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This study successfully prepared different loading levels of cyano-functionalized RCC3 molecular cage silica gel stationary phase (RCC3-CN@SiO 2 ) through aldehyde-amine condensation reaction and subsequent modification strategies. Fourier transform infrared spectroscopy, thermogravimetric analysis, nitrogen adsorption-desorption, and scanning electron microscopy confirmed the successful synthesis of RCC3-CN@SiO 2 chromatographic stationary phase. The research demonstrates that due to hydrophobic/hydrophilic interactions, π-π interactions, hydrogen bonding, and size-selective porous structure, the stationary phase effectively separates moderately polar and weakly polar compounds in reversed-phase liquid chromatography (RPLC) mode, exhibiting hydrophobic selectivity comparable to the commercial DaisoC18-RP columns. Additionally, the tertiary amine and cyanogen groups on the molecular cage surface enhance the interaction with polar compounds, successfully separating nucleosides, sulfonamides, amino acids, and sugars in hydrophilic interaction chromatography (HILIC) mode. Further applications in the separation analysis of acidic drugs, alkaline drugs, cinnamic acid natural products, and chiral compounds demonstrate the multifunctional chromatographic capabilities for diverse compound types. Compared to Unitary Diol commercial columns, the prepared stationary phase showed significant advantages in wide polarity range separation performance. Moreover, through nucleoside compound separation mode switching analysis, RCC3-CN@SiO 2 stationary phase further validates its favorable performance in both RPLC and HILIC modes, demonstrating extensive potential applications in the field of analytical chemistry. Importantly, the stationary phase exhibits efficient separation of nucleoside compounds in pure water systems, aligning with the principles of green analysis., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The separation of enantiomers using chiral membranes has garnered much research interest. In this study, the enantioseparation of amino acids using chiral membranes, namely graphene oxide-ethylenediamine-maltodextrin (GO-EDA-MD) and GO-EDA-hydroxypropyl-MD (GO-EDA-HP-MD), was evaluated. HP-MD and MD were investigated as chiral selectors due to their inherent chirality. Various characterization techniques, including atomic force microscopy, Fourier transform infrared spectrometry, field emission scanning electron microscopy, water contact angle analysis, tensile properties, and thermal gravimetric analysis were employed to analyze the membrane structures. The evaluation of enantioseparation performance was conducted by employing tryptophan, phenylalanine, and tyrosine enantiomers. Optimal conditions for enantiomer separation were achived using a GO-EDA-HP-MD chiral composite (1.75 wt%), a feed concentration of 10 mg/L for each enantiomer, a separation time of 15 min, and a membrane effective surface area of 1.0 cm 2 . Also, the bovine serum albumin rejection was 90.0 %, and the water flux reached 37.1 L m -2 h -1 . The highest enantiomeric excess (ee.%) values were 46.33 %, 76.97 %, and 73.04 % for tryptophan, phenylalanine, and tyrosine, respectively. The impact of voltage on ee.% and substance flux was also explored. This membrane was able to separate enantiomers successfully., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Amino compounds are of significant interest in dietary, clinical, and quality control fields. Efficient extraction is crucial for comprehensive metabolomics, especially for amino acids and biogenic amines, but traditional solid-phase extraction (SPE) methods are costly and require large solvent volumes. Miniaturized SPE techniques, like pipette-tip micro-solid-phase extraction (PT-µ-SPE), offer promising alternatives by improving throughput and reducing solvent and sorbent usage. This study presents PT-µ-SPE for the screening and quantification of amino compounds in bee products, particularly honey. The method involves derivatization with diethyl ethoxymethylenemalonate (DEEMM) and analysis using liquid chromatography-triple quadrupole mass spectrometry. Silica-based SCX sorbents were effective for a broad range of amino compounds, while WCX sorbents were better for aliphatic amines. The method's extraction efficiency was assessed across sample loading, washing, and elution solution, with recovery rates of 70 - 120% in oat bran, sea buckthorn leaves, and honey extracts. Matrix effects were observed for four amino compounds in honey. Limits of detection (LoD) and quantification (LoQ) ranged from 0.37 to 57 µg L⁻¹ and 1.13 to 174 µg L⁻¹, respectively. Covering 48 amino compounds under different PT-µ-SPE conditions, this method has been applied to several samples, demonstrating accuracy, environmental sustainability, cost-effectiveness, portability, and versatility in amino compound analysis., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The epoxy propanol molecular cage bonded silica stationary phase, RCC3-GLD@silica, synthesized through the ring-opening reaction of secondary amine with epoxy propanol using RCC3-R as the scaffold unit, was successfully prepared as confirmed by infrared spectroscopy, thermogravimetric analysis, and nitrogen adsorption-desorption characterization. This stationary phase demonstrated excellent separation performance in both reversed-phase and hydrophilic chromatography modes, effectively separating a wide variety of compounds including alkylbenzenes, polycyclic aromatic hydrocarbons, phenols, anilines, sulfonamides, nucleosides, amino acids, sugars, and acids. The development of RCC3-GLD@silica benefits from the synergistic effects of its hydrophobic and hydrophilic actions, as evidenced by the U-shaped characteristic of the retention factor for nucleoside compounds with changes in the aqueous content of the mobile phase, further confirming the simultaneous presence of reversed-phase and hydrophilic chromatography mechanisms. Not only did this stationary phase successfully separate 33 compounds in reversed-phase chromatography mode, but it also separated 54 compounds in hydrophilic interaction chromatography mode, showcasing its broad separation capability from weakly polar to strongly polar compounds on a single chromatographic column. This indicates a wide application prospect in the field of chromatographic analysis., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Enantioseparation of amino acids is considered as a challenging task due to the extreme structural similarity of their enantiomers. Herein, teicoplanin was modified with different chemical equivalents of azide groups and attached to silica particles by employing Click Chemistry for resolution of chiral amino acids for the first time. Interestingly, teicoplanin modified with 5-fold the chemical equivalent of azide groups (TK-2 CSP) exhibited superior amino acid separation ability compared to two other columns: one modified with only 1-fold the chemical equivalent of azide groups (TK-1 CSP), and the other modified with excess azide groups (TK-3 CSP). Additionally, the TK-2 CSP exhibited superior enantioselectivity when separating amino acids containing hydrophobic alkyl side chains in comparison to other teicoplanin-based CSPs. The TK-2 CSP column allows the baseline separation of 7 native amino acids. Molecular docking demonstrates that effective enantioseparation arises from distinct patterns of interaction between the host and guest molecules. Moreover, (p-methyl) phenylcarbaminoylated-teicoplanin CSP (TK-4, TK-5 CSP) were prepared by post-modification from TK-1 CSP and TK-2 CSP to isolate Fmoc-modified amino acids. This work explores the impact of various modification methods on the enantioseparation effects of host molecules and paves the way for expanding the potential applications of teicoplanin and macrocyclic glycopeptide molecules., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Through an appropriate computational protocol and environmental simulation, a satisfactory fit was observed for the theoretical electronic circular dichroism (ECD) spectra of 19 chiral amino acids (AAs), which correspondeds to the forms of the AAs in aqueous solution. Methods for enantioseparation of these chiral AAs by capillary electrophoresis (CE) and high-performance liquid chromatography (HPLC) were developed. Combining ECD with chromatographic separation methods, enantiomers were identified and quantified independent of a single enantiomer standard., Competing Interests: Declaration of Competing Interest There are no known conflicts to declare., (Copyright © 2021. Published by Elsevier B.V.)

