Separation Of Dansyl Amino Acids Research Articles

Novel methoxypropylimmidazolium β-cyclodextrin for improved enantioseparation of amino acids

A new single-isomer cationic cyclodextrin, mono-6A-[3-(3-methoxypropyl)imidazol-1-ium]-6A-β-cyclodextrin chloride, has been synthesized and successfully used for the chiral separation of dansyl amino acids in capillary electrophoresis. With methoxy functionality, the new cationic cyclodextrin exhibits significantly improved enantioselectivities. Excellent enantioseparations for amino acids are obtained in chiral selector concentration range between 2.5mM to 15mM at pH 6.0. Chiral resolution as high as 7.3 was achieved for Dns-Aca with 5mM chiral selector. Comparison study and theoretical calculation with Wren’s model attribute the enhanced enantioseparation to the stronger inclusion complexation between amino acids and cyclodextrin. The binding constants for dansyl amino acids and the cationic cyclodextrins are calculated to be 173–253M−1, while the optimum cyclodextrin concentrations were estimated to be 4.1–7.6mM.

Optimisation methodology in the chiral and achiral separation in electrokinetic chromatography in the case of a multicomponent sample of dansyl amino acids

Two different chiral selectors synthesised in our laboratory were used to test the possibility of separation for a sample consisting of ten different enantiomeric pairs of dansyl-derivatives of α-amino acids in electrokinetic chromatography. It was possible to observe all the peaks, though only partly resolved, due to the twenty analytes through an accurate strategy of choice of the experimental conditions. As a part of this strategy, a procedure of identification of the single peaks in the electropherograms called LACI (lastly added component identification) has been developed.

A Silica Monolithic Column with Chemically Bonded l-Pipecolic Acid as Chiral Stationary Phase for Enantiomeric Separation of Dansyl Amino Acids by CEC–MS

A silica monolithic column chemically modified with l-pipecolic acid as chiral stationary phase has been developed for chiral separation of dansyl amino acids by capillary electrochromatography–mass spectrometry (CEC–MS). The monolithic column was prepared by a sol–gel process and subsequent chemical modification by l-pipecolic acid as chiral selector with 3-glycidoxypropyltrimethoxysilane as spacer. Interestingly, it was found that the l-pipecolic acid-modified monolithic column can hold copper(II) ions tightly after loading Cu(II) ions during column preparation and conditioning and allows CEC separation to be conducted based on chiral ligand exchange with MS detection by a mobile phase without copper ions. It has been demonstrated that the chiral monolithic column operates well for enantioseparation of several dansyl amino acids by CEC–MS.

Chiral separation of dansyl amino acids by ligand exchange capillary electrochromatography in a low molecular weight organogel

Chiral electroseparation is demonstrated, for the first time, by a low molecular weight organogel filled capillary. Five pairs of dansylated amino acids were separated by copper ligand exchange on a trans-(1S,2S)-1,2-bis-(dodecylamido) cyclohexane (1) gel in methanol. Low molecular weight organogels are emerging materials that form stable, fibrillar, thermoreversible and thixotropic gels without covalent bonding of their monomeric building blocks. The dependence of chiral resolution and complex formation stability on the pH*, the ratio between copper and the D-valine selector, as well as other parameters were investigated revealing trends that were unparalleled in previously reports on copper ligand exchange of dansylated amino acids. These observations were explained in view of a simple stacking model of (1) and the difference in axial ligation of the amide carbonyl backbone of the gel to the dansyl D- or L-amino acid:D-valine:copper ternary complexes.

Chiral separation of dansyl amino acids in capillary electrophoresis using mono‐(3‐methyl‐imidazolium)‐β‐cyclodextrin chloride as a selector

Journal of Separation ScienceVolume 30, Issue 11 p. 1806-1806 ErratumFree Access Chiral separation of dansyl amino acids in capillary electrophoresis using mono-(3-methyl-imidazolium)-β-cyclodextrin chloride as a selector This article corrects the following: Chiral separation of dansyl amino acids in capillary electrophoresis using mono-(3-methyl-imidazolium)-β-cyclodextrin chloride as selector Weihua Tang, Teng Teng Ong, Siu-Choon Ng, Volume 30Issue 9Journal of Separation Science pages: 1343-1349 First Published online: May 9, 2007 Weihua Tang, Weihua Tang Department of Chemistry, National University of Singapore, SingaporeSearch for more papers by this authorTeng Teng Ong, Teng Teng Ong Division of Chemical and Bimolecular Engineering, College of Engineering, Nanyang Technological University, Singapore. Fax: +65-6794-9220Search for more papers by this authorSiu-Choon Ng, Siu-Choon Ng [email protected] Search for more papers by this author Weihua Tang, Weihua Tang Department of Chemistry, National University of Singapore, SingaporeSearch for more papers by this authorTeng Teng Ong, Teng Teng Ong Division of Chemical and Bimolecular Engineering, College of Engineering, Nanyang Technological University, Singapore. Fax: +65-6794-9220Search for more papers by this authorSiu-Choon Ng, Siu-Choon Ng [email protected] Search for more papers by this author First published: 05 July 2007 https://doi.org/10.1002/jssc.200790042Citations: 2AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article.Citing Literature Volume30, Issue11Special Issue: ReviewsJuly 2007Pages 1806-1806 RelatedInformation

