Retention Behavior Research Articles

HPLC Retention Behavior of Oligonucleotides on an Anion-Exchange HPLC with a High Concentration of Urea

HPLC Retention Behavior of Oligonucleotides on an Anion-Exchange HPLC with a High Concentration of Urea

Ionic liquid/covalent organic framework/silica composite material: Green synthesis and chromatographic evaluation

BackgroundDue to their large surface area and distinctive adsorption affinity, covalent organic frameworks (COFs) appear to be good candidates as liquid chromatographic separation materials with good application prospect. The development of COF materials in chromatographic science is currently in an exploratory stage. Especially, the practicability of COF@silica composite materials as liquid chromatographic stationary phases needs further exploration. Reasonably integrating a functional component such as ionic liquid (IL) into the COF@silica composite materials may provide customized functionality to achieve the purpose of synthesizing multi-functional COF based stationary phases. ResultsIn this study, an IL modified COF bonded silica composite material (IL-COF@SiO2) was successfully synthesized by using an environmentally friendly deep eutectic solvent as the reaction medium instead of the frequently-used organic solvent. The synthesized IL-COF@SiO2 composite material combines the excellent separation ability of COF and the excellent mass transfer function of spherical porous silica microsphere, and meanwhile, the introduction of IL endows COF@SiO2 with preferable separation performance. The slurry-packed IL-COF@SiO2 liquid chromatographic column could be applied to effectively separate hydrophobic and hydrophilic compounds with preferable separation selectivity and high column efficiency. By investigating the retention behavior and influencing factors, a mixed-mode retention mechanism was found. Multiple interaction forces endow the IL-COF@SiO2 with a hydrophilic-hydrophobic balance performance, demonstrating a good application prospect as a versatile liquid chromatographic separation material. SignificanceIn this study, a new strategy is proposed for greenly synthesizing a novel IL-COF@SiO2 composite material under mild conditions, which expands the potential application of COF materials in chromatographic science. One particular point to note is that the reaction medium in each step of the preparation process is low toxic and degradable deep eutectic solvent, which conforms to the concept of green chemistry.

Dimethyl carbonate as a green alternative to acetonitrile in reversed-phase liquid chromatography. Part I: Separation of small molecules

Nowadays, environmental problems are drawing the attention of governments and international organisations, which are therefore encouraging the transition to green industrial processes and approaches. In this context, chemists can help indicate a suitable direction. Beside the efforts focused on greening synthetic approaches, currently also analytical techniques and separations are under observation, especially those employing large volumes of organic solvents, such as reversed-phase liquid chromatography (RPLC). Acetonitrile has always been considered the best performing organic modifier for RPLC applications, due to its chemical features (complete miscibility in water, UV transparency, low viscosity etc); nevertheless, it suffers of severe shortcomings, and most importantly, it does not fully comply with Environmental, Health and Safety (EHS) requirements. For these reasons, alternative greener solvents are being investigated, especially easily available alcohols.In this work, chromatographic performance of the most common solvents used in reversed-phase chromatography, i.e., acetonitrile, ethanol and isopropanol, have been compared to a scarcely used solvent, dimethyl carbonate (DMC). The analytes of interest were two small molecules, caffeine and paracetamol, whose kinetics and retention behaviour obtained with the four solvents have been compared, and all contributions to band broadening have been assessed. Results about kinetic performance are very promising, indicating that a small amount (7 % v/v) of DMC is able to produce the same efficiency as a 2.5-times larger ACN volume (18 % v/v), and larger efficiency than alcohols.This paper reports, for the first time, fundamental studies concerning the mass transfer phenomena when DMC is used as an organic solvent in RPLC, and, together with the companion paper, represents the results of a research whose final aim was to discover whether DMC is suitable for chromatographic applications both in linear and preparative conditions.