Enantioseparation of nineteen ß 2 -amino acids has been performed by liquid chromatography on chiral stationary phases based on native teicoplanin and teicoplanin aglycone covalently bonded to 2.7 µm superficially porous silica particles. Separations were carried out in unbuffered (water/methanol), buffered [aqueous triethylammonium acetate (TEAA)/methanol] reversed-phase (RP) mode, and in polar-ionic (TEAA containing acetonitrile/methanol) mobile phases. Effects of pH in the RP mode, acid and salt additives, as well as counter-ion concentrations on chromatographic parameters have been studied. The structure of selectands (ß 2 -amino acids possessing aliphatic or aromatic side chains) and selectors (native teicoplanin or teicoplanin aglycone) was found to have a considerable influence on separation performance. Analysis of van Deemter plots and determination of thermodynamic parameters were performed to further explore details of the separation performance., Competing Interests: Declaration of Competing Interest The authors declare no conflict of interest., (Copyright © 2021 The Author(s). Published by Elsevier B.V. All rights reserved.)

Reliable separation of peptides, amino acids and proteins as accurate as possible with the maximum conformation and biological activity is crucial and essential for drug discovery. Polysaccharide, as one of the most abundant natural biopolymers with optical activity on earth, is easy to be functionalized due to lots of hydroxyl groups on glucose units. Over the last few decades, polysaccharide derivatives are gradually employed as effective separation media. The highly-ordered helical structure contributes to complex, diverse molecular recognition ability, allowing polysaccharide derivatives to selectively interact with different analytes. This article reviews the development, application and prospects of polysaccharides as separation media in the separation of proteins, peptides and amino acids in recent years. The chiral molecules mechanism, advantages, limitations, development status and challenges faced by polysaccharides as separation media in molecular recognition are summarized. Meanwhile, the direction of its continued development and future prospects are also discussed., (Copyright © 2021 Elsevier B.V. All rights reserved.)

We designed and synthesized three novel derivatization reagents bearing chiral 4-imidazolidinone, namely succinimidyl 2-(3-((benzyloxy)carbonyl)-1-methyl, ethyl, and -phenyl-5-oxoimidazolidin-4-yl)acetates (CIMs), for use in liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. The CIMs were able to discriminate primary amines from other compounds such as secondary amines and phenols, based on their unique m/z reduction of precursor ion to form product ion in MS/MS. As amino acid derivatization reagents, the CIMs were compared in terms of enantioseparation of amino acid and detection sensitivity. CIM a -OSu with 1-methyl-5-oxoimidazolidinone moiety gave the best optical resolution and detection sensitivity among the CIM reagents. Next, we applied (R)-CIM a -OSu to determine amino acids in miso by LC-triple-quadrupole MS. The proposed method achieved simultaneous determination of 20 l-amino acids and two d-amino acids (d-alanine and d-serine) in the sample with a high sensitivity (limits of detection 5-238 fmol, signal-to-noise ratio 3.3). After derivatization with CIM a -OSu, it was possible to determine whether each peak in the chromatogram was a component of primary amine or not, by using a high-resolution orbitrap MS instrument., Competing Interests: Declaration of Competing Interest There are no conflicts of interest to declare., (Copyright © 2021. Published by Elsevier B.V.)

Herein, the fabrication of a fascinating multifunctional cyclodextrin (CD) chiral stationary phase and its chiral separation performance in capillary electrochromatography are proposed. A facile interfacial polymerization was used to anchor ethanediamine-β-cyclodextrin (EDA-β-CD) polymerized with trimesoyl chloride (TMC) and to form the chiral stationary phase (CSP) composite onto the surface wall of the capillary. The characters of prepared columns were confirmed by Fourier transform infrared spectroscopy (FT-IR), X-ray Photoelectron Spectrometer (XPS), scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDS). This novel CSP offers multi-typical interactions including hydrogen bonding, π-interaction, hydrophobic and electrostatic interaction as well as steric effects which contribute to prominent chiral recognition for Dansyl-DL-amino acids in CEC modes. The EDA-β-CD modified column showed eminent enantioseparation performance towards five Dansyl-DL-amino acids (the DL-forms of valine, threonine, leucine, phenylalanine, serine). Besides, the prepared columns were perfectly reproducible and stable. The relative standard deviations of the enantiomer retention times for intra-day (n = 5), inter-day (n = 3) runs and column-to-columns (n = 3) are below 0.54%, 1.35% and 4.89%, individually. This innovative chiral stationary phase shows a broader application view and scope in chiral recognition domain., Competing Interests: Declaration of Competing Interest Authors declare no conflict of interest., (Copyright © 2021. Published by Elsevier B.V.)

Evaluation of the chromatographic properties of covalently bonded hyperbranched stationary phase based on poly(styrene-divinylbenzene) (PS-DVB) and containing zwitterionic fragments in the structure of functional layer was conducted in suppressed ion chromatography (IC), reversed phase high performance liquid chromatography (RP HPLC), and hydrophilic interaction liquid chromatography (HILIC) modes. Besides the possibility of resolving 20 inorganic anions and organic acids using KOH eluent in suppressed IC, prepared resin provided the separation of alkylbenzenes in RP HPLC, water-soluble vitamins, amino acids, and sugars in HILIC mode. Trends in the retention of hydrophobic and polar analytes on the prepared stationary phase indicated the dominating effect of analyte nature on the retention mechanism and proved satisfactory hydrophilization of PS-DVB surface with hyperbranched functional layer for retaining polar compounds. The obtained results revealed good prospects of using hydrophobic PS-DVB substrate for preparing stationary phases for mixed-mode chromatography., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021. Published by Elsevier B.V.)

Herein, D- and L-oligopeptides were explored for the first time as chiral ligands in a chiral ligand exchange capillary electrophoresis (CLE-CE) protocol with Zn(II) as central ion for separation of derived d,l-amino acid enantiomers (Dns-D,L-AAs). The effect of four D- and L-oligopeptides, including glycine-l-lysine (Gly-L-Lys), glycine-d-lysine (Gly-D-Lys), l-lysine-lysine-OH and l-lysine-lysine-lysine-lysine-OH on the CLE-CE separation efficiency were evaluated. Thermodynamic calculations and circular dichroism spectra properties showed that the ternary species [(Gly-L-Lys)Zn(II)(D-AAs)] and [(Gly-L-Lys)Zn(II)(L-AAs)] presented the best stereoselectivity, possibly due to entropic effects. Notably, the migration order of Dns-D-AAs and Dns-L-AAs could be tuned by using Gly-D-Lys as the ligand for the CLE-CE system. To obtain satisfactory CLE-CE performance, the concentration ratio of Zn(II) to Gly-L-Lys, the pH of the buffer solution, and the concentration of Zn(II) were investigated. Under the optimized CLE-CE conditions using 100.0 mM H 3 BO 3 , 10.0 mM NH 4 Ac, 3.0 mM Zn (II) and 12.0 mM Gly-L-Lys as the buffer solution at pH 8.30, nine pairs of Dns-D,L-AAs achieved baseline separation, with the partial separation of another five pairs. Furthermore, the proposed CLE-CE protocol, which presented a good linear relationship with the concentration of the test analytes in the range of 75.0-625.0 μM (r 2  ≥ 0.994) and the limit of detection of the method was 5.0 μM, was successfully applied in the kinetics study of l-asparaginase using l-asparagine as the substrate. Our strategy shows the great potential of L-dipeptides in the CLE-CE separation of D,L-AAs enantiomers and bio-applications., Competing Interests: Declaration of competing interest There is no conflict of interest., (Copyright © 2020 Elsevier B.V. All rights reserved.)

