RP Phases Research Articles

Electronic and optical properties of two-dimensional perovskite materials in DJ and RP phases: density functional theory approach

Electronic and optical properties of two-dimensional perovskite materials in DJ and RP phases: density functional theory approach

Exogenous IBA stimulated adventitious root formation of Zanthoxylum beecheyanum K. Koch stem cutting: Histo-physiological and phytohormonal investigation

Poor rooting performance of Chinese pepper (Zanthoxylum beecheyanum K. Koch) shrub is a restriction for its commercial production. This investigation was carried out to assess the effectiveness of the exogenous application of indole-3-butyric acid (IBA) on adventitious root (AR) formation and some morpho-physiological, biochemical, and histological alterations associated with rhizogenesis events. IBA, at 1500 or 2000 mg kg-1, gave comparable effects for improving the performance of rooting architecture compared to the control treatment. The AR primordia of Z. beecheyanum originated from two distinct developmental pathways: (i) direct genesis from cells in the cambial zone and nearby tissues, and (ii) indirect genesis from cells in callus tissues. Rooting process involved four phases: (i) induction at 0–10 days after planting (DAP), (ii) initiation at 10–15 DAP, (iii) formation of the root primordia (Rp) at 15–20 DAP, and (iv) root extension at 20–30 DAP. Cuttings' inductive phase correlated temporarily with intensive cell divisions, high levels of endogenous indole-3-acetic acid (IAA) and gibberellins (GA3). However, IBA application led to a pronounced increase in soluble sugars and phenolic content. The initiation phase was accompanied by a histological appearance of meristemoids. This phase was also stimulated by the subsequent generation of low IAA and high GA3 contents. In the development of Rp and root extension phases, prominent Rp formation in the cambium and complete differentiation with vascular tissues continued with that of the stem cuttings. In essence, the current study provides insights into the morphological, histo-physiological, and phytohormonal alterations in stem cuttings.

Optimization of chromatographic systems for detection and determination of carbamazepine in pharmaceutical formulations, serum, and saliva by HPLC-DAD

Carbamazepine (CBZ) is an anticonvulsant drug, widely used also in various disorders like neuropathic pain, bipolar affective disorder, resistant schizophrenia, and trigeminal neuralgia. Appropriate analytical procedures are necessary to monitor, detect and quantify CBZ in pharmaceutical formulations and biological samples. The search for new methods for drug determination is one of the most important challenges of modern scientific research. It is important to study the chromatographic conditions of CBZ analysis, which is necessary for the further development of efficient drug determination methods. In this work, retention, peak symmetry, and system efficiency of CBZ on Polar RP and Phenyl-Hexyl stationary phases were investigated. Various mobile phases containing methanol (MeOH) and/or acetonitrile (ACN) as organic modifiers, acetate buffer, and the addition of diethylamine (DEA) were applied. Different chromatographic systems were compared to obtain satisfying retention, peak shape, and system efficiency. The most optimal chromatographic system with Polar RP column was applied for the determination of CBZ in pharmaceutical formulations, human serum, and saliva by the high-performance liquid chromatography with diode array detection (HPLC-DAD) method. Solid-phase extraction (SPE) method was applied for sample preparation prior to chromatographic analysis. The proposed method was validated for linearity, selectivity, precision, and accuracy. Confirmation of the presence of CBZ and its main metabolites in biological samples obtained from patients was performed using the ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method.

Physiological changes of sweet pepper under low irrigation regimes applied in three phenological stages of vegetative growth, reproductive growth, and fruit set

ABSTRACT A factorial experiment based on a completely randomised design (CRD) with 10 replicates was planned to evaluate if commercially low irrigation reduced output and how physiologically low irrigation influenced yield at different plant growth stages. In three phonological phases of the vegetative stage (VG), reproductive stage (RP), and fruit set (FS), two irrigation regimes of 100% of field capacity (FC) and 80% field capacity (low irrigation = LI) were employed. The results demonstrated that the shoot's fresh weight did not vary between the VG and RP phases, but rose during the FC stage. In FS, both photosynthesis and transpiration were reduced. VG had the highest amounts of photosynthesis and transpiration. Nevertheless, fruit yield rose during the second and third weeks of FS. As starch dropped and glucose, sucrose, and fructose increased, plasma membrane aquaporins (PIP) gene expression and abscisic acid (ABA) levels climbed. In conclusion, it was proved that lowering water consumption to 80% FC did not impact yield at any development stage, including FS, due to the larger sink of fruit rather than maintaining ideal photosynthetic conditions. ABA and PIP expression increased, which may serve as a signal for the plant to overcome the moderate stress generated by LI.

