Peak Capacity Research Articles

A detailed evaluation of the advantages and limitations of online RP-LC×HILIC compared to HILIC×RP-LC for phenolic analysis

The combination of hydrophilic interaction chromatography (HILIC) and reversed-phase liquid chromatography (RP-LC) has proved effective in the LC × LC analysis of polyphenols due to the high degree of orthogonality associated with these separation modes for various classes of phenolic compounds. However, despite the growing number of such applications, HILIC is almost exclusively used as the first dimension (1D) separation mode, and RP-LC in the second dimension (2D). This is somewhat surprising in light of the potential advantages of swapping these separation modes. In this contribution, we present a detailed evaluation of the potential of online RP-LC × HILIC-MS for the analysis of phenolic compounds, comparing the performance of this system to the more established HILIC × RP-LC-MS configuration.Method development was performed using a predictive optimisation program, and fixed solvent modulation was employed to combat the solvent incompatibility between HILIC and RP-LC mobile phases. Red wine, rooibos tea, Protea and chestnut phenolic extracts containing a large diversity of phenolic compound classes were analysed by both HILIC × RP-LC- and RP-LC × HILIC-MS in order to compare the separation performance.Overall, the kinetic performance of HILIC × RP-LC was found to be clearly superior, with higher peak capacities and better resolution obtained for the majority of samples compared to RP-LC × HILIC analyses using similar column dimensions. Dilution of the 1D solvent combined with large volume injections proved insufficient to focus especially phenolic acids in the 2D HILIC separation, which resulted in severe 2D peak distortion for these compounds, and negatively impacted on method performance. On the other hand, a noteworthy improvement in the sensitivity of RP-LC × HILIC-MS analyses was observed due to higher ESI-MS response for the 2D HILIC mobile phase and greater sample loading capacity of the 1D RP-LC column, brought on by the high solubility of phenolic samples in aqueous solutions. As a result, a significantly higher number of compounds were detected in the RP-LC × HILIC-MS separations. These findings point to the potential advantage of RP-LC × HILIC as a complementary configuration to HILIC × RP-LC for phenolic analysis.

Multi-2D LC × LC as a Novel and Powerful Implement for the Maximum Separation of Complex Samples.

Achieving complete information about the chemical composition of complex samples requires the use of multianalytical platforms able to maximize the acquisition of high-quality data for unequivocal identification. However, this process requires long analysis times and several instruments. Food analysis is one of the analytical fields where the analysis of very complex samples has a huge impact. One of these complex samples is vermouth, a fortified wine based on the maceration of a large number of herbs, fruits, barks, seeds, and leaves. The application of conventional or even advanced analytical techniques like comprehensive two-dimensional (2D) liquid chromatography (LC × LC) does not provide enough separation power to resolve the complete profile of this sample. In this work, a novel 2DLC strategy called multi-2D LC × LC is developed. This new setup consists of the use of two different columns with different separation properties in the second dimension (2D) that can be selected during the LC × LC analysis accordingly to the chemical nature of the compounds eluted from the first dimension (1D). The vermouth sample was analyzed using a 1D-PFP and a combination of HILIC (from 0 to 30 min) and C18 (from 30 to the end) columns in the 2D. This setup increased both the peak capacity and the orthogonality of the analysis in comparison to the use of only one of the columns in the 2D. Multi-2D LC × LC is presented as an integrated 2DLC tool that maximizes the separation capacity for very complex samples.

Automated method using direct-immersion solid-phase microextraction and on-fiber derivatization coupled with comprehensive two-dimensional gas chromatography high-resolution mass spectrometry for profiling naphthenic acids in produced water