In this study, 31 racemates of Nα-FMOC (fluorenylmethoxycarbonyl) amino acids (AAs) with different chemico-physical characteristics (neutral nonpolar, neutral polar, acidic and basic) have been successfully resolved in fast enantioselective chromatography on recently-developed zwitterionic-teicoplanin chiral stationary phases (CSPs). The CSPs were prepared by covalently bonding the teicoplanin selector on fully-porous particles of narrow dispersion particle-size distribution (particle diameter 1.9 µm) and superficially-porous particles (2.0 µm). Both the zwitterionic-teicoplanin CSPs have proved to be ideal media for the separation of this important class of compounds. In particular, the zwitterionic CSP prepared on superficially-porous particles exhibited superior enantioselectivity and resolution, compared to that made of fully porous particles, in virtue of more favorable thermodynamics. The zwitterionic nature of these CSPs allowed avoiding the annoying effect of Donnan's exclusion of enantiomers from the stationary phase. This effect, on the opposite, was frequently observed on a commercial teicoplanin CSP (Teicoshell) employed for comparative purposes. Noticeably, on the zwitterionic-teicoplanin CSPs, by using either acetonitrile- or methanol-rich mobile phases (MPs), it was possible to favor speed over enantioresolution and vice versa. This work gives further replies to the request for rapid determination of enantiomeric excess of Nα-FMOC proteinogenic (and non-proteinogenic) AAs, typically used as preferred chiral synthons in the solid-phase synthesis of therapeutic peptides., Competing Interests: Declaration of competing interest The authors declare no conflict of interest., (Copyright © 2020 Elsevier B.V. All rights reserved.)

A diethylammonio-propylsulfate amphoteric ionic resin was synthesized and employed as the stationary phase for high-performance liquid chromatography-mass spectrometry (LC-MS) separation and detection of amino acids. The influence of experimental conditions such as mobile phase composition, column length and temperature upon the amino acid separations was evaluated. However, temperature, addition of water-miscible organic solvent to the mobile phase and mobile phase gradients were not effective at improving the separations. In contrast, the use of an unbuffered pure water mobile phase proved successful for the separation and detection of amino acids. The observed order of elution seems to parallel the isoelectric points of the respective amino acids and suggests that this diethylammonio-propylsulfate stationary phase column functions as an amphoteric ion-exchanger. Under optimized chromatographic conditions, the detection limits for the amino acids were in range of 0.07-0.44 pmol (pico-mole). The method was also successfully applied for the analysis of an actual commercial sample., Competing Interests: Declaration of Competing Interest The authors declare no competing financial interest., (Copyright © 2020 Elsevier B.V. All rights reserved.)

New zwitterionic (ZIC) stationary phases (SPs) are synthesized with the click and conventional bonding of tyrosine to silica gel. Infrared spectra and elemental analysis demonstrate the successful click and conventional bonding of this ZIC group on silica particles by the surface coverage including 2.36 and 0.75 µm m -2 , respectively. Given the above-mentioned explanation, the present study evaluated the retention mechanism and chromatographic manners of polar compounds on these new materials under hydrophilic interaction liquid chromatography (HILIC) conditions. Based on the results, the Click-Tyrosine Stationary Phase provided good HILIC characteristics when it was applied to separate phenolic compounds, amino acids, alkaloids, and nucleobases compared to bare silica gel SP and even conventional tyrosine SPs. Further, this new Click-Tyrosine-SP represented appropriate HILIC features and column efficiency (the theoretical plate number was up to 50,000 plates m -1 for thebaine). Furthermore, the study investigated the effect of solute polarity (the number of the hydroxyl group of phenolic compounds) and hydrophobicity (the number of the side chain of aliphatic amino acids) on retention behaviors. Finally, some important factors were studied as the potential variables for guiding the retention behavior of the polar compound in HILIC condition including solvent composition, salt concentration, and the buffer pH of the mobile phase., Competing Interests: Declaration of Competing Interest The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript, apart from those disclosed. No writing assistance was utilized in the production of this manuscript. The authors declare no conflict of interest., (Copyright © 2020. Published by Elsevier B.V.)

An ethylenediamine dicarboxyethyl diacetamido-bridged bis(β-cyclodextrin) was firstly synthesized through the reaction of 6-deoxy-6-amino-β-cyclodextrin (NH 2 -CD) with ethylenediaminetetraacetic dianhydride. Then it was bonded onto the surface of silica gel SBA-15 to obtain an ethylenediamine dicarboxyethyl diacetamido-bridged bis(β-CD)-bonded chiral stationary phase (EBCDP). The structures of the bridged bis(β-CD) and EBCDP were characterized by infrared spectroscopy, mass spectrometry, elemental analysis and thermogravimetric analysis, accordingly. The chiral chromatographic performances of EBCDP were systematically evaluated by separating 28 racemic analytes in the reversed-phase or polar organic mode, including eight flavanones, eight bolckers, five dansyl-amino acids, three DL-amino acids and four other common drugs. As a result, the relatively high enantioselectivity of EBCDP was observed in comparison with a native β-CD-CSP (CDSP). All selected analytes were separated on EBCDP, of which 20 analytes had resolutions up to baseline, 2'-hydroxyflavanone and arotinolol had resolutions up to 4.35 and 2.05 in about 30 min, respectively, whereas CDSP only separated 11 analytes with low resolutions (0.55~1.69). Moreover, EBCDP was able to utilize the complexation of the bridging linker (ethylenediamine dicarboxyethyl diamide group, EDTA-based) to realize direct separations of DL-amino acids with a mobile phase containing copper ion (Cu 2+ ), which was similar to the chiral ligand exchange chromatography. Unlike the native cyclodextrin with small cavity (~242 Å 3 ), the bridged bis(β-CD) combined two β-CD units with a bridging linker, having a well-organized "pseudo-cavity" as an organic whole to encapsulate more analytes, which made EBCDP have broad-spectrum applications in chiral separations., Competing Interests: Declaration of Competing Interest The authors have declared no conflict of interest., (Copyright © 2020. Published by Elsevier B.V.)

Flow injection chromatography (FIC) or sequential injection chromatography (SIC) is a low-pressure liquid chromatography technique that uses flow injection or sequential injection hardware. Due to the constraints of this hardware, the separation resolution is low; often no more than 3-5 components are resolved. We have recently demonstrated the excellent resolving power of narrow open tubular (OT) columns for various biomolecules, and only moderate elution pressures are needed to carry out these separations. In this paper, we incorporate a narrow OT column with FIC and construct an FIC system using a pressure chamber and two injection valves to implement gradient elution. The resultant system not only improves the resolution but also reduces the system cost. When we use the system to separate peptides from trypsin-digested cytochrome C, we can resolve dozens of peptides (with resolutions of 0.5 or greater) at a speed of 12 samples per hour. When we use this system to separate a mixture containing 3 amino acids, we can base-line resolve these compounds at a speed of 1800 sample per hour., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Most HPLC enantiomer separations are performed with columns packed with a chiral stationary phase (CSP) operated with an achiral mobile phase. The intrinsically limited chemical selectivity of most CSPs to the simultaneous resolution of several pairs of enantiomers means that complex mixtures of diverse pairs of enantiomers cannot be resolved in a single run due to peak overlapping. Moreover, some drawbacks remain when the analyte is present in very complex samples containing other achiral compounds which can co-elute with the enantiomer peaks. Multidimensional chromatography becomes an option to increase peak capacity and resolve these samples. The aim of this work was to study an online fully comprehensive 2D-LC mode utilizing a combination of a chiral column in the first dimension and an achiral column in the second dimension. The 2D-LC system was built with an active flow splitter pump in order to easily adjust the volume of sample transferred into the second dimension and to independently optimize the flow rate in the first dimension. The present LCxLC method was optimized for the separation of amino acids present in honey samples, taking into account key parameters that influence the bidimensional peak capacity (orthogonality, sampling frequency, etc.). The amino acids have been preconcentrated on a cation-exchange column followed by derivatization. Several amino acids present in different honey samples have been identified and the data generated has been analyzed by principal component analysis., (Copyright © 2019. Published by Elsevier B.V.)