Hybrid perovskites as oxygen evolution electrocatalysts for high-performance anion exchange membrane water electrolyzers

Highly active and platinum group metal-free (PGM-free) oxygen evolution reaction (OER) electrocatalysts are essential for producing low-cost and clean hydrogen in anion exchange membrane water electrolyzers (AEMWEs). Thanks to the unique characteristics of perovskite oxides, which include low cost, tunable electronic structure and cation deficiency, high electronic conductivity, high durability, high specific catalytic activity, and environmental friendliness, they have been widely designed and employed as the OER electrocatalysts. Here, a set of novel hybrid perovskites, LaxSr4-xNiyFe3-yO10-δ (LxS4-xNyF3-y), were demonstrated, which consist of a single-layer perovskite phase (P phase) and two Ruddlesden–Popper perovskite phases (RP phases). These hybrid perovskites synergize the advantages of the P phase and RP phases, which improves the oxygen-ion diffusion rate, leading to enhanced OER activity. Furthermore, the concentration of each phase can be tuned by alternating the compositional stoichiometry. A relatively uniform distribution of the P phase and RP phases can maximize the interfacial area and achieve the highest oxygen-ion diffusion rate. L3S1N2F1, L2S2N1F2, and L2S2N1.5F1.5 exhibit outstanding OER activity, which achieve 10 mA/cm2 at a low overpotential of less than 360 mV in 1.0 M KOH. Additionally, herein, the hybrid perovskites are implemented as the anodes of AEMWEs, which deliver an exceptional current density of > 1.0 A/cm2 at 1.8 V.

Alloy CsCd x Pb1-x Br3 Perovskite Nanocrystals: The Role of Surface Passivation in Preserving Composition and Blue Emission.

Various strategies have been proposed to engineer the band gap of metal halide perovskite nanocrystals (NCs) while preserving their structure and composition and thus ensuring spectral stability of the emission color. An aspect that has only been marginally investigated is how the type of surface passivation influences the structural/color stability of AMX3 perovskite NCs composed of two different M2+ cations. Here, we report the synthesis of blue-emitting Cs-oleate capped CsCdxPb1–xBr3 NCs, which exhibit a cubic perovskite phase containing Cd-rich domains of Ruddlesden–Popper phases (RP phases). The RP domains spontaneously transform into pure orthorhombic perovskite ones upon NC aging, and the emission color of the NCs shifts from blue to green over days. On the other hand, postsynthesis ligand exchange with various Cs-carboxylate or ammonium bromide salts, right after NC synthesis, provides monocrystalline NCs with cubic phase, highlighting the metastability of RP domains. When NCs are treated with Cs-carboxylates (including Cs-oleate), most of the Cd2+ ions are expelled from NCs upon aging, and the NCs phase evolves from cubic to orthorhombic and their emission color changes from blue to green. Instead, when NCs are coated with ammonium bromides, the loss of Cd2+ ions is suppressed and the NCs tend to retain their blue emission (both in colloidal dispersions and in electroluminescent devices), as well as their cubic phase, over time. The improved compositional and structural stability in the latter cases is ascribed to the saturation of surface vacancies, which may act as channels for the expulsion of Cd2+ ions from NCs.