Chiral separation of dansyl amino acids in capillary electrophoresis using mono‐(3‐methyl‐imidazolium)‐β‐cyclodextrin chloride as selector

Enantioseparations of fourteen dansyl amino acids were achieved by using a positively-charged single-isomer beta-cyclodextrin, mono-(3-methyl-imidazolium)-beta-cyclodextrin chloride, as a chiral selector. Separation parameters such as buffer pH, selector concentration, separation temperature, and organic modifier were investigated for the enantioseparation in order to achieve the maximum possible resolution. Chiral separation of dansyl amino acids was found to be highly dependent on pH since the degree of protonation of these amino acids can alter the strength of electrostatic interaction and/or inclusion complexation between each enantiomer and chiral selector. In general, the chiral resolution of dansyl amino acids was enhanced at higher pH, which indicates that the carboxylate group on the analytes may interact with the imidazolium group of cationic cyclodextrin. For most analytes, a distinct maximum in enantioresolution was obtained at pH 8.0. Moreover, the chiral separation can be further improved by careful tuning of the separation parameters such as higher selector concentration (e.g. 10 mM), lower temperature, and addition of methanol. Enantioseparation of a standard mixture of these dansyl amino acids was further achieved in a single run within 30 min.

Enantiomeric separation of dansyl amino acids using macrocyclic antibiotics as chiral mobile phase additives by narrow-bore high-performance liquid chromatography.

Seven macrocyclic antibiotics were evaluated as chiral selectors for the enantiomeric separation of 11 dansyl amino acids using narrow-bore high-performance liquid chromatography (HPLC). The macrocyclic antibiotics were incorporated as mobile phase additives to determine the enantioselective effects on the chiral analytes. The resolution and capacity factor (k') of each analyte were assessed while varying the structure of macrocyclic antibiotic and the mobile phase buffer pH. The selectivity of the chiral selectors was measured as a function of changes in these parameters. All 11 dansyl amino acids were separated by at least one of the chiral selectors. Three-dimensional computer modeling of the more effective chiral selectors illustrated the importance of macrocyclic antibiotic structure concerning stereospecific analyte interaction.

Investigation of Mixed Chiral Selectors of Different Metal Ion‐L‐Alanine Complex and β‐Cyclodextrin on the Chiral Separation of Dansyl Amino Acids with Capillary Electrophoresis

AbstractChiral separation of dansyl amino acids by capillary electrophoresis using mixed selectors of Mn (II)‐L‐alanine complex and β‐cyclodextrin (β‐CD) was studied. Resolution was considerably superior to that obtained by using either Mn(II)‐L‐alanine complex or β‐CD alone. The effects of separation parameters, such as pH value of buffer solution, capillary temperature, the concentration of Mn (II)‐L‐alanine complex, the types of CD and ligand on the migration times and resolutions were investigated. Six different transition metal complexes, Cu(II), Zn(II), Co(II), Ni(II), Hg(n) and Cd(n)‐L‐alanine complexes have been employed and compared with Mn(II) complex. Differences in retention and selectivity were found. The substitution of Cu(II), Zn(H), Co(II) and Ni(II) for Mn (II) resulted in a better chiral resolution while Hg(II) and Cd (II) showed poorer resolution abilities. The chiral separation mechanism was also discussed briefly.

Chemically L-prolinamide-modified monolithic silica column for enantiomeric separation of dansyl amino acids and hydroxy acids by capillary electrochromatography and mu-high performance liquid chromatography.

A silica-based chiral monolithic column prepared by sol-gel process and chemical modification of chiral selector was used for enantioseparation of dansyl amino acids and hydroxy acids by capillary electrochromatography (CEC) and mu-high-performance liquid chromatography (mu-HPLC). L-Prolinamide was modified as a chiral selector. The chiral stationary phase (CSP), the chiral complex of Cu(II) with L-prolinamide, provides an anodic electroosmotic flow (EOF) in CEC. The EOF was found to be dependent on applied electric field strength, the pH, and the composition of mobile phases. Scanning electron micrograph showed that monolithic columns have the morphology of continuous skeleton and large through-pore. D-Enantiomers migrated before L-enantiomers except for dansyl-(Dns)-DL-Ser. The separation efficiencies of up to 17600 (D) and 13,200 plates m(-1) (L) were achieved for the separation of DL-indole-3-lactic acid.