Two new copolymer-grafted silica stationary phases were prepared and employed in hydrophilic interaction chromatography (HILIC). 2-(Dimethylamino)ethyl methacrylate (DMAEMA) are copolymerized with itaconic acid (IA) and acrylic acid (AA) respectively, via thiol-ene click reaction on silica surface with deep eutectic solvents (DES) as new solvents. The obtained poly(DMAEMA-co-itaconic acid)-grafted silica (Sil-PDM-PIA) and poly(DMAEMA-co-acrylic acid)-grafted silica (Sil-PDM-PAA) were characterized by Fourier transform infrared spectroscopy, elemental analysis and solid-state 13 C NMR spectra. Their hydrophilic interaction performances were evaluated by separating nucleosides, nucleobases, saccharides, and amino acids. Compared with previous reported poly(itaconic acid)-grafted silica (Sil-PIA) and poly(acrylic acid)-grafted silica (Sil-PAA) stationary phases, these two new copolymer-grafted silica performed higher selectivity and better separation for polar analytes in HILIC., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Four covalently-bonded hyperbranched anion exchangers based on poly(styrene-divinylbenzene) (PS-DVB) substrate with different structure of the functional layer were prepared using mono- and dianionic amino acids such as glycine, β-alanine, aspartic acid, and glutamic acid in the internal part of the functional layer. Selectivity of all anion exchangers toward weakly retained organic acids was investigated at different temperatures in order to evaluate the effect of the number of carboxylic groups in the functional layer and its hydrophilicity on the separation. It was found that dianionic amino acids used in the first modification cycle of hyperbranching provide the best resolution for mono- and divalent organic acids, which makes the number of carboxylic groups in the structure of amino acid a key factor in the separation of such analytes with covalently-bonded hyperbranched anion exchangers, while the role of amino acid hydrophilicity is not that significant. Stationary phases prepared using aspartic and glutamic acids provided baseline resolution for quinic, glycolic, acetic, lactic, formic, and galacturonic acids, which are not resolved to baseline with modern commercially available anion exchangers; the increase of temperature was found to be favorable for improving the resolution even further., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Amino acids play an important role in cellular processes and are building blocks for peptides and proteins, which take part in regulatory processes within each organism. Hence a large variety of biotechnologically or synthetically produced therapeutic drugs are peptides and proteins. Due to the chiral nature of amino acids and the large variety of common, uncommon and newly synthesized amino acid type compounds, stereoselective separation tools combined with mass spectrometric detection are important in research as well as purity control of therapeutics in industry. Since structural isomers and epimers of common amino acids are isobaric to each other, stereoselective separation is key to their identification. For this purpose zwitterionic quinine and quinidine type chiral stationary phases Chiralpak ZWIX(+) and Chiralpak ZWIX(-) were investigated for their separation performance for underivatized and 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC; AccQ) derivatized proteinogenic amino acids, uncommon amino acids and their isobaric analogs such as allo-threonine, homoserine, allo-isoleucine and homocysteine by HPLC-ESI-QTOF-MS. Cystine and homocystine were reduced with dithiothreitol and S-alkylated with iodoacetic acid and iodoacetamide. In general, derivatization with AQC and thiol alkylation increased the detection sensitivity and resolution of acidic, basic and polar amino acids significantly (e.g. separation factor of Asp increased from 1.00 to 2.29 for Asp-AQC). In addition, throughout this study a u- 13 C 15 N-L-amino acid metabolomics mixture was added to the DL-amino acid test solution and used as a co-eluting peak assignment standard to identify the corresponding u- 12 C 14 N-L-amino acid peak and hence determine the elution order of the enantiomer pairs for complex mixtures within a single run, employing the same separation conditions for underivatized and AQC-derivatized amino acids and their isobaric analogs., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Novel sophisticated derivatizing agents for the efficient enantioselective separation and mass spectrometric detection of d- and l-amino acids have been developed. Two new axially chiral reagents derived from 6,6'-dimethyl-2,2'-biphenyldiamine were synthesized. Their chiral separation and detection abilities were evaluated by derivatizing proteinogenic amino acid standards in reversed-phase liquid chromatography-tandem mass spectrometry (LC-MS/MS). The resulting diastereomers derived from the developed derivatizing agents and amino acids could be completely separated, because of the effective chiral environment constructed by the axially chiral biphenyl moiety. After optimizing the reactive group, (R)-4-nitrophenyl N-[2'-(diethylamino)-6,6'-dimethyl-[1,1'-biphenyl]-2-yl]carbamate hydrochloride ((R)-BiAC) was found to be the best reagent for highly sensitive simultaneous d,l-amino acid analysis. Using (R)-BiAC, the complete chiral separation of all derivatized proteinogenic amino acids was achieved within 11.5 min with R s greater than 1.9, except for certain allo-isomers. An exceptional feature of this reagent was its control of elution order, i.e., it afforded elution of the diastereomers derived from d-amino acids before their l-amino acid counterparts for all 19 proteinogenic amino acids. Sensitive detection was also achieved by introducing a dialkyl amino group and selectively cleaving it at the binding site between the reagent and amino acid. Attomole (amol) detection limits (signal-to-noise ratio = 3) were obtained for the tested d,l-amino acids, in the range 7.0-127 amol. As an example of application, the method was applied to food sample analysis, and detected several d-amino acids. Consequently, the developed method seems likely to facilitate simultaneous determination of enantiomers, including the tiny amounts of d-amino acids found in nature., (Copyright © 2019 Elsevier B.V. All rights reserved.)

An O-[2-(methacryloyloxy)-ethylcarbamoyl]-10,11-dihydroquinidine (MQD)-silica hybrid monolithic column was prepared by a facile "one-step" strategy within a 100 μm I.D. capillary. The influence of the methanol, ethylene glycol and water volume ratio, reaction temperature and time, cetyltrimethylammonium bromide and MQD monomers content and volume ratio of tetramethoxysilane and vinyltrimethoxysilane was investigated to obtain a satisfactory morphology of monolithic columns. The optimized MQD-silica hybrid monolithic column was evaluated in terms of permeability, stability, efficiency, reproducibility, and was characterized by scanning electron microscopy and nano-liquid chromatography. Among the 52 N-derivatized protein and non-protein amino acids, a total of 44 analytes could be baseline enantioseparated using the optimized conditions in either reversed phase mode (RPM) or polar organic phase mode (POM). The results showed that POM (ACN/MeOH/HAc/TEA (60/40/0.055/0.005, v/v/v/v)) offered better performance than RPM (10 mM ammonium acetate/ACN (30/70, v/v) (apparent pH=5.3)) in terms of enantioresolution and efficiency with shorter analysis times., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Utilizing block copolymers as coatings, a protocol of chiral ligand exchange capillary electrochromatography (CLE-CEC) protocol was designed and developed with dual ligands for D,L-amino acids enantioseparation. Four block copolymers including poly maleic anhydride-co-styrene-co-N-methacryloyl-L-histidine methyl ester [P(MAn-St-MAH)], poly maleic anhydride-co-styrene-co-N-methacryloyl-L-lysine methyl ester [P(MAn-St-MAL)], poly maleic anhydride-co-styrene-co-N-methacryloyl-L-phenylalanine methyl ester [P(MAn-St-MAP)] and poly maleic anhydride-co-styrene-co-N-methacryloyl-L-threonine methyl ester [P(MAn-St-MAT)] were synthesized by reversible addition fragmentation chain transfer polymerization reaction. Key factors affecting the enantioresolution were optimized, including the concentration of Zn (II) central ion, pH value of buffer solution and monomers of the block copolymers. The enantioresolution of the proposed CLE-CEC system could be enhanced dramatically by employing P(MAn-St-MAH) as the immobilized chiral ligand and by coordinating the synergistic effect of free ligand in buffer solution. The principle of improved enantioresolution of the CLE-CEC system with dual ligands was discussed. Well enantioseparation was successfully realized with 7 pairs of D,L-amino acids enantiomers baseline separation and 5 pairs part separation. For quantitative analysis of D,L-alanine, a good linearity was established in the range of 9.4 μM to 1.5 mM (r 2 = 0.997) with the limits of detection (LODs) 3.7 μM of D-alanine, 2.0 μM for L-alanine, and limits of quantification (LOQs) 9.0 μM for D-alanine and 6.0 μM for L-alanine. The peak area and migration time reproducibility (n = 6) were 4.1% and 3.5% for D-alanine, 3.7% and 3.1% for L-alanine. Further, the enzyme kinetics study of alanine aminotransferase was investigated with the constructed CLE-CEC system., (Copyright © 2018 Elsevier B.V. All rights reserved.)