The importance of the microstructure on hydro-mechanical behaviour of compacted granular bentonite

Granular bentonite (GB) with extended grain size distribution, a candidate material to construct engineered barriers, has low water permeability, high swelling potential and self-sealing capacity and is desirable in portability and workability. However, few systematic data combining microstructural descriptions and hydro-mechanical (HM) behavioural features are available. The present work investigates the HM performance of Wyoming (MX80)-type GB samples compacted at different initial water contents and at a fixed dry density of 1550 kg/m3. The samples' microstructure and its evolution along stress paths were studied using X-ray micro-computed tomography and mercury intrusion porosimetry. The results highlighted that the compacted GB presented local density heterogeneity and a multi-porosity network. Compaction at low initial water content increased the proportion of macropores and contributed to the enhancement of the compressibility and collapse on wetting under high stresses. During isochoric saturation, two stages of swelling development were identified. First, the flooding of macropores and matric suction reduction was related to the initial increase in swelling pressure. The secondary swelling was due to the water absorption of clay sheets in micropores and the expansion of micropores within granules and aggregates, during which the density of pore water increased. A decrease in the compaction water content can result in a higher pore water density after isochoric saturation and a lower water permeability. Finally, the water retention behaviour of the compacted sample within drying/wetting cycles was less sensitive to the initial pore size distribution. The current outcomes underline the critical role of the microstructure on the HM behaviour of compacted GB.

First-principles study on mechanical properties and retention behaviors of hydrogen in W by additions of Re and Mo

Understanding the alloying effects on service performances of hydrogen in W has been regarded as a hot issue for designing plasma-facing materials. In our work, first-principles calculation was used to comparatively investigate the thermodynamic stabilities, mechanical properties and retention behaviors of hydrogen in W by additions of Re and Mo. It is shown that the ductility and damage tolerance of WH phases are improved through the alloying of Re and Mo, and one of Re plays a more significant role. Moreover, the temperature-dependent solubility, diffusivity, and permeability of hydrogen in W, WRe and WMo alloys are calculated by combining Sievert's law and transition state theory. The derived results match well with experimental observations in the literature, and offer direct explanations for different influences of additive Re and Mo on hydrogen retention.

Borderline Personality Features and Mate Retention Behaviors: The Mediating Roles of Suspicious and Reactive Jealousy

We investigated the roles that suspicious jealousy and reactive jealousy might play in the associations between borderline personality features (BPF) and mate retention behaviors. Study 1 (N = 406) found that BPF had positive indirect associations with benefit-provisioning behaviors and cost-inflicting behaviors through suspicious jealousy but not through reactive jealousy. Study 2 (N = 334 (a dyadic sample of 167 romantic couples)) revealed actor effects such that BPF had positive indirect associations with benefit-provisioning behaviors and cost-inflicting behaviors through suspicious jealousy for both men and women. In addition, the positive association between BPF and benefit-provisioning behaviors was mediated by reactive jealousy in women but not in men. The only partner effect that emerged from these analyses showed that BPF in women were negatively associated with the benefit-provisioning behaviors reported by their male partners. Discussion focuses on the implications of these results for the function that jealousy might serve in the strategies used by individuals with BPF to maintain their romantic relationships.

Chitosan-Delivered Chlorantraniliprole for Pest Control: Preparation Optimization, Deposition Behavior, and Application Potential.

Chitosan has emerged as a promising biopolymer carrier for the sustained release of pesticides owing to its good biocompatibility, biodegradability, and bioactivity. In this work, a controlled-release formulation of insecticide chlorantraniliprole was fabricated through coprecipitation-based synchronous encapsulation with chitosan, where the optimum preparation conditions, storage stability, deposition behavior, and application potential were investigated. Preparation of optimization data from response surface methodology showed high correlation coefficient (R2) of 0.9875 and adjusted coefficient (Radj2) of 0.9715. The resulting formulation displayed good loading content of 28.39%, high encapsulation efficiency of 75.71%, and good storage stability. Compared with the commercial suspension concentrate, the formulation exhibited better wettability and retention behaviors on plant leaves. Excitingly, effective control against one species of mealybug genus Paraputo Laing (outside the killing spectrum) on the Hippeastrum reticulatum plant was successfully achieved by spraying the controlled-release formulation at different time intervals. This work indicates the good potential of the developed formulation in expanding the application scope of chlorantraniliprole, which shows a new strategy for sustainable pest management.