Fragment-based Design of Zwitterionic, Strong Cation- and Weak Anion-Exchange Type Mixed-mode Liquid Chromatography Ligands and their Chromatographic Exploration

The role of individual functional groups has been assessed with regard to surface charge and chromatographic retention. Coatings were prepared from various fragments of the chiral zwitterionic materials Chiralpak ZWIX(+) and ZWIX(-). The different chromatographic ligands allowed fine tuning of the surface charge. Chiralpak ZWIX phases showed strongly negative ζ-potentials over the entire pH-range. Zwitterionic congeners with quinuclidine and sulfonic acid moieties but lacking the quinolone ring in the ligand structure exhibited shifted ζ-potentials of around + 5 to 20 mV depending on the surrounding residues. Capillary electrophoretic mobilitiy measurements with the chromatographic ligands and molecular dynamics simulations were carried out to offer some explanation of these surface charge differences of the distinct zwitterionic stationary phases. The new mixed-mode phases were also chromatographically characterized by simple RP and HILIC tests. The results allowed their positioning within a large variety of different commercially available RP, HILIC and mixed-mode phases, which were evaluated as well, by multivariate data processing using principal component analysis. The new mixed-mode phases overall exhibit reasonable hydrophilicity-lipophilicity balance and enable retention of ionic compounds by additional ionic interactions through weak anion-exchange (WAX-type), strong cation-exchange (SCX-type) or both (RP/ZWIX-type). Hence, the new RP/ZWIX phases can be flexible tools for selectivity tuning in RP and HILIC separations.

Stable-bond polymeric reversed-phase/weak anion-exchange mixed-mode stationary phases obtained by simultaneous functionalization and crosslinking of a poly(3-mercaptopropyl)methylsiloxane-film on vinyl silica via thiol-ene double click reaction

A polymeric reversed-phase/weak anion exchange (Poly-RP/WAX) mixed-mode stationary phase has been prepared by coating of a poly(3-mercaptopropyl)methylsiloxane film on vinyl-modified silica (100 Å, 5 μm) and simultaneous in situ functionalization with N-(10-undecenoyl)-3-aminoquinuclidine as well as crosslinking to the vinyl silica surface by solventless thiol-ene double click reaction. Such bonding chemistry showed greatly enhanced stability compared to brush-type analogs with bifunctional siloxane bonding to silica. Solid-state 29Si-CP/MAS NMR confirmed the immobilization of the siloxane layer. pH-Dependent ζ-potential determinations revealed a high anion-exchange capacity over the entire pH range with a maximum around pH 5. Oxidation of residual thiols yielded a zwitterionic Poly-RP/WAX/SCX mixed-mode phase with sulfonic acid endcapping and shifted the still net positive surface charge to lower ζ-potentials. It allowed a faster elution of strongly retained anionic species in particular of multiply negatively charged analytes such as oligonucleotides. Chromatographic tests under RPLC and HILIC elution mode with various test substances documented the multimodal utility and complementarity in retention profiles compared to RP, HILIC and commercial mixed-mode phases.

Surface charge fine tuning of reversed-phase/weak anion-exchange type mixed-mode stationary phases for milder elution conditions

A series of new mixed-mode reversed-phase/weak anion-exchange (RP/WAX) phases have been synthesized by immobilization of N-undecenyl-3-α-aminotropane onto thiol-modified silica gel by thiol-ene click chemistry and subsequent introduction of acidic thiol-endcapping functionalities of different type and surface densities. Click chemistry allowed to adjust a controlled surface concentration of the RP/WAX ligand in such a way that a sufficient quantity of residual thiols remained unmodified which have been capped by thiol click with either 3-butenoic acid or allylsulfonic acid as co-ligands. In another embodiment, performic acid oxidation of N-undecenyl-3-α-aminotropane-derivatized thiol-modified silica gave a RP/WAX phase with high density of sulfonic acid end-capping groups. ζ-Potential determinations confirmed the fine-tuned pI of these mixed-mode stationary phases which was shifted from 9.5 to 8.2, 7.8, and 6.5 with 3-butenoic acid and allylsulfonic acid end-capping as well as performic acid oxidation. For acidic solutes, the co-ionic endcapping leads to strongly reduced retention times and clearly allowed elution of these analytes under lower ionic strength thus milder elution conditions. In spite of the acidic endcapping, the new mixed-mode phases maintained their hydrophobic and anion-exchange selectivity as well as their multimodal nature featuring RP and HILIC elution domains at acetonitrile percentages below and above 50%, respectively. Column classification by principal component analysis of an extended retention map in comparison to a set of polar commercial and in-house synthesized stationary phases confirmed complementarity of the new mixed-mode phases with respect to HILIC, polar RP, amino and commercial mixed-mode phases.