An enantiomeric separation method for underivatized free amino acids (AAs) using a partial filling technique with CE-MS was developed for the determination of D-AAs in vinegars. A typical chiral separation method was performed with different concentrations of (18-crown-6)-2,3,11,12-tetracarboxylic acid (18C6H4) dissolved in water or formic acid as the background electrolyte. Seventeen AAs, excluding proline and asparagine, were separated, showing chiral resolution values (Rs) ranging from 0.5 to 21.0. These results included baseline separations of 11 AAs, the peaks of which were observed as the ions [AA+18C6H4+H] + . The migration order of the chiral AAs was also evaluated, and the L-AAs migrated faster than the counterpart D-AAs except for serine, threonine and methionine when using (+)-18C6H4. To reduce contamination of the ESI source by the nonvolatile chiral selector and improve the ionization efficiency in partial filling technique, the separation zone length was adjusted to 70% of the capillary, which was filled with 30 mM 18C6H4 in water. This method showed a similar separation efficiency as the typical method, and the separated AA peaks were observed as free AA ions, [AA+H] + . The optimized method provided limits of detection (LODs) ranging from 0.07 to 1.03 μg/mL and good linearity (R 2 > 0.99) up to 50 μg/mL for DL-AAs. The developed method was utilized to determine DL-AAs in vinegars with a simple pretreatment process. It may be extended to sensitive AA analysis in the determination of minor enantiomeric impurities in the major component., (Copyright © 2018 Elsevier B.V. All rights reserved.)

In this short communication preliminary results are reported on the separation of enantiomers of underivatized amino acids on polysaccharide-based chiral columns in sub/super-critical fluid chromatography (SFC). Racemic mixtures of 14 amino acids were used to evaluate the chiral recognition ability of 8 different polysaccharide-based chiral columns with coated or covalently immobilized chiral selectors. Among the studied columns, the one based on cellulose (3,5-dichlorophenylcarbamate) exhibited the most universal chiral recognition ability providing baseline resolution for the enantiomers of 10 studied amino acids. In addition, the effect of mobile phase composition (in particular, of the amount of additive used), as well as the potential contribution of evaporative light scattering detector (ELSD) to extra column band-broadening was evaluated., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Changes in the levels of amino-acid enantiomers are associated with some serious diseases; consequently, amino acid monitoring in peripheral blood can be used to diagnose and predict the onset of disease. Herein, we report the design and synthesis of a new chiral derivatization reagent, namely succinimidyl (4S)-(3-[(benzyloxy)carbonyl]-5-oxo-1,3-oxazolidin-4-yl)acetate ((S)-COXA-OSu), for the separation of dl-amino-acid enantiomers. The usefulness of (S)-COXA-OSu was examined as a derivatization reagent for LC-MS/MS following certification of its total optical purity (>99%). The enantiomeric separations of amino-acid derivatives tagged with the reagent were examined using a triazole-bonded phase. (S)-COXA-OSu enabled the simultaneous enantiomeric separation of more than 40 α-amino acids. (S)-COXA-amino-acid derivatives were efficiently converted into their product ions, from which formaldehyde (CH 2 O) was eliminated [M-30] from the oxazolidinone moiety of COXA by collision-induced dissociation during LC-MS/MS. Limits of detection were in the 0.0138-0.518 pmol/injection range. For precise and accurate quantitation, we synthesized and used a stable-isotope-labeled (S)-COXA-OSu that was used as an internal standard in LC-MS/MS-determination experiments. Finally, changes in plasma amino-acid levels in rats, following administration of S-methyl-l-cysteine, an alanine-serine-cysteine transporter-1 (Asc-1) inhibitor, were successfully detected by LC-MS/MS using (S)-COXA-OSu., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The separation mechanism of amino acid enantiomers using a chiral crown ether-bonded stationary phase, CROWNPAK CR-I(+), and acetonitrile (ACN)-rich mobile phases (MPs) was studied. The retention factors of proteinogenic l-amino acids (except proline) formed U-shaped plots against the ACN content in the MP with a sharp increase at a high ACN content, while d-amino acids showed much smaller increases or monotonous decreases in retention within the same range. The use of an acidic, highly organic MP with trifluoroacetic acid (TFA) provided a high enantioselectivity with a short separation time from the contribution of the increased binding of the ammonium group of the analytes to the crown ether functionality of the stationary phase and electrostatic repulsion counteracting the hydrophilic partition mechanism. Optimizing the sample diluent and MP alleviated the peak distortion caused by a moving water band that accompanied the hydrophilic interaction liquid chromatography-like elution conditions. The liquid chromatography/time-of-flight mass spectrometry method with the optimized MP - ACN/ethanol/water/TFA = 80/15/5/0.5 (v/v/v/v) - enabled the determination of eighteen pairs of proteinogenic amino acid enantiomers within 10 min. The conditions also provided the following advantages: (i) fast and highly reproducible separations under isocratic conditions, (ii) high sensitivity and low backpressure using the MP with a high organic content, and (iii) highly reliable peak identification by combining two columns (CR-I(+) and CR-I(-)), reversing the elution orders of the enantiomers., (Copyright © 2018 Elsevier B.V. All rights reserved.)

In this work the simultaneous separation of chiral active pharmaceutical ingredients (API) in salt form from their counterions has been performed by using different high-efficiency macrocyclic glycopeptide-based chiral stationary phases (CSPs). Not only a new zwitterionic vancomycin-based CSP has been prepared (similarly to what was done for teicoplanin) but macrocyclic selectors have also been bonded to sub-2 μm fully porous silica particles through traditional ureidic linkage to obtain versions of CSPs suitable for ultra-high performance applications. The direct separation of chiral APIs and counterions is particularly attracting since it simplifies the workflow traditionally used with reduction of analysis time and costs. The wide selection of macrocyclic antibiotics CSPs now available has allowed to manage different cases that can happen in the simultaneous separation of APIs and their counterions (either cations or anions). Indeed, while inorganic cations are retained on traditional vancomycin- and teicoplanin-based CSPs, inorganic anions are almost unretained (due to Donnan's effect). On the other hand, cations and anions can be both retained on the zwitterionic versions of these CSPs. Afterwards, zwitterionic CSPs allowed the separation of other compounds including N-derivative amino-acids, profens, polyols, sugar anomers, oligosaccharides and inorganic anions/cations opening new perspectives in the use of this family of CSPs., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Liquid chromatographic ligand-exchange chiral stationary phases (CSPs) have been developed for the resolution of racemic compounds, which can be used as bidentate or tridentate ligands. In this paper, we review the development of liquid chromatographic ligand-exchange CSPs based on amino alcohols or their derivatives coated dynamically on octadecylsilica gel or bonded covalently to silica gel and their applications to the resolution of α-amino acids, β-amino acids, α-hydroxycarboxylic acids and proton pump inhibitors (PPIs). The relationship between the structures of CSPs and chromatographic resolution behaviors is discussed. In particular, a rational approach to the development of improved ligand-exchange CSPs based on amino alcohols derived from α-amino acids is followed., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The mushroom Stereum hirsutum is parasitized by Tremella aurantia to form a heterogeneous basidiocarp Jin'er, which has been used as food and folk medicine in Chinese society. In present work, the S. hirsutum was fermented in YMG broth, and four novel mixed terpenes, stereumamides A-D (1-4), which are sesquiterpenes combined with α-amino acids to form quaternary ammonium hybrids, were isolated from the Stereum hirsutum FP-91666 and their structures were elucidated by spectroscopic data analysis. Stereumamides A and D showed antibacterial activity against Escherichia coli, Staphylococcus aureus, and Salmonella typhimurium, with the minimum inhibitory concentration (MIC) values of 12.5-25.0 μg/mL. The stereumamides A-D should be apparently the first example of naturally occurring a quaternary ammonium compound (QAC) conjugated by sesquiterpene with an α-amino acid. QAC is a common antibacterial agent in food industry, which is found in the mycelium of Stereum hirsutum would suggest that the complex basidiocarp is a functional food and veritable folk medicine., (Copyright © 2018. Published by Elsevier B.V.)