Naphthenic acids (NAs) are naturally occurring organic acids in petroleum and are found in waste waters generated during oil production (produced water, PW). Profiling this class of compounds is important due to flow assurance during oil exploration. Compositional analysis of PW is also relevant for waste treatment to reduce negative impacts on the environment. Here, comprehensive two-dimensional gas chromatography coupled with high-resolution mass spectrometry (GC×GC–HRMS) was applied as an ideal platform for qualitative analysis of NAs by combining the high peak capacity of the composite system with automated scripts for group-type identification based on accurate mass measurements and fragmentation patterns. To achieve high-throughput profiling of NAs in PW samples, direct-immersion solid phase microextraction (DI-SPME) was selected for extraction, derivatization and preconcentration. A fully automated DI-SPME method was developed to combine extraction, fiber rinsing and drying, and on-fiber derivatization with N-methyl-N‑tert-butyldimethylsilyltrifluoroacetamide (MTBSTFA). Data processing was based on filtering scripts using the Computer Language for Identifying Chemicals (CLIC). The method successfully identified up to 94 NAs comprising carbon numbers between 6 and 18 and hydrogen deficiency values ranging from 0 to -4. The proposed method demonstrated wider extraction coverage compared to traditional liquid-liquid extraction (LLE) – a critical factor for petroleomic investigations. The method developed also enabled quantitative analysis, exhibiting detection limits of 0.5 ng L−1 and relative standard deviation (RSD) at a concentration of NAs of 30 µg L−1 ranging from 4.5 to 25.0%.

Survey evidence on COVID-19 and its impact on rail commuting patterns in Great Britain

The COVID-19 pandemic saw a large proportion of the working population in the United Kingdom working from home for an extend period of time. In September 2021, a substantial number continued to work from home on a regular basis, a stark contrast to the situation pre-pandemic. Prior to 2020, although there was a growing trend for increased home working, this was still not a widespread practice across UK businesses, with the majority of staff working full-time from the employment location.The aim of this paper is to report the main changes in commuting and working patterns among commuters in Great Britain (GB) brought about by the COVID-19 pandemic with a special emphasis on the rail commuting market. The paper is informed by a panel survey of 3,892 GB respondents who commuted regularly to work prior to the pandemic in two waves. The first wave was conducted in Summer 2020 and focused on respondents’ pre-pandemic travel patterns. The second wave was conducted in the Autumn 2021 and asked respondents about their current travel patterns. Although the focus was on rail travel, many of the conclusions of this paper are applicable to all modes of transport.Although a majority of pre-pandemic commuters have returned to commuting at least once per week to their place of work, there is a significant share of pre-pandemic commuters who are still working from home full-time. The return to the workplace has been slower among individuals who used to commute by rail compared to other modes. This is partially explained by current workplace arrangements being strongly linked with an individual’s occupation and mode of transport. Individuals in office-based occupations are much more likely to work from home compared to those who work in other occupations.The pandemic has brought additional challenges to transport systems in addition to the reduced ridership level. Some of the emerging issues include managing post-pandemic peak travel volumes across a curtailed working week and the associated funding for peak capacity. Nonetheless, the research has highlighted some potential strategies to boost a faster recovery for travel demand.

Novel open‐tubular columns with highly hydrophobic stationary phase for peptide and protein separation by nano‐liquid chromatography

AbstractIn this study, novel open‐tubular nano‐columns with highly hydrophobic stationary phase were prepared via the surface graft polymerization of polyhedral oligomeric silsesquioxane‐methacrylate and 2‐vinylnaphthalene in a narrow capillary (i.e., 20 μm i.d. In this preparation, polyhedral oligomeric silsesquioxane‐methacrylate was used as a reactive and stable monomer while 2‐vinylnaphthalene imparts hydrophobic character for the stationary phase. Toluene and dodecanol were used as the porogenic solvent. Scanning electron microscope images of the columns showed that polyhedral oligomeric silsesquioxane and 2‐vinylnaphthalene were bound to the surface of the capillary. The chromatographic characterization of the open‐tubular columns was performed using homologous alkylbenzenes, including toluene, ethylbenzene, propylbenzene, and butylbenzene. The satisfactory separation of alkylbenzenes could be obtained using the final open‐tubular column with 17.1% of 2‐ vinylnaphthalene. Theoretical plates number up to 34000 plates/m in the isocratic mode for ethylbenzene were achieved. The open‐tubular column with various lengths was used for the separation of intact proteins in nano‐liquid chromatography, allowing a notable change in the retention time of each intact protein, including ribonuclease A, Lysozyme, and α‐Chymotryp A. The final open‐tubular column was then applied to the peptide separation of trypsin‐digested cytochrome C. It was shown that the open‐tubular column yielded a high‐resolution analysis of peptides, providing a high peak capacity of up to 1000.