Enantiomeric separation by capillary electrochromatography I. Chiral separation of dansyl amino acids and organochlorine pesticides on a diol-silica dynamically coated with hydroxypropyl-β-cyclodextrin

In this work, a commercially available diol-silica stationary phase was converted in situ to a chiral stationary phase by dynamically coating it with hydroxypropyl-beta-cyclodextrin (HP-beta-CD). This stationary phase was shown useful for the capillary electrochromatography (CEC) separation of neutral and anionic enantiomers such as some organochlorine pesticides and dansyl amino acids, respectively. The inclusion of HP-beta-CD in the mobile phase to produce the in situ chiral stationary phase allowed the rapid separation of the anionic dansyl amino acid enantiomers at relatively low electroosmotic flow (EOF). The formation of host-guest complexes between the dansyl amino acids and the neutral HP-beta-CD in the mobile phase lowered the actual charge-to-mass ratios of the anionic solutes, thus speeding up their transport by the EOF across the packed capillary column. Several parameters affecting enantioseparation were investigated, including the concentration of HP-beta-CD, ionic strength, pH, and organic modifier content of the mobile phase.

Enantiomeric separation by capillary electrochromatography. II. Chiral separation of dansyl amino acids and phenoxy acid herbicides on sulfonated silica having surface-bound hydroxypropyl-beta-cyclodextrin.

A chiral silica-based stationary phase having surface-bound hydroxypropyl-beta-cyclodextrin (HP-beta-CD) with a relatively strong electroosmotic flow (EOF) was introduced for enantioseparation by capillary electrochromatography (CEC). The stationary phase contained a hydrophilic sulfonated sublayer to which a chiral top layer of HP-beta-CD was immobilized. While the sulfonated sublayer was to provide a relatively strong EOF, the top HP-beta-CD was to confer the desired chiral recognition towards enantiomeric solutes. This HP-beta-CD sulfonated silica (CDSS) stationary phase proved useful for the rapid separation of anionic enantiomers such as dansyl amino acids and phenoxy acid herbicides. The effects of the organic modifier content, pH, and ionic strength of the mobile phase on enantioseparation were investigated. Under the optimized separation conditions, ten dansyl amino acids and six phenoxy acid herbicides were enantioseparated with a resolution greater than unity.

Comparison of enantioseparation of amino acid derivatives in aqueous and mixed aqueous-organic media by capillary zone electrophoresis

The chiral separation of dansyl-amino acids has been performed by capillary zone electrophoresis using ¶β-cyclodextrin as a chiral selector, urea as an additive and 2-propanol and methanol as organic modifiers. The enantiomeric separations of dansyl-amino acids were investigated in aqueous medium and compared with the separation in mixed aqueous-organic medium as background electrolytes. The separation conditions, (concentration of buffer, β-cyclodextrin, methanol, urea and the pH value of buffer) were optimized. In the absence of organic modifier, only five pairs of 8 separated dansyl-amino acids were resolved when run separately. A mixture of up to eight chiral amino acids can be baseline resolved in less than 19 min by β-cyclodextrin-modified capillary zone electrophoresis with a buffer of 60 mmol L–1 H3BO3-KCl/40 mmol L–1 NaOH (pH 9.0), 4 mol L–1 urea, 100 mmol L–1β-cyclodextrin and 10% (v/v) methanol.

Chiral separation of dansyl amino acids by capillary electrophoresis: Comparison of formamide andN-Methylformamide as background electrolytes

Chiral separation of 12 dansyl amino acids has been achieved by capillary electrophoresis using β-cyclodextrin dissolved inN-methylformamide or formamide. The viscosity and the dielectric constants of these two solvents are very different, giving them disimilar electrophoretic properties. Intense electroosmotic flow, high electrophoretic mobilities and high efficiency were achieved inN-methylformamide, but high chiral selector concentration was needed for sufficient resolution. In contrast, the separation of dansyl amino acids in formamide was characterized by longer analysis time and lower efficiency, but the resolution and selectivity of the separation were better and baseline separation could be achieved at lower β-cyclodextrin concentrations.

Enantiomeric separation of dansyl amino acids using MECC with a ligand exchange mechanism

Enantiomeric separation of 11 dansyl amino acids is reported using micellar electrokinetic capillary chromatography. The chiral phase consisted of a copper complex of N, N-di-decyl-D-alanine dissolved in the running buffer. Several factors affecting the separation were studied. The partitioning of the copper complex between the micelles and the buffer interface was investigated, and an attempt to describe the mechanism of separation is presented. © 1996 John Wiley & Sons, Inc.