Nowadays, the safety of cosmetics is a widespread concern. Amines are common cosmetic additives. Some of them such as amino acids are beneficial. Another kind of amines, however, ε-aminocaproic acid (EACA) is prohibited to add into cosmetics for its adverse reactions. In this study, a simple, rapid, sensitive and eco-friendly one-step ultrasonic-assisted extraction and derivatization (UAE-D) method was developed for determination of EACA and amino acids in cosmetics by coupling with high-performance liquid chromatography (HPLC). By using this sample preparation method, extraction and derivatization of EACA and amino acids were finished in one step in ultrasound field. During this procedure, 4-fluoro-7-nitrobenzofurazan (NBD-F)was applied as derivatization reagent. The extraction conditions including the amount of NBD-F, extraction and derivatization temperature, the ultrasonic vibration time and pH value of the aqueous phase were evaluated. Meanwhile, the extraction mechanism was investigated. Under optimized conditions, the method detection limits were 0.086-0.15 μg/L, and method quantitation limits were 0.29-0.47 μg/L with RSDs less than 3.7% (n = 3). The recoveries of EACA and amino acids obtained from cosmetic samples were in range from 76.9% to 122.3%. Amino acids were found in all selected samples and quantified in range from 1.9 ± 0.9 to 677.2 ± 17.9 μg/kg. And EACA was found and quantified with the contents of 1284.3 ± 22.1 μg/kg in a toner sample. This UAE-D-HPLC method shortened and simplified the sample pretreatment as well as enhanced the sensitivity of analytical method. In our record, only 10 min was needed for the total sample preparation process. And the method detection limits were two orders of magnitude less than literature reports. Furthermore, we reduced the consumption of solvent and minimized the usage of organic solvents, which made our method moving towards green analytical chemistry. In brief, our UAE-D-HPLC method is a simple, rapid, sensitive and eco-friendly analytical method for the determination of EACA and amino acids in cosmetics., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The intermittently pressed tubing was introduced in type-I counter-current chromatographic system as the separation column to improve the separation performance in the present study. The separations were performed with two different solvent systems composed of 1-butanol-acetic acid-water (4:1:5, v/v) (BAW) and hexane-ethyl acetate-methanol-0.1 M HCl (1:1:1:1, v/v) (HEMW) using dipeptides and DNP-amino acids as test samples, respectively. The chromatographic performance was evaluated in terms of retention of the stationary phase (Sf), theoretical plate (N) and peak resolution (Rs). In general, the type-I planetary motion with the multilayer coil of non-modified standard tubing can yield the best separation at a low revolution speed of 200 rpm with lower flow rate. The present results with intermittently pressed tubing indicated that the performance was also optimal at the revolution speed of 200 rpm where the lower flow rate was more beneficial to retention of stationary phase and resolution. In the moderately hydrophobic two-phase solvent system composed of hexane-ethyl acetate-metanol-0.1 M hydrochloric acid (1:1:1:1, v/v), DNP-amino acids were separated with Rs at 1.67 and 1.47, respectively, with 12.66% of stationary phase retention at a flow rate of 0.25 ml/min. In the polar solvent system composed of 1-butanol-acetic acid-water (4:1:5, v/v), dipeptide samples were resolved with Rs at 2.18 and 18.75% of stationary phase retention at a flow rate of 0.25 ml/min. These results indicate that the present system substantially improves the separation efficiency of type-I counter-current chromatographic system., (Published by Elsevier B.V.)

In the present study, a novel model of type-I counter-current chromatography was developed to simplify the separation column manufacture and extend its application ranges. In this system, a multilayer coil was used as the separation column of type-I counter-current chromatography for the first time. The chromatographic performance of this apparatus was evaluated in terms of retention of the stationary phase (Sf), theoretical plate (N) and peak resolution (Rs) using dipeptides and DNP-amino acids as test samples with two classic solvent systems composed of 1-butanol-acetic acid-water (4:1:5, v/v) (BAW) and hexane-ethyl acetate-methanol-0.1 M HCl (1:1:1:1, v/v) (HEMW), respectively. The results indicated that the performance was optimal at the revolution speed of 200 rpm. The lower flow rate was more beneficial to retention of stationary phase and peak resolution. Over all results of our study revealed that the new type-I counter-current chromatography with a multilayer coil has a high application potential., (Copyright © 2018. Published by Elsevier B.V.)

Hypercrosslinked polymers (HCPs) are currently receiving great attention due to their unique characteristics and potential uses in diverse areas. However, the field of HCPs for open-tubular capillary electrochromatography (OT-CEC) separations has not been explored. Here, a knitted aromatic polymer (KAP) was in-situ grown on the inner wall of the capillary column for OT-CEC for the first time. The silylating reagent containing phenyl was served as monomer, immobilized on the inner wall of the capillary column, and then KAPs-modified capillary column was prepared through in-situ hypercrosslinking reaction. The surface structure and morphology of KAPs-modified capillary column was characterized by Fourier transform infrared spectra (FT-IR) and scanning electron microscopy (SEM). The prepared capillary columns showed good separation performance for neutral compounds, small biomolecules, such as nucleosides, amino acids, small peptides, and non-steroidal anti-inflammatory drugs, sulfa drugs. In addition, the KAPs-modified capillaries showed good reproducibility, with relative standard deviations for intra-day, inter-day and column-to-column runs less than 1.59%, 2.55%, and 5.19% respectively. The strategy of in-situ immobilization of KAPs provides a new approach for the application of the material in the analytical fields., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Hybrid monolithic stationary phase based HPLC is a typical example of practices in separation science. In this study, we developed a dual polyhedral oligomeric silsesquioxanes (POSS) polymerization approach to the preparation of a hybrid monolithic stationary phase of tri-porous structure and various surface chemistry. N-phenylaminopropyl-POSS (PA-POSS) and glycidyl-POSS (EP-POSS) were exemplified to demonstrate effective mutually-mediated separation mechanisms of the hybrid monolithic stationary phase and mobile phase towards diverse small molecules. PA-POSS and EP-POSS can be the monomer and/or crosslinker each other. They were polymerized via the epoxy-ring opening reaction to form the poly[(PA-POSS)-(EP-POSS)] (polyPOSS) monolithic stationary phase of 110.6/164.6 Å 3 micropore (as a cube/ball), 10 nm mesopore and 0.95 μm macropore with the native siloxane cage and remaining phenyl/epoxy as well as chemically generated positive-chargeable tertiary phenylamine and hydrophilic hydroxyl groups. Such pore-structure and surface chemistry allow us to perform the effective separation of targeted small molecules, such as alkylbenzenes and alkylbenzene ketones, nucleic acid bases and amino acids, as well as phenols and phenolic acids, under reversed-phase, HILIC and mixed mode (polarity, size-exclusion and hydrogen-bonding) by just changing the molar ratio of POSS-precursors, and the composition and pH of a mobile phase as well. We believe that the approach developed herein can be extended to fabricate other kinds of hybrid monolithic stationary phases that are suitable for the separation of biomacromolecules and chiral molecules when choosing the existed POSS and/or designing new POSS with the substituted pendant groups of different physicochemical properties., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Acid-soluble collagen (ASC) and pepsin-soluble collagen (PSC) were extracted from loach skin. The yields of ASC and PSC were 22.42% and 27.32%, respectively. Sodium dodecyl sulfate-polyacrylamide-gel electrophoresis and peptide mass fingerprint analysis revealed that loach skin contained type I collagen. There were 212 imino acids/1000 residues in ASC and 193 imino acids/1000 residues in PSC. Fourier transform infrared spectrometry analysis, UV measurements and circular dichroism confirmed that loach skin collagen had a triple helical structure. The denaturation temperatures of ASC and PSC were 36.03°C and 33.61°C, respectively. Zeta potential analysis revealed that net zero charge values of ASC and PSC were 6.42 and 6.51, respectively. Therefore, loach skin collagen may be an alternative to terrestrial mammalian collagen and may enhance the added value of this fish species., (Copyright © 2017 Elsevier B.V. All rights reserved.)

