that the heat flux is reduced by a significant ≃35% for the true circular magnetohydrodynamic magnetic equilibrium as compared to ad hoc concentric circular equilibrium reported in Singh et al (2023 Nucl. Fusion 63 086029). A further ≃10% reduction in the heat flux is seen with magnetic equilibrium shaping. In the second part, linear collisionless electrostatic simulation studies of ITG coupled with fully kinetic electrons (both trapped and passing electrons are treated kinetically) using a drift-kinetic ordering is performed. It can be seen from the linear results that, in presence of kinetic electrons, the growth rate and real frequency of the ITG mode are increased significantly for ADITYA-U parameters and a mode propagating in the electron diamagnetic direction is identified at high toroidal wavenumbers.