Exploring the interplay between attitudinal and behavioural determinants of fitness centre member retention

ABSTRACT Purpose: This research explores and evaluates both attitudinal and behavioural determinants of fitness centre member retention. In considering retention predictors prominent in past work, service quality, value and satisfaction are modelled, while we add multi-dimensional measures for loyalty, which are less prominent in research to date. Methodology: Partial Least Squares Structural Equation Modelling (PLS-SEM) was used to explore relationships between survey-based measurements from 661 members of a single fitness centre, with behavioural loyalty and retention collected over a 56-week period. Findings: Results demonstrate behavioural intention (i.e. intention to renew membership) and, critically, behavioural loyalty (i.e. observed fitness centre attendance and consistency) as most useful in explaining variance in member retention. Practical implication: Practically, insights guide the collection and use of member data towards the most relevant predictors of member retention. Research contribution: Our research enhances theory relevant to retention behaviours in subscription settings, supporting the utility of behavioural loyalty and behavioural intention as direct determinants of fitness centre member retention. Value: The present research combines commonly used attitudinal measures with a more novel analysis of member attendance behaviours.

Hydro-mechanical modelling of swell behaviour of bentonite buffer

Hydro-mechanical modelling of swell behaviour of bentonite buffer

Identification and characterization of phenolamides in tea (Camellia sinensis) flowers using ultra-high-performance liquid chromatography/Q-Exactive orbitrap mass spectrometry.

Phenolamides (PAs) are important secondary metabolites present in plants with multiple bioactivities. This study aims to comprehensively identify and characterize PAs in tea (Camellia sinensis) flowers using ultra-high-performance liquid chromatography/Q-Exactive orbitrap mass spectrometry based on a lab-developed in-silico accurate-mass database. The PAs found in tea flowers were conjugates of Z/E-hydroxycinnamic acids (p-coumaric, caffeic and ferulic acids) with polyamines (putrescine, spermidine and agmatine). The positional and Z/E isomers were distinguished through characteristic MS2 fragmentation rules and chromatographic retention behavior summarized from some synthetic PAs. 21 types of PAs consisting of over 80 isomers were identified, and the majority of them were found in tea flowers for the first time. Among 12 tea flower varieties studied, they all possessed tris-(p-coumaroyl)-spermidine with the highest relative content, and C. sinensis 'Huangjinya' had the highest total relative contents of PAs. This study shows the richness and structural diversity of PAs in tea flowers.

Comparison of ZIC-HILIC Columns for the Simultaneous Analysis of Antiviral Drugs in Dosage Forms by Hydrophilic Interaction Liquid Chromatography

Background:: Antiviral drugs are vital since many viruses can produce fatal infections, as we have recently seen with the COVID-19 pandemic. Antiviral drugs can battle viruses at multiple stages of their life cycles, including neuraminidase, nucleic acid synthesis, protease, and virion fusion or entry [1]. Objective:: Antiviral drugs have poor retention in reversed-phase liquid chromatography, which makes it difficult to analyze a mixture of antiviral medications using high-performance liquid chromatography. Using zwitterionic hydrophilic interaction liquid chromatography (ZICHILIC), the paper highlights the simultaneous quantification of three antiviral drugs as active constituents in pharmaceutical formulations. Moreover, the influence of the length of the spacer between the two charges in two stationary phases on the retention behavior of antiviral drugs has been discussed. Methods:: Two homemade stationary phases (ZIC1-HILIC and ZIC5-HILIC) were utilized for the qualitative and quantitative analysis of three antiviral drugs, and UV was used as the detector. Several chromatographic conditions were examined, such as the organic modifier concentration, buffer concentration, and pH value. Results:: After optimizing the parameters, the devised method was applied to analyse three antiviral medications quantitatively. The initial results demonstrated the current procedure for separating and determining these three antiviral drugs to be sensitive, robust, and effective. Consequently, the present method has shown excellent repeatability, a broad linear range (0.1- 16.5 μgml-1), and excellent sensitivity (LOD 0.04-0.072 μgml-1). The RSD value of the method was less than 1. Conclusion:: A mixed mode of hydrophilic and ion exchange interactions was the predominant mode of antiviral medications with two ZIC-HILIC stationary phases. The ZIC5-HILIC stationary phase had a lower detection and limit of quantitation for three antiviral drugs and a prolonged retention time compared to the ZIC1-HILIC stationary phase with a shorter chain length.