A novel N-benzyl-phenethylamino-β-cyclodextrin-bonded ordered mesoporous SBA-15 chiral stationary phase (BZCDP) for high-performance liquid chromatography (HPLC) was prepared. The structure and morphology of the ligand and the stationary phase were characterized by mass spectrometry, elemental analysis, infrared spectroscopy, scanning electron microscopy, transmission electron microscopy and thermogravimetric analysis. The enantiomers of chiral compounds including nine common β-adrenergic blocker drugs (β-blockers), eight dansyl amino acids (DNS-AA) and six flavanones were successfully separated by polar organic solvent and reversed-phase chromatography, respectively. The results showed that BZCDP was a kind of multimode chiral separation materials with an excellent chromatographic performance for the above compounds. In polar organic solvent mode, BZCDP can effectively separate β-blockers, in which the enantioselectivity factors and resolutions of β-blockers were up to 1.30 and 1.97 within 20min, respectively. Under the reversed-phase mode, BZCDP exhibited high enantioselectivities for DNS-AA, among them the resolution of dansyl-tyrosine was 3.29 with 20min. BZCDP was also successfully used to separate the flavanone compounds with methanol or acetonitrile as mobile phase. The resolution of 4'-hydroxy flavanone enantiomers reached to 3.65 about 15min. Compared with the native β-cyclodextrin and γ-cyclodextrin-bonded stationary phases in the literature, the separation speed of BZCDP containing mono-N-benzyl-phenethylamino-β-cyclodextrin ligand was faster and the separation selectivity was better, which indicated that the N-benzyl-phenethylamino group could also take part in the chiral recognition. After further study, we found that in polar organic solvent mode, the inclusion and hydrogen bonding were the main forces of chiral separations, and in reversed-phase mode, the inclusion and hydrophobic interaction are the main driving forces for chiral separations. Besides excellent chromatographic performance, the home-made cyclodextrin column with mesoporous SBA-15 as the matrix was much cheaper than commercial columns, and good permeability, which can reduce the cost of test and provide fast separation. BZCDP has a good prospect in chiral drug analysis., (Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.)

A new approach for high voltage capillary electrophoresis (CE) is proposed, which replaces the standard high voltage power supply with a Van de Graaff generator, a low current power source. Because the Van de Graaff generator is a current-limited source (10μA), potentials exceeding 100kV can be generated for CE when the electrical resistance of the capillary is maximized. This was achieved by decreasing the capillary diameter and reducing the buffer ionic strength. Using 2mM borate buffer and a 5μm i.d. capillary, fluorescently labeled amino acids were separated with efficiencies up to 3.5 million plates; a 5.7 fold improvement in separation efficiency compared to a normal power supply (NPS) typically used in CE. This separation efficiency was realized using a simple set-up without significant Joule heating, making the Van de Graaff generator a promising alternative for applying the high potentials required for enhancing resolution in the separation and analysis of highly complex samples, for example mixtures of glycans., (Copyright © 2017 Elsevier B.V. All rights reserved.)

An effective pretreatment method for wine color removal by a PS-DVB SPE cartridge and online alcohol elimination by valve switching was presented. The optimum parameters for color removal were investigated: 40-μm and 100Å poly (styrene)-divinylbenzene (PS-DVB) (0.4g) was selected as the color removal material and 5mL of ethanol (10%) as the elution solvent for sample pretreatment under given condition. Moreover, an accurate and automated two-dimensional ion chromatography method for the simultaneous detection of amino acids and sugars was achieved with two valves after injection without alcohol interference. The method had a mean correlation coefficient of >0.99 and a repeatability of 0.92%-4.30% for eight replicates. The mean recovery of six red wine samples were 97.6%, 96.6%, 96.1%, 95.9%, 97.3% and 96.4% respectively. And this method successfully analyzed the amino acid and sugar contents of six wine samples of different origins., (Copyright © 2017. Published by Elsevier B.V.)

Over the last 30years, (±)-1-(9-fluorenyl)ethyl chloroformate ((±)-FLEC) was used as a chiral derivatizing agent in various analytical applications involving a wide range of endogenous, pharmaceutical and environmentally relevant molecules. This comprehensive review aims to present all the significant aspects related to the state of the art in FLEC labeling and subsequent chiral separation of the resulting diastereomers using LC, SFC and CE techniques., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Thyme as a perennial herb has been recognized globally for its antimicrobial, antiseptic and spasmolytic effects. In this investigation, we have used non-targeted metabolite and volatile profiling combined with the morpho-physiological parameters in order to understand the responses at the metabolite and physiological level in drought sensitive and tolerant thyme plant populations. The results at the metabolic level identified the significantly affected metabolites. Significant metabolites belonging to different chemical classes consisting amino acids, carbohydrates, organic acids and lipids have been compared in tolerant and sensitive plants. These compounds may take a role through mechanisms including osmotic adjustment, ROS scavenging, cellular components protection and membrane lipid changes, hormone inductions in which the key metabolites were proline, betain, mannitol, sorbitol, ascorbate, jasmonate, unsaturated fatty acids and tocopherol. Regarding with volatile profiling, sensitive plants showed an increased-then-decreased trend at major terpenes apart from alpha-cubebene and germacrene-D. In contrast, tolerant populations had unchanged terpenes during the water stress period with an elevation at last day. These results suggesting that the two populations are employing different strategies. The combination of metabolite profiling and physiological parameters assisted to understand precisely the mechanisms of plant response at volatile metabolome level., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Amino acids are crucial compounds involved in most biochemical processes essential for life. Since their dynamic turnover reflects the actual physiology of the cell/organism, a turnover assessment may provide valuable information related to multiple physiological and pathophysiological conditions. The sensitive determination of amino acids is predominantly associated with their derivatization which might be laborious, time-consuming and difficult to standardize. However, capillary electrophoresis offers the automatic injection and mixing of reactants, incubation of the reaction mixture, separation and detection of the reaction products in one on-capillary procedure. Among the on-capillary mixing strategies, electrophoretically mediated microanalysis (EMMA) is superior in terms of mixing efficiency. In this paper, we present an optimization of EMMA for the simultaneous derivatization of standard amino acids by naphthalene-2,3-dicarboxaldehyde/NaCN and its application to targeted human embryo metabolomics. For such a purpose, novel separation conditions were developed involving the background electrolyte, comprised of 73mM sodium dodecyl sulfate, 6.7 % (v/v) 1-propanol, 0.5mM (2-hydroxypropyl)-β-cyclodextrin and 135mM boric acid/sodium hydroxide buffer (pH 9.00). Finally, the optimized EMMA was compared to a fundamentally different mixing strategy, namely the transverse diffusion of laminar flow profiles, and proved to be also suitable for human plasma analysis., (Copyright © 2017 Elsevier B.V. All rights reserved.)