Experiments and a tension-bending catenary model for the progressive collapse resistance of concrete beam-column structures

Catenary action (CA) is an extremely vital resistance mechanism for the progressive collapse of concrete beam-column structures. However, the systematically theoretical researches on CA are rather scarce due to the complexity of structural forces in the large deformation stage. To address this dilemma, an evaluation method for distinguishing the types of structural anti-progressive collapse performance was put forward and applied in 75 existing beam-column structures, by which the conditions of potential CA were revealed. Based on our experiments and collected databases, an innovative Tension-Bending Catenary (TBC) model was proposed, which considers the eccentric tension of the beam, the deformation compatibility conditions of the overall structure, and the plastic rotation capacity of the beam. The CA peak capacity, displacement, and horizontal resultant force can be predicted by the proposed model, whose accuracy and feasibility were verified via 16 specimens. Moreover, the main influencing factors on the CA capacity were revealed via a series of parametric analyses, including the beam depth-span ratio (h/ln), the properties of beam top longitudinal reinforcements (area As, ultimate strength fu, and ultimate tensile strain εsu), and the relative axial stiffness (ra). Parametric analysis results indicate that the CA capacities positively correlate with the beam top longitudinal reinforcements (As, fu, and εsu). Nevertheless, the CAcapacity markedly declines for a relative axial stiffness of end supports of less than 1.0. The CA capacity first displays an ascendant trend and then decreases with the beam depth-span ratio. Meanwhile, the bearing capacity of CA is superior to that of compressive arch action (CAA) until a critical depth-span ratio. Furthermore, the ultimate strain of the longitudinal reinforcements εsu is recommended to be as large as possible and not less than about 0.1 because a minor εsu causes the CA capacity to drop significantly. Especially, εsu should exceed 0.05 to make CA greater than CAA. Finally, practical anti-progressive collapse strategies were summarized and proposed.

Solar power from schools and homes

Solar installations are becoming commonplace in the UK as our nation forges a path towards Zero Carbon. A brief description is given of installations at two schools in Irlam, Manchester, UK, and a more detailed discussion is given of a domestic photovoltaic array on the author’s home. This domestic array, specified with a peak capacity of 4 kW, was purchased in 2011 and erected on a south—facing roof in the suburbs of Manchester, UK. The Irlam installations were more recent (2017). In bright sunlight the domestic array has consistently generated an output of 3.6 kW peak and this power is exported to the National Grid. The Irlam arrays have maintained 28.6 kW and 29.6 kW, peak, over the past five years. Similar installations exist in many schools and homes around the country so providing a significant carbon saving to the nation.

Enhancing the compatibility of normal-phase chromatography x reversed−phase chromatography by combination of low−temperature sensitive aqueous-phase compatible normal- phase chromatography and at−column dilution modulation

The nearly opposite retention mechanism in the two-dimensional liquid chromatography (2D−LC), which combines normal phase liquid chromatography (NPLC) and reversed phase liquid chromatography (RPLC), shows extremely high orthogonality and theoretical peak capacity. However, peak breakthrough and peak distortion caused by the highly incompatible 2D mobile phases counteracts the advantages offered by high orthogonality. To address this difficulty, this study proposes a comprehensive two-dimensional NPLC × RPLC integrating temperature-sensitive aqueous-phase compatible normal-phase chromatography (TSACNPLC) and at-column dilution modulation (ACDM). The proposed 2D−LC system uses an aqueous-miscible acetonitrile/methanol eluent in the 1st D NPLC, instead of an aqueous-phase immiscible eluent, such as n-hexane/methanol, to increase the miscibility with the RP mobile phase system. Additionally, the system exploits temperature-sensitive retention behavior to enhance the retention ability of aqueous-phase compatible NPLC. To verify the feasibility of the proposed 2D−LC, this study selected three multi-component samples with mid-to-low polarity, including ethoxylated (n ≈ 6) bisphenol A (BPA-6EO), ethoxylated (n ≈ 6) tristearylphenol (TSP-6EO), and safflower methanol extract. Next, the effectiveness of the constructed 2D−LC was systematically investigated, including low temperature-induced retention enhancement of NPLC, overcoming solvent incompatibility by ACDM, and optimization of 2 D separation conditions, was systematically investigated.