N-Acetylcysteine Displaces Glutathionyl-Moieties from Hg2+ and MeHg+ to Form More Hydrophobic Complexes at Near-Physiological Conditions.

The anthropogenic release of Hg is associated with an increased human exposure risk. Since Hg2+ and MeHg+ have a high affinity for thiols, their interaction with L-glutathione (GSH) within mammalian cells is fundamentally involved in their toxicological chemistry and excretion. To gain insight into the interaction of these mercurials with multiple small molecular weight thiols, we have investigated their competitive interactions with GSH and N-acetylcysteine (NAC) at near-physiological conditions, using a liquid chromatographic approach. This approach involved the injection of each mercurial onto a reversed-phase (RP)-HPLC column (37 °C) using a PBS buffer mobile phase containing 5.0 mM GSH to simulate cytosolic conditions with Hg being detected in the column effluent by an inductively coupled plasma atomic emission spectrometer (ICP-AES). When the 5.0 mM GSH mobile phase was amended with up to 10 mM NAC, gradually increasing retention times of both mercurials were observed. To explain this behavior, the experiment with 5.0 mM NAC and 5.0 mM GSH was replicated using 50 mM Tris buffer (pH 7.4), and the Hg-containing fractions were analyzed by electrospray ionization mass spectrometry. The results revealed the presence of Hg(GS)(NAC) and Hg(NAC)2 for Hg2+ and MeHg(GS) and MeHg(NAC) for MeHg+, which suggests that the coordination/displacement of GS-moieties from each mercurial by the more hydrophobic NAC can explain their retention behavior. Since the biotransformations of both mercurials were observed at near-physiological conditions, they are of toxicological relevance as they provide a biomolecular explanation for some results that were obtained when animals were administered with each mercurial and NAC.

Encapsulation of phenolic-rich lemon-scented tea tree extract in lemon pomace powder

The Australian native plant, lemon-scented tea tree (LSTT) is rich in polyphenols with strong antioxidant activities. Encapsulation enhances the potential applications of plant extracts and additionally protects them from degradation. The encapsulating agent is one of the key elements in the encapsulation process. In this study, lemon pomace powder (LPP) was investigated as a new carrier agent for LSTT leaf phenolic extract, and its performance was compared with the commonly used polysaccharide (i.e., maltodextrin (MD)) and protein-based (i.e., soy protein isolate (SPI)) coating materials. The encapsulation efficiency, colour, polyphenol and antioxidant property retention, particle morphology, crystallinity, flow properties, and release behaviour in food simulants and gastrointestinal fluid were studied to compare the performance of the carrier agents individually and in combinations. The encapsulation efficiency of lemon pomace powder (LPP) was above 95 % and the order for the retention of polyphenol and antioxidant capacities were MD>LPP>SPI. LPP offers better flow properties and unique particle morphology, which was also amorphous in nature with some degree of crystallinity. The release profile in the food simulants showed a controlled and sustained release rate over the tested period, which was comparable with MD and SPI. In gastrointestinal fluids, the percent release followed the order of SPI>LPP>MD for the carrier agents. The incorporation of LPP with MD and SPI can improve several properties of the individual carrier agents. Thus, LPP can be used as a potential carrier agent for polyphenols in functional food formulation either on its own or in combination with other coating materials.

Enhanced sensitivity of multifunctional wearable sensor based on Mxene-Ag QDs organo-hydrogel for human-machine interface

Recently, flexible, stretchable, and wearable sensors have received breakthrough due to wide applications in next generation portable electronics. Despite the use of many nanostructured hydrogels to construct stretchable devices, the integrated excellent optical and mechanical properties as well as intended functionality and satisfactory sensing performance are difficult to achieve with flexible/stretchable devices. Herein, we developed a multifunctional poly dopamine-titanium dioxide/silver quantum dots@ MXene organo-hydrogel (PDA-TiO2/AgQDs@MXene organo-hydrogel) as an optoelectronic wearable strain sensor with superior mechanical properties. The results reveal a promising sensor capability of monitoring and tracking human activities, vital signs, sign language, vocal cords vibrations during vocalization, touch, temperature, and photodetection of visible light. The developed sensor demonstrated superior anti-freezing point of − 45 °C, results in high performance capability at sub-zero temperatures. Additionally, it exhibited self-healing after 5 min with a healing efficiency (HE) 57% and an electrical healing efficiency (EHE) 70%. The water retention behavior (maintain 94.12% of the initial weight after 102 days) and excellent mechanical properties (570 kPa at strain 455%) were introduced. The sensor exhibited ultra-sensitivity (810%) during stretching to 400%, response time (19 ms), and also operated in other harsh circumstances such as bending, twisting, and compression with high reliability. The results provide a new path for future applications of the developed sensor in smart wearable electronics, soft robotics, artificial throat, optoelectronics, and smart healthcare monitoring and diagnosis.