Lipophilicity of porphyrins and their retention in IAM, C8–C18 and HILIC chromatographic systems

Porphyrins are a class of photosensitizers used in photodynamic therapy (PDT). Understanding the interaction of porphyrins with membrane cells components is important in order to improve this therapy. Many analytical methods can be used for this aim. High performance liquid chromatography (HPLC) was used for the separation of porphyrins on RP and HILIC stationary phases as well as on a biomimetic membrane IAM phase. Twenty-six tetraphenyl porphyrins (TPP) were successfully separated on an IAM column, a C18 Gravity RP column, a C8 Gravity RP column, a PolarTec RP column and a HILIC column. Stationary phases were chosen as the most appropriate to cover the study of different types of interactions. Elution was performed with a 45min linear gradient. Obtained gradient retention times were converted to gradient chromatography hydrophobicity index (CHI) and to an apparent retention factor (kapp). The partition coefficients (logP) of the 26 compounds were measured in a 2-octanol/PBS system and estimated in silico. Correlation between kapp values was studied. Moreover, a multivariate analysis was performed to explain columns relationships. Obtained results show that porphyrins are separated mainly according to hydrophobic interactions that are relative to their structure (sugar number and the disposition around the porphyrin macrocycle).

A Comparative Quantitative Structure-Retention Relationships Study for Lipophilicity Determination of Compounds with a Phenanthrene Skeleton on Cyano-, Reversed Phase-, and Normal Phase-Thin Layer Chromatography Stationary Phases

The phenanthrene skeleton is an important moiety in medical chemistry as it is present in steroidal drugs used as anti-inflammatory and anti-asthmatic agents as well as synthetic hormones or potassium sparing diuretics. Chromatographic properties of 14 derivatives containing the phenanthrene skeleton in their structure with known lipophilicity have been studied. NP, RP, and cyano-bonded silica stationary phases with three binary mobile phases (acetonitrile-water, acetone-water, and acetone-petroleum ether) were tested. Obtained chromatographic data were correlated with the lipophilicity expressed as values of log partition coefficient (P). The presented study was undertaken to find the best TLC system and chromatographic data processing method in order to predict log P values. Correlations between chromatographic data and measurements of lipophilicity of compounds were presented as results of established quantitative structure-retention relationships. Principal component analysis and cluster analysis were used to investigate the similarities among chromatographic systems.

Electronic and dielectric properties of Ruddlesden–Popper type and Magnéli type SrTiO3

We have investigated the electronic and dielectric properties of the Srn+1TinO3n+1 (Ruddlesden–Popper, RP) Sr-rich and SrnTin+1O3n+2 (Magnéli, M) Ti-rich phases of SrTiO3 using the LDA and HSE06 first principles methods. The calculated densities of states indicate that the width of band gap decreases monotonically with increasing n in the RP phases, but increases with n in the M phases. In contrast to the M phases, the RP phases exhibit better tunable dielectric properties with variations in n and also have lower dielectric loss than SrTiO3 in the lower energy range. In the case of n=1, the real and imaginary parts of the dielectric functions of both the RP and M phases are remarkably different from stoichiometricSrTiO3 due to rumpling of the interfaces between the SrO or TiO2 bilayers and the abnormal hybridization of the Ti 3d and O 2p orbitals. The optical dielectric constant ɛ1(0) increases with decreasing Sr/Ti ratio, meaning that Ti-rich M phases give higher optical dielectric constants than Sr-rich RP phases. For M phases, planar defects are formed by edge-sharing TiO6 octahedra and interface rumpling of TiO2 bilayers caused by displacements of O atoms normal to the interface that create distorted octahedra. These distortions produce a crystal field that gives rise to atypical electron transfers between the Ti and O atoms within these octahedra that significantly influence the structural stability and dielectric properties of the M phases.