Nano-liquid chromatography with monolithic stationary phase based on naphthyl monomer for proteomics analysis

Monolithic poly(2-vinylnaphthalene-co-divinylbenzene) columns were introduced, for the first time, and were evaluated as the separation media for nano-liquid chromatography (nano-LC). These columns were prepared by in-situ polymerization of 2-vinylnaphthalene (2-VNA) as the functional monomer and divinylbenzene (DVB) as the crosslinker in a fused silica capillary column of 50 µm i.d. Various porogenic solvents, including tetrahydrofuran (THF), dodecanol and toluene were used for morphology optimization. Final monolithic column (referred to as VNA column) was characterized by using scanning electron microscopy (SEM) and chromatographic analyses. Alkylbenzenes (ABs), and polyaromatic hydrocarbons (PAHs) were separated using the VNA column while the column offered excellent hydrophobic and π-π interactions under reversed-phase conditions. Theoretical plates number up to 41,200 plates/m in isocratic mode for ethylbenzene could be achieved. The potential of the final VNA column was demonstrated with a gradient elution in the separation of six intact proteins, including ribonuclease A (RNase A), cytochrome C (Cyt C), lysozyme (Lys), β-lactoglobulin (β-lac), myoglobin (My) and α-chymotrypsinogen (α-chym) in nano LC system. The column was then applied to the peptide analysis of trypsin digested cytochrome C, allowing a high peak capacity up to 1440 and the further proteomics analysis of COS-7 cell line was attempted applying the final monolithic column in nano-LC UV system.

Shear connection performance of cold-formed steel and plywood composite flooring systems: Experimental and numerical investigation

This study carries out numerical and experimental investigation on shear connection performance of flooring systems comprising of cold-formed steel joists and engineered plywood panels. A 3-D finite element model has been developed using ANSYS software which considers the nonlinear behaviour and damage of plywood panels using a maximum stress-based criterion incorporated in the FE model. The yielding behaviour of steel joists and fasteners (screws and bolts) is defined as a multilinear plastic hardening material model defined in ANSYS software. The FE model was validated against the experimental results obtained from push-out tests conducted on specimens utilising different connection arrangements. The validated FE models showed a good agreement with the experimental results of the push-out tests in terms of load-slip behaviour, ultimate peak capacity, and failure modes. Finally, the validated FE models are utilised to perform a parametric study that investigates the effect of varying various parameters, including diameter and yield strength of self-drilling screws, the thickness of plywood panels, value of friction coefficient, and the ratio of fastener diameter to the joist thickness, on the initial stiffness, failure mode and ultimate load capacity of the cold-formed steel and plywood composite connections.

Galvanostatic stimulated Na3Mn2(P2O7)(PO4) as a high-voltage cathode material for aqueous zinc-ion batteries

To meet the application requirements of different scenarios, expanding the selection of cathode materials is a crucial step for the development of aqueous zinc-ion batteries (AZIBs). Manganese phosphates are a type of important and representative cathodes for rechargeable batteries, but they are rarely reported in AZIBs due to their electrochemical sluggishness in aqueous zinc electrolyte. Herein, carbon coating technic and galvanostatic stimulation process are combined to solve the issue and obtain an electrochemically active Na3Mn2(P2O7)(PO4) as cathode material for AZIBs. Carbon coated Na3Mn2(P2O7)(PO4) (NMPP@C) is synthesized by using a liquid-phase method assisted with freeze-drying process. After galvanostatic stimulation (100 mA g−1 for 5 cycles and following at 10 mA g-1), the originally inactive NMPP@C cathode shows a peak capacity of 150 mAh g-1 and then stabilizes at 90 mAh g−1 with a discharge plateau at 1.45 V vs. Zn2+/Zn. It is found that the NMPP@C cathode undergoes a structural decomposition during stimulation process, then α-MnO2 and Zn2P2O7•5H2O jointly serve as electrochemical reaction agents eventually. The electron/proton host (α-MnO2) and the Zn2+ host (Zn2P2O7•5H2O) are generated from the same conductive matrix of NMPP@C, which guarantees a satisfactory rate ability and a decent cycle performance in AZIBs.