High Performance Micellar Liquid Chromatography with Silica Micro-Particles Having Surface-Bound Cationic Surfactant Moieties. I. Comparison with Octadecylsilica and Applications to the Separation of Dansyl Amino Acids, Herbicides, and Catecholamines

Abstract The usefulness of silica microparticles having surface-bound cationic surfactant ligands in reversed phase chromatography (RPC) and micellar liquid chromatography (MLC) was examined, and the influence of surfactant type on retention and separation selectivity was studied. Different selectivities were observed by using silica microparticles having surface-bound cationic surfactant ligands, such as noctadecyldimethyl(propylsilyl)ammonium groups (C18N+(Me)2Pr) when compared to a C18-silica column in the separation of dansyl amino acids (Dns-AA), herbicides and catecholamines by RPC and MLC. The presence of surface-bound charged moieties affected the amount of surfactant adsorbed onto the surface of the stationary phase from a given micellar mobile phase, which in turn influenced the retention behavior of neutral and charged species, thus leading to a unique chromatographic selectivity.

Capillary electrophoretic separation of amino acids: Fraction collection

AbstractA simple method is described which enables solutes to be collected at an electrically isolated exit after they have been separated by a free solution capillary electrophoretic system. The method is illustrated by the separation of dansyl amino acids using multiple separation capillaries.

The role of bonded phase composition on the ligand-exchange chromatography of dansyl- D, L-amino acids

This paper examines the role of bonded phase composition in the ligand-exchange chromatographic separation of dansyl amino acids (Dns- D, L-AAs). As the bonded optically active chelate, we have synthesized N-ϖ-(dimethylsiloxyl)undecanoyl- L-valine and as the metal, we used Cu(II). Bonded phases, where the chelate coverage is 2.5 μmol/m 2, have been compared with mixed or diluted phases, in which the contribution of the bonded chelate to the total coverage is less than 0.2 μmol/m 2. Using a decyl group as diluent, it has been shown that capacity factors and enantio selectivities of Dns- D, L-AAs are much higher on the diluted phases relative to the concentrated phase, in spite of the fact that the amount of copper loaded on the latter column is roughly 40 times greater. This result has been interpreted in terms of the formation of his complexes between the metal ion and the bonded phase chelate, i. e., 2:1 chelate to metal, in the case of the concentrated phase. For the diluted phases, the mono complex, i.e., 1:1 metal to chelate, is the predominant form. Not only does the diluted phase yield improved separation, but it is in principle a simpler system to manipulate and optimize. We have been able to develop a simple model to analyze the chromatographic behavior on diluted phases relative to the concen trated phase. Based on this model, we have compared four diluents: a polyether, n- butyl, n-decyl and n-eicosyl ligands. By normalizing for the amount of copper loaded on the stationary phase, it is shown that the apparent complexation constants in crease from the ether to the C 20 phase. Moreover, due to differences in the character of the side chains of the amino acids, additional selectivity is observed between the different solutes. This selectivity is useful in separation applications. In addition, it is shown that the diluted bonded phases yield high performance, approximately 4000 plates for 15 cm columns, with good peak symmetry. Also included is a detailed discussion of the characterization of the bonded phases along with its optical purity.

The Separation of Dansyl Amino Acids by Reversed-Phase High Performance Liquid Chromatography

The Separation of Dansyl Amino Acids by Reversed-Phase High Performance Liquid Chromatography

Chromatographic separation of dansyl amino acids and dansyl amines on Amberlite IRC-50

A column chromatographic method for the separation of dansyl amino acids and dansyl amines is described in which Amberlite IRC-50 equilibrated with the eluent is used as the stationary phase and six solvent mixtures, which are composed of a buffer or 2 % acetic acid and tetrahydrofuran, methyl ethyl ketone and acetone, are used as eluents. Neutral and acidic dansyl derivatives were separated at low pH, and those having a positive charge or present as the dipolar ion at pH 5.60 were separated at high pH. Quantitative determination of histamine as its monodansyl derivative was successful, and an analysis for histamine in a rat liver extract is described.

Column chromatographic separation of dansyl amino acids

A column chromatographic separation of dansyl amino acids is described in which polyamide is used as the sorbent and three systems with different benzene-acetic acid ratios are used as the eluent. The separation method offers good possibilities for quantitative determinations. Additional correlations can be made by using the same material for identifying an unknown amino acid. The column effluent is monitored by an adapted Farrand spectrofluorimeter equipped with a flow-through cell and a reduced chart speed gear box.