Investigation of porosity variation on water retention behaviour of unsaturated granular media by using pore scale Micro-CT and lattice Boltzmann method

Most soils in nature are in unsaturated states. The key to correctly understanding its hydraulic characteristics lies in mastering the correlation between its microstructure and macro water retention characteristics. Based on an independently developed miniaturized in-situ unsaturated soil–water characteristic instrument, three-phase topological morphology and micrographic information (pore throat, liquid cluster, interface area) of unsaturated granular media were explored, supplemented by CT scanning under a high resolution (5.6 μm/pixel). In addition, three-dimensional reconstruction of CT images was performed for simulating two-phase flow in porous granular media using the lattice Boltzmann method. The experimental results indicate that the water retention capacity, air-entry value, and residual saturation of unsaturated granular specimens are negatively correlated with the porosity of specimens. As the saturation decreases, the specific air–water interfacial area first increases and then decreases, with the peak value appearing around 20% of saturation. Based on LBM simulation, the water retention capacity of the specimen is negatively correlated with the contact angle, while the liquid–solid characteristic interface area and relative permeability are positively correlated. The experimental and simulation results demonstrate good consistency with each other.

In-pile tritium release behavior and the post-irradiation experiments of Li4SiO4 fabricated by melting process

Understanding the tritium release and retention behavior of candidate tritium breeder materials is crucial for breeder blanket design. Recently, a melt spraying process was developed to prepare Li4SiO4 pebbles, which were subsequently subjected to the in-pile tritium production and extraction platform in China Mianyang Research Reactor (CMRR) to investigate their in-situ tritium release behavior and irradiation performance. The results demonstrate that HT is the main tritium release form, and adding hydrogen to the purge gas reduces tritium retention while increasing the HT percent in the purge gas. Post-irradiation experiments reveal that the irradiated pebbles darken in color and their grains swell, but the mechanical properties remain largely unchanged. It is concluded that the tritium residence time of Li4SiO4 made by melt spraying method at 467 °C is approximately 23.34 h. High-density Li4SiO4 pebbles exhibit tritium release at relatively low temperatures (＜600 °C) that is mainly controlled by bulk diffusion. The diffusion coefficient at 525 °C and 550 °C is 1.19 × 10−11 cm2/s and 5.34 × 10−11 cm2/s, respectively, with corresponding tritium residence times of 21.3 hours and 4.7 hours.

Bismuth sulfide based resistive switching device as the key to advanced logic gate fabrication

A memristor is a two-terminal electrical component with the scope of future computing applications and analog electronics. In this report, bismuth sulfide decorated one-dimensional carbon nitride nanotube was synthesized and characterized with various analytical techniques. The electrical property of the synthesized material was measured using a two-terminal metal–insulator–metal type of device that exhibited the resistive switching characteristics with the ON to OFF ratio of 2 × 103. The electron transport mechanism of the device was followed by Schottky emission and Poole–Frenkel emission for a low conductance state and Ohmic conduction behavior at the high conductance state. A decrease in the trap depth was identified in the simulation study with increasing applied potential and that supported the proposed mechanism. Read endurance and retention behavior of the device are stable in nature, supported by the statistical analysis. Furthermore, a hybrid logic gate was designed using two identical memristors, one CMOS inverter, one resistor, one voltage divider, and a buffer gate. The designed logic gate exhibited stable nand and nor gate operation based on the control signal.