Diagnosis and Analysis of Thermal Power Plant Operation in Heating Season

In order to further improve the operation level of the thermal power units of the provincial grid thermal power plant, optimize the data quality of the online monitoring system of the provincial thermal power units, through the diagnosis and analysis of the operation data of the thermal power online monitoring system, and from an all-round perspective, analyze and evaluate the peak shaving and frequency modulation capabilities of the heat supply units of the thermal power plant from the aspects of the load carrying capacity of the heat supply units, the optimization of the startup mode of the whole plant, and the heating capacity, to provide support for the accurate scheduling of the heat supply units. This paper analyzes the heat supply, peak regulation and frequency regulation capacity of the whole thermal power plant through the operation data, draws the peak regulation interval and heat supply capacity interval, and provides support for the optimal operation of the whole plant.

Triaxial high temperature mechanical properties of Longmaxi shale at different depths

Based on the high temperature and confining pressure conditions at different depths, triaxial high temperature mechanical tests were carried out on Longmaxi shale with horizontal and vertical bedding, respectively. The results show that shale?s peak strength and deformation capacity increase with burial depth. The failure mode of shale is a typical brittle failure, and the brittle index can quantitatively describe the brittle mechanical behavior of shale. Because shale has an apparent thin bedding structure, shale with different bedding directions shows pro?nounced anisotropy in mechanical parameters and deformation characteristics. The burial depth and bedding direction significantly impact the energy evolution law of Longmaxi shale during the mechanical process.

A rule-based energy management strategy for a low-temperature solar/wind-driven heating system optimized by the machine learning-assisted grey wolf approach

This work presents an innovative, practical, and cost-effective solution for advancing state-of-the-art intelligent building energy systems and aiding the intended worldwide green transition with maximum renewable integration. The vanadium chloride cycle, electrolyzer unit, and Alkaline fuel cell are powered by the sun's and wind's energy to produce/store/use hydrogen. A rule-based control scheme is designed to provide a sophisticated interplay between the demand/supply sides, components, and local energy networks to reduce peak capacity, lower emissions, and save energy costs. TRNSYS is used to analyze and compare the techno-economic-environmental indicators of the conventional system and the suggested smart model for a multi-family building in Sweden. A grey wolf method is built in MATLAB with the help of machine learning to determine the optimum operating state with the maximum accuracy and the least amount of computational time. The results reveal that the suggested smart model considerably saves energy and money compared to the conventional system in Sweden while lowering CO2 emissions. According to the optimization results, the grey wolf optimizer and machine learning techniques enable greater total efficiency of 13 %, higher CO2 mitigation of 8 %, a larger cost saving of 38 %, and a reduced levelized energy cost of 41 $/MWh. The scatter distribution of important design parameters shows that altering the fuel cell current and electrode area considerably impacts the system's performance from all angles. The bidirectional connection of the proposed smart system with the heating and electrical networks through the rule-based controller demonstrates that it can supply the building's energy requirements for more than 300 days of the year. Eventually, the major contribution of the vanadium chloride cycle in the summer and the electrolyzer in the winter to the creation of hydrogen highlights the significance of renewable hybridization in reducing the dependence of buildings on energy networks.