A fluoro versus a nitro derivative—a high-performance liquid chromatography study of two basic analytes with different reversed phases and silica phases as basis for the separation of a positron emission tomography radiotracer

To develop a basis for the separation of a 18F-labeled PET radiotracer from its nitro precursor, we performed an analytical HPLC study using the unlabeled reference compound and the corresponding nitro precursor. Aim of the study was to find a separation in which the fluoro derivative elutes in front of the nitro precursor with appropriate separation parameters. Several RP phases as well as a bare silica column were investigated with ACN and MeOH as organic modifiers and aqueous NH4OAc because of the basic character of the analytes. Four types of separation were observed based on different interaction mechanisms. When ACN/20mM NH4OAc aq. was used mainly cationic-exchange and hydrophobic interactions contributed to the retention. A reversal of elution order could be observed starting from 95% ACN and subsequent increasing of the water content. This phenomenon was observed for all RP phases and seems to be independent of the different spacers bound to the silica. By contrast, using MeOH/20mM NH4OAc aq. the elution order depends on the phase material. Two columns with the potential to perform π–π interactions showed different separation behavior compared to the other RP phases.

Accessible silanol sites – Beneficial for the RP-HPLC separation of constitutional and diastereomeric azaspirovesamicol isomers

Different RP-HPLC columns (phenyl, conventional ODS, cross-linked C 18 and special end-capped C 8 and C 18 phases) were used to investigate the separation of four basic ionizable isomers. Using ACN/20 mM NH 4OAc aq., a separation was observed exclusively on RP columns with higher silanol activity at unusual high ACN concentration, indicating cation-exchange as main retention mechanism. Using MeOH/20 mM NH 4OAc aq., another separation at low MeOH concentrations was observed on both, RP columns with higher as well as RP columns with lower silanol activity, which is mainly based on hydrophobic interactions. The isomers were also separated on a bare silica column at higher MeOH content using NH 4OAc. Since cation-exchange governs this retention, the elution order was different compared to the RP phases. A strong retention on the silica column was observed in ACN, which could be attributed to partition processes as additional retention mechanism.

Determination of water-soluble vitamins in vitamin premixes, bioacitve dietary supplements, and pharmaceutical preparations using high-efficiency liquid chromatography with gradient elution

The influence of the pH and temperature of the mobile phase on the retention and separation of 14 vitamins and vitameric forms has been studied for four different stationary phases. The chromatographic conditions allowing the separation of 12 water-soluble vitamins and vitameric forms have been proposed. It has been established that the best separation of water-soluble vitamins can be achieved by employing gradient elution. The mobile phase A, (0.6% phosphoric acid) pH 1.5–1.8; mobile phase B, acetonitrile. For the separation of nicotinic and ascorbic acid it is preferable to use stationary phases Luna C18(2) and Gemini C18, while for the separation of riboflavin and riboflavin-5-phosphate the Synergy Hydro RP and Zorbaz SB-C18 stationary phases should be used. The selected conditions have been used for the determination of vitamins in commercial samples of vitamin preparations. The results are in good accordance with the producer data.

Characterization of sialylated and fucosylated glycopeptides of β2‐glycoprotein I by a combination of HILIC LC and MALDI MS/MS

Characterization of low microgram levels of glycoprotein remains a challenge due to extensive heterogeneity of the conjugated N-glycans at each individual glycosylation site. We present an optimized, sensitive workflow for glycopeptide isolation and characterization that exploits the complementary features of RP (Poros R2) and hydrophilic (zwitter-ionic hydrophilic interaction chromatography) chromatographic resins. The glycopeptide analysis workflow was applied to human beta2-glycoprotein I (beta2-GPI, apolipoprotein H), which contains multiple N-glycosylation sites. Conditions for rapid proteolytic digestion of beta2-GPI using low-specificity proteases were optimized to detect beta2-GPI glycopeptides by MS. We demonstrate the importance of ensuring sufficient column capacity of both hydrophobic and hydrophilic stationary phases for optimal glycoprofiling by MS. The enriched glycopeptides were characterized using MALDI quadrupole TOF MS/MS. A total of 23 glycan structures, including sialylated bi- and tri-antennary complex type glycans, were characterized at three N-glycosylation sites, namely Asn-143, Asn-174 and Asn-234, of beta2-GPI. Further exploration of the complementary nature of RP and HILIC stationary phases for glycopeptide isolation prior to MS analysis may eventually enable systematic analysis of complex glycoprotein samples in functional proteomic research and advance our understanding of the biological role of protein glycosylation.