Incense smoke (IS) inhalation exposure system: Physicochemical characterization, IS particle deposition and clearance in human airway using MPPD model

Incense smoke (IS) is source of indoor air pollution and key risk for diverse human diseases. Less information is available regarding controlled IS rodent inhalation exposure system and IS particulate matter (PM) deposition in human airways. Study aimed to demonstrate stable ISPM physicochemical parameters of 10 incense products inside the customized whole body inhalation exposure chamber (without animal) connected to smoke generation unit via aerosol mixing device. IS analyzed for size segregated PM emission, ISPM in vitro aerodynamics (MMAD and GSD determination), fine and ultrafine particle's SEM, SEM-EDX and PAH analysis. Using real life exposure scenario by utilizing MMAD, GSD and PM concentration after Tier 1 exposure assessment as key input parameters, ISPM dosimetry in infant (3 months) and adult (21 years male and female) human airways was calculated using multiple-path particle dosimetry (MPPD 3.04) modeling. Mass median aerodynamic diameter (MMAD) and geometric standard deviation (GSD) ranged between 0.55 and 2.10 μm and 1.22 to 1.77 (polydisperse) respectively. PM1.0 and PM0.1 showed multiple morphology and presence of heavy and trace elements. PAH like acenaphthylene, anthracene, fluorene, naphthalene and phenanthrene were detected (0.84–143.17 μg/g). MPPD results showed higher ISPM deposition in pulmonary region and lowest in trachea bronchial region. ISPM deposition in tissue was higher in lower, peripheral lung as compared to upper and central lung tissue. Whole body inhalation exposure system showed stable IS atmosphere (physicochemical parameters) indicating the device suitability in future inhalation studies. MPPD ISPM deposition fraction and clearance data showed deep lung penetrating and retention behavior with higher risk in infant followed by female and then male. These modeled particle deposition and clearance data may be useful in risk assessment analysis of IS.

Theoretical Study of Non-Isothermal Gradient Elution Liquid Chromatography.

A two-component model of gradient elution chromatography is investigated to theoretically study the effects of simultaneous variations in temperature and solvent strength on the retention behaviors of elution profiles in thermally insulated liquid chromatographic columns. The gradient elution technique is based on the gradual increase or decrease in eluent strength during the chromatographic operation by varying the composition of the mobile phase. The enthalpy of adsorption is primarily responsible for internal temperature variations inside the column, as heat adsorbs during the adsorption process and releases in the desorption phase. Both types of variations change the propagation speeds of moving pulses inside the column which can lead to better separation of the components and a reduction in the recycling time for the next injection. The equilibrium dispersive model (EDM) coupled with the energy balance equation for temperature and transport equation for the volume fraction of the solvent is utilized to simulate this complex process. The resulting nonlinear model equations are approximated by applying a semi-discrete second-order finite volume scheme. The numerical solutions are used to study the impact of a gradient starting and ending times, volume-fraction of the solvent, solvent strength parameter, the slope of gradient, enthalpy of adsorption, injection temperature, and the ratio of specific heats on the concentration profiles.

A multi-target QSRR approach to model retention times of small molecules in RPLC

Quantitative structure-retention relationship models (QSRR) have been utilized as an alternative to costly and time-consuming separation analyses and associated experiments for predicting retention time. However, achieving 100 % accuracy in retention prediction is unrealistic despite the existence of various tools and approaches. The limitations of vast data availability and time complexity hinder the use of most algorithms for retention prediction. Therefore, in this study, we examined and compared two approaches for modelling retention time using a dataset of small molecules with retention times obtained at multiple conditions, referred to as multi-targets (five pH levels: 2.7, 3.5, 5, 6.5, and 8 at gradient times of 20 min of mobile phase). The first approach involved developing separate models for predicting retention time at each condition (single-target approach), while the second approach aimed to learn a single model for predicting retention across all conditions simultaneously (multi-target approach). Our findings highlight the advantages of the multi-target approach over the single-target modelling approach. The multi-target models are more efficient in terms of size and learning speed compared to the single-target models. These retention prediction models offer two-fold benefits. Firstly, they enhance knowledge and understanding of retention times, identifying molecular descriptors that contribute to changes in retention behaviour under different pH conditions. Secondly, these approaches can be extended to address other multi-target property prediction problems, such as multi-quantitative structure Property(X) relationship studies (mt-QS(X)R).