Increase the flow rate and improve hydrogen deuterium exchange mass spectrometry

Reversed-phase peptide separation in hydrogen deuterium exchange (HDX) mass spectrometry (MS) must be done with conditions where the back exchange is the slowest possible, the so-called quench conditions of low pH and low temperature. To retain maximum deuterium, separation must also be done as quickly as possible. The low temperature (0 °C) of quench conditions complicates the separation and leads primarily to a reduction in separation quality and an increase in chromatographic backpressure. To improve the separation in HDX MS, one could use a longer gradient, smaller particles, a different separation mechanism (for example, capillary electrophoresis), or multi-dimensional separations such as combining ion mobility separation with reversed-phase separation. Another way to improve separations under HDX MS quench conditions is to use a higher flow rate where separation efficiency at 0 °C is more ideal. Higher flow rates, however, require chromatographic systems (both pumps and fittings) with higher backpressure limits. We tested what improvements could be realized with a commercial UPLC/UHPLC system capable of ∼20,000 psi backpressure. We found that a maximum flow rate of 225 µL/min (using a 1 × 50 mm column packed with 1.8 µm particles) was possible and that higher flow rate clearly led to higher peak capacity. HDX MS analysis of both simple and particularly complex samples improved, permitting both shorter separation time, if desired, and providing more deuterium recovery.

Zero-Degree Celsius Capillary Electrophoresis Electrospray Ionization for Hydrogen Exchange Mass Spectrometry

Currently, fast liquid chromatographic separations at low temperatures are exclusively used for the separation of peptides generated in hydrogen deuterium exchange (HDX) workflows. However, it has been suggested that capillary electrophoresis may be a better option for use with HDX. We performed in solution HDX on peptides and bovine hemoglobin (Hb) followed by quenching, pepsin digestion, and cold capillary electrophoretic separation coupled with mass spectrometry (MS) detection for benchmarking a laboratory-built HDX-MS platform. We found that capillaries with a neutral coating to eliminate electroosmotic flow and adsorptive processes provided fast separations with upper limit peak capacities surpassing 170. In contrast, uncoated capillaries achieved 30% higher deuterium retention for an angiotensin II peptide standard owing to faster separations but with only half the peak capacity of coated capillaries. Data obtained using two different separation conditions on peptic digests of Hb showed strong agreement of the relative deuterium uptake between methods. Processed data for denatured versus native Hb after deuterium labeling for the longest timepoint in this study (50,000 s) also showed agreement with subunit interaction sites determined by crystallographic methods. All proteomic data are available under DOI: 10.6019/PXD034245.

Challenging the Hemodynamic Hypothesis in Heart Failure With Preserved Ejection Fraction: Is Exercise Capacity Limited by Elevated Pulmonary Capillary Wedge Pressure?

Exercise intolerance is a defining characteristic of heart failure with preserved ejection fraction (HFpEF). A marked rise in pulmonary capillary wedge pressure (PCWP) during exertion is pathognomonic for HFpEF and is thought to be a key cause of exercise intolerance. If true, acutely lowering PCWP should improve exercise capacity. To test this hypothesis, we evaluated peak exercise capacity with and without nitroglycerin to acutely lower PCWP during exercise in patients with HFpEF. Thirty patients with HFpEF (70±6 years of age; 63% female) underwent 2 bouts of upright, seated cycle exercise dosed with sublingual nitroglycerin or placebo control every 15 minutes in a single-blind, randomized, crossover design. PCWP (right heart catheterization), oxygen uptake (breath × breath gas exchange), and cardiac output (direct Fick) were assessed at rest, 20 Watts (W), and peak exercise during both placebo and nitroglycerin conditions. PCWP increased from 8±4 to 35±9 mm Hg from rest to peak exercise with placebo. With nitroglycerin, there was a graded decrease in PCWP compared with placebo at rest (-1±2 mm Hg), 20W (-5±5 mm Hg), and peak exercise (-7±6 mm Hg; drug × exercise stage P=0.004). Nitroglycerin did not affect oxygen uptake at rest, 20W, or peak (placebo, 1.34±0.48 versus nitroglycerin, 1.32±0.46 L/min; drug × exercise P=0.984). Compared with placebo, nitroglycerin lowered stroke volume at rest (-8±13 mL) and 20W (-7±11 mL), but not peak exercise (0±10 mL). Sublingual nitroglycerin lowered PCWP during submaximal and maximal exercise. Despite reduction in PCWP, peak oxygen uptake was not changed. These results suggest that acute reductions in PCWP are insufficient to improve exercise capacity, and further argue that high PCWP during exercise is not by itself a limiting factor for exercise performance in patients with HFpEF. URL: https://www. gov; Unique identifier: NCT04068844.