Long-term structural surface modifications of mixed conducting La2NiO4+δ at high temperatures

Abstract Long-term annealing of La2NiO4+δ single crystals at 1,273 K in air leads to the formation of nickel-rich Ruddlesden–Popper phases at the single-crystal surfaces. Both the composition and the morphology of these phases depend on the surface orientation; whereas only crystallites of La4Ni3O10−δ were observed on (001) surfaces, both La3Ni2O7−δ and La4Ni3O10−δ were formed on (100) surfaces. The formation of the nickel-rich RP phases is believed to be due to surface segregation of nickel or evaporation of a volatile lanthanum species. The crystallographic (001) planes inside the La3Ni2O7−δ and La4Ni3O10−δ crystallites were found to be oriented in the direction of preferential crystallite growth, which indicates that the diffusion of lanthanum and nickel cations is faster along the crystallographic (001) planes than perpendicular to these planes.

Contribution of sulfonyl–aromatic and sulfonic acid–aromatic interactions in novel sulfonyl/sulfonic acid-embedded reversed phase materials

Two novel sulfonyl-embedded reversed phase materials with sulfonic acid moieties (SO X -RP) were prepared by a simple oxidation of two silica-based sulfur-embedded RP-phases (S-RP). The chromatographic behavior of the resultant sulfonyl/sulfonic acid-embedded phase C3-SO 2-C18/SO 3H and the sulfonyl-embedded phase C3-SO 2-C14 e.c. (silanol endcapped) was extensively elucidated with a number of well-established as well as self-assembled column tests. These SO X -RP phases were also compared with their corresponding S-RP phases as well as with two commercial carbonyl-containing RP phases (CO-RP) with amide- and urea-embedding. The SO X -RP phases were found to exhibit exceptionally high planar recognition ability for polyaromatic analytes at comparable retention times to the investigated CO-RP phases and highly reduced retention compared to the parent, non-oxidized S-RP-materials. The results of this study suggest that the selectivity enhancement observed with the S-oxidized phases is due to sulfonyl–π and sulfonic acid–π interactions. Furthermore these novel SO X -RP phases proved to be fully applicable under 100% aqueous mobile-phase conditions making them a useful alternative to conventional RP as well as polar-embedded CO-RP phases.

Investigations on the chromatographic behavior of hybrid reversed-phase materials containing electron donor–acceptor systems: I. Contribution of sulfur–aromatic interactions

The influence of sulfur–aromatic interactions on the chromatographic separation behavior of hybrid RP phases, containing thiol-groups and/or embedded sulfide-groups (S-RP) has been investigated. To allow a precise outline of this new interaction mode, a wide variety of S-RP phases with different alkyl chain length, with and without residual thiol-groups and silanol-endcapping were prepared and tested in comparison to some conventional monomerical as well as polymerical n-alkyl type RP phases. The solute test sets employed in this study comprised the classical chromatographic column tests from Engelhardt and Tanaka as well as test assemblies containing polycyclic aromatic hydrocarbons, stilbene-based cis/ trans isomers and functional isomers of benzene. In general, a pronounced strong planar recognition ability as well as a strong increase in the retention for aromatic compounds have been noticed. It was furthermore found that not only the sulfur atom incorporated into the alkyl chain, but also the residual thiol-groups of the 3-propylthiol silica backbone contribute to the overall retention behavior of these novel S-RP type phases.

Bismuth for calcium substitution in Ca 4Mn 3O 10: preparation and study

Bismuth for calcium substitution in the RP phase Ca 4Mn 3O 10 is reported. Structural, chemical and physical characterization of the sample indicate that a non-stoichiometric compound Ca 3.09Bi 0.69Mn 3O 10 was obtained, although some perovskite phase was also present. The RP substituted phase is antiferromagnetically ordered below 105 K. Based on the obtained results, the influence of electron doping by bismuth substitution on the RP phases is discussed.