The chiral separation of d- and l- FMOC amino acids was undertaken using the Lux Cellulose-1 polysaccharide based chiral column in HPLC (normal phase and reverse phase) and SFC conditions. This was done to compare the relative selectivity and separation between the three separation modes and to evaluate the potential benefits of SFC separations with regards to resolution, throughput, economic and environmental impact. It was established that the separation of d- and l- FMOC amino acids in SFC displayed behaviours that were similar to both normal phase and reversed phase, rather than distinctly one or the other. Additionally, although reversed phase conditions yielded significantly higher resolution values between enantiomers across the range of amino acids studied, improvements in selectivity in SFC via the introduction of higher concentrations of formic acid in the mobile phase allowed for better resolution per unit of time. Moreover since the SFC mobile phase is composed mostly of recyclable CO 2 , there is a reduction in organic solvent consumption, which minimises the economic and environmental costs., (Copyright © 2017. Published by Elsevier B.V.)

A new, recyclable solid-liquid resolution system was developed based on tropin ionic liquids [C n DTr][L-Pro] 2 for the enantiomeric resolution of racemic phenylalanine and other α-substituted carboxylic acids including tryptophan, tyrosine, benzene glycine and mandelic acid. With racemic phenylalanine as resolution model, effect factors were investigated for better resolution conditions. On the conditions, some efficient resolution were achieved, for instance the e.e. (98%) and product yield (76%) in solid phase for phenylalanine, and the e.e. 99.71% in solid phase for tryptophan. Chiral product was verified with fourier transform infrared spectroscopy (FT-IR), Raman spectrum, thermal gravity analysis (TG), elemental analysis (EA) and chiral HPLC. Further, the resolution mechanism was studied with computer molecular dynamic simulations and UV-vis. The resolution was closely related to the formation of complexes (L-Phe-Cu(Ⅱ)-L-pro - ) and the spatial configuration of D/L-Phe. The system is characteristic of high resolution, no organic solvent, easy isolation of solid-liquid and recycle of all chemical materials as much as possible., (Copyright © 2017 Elsevier B.V. All rights reserved.)

This study presents an effective method of using miniaturized matrix solid phase dispersion (MSPD) for the microextraction of inorganic iodine and iodinated amino acids from seaweed samples. Quantification of the target analytes was performed by ultrahigh performance liquid chromatography with UV detection. Molecular sieve (SBA-15) was chosen as the dispersing adsorbent with an ionic liquid (1-dodecyl-3-methylimidazolium bromide) as the elution solvent. The experimental conditions for the MSPD, such as the type of sorbent, ratio of sorbent to sample, type and concentration of the elution solvent, and grinding time were evaluated and optimized. Under the final working conditions, good recoveries were obtained in the range of 86.5-95.4%, with relative standard deviation values below 6.0% in all cases. The limits of detection and limits of quantitation were in the ranges of 3.7-16.7ng/mL and 12.4ng/mL, respectively. Compared with common ultrasound assisted extraction, the advantages of this green approach are low consumption of the sorbent and solvent, short extraction time and good selectivity, even in complicated matrices. The proposed SBA-15-based MSPD method was successfully applied to the microextraction of potassium iodide, 3-iodo-l-tyrosine, and 3,5-diiodo-l-tyrosine from kelp, nori and undaria pinnatifida, respectively., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Various amino acids, dipeptides and their isomers were (enantio)separated using sulfobutylether-β-cyclodextrin as a chiral selector. Two different approaches were employed: first, dynamic coating of sulfobutylether-β-cyclodextrin onto a strong anion-exchange stationary phase and, second, use of sulfobutylether-β-cyclodextrin as a mobile phase additive in a separation system with a C18 column. Measurements were carried out using RP-HPLC and hydrophilic interaction liquid chromatography. Mobile phases composed of organic modifier (methanol) and four different aqueous parts: (i) deionized water, (ii) an aqueous solution of formic acid (pH 2.1), (iii) ammonium acetate buffer (pH 4.7), and (iv) ammonium acetate buffer (pH 8.8) in various volume ratios. Under these separation conditions, out of 23 chiral analytes, 9 were baseline enantio-resolved and 7 were partially separated. Of 9 mixtures of dipeptide isomers, 8 were baseline-separated. Sulfobutylether-β-cyclodextrin proved to be suitable for the separation of chiral and also achiral analytes. The use of sulfobutylether-β-cyclodextrin as a dynamic coating agent or as a mobile phase additive depends on the particular chromatographic system and analytes of interest., (Copyright © 2016 Elsevier B.V. All rights reserved.)

New analytical methodologies enabling the enantiomeric separation of a group of non-protein amino acids of interest in the pharmaceutical and food analysis fields were developed in this work using Electrokinetic Chromatography. The use of FMOC as derivatization reagent and the subsequent separation using acidic conditions (formate buffer at pH 2.0) and anionic cyclodextrins as chiral selectors allowed the chiral separation of eight from the ten non-protein amino acids studied. Pyroglutamic acid, norvaline, norleucine, 3,4-dihydroxyphenilalanine, 2-aminoadipic acid, and selenomethionine were enantiomericaly separated using sulfated-α-CD while sulfated-γ-CD enabled the enantiomeric separation of norvaline, 3,4-dihydroxyphenilalanine, 2-aminoadipic acid, selenomethionie, citrulline, and pipecolic acid. Moreover, the potential of the developed methodologies was demonstrated in the analysis of citrulline and its enantiomeric impurity in food supplements. For that purpose, experimental and instrumental variables were optimized and the analytical characteristics of the proposed method were evaluated. LODs of 2.1×10 -7 and 1.8×10 -7 M for d- and l-citrulline, respectively, were obtained. d-Cit was not detectable in any of the six food supplement samples analyzed showing that the effect of storage time on the racemization of citrulline was negligible., (Copyright © 2016 Elsevier B.V. All rights reserved.)

In the context of bioanalytical method development, process automatization is nowadays a necessity in order to save time, improve method reliability and reduce costs. For the first time, a fully automatized micellar electrokinetic chromatography-mass spectrometry (MEKC-MS) method with in-capillary derivatization was developed for the chiral analysis of d- and l-amino acids using (-)-1-(9-fluorenyl) ethyl chloroformate (FLEC) as labeling reagent. The derivatization procedure was optimized using an experimental design approach leading to the following conditions: sample and FLEC plugs in a 2:1 ratio (15s, 30mbar: 7.5s, 30mbar) followed by 15min of mixing using a voltage of 0.1kV. The formed diastereomers were then separated using a background electrolyte (BGE) consisting of 150mM ammonium perfluorooctanoate (APFO) (pH=9.5) and detected by mass spectrometry (MS). Complete chiral resolution was obtained for 8 amino acids, while partial separation was achieved for 6 other amino acid pairs. The method showed good reproducibility and linearity in the low micromolar concentration range. The applicability of the method to biological samples was tested by analyzing artificial cerebrospinal fluid (aCSF) samples., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Low column efficiency for enantioseparations in capillary liquid chromatography (CLC) is a major problem commonly encountered with β-cyclodextrin (β-CD) functionalized polymer-based monoliths. In order to investigate the effect of the crosslinker type on enantioseparation performance, three commonly used crosslinkers, i.e. 1,4-bis(acryloyl)piperazine (PDA), ethylene dimethacrylate (EDMA) and N,N-methylenebisacrylamide (MBA), were copolymerized using the one-pot approach with glycidyl methacrylate-mono-6-amino-6-deoxy-β-CD (GMA-NH 2 -β-CD) as functional monomer. The three monolithic columns, including poly(GMA-NH 2 -β-CD-co-PDA) and poly(GMA-NH 2 -β-CD-co-MBA), as well as the previously reported column poly(GMA-NH 2 -β-CD-co-EDMA) were systematically compared with respect to morphology, permeability, β-CD density, retention mechanism and efficiency. The enantioseparation ability of each column was evaluated using 14 chiral compounds, including mandelic acid derivatives, profens, N-derivatized amino acids, and herbicides, as test substances. The β-CD-functionalized monolith with MBA as crosslinker was found to exhibit higher polarity, higher column efficiency and better enantioseparation performance than those with PDA or EDMA as crosslinker., (Copyright © 2016 Elsevier B.V. All rights reserved.)