Fisher ratio feature selection by manual peak area calculations on comprehensive two-dimensional gas chromatography data using standard mixtures with variable composition, storage, and interferences.

Comprehensive two-dimensional gas chromatography (GC×GC) is becoming increasingly more common for non-targeted characterization of complex volatile mixtures. The information gained with higher peak capacity and sensitivity provides additional sample composition information when one-dimensional GC is not adequate. GC×GC generates complex multivariate data sets when using non-targeted analysis to discover analytes. Fisher ratio (FR) analysis is applied to discern class markers, limiting complex GC×GC profiles to the most discriminating compounds between classes. While many approaches for feature selection using FR analysis exist, FR can be calculated relatively easily directly on peak areas after any native software has performed peak detection. This study evaluated the success rates of manual FR calculation and comparison to a critical F-value for samples analyzed by GC×GC with defined concentration differences. Long-term storage of samples and other spiked interferences were also investigated to examine their impact on analyzing mixtures using this FR feature selection strategy. Success rates were generally high with mostly 90-100% success rates and some instances of percentages between 80 and 90%. There were rare cases of false positives present and a low occurrence of false negatives. When errors were made in the selection of a compound, it was typically due to chromatographic artifacts present in chromatograms and not from the FR approach itself. This work provides foundational experimental data on the use of manual FR calculations for feature selection from GC×GC data.

Hydrogenated V2O5 with fast Zn-ion migration kinetics as high-performance cathode material for aqueous zinc-ion batteries

The scarce inventory of cathode materials with mild interaction between Zn2+ and cathode lattice is the main obstacle to the development for aqueous rechargeable Zinc-ion batteries. In this paper, based on the first-principles calculations, we show that the insertion of protons in V2O5 effectively reduces the electrostatic interaction and the Zn-ion diffusion energy barrier in V2O5 substantially decreases after hydrogenation. Hence, the hydrogenated V2O5 (HV2O5) nanospheres are first proposed as a high capacity cathode for aqueous rechargeable Zinc-ion batteries by microwave-assisted chemical precipitation synthesis. It is demonstrated to exhibit high peak capacities of 602 mAh g−1 at 0.1 A g−1, high rate capacity as well an excellent cycle lifespan with a capacity retention of 86% after 5000 cycles at 10 A g−1. The mechanism of ions-diffusion in different charge and discharge states is also studied, and it proves dual-ion energy storage mechanism that HV2O5 can attract Zn ions and H ions at discharging.

Application of an in-house packed octadecylsilica-functionalized graphene oxide column for capillary liquid chromatography analysis of hormones in urine samples

Graphene oxide-based LC stationary phases were developed and applied for separating hormones from urine using capillaryLC-MS/MS. Using two analytical approaches – direct injection and column-switching arrangement – it was possible to evaluate the chromatographic parameters and perform tests on the raw biological fluid. Two stationary phases (SPs) were produced, varying the amino silica support particle diameter (Si, 5, and 10 μm). Graphene oxide was covalently bonded to the surface of Si particles, and this material was functionalized by the insertion of octadecylsilica groups, generating the SiGO-C18. Infra-red spectroscopy assays revealed that both steps were successful – supporting GO onto Si and further C18 customization. Scanning electron microscopy showed spherical geometries with minor irregularities and narrow particle size distribution for the produced SPs. The GO-coating rate was higher on the Si particles of 10 μm. As a result, the 10 μm produced column reported better resolution, efficiency, and peak capacity. Therefore, this SiGO-C18 capillary column (100 mm × 0.32 mm i.d., 10 μm dp) was applied successfully in a column-switching method to separate hormones in urine. Linearity (R2 above 0.99), quantification limits (between 1.0 and 5 μg/L), and other figures of merit of the method were determined. It is worth mentioning that the SiGO-C18 capillaryLC column performed adequately, separating the target compounds in less than 6 min. We hope this work could significantly contribute to shedding some light on graphene-based materials as a promising class of stationary phase for miniaturized liquid chromatography.