Chiral Capillary Column Research Articles

Synthesis of hyperbranched polycarbosilane modified with cyclodextrin derivatives and its application in coated capillary electrophoresis columns

AbstractA series of hyperbranched polycarbosilanes were synthesized and coated on the inner surface of fused‐silica capillaries by chemical bonding. The end groups of the hyperbranched polycarbosilanes were modified with β‐cyclodextrin derivatives. The chiral isomers of ofloxacin and chlorpheniramine were separated by this new type of chiral capillary electrophoresis column and high‐column efficiency was achieved. The results showed that ofloxacin was completely separated at pH 3.0; the separation resolution was 2.32, and theoretical plates were greater than 4.5 × 104 plates m−1. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.

One-step preparation and properties of allyl-β-cyclodextrin chiral monolithic capillary electrochromatography column

Allyl-β-cyclodextrin chiral monolithic capillary electrochromatography column was prepared by one- step reaction with allyl-β-cyclodextrin (allyl-β-CD), glycidyl methacrylate and ethylene glycol dimethacrylate as functional monomers. In capillary electrochromatography (CEC) mode, 18 kinds of amino acid enantiomers were separated successfully. The study found that the capillary monolithic column prepared by modified CD derivatives as the functional monomer had good retention ability to hydrophobic chiral compounds containing amido or benzene ring. Meanwhile, it had good stability and reproducibility. The new column had also been applied to separation of chiral drugs.

Investigation on chiral capillary columns and their application in separation of enantiomers

Six chiral diamide stationary phases (CSPs), namely N-(3-carbobenzoxypropionyl)-L-Val-tert-butylamide (CSP-1), N-undecenoyl-L-Val-S-α-phenylethylamide (CSP-2), N-undecenoyl-L-Val-R-α-phenylethylamide (CSP-3), OV-225-L-Val-tert-butylamide (CSP-4), XE-60-L-Val-tert-butylamide (CSP-5) and polycyanoethyl vinyl siloxane-L-Val-tert-butylamide (CSP-6), were investigated and CSP-6 was crosslinked within narrow bore (70 μm) fused silica capillary columns. The separation of amino acid enantiomers on this narrow bore column by gas chromatography (GC) is illustrated.

Enantioseparation on cellulose dimethylphenylcarbamate-modified zirconia monolithic columns by reversed-phase capillary electrochromatography

This work reports the preparation of monolithic zirconia chiral columns for separation of enantiomeric compounds by capillary electrochromatography (CEC). Using sol–gel technology, a porous monolith having interconnected globular-like structure with through-pores is synthesized in the capillary column as a first step in the synthesis of monolithic zirconia chiral capillary columns. In the second step, the surface of the monolith is modified by coating with cellulose tris(3,5-dimethylphenylcarbamate) (CDMPC) as the chiral stationary phase to obtain a chiral column (CDMPCZM). The process of the preparation of the zirconia monolithic capillary column was investigated by varying the concentrations of the components of the sol solution including polyethylene glycol, water and acetic acid. CDMPCZM is mechanically stable and no bubble formation was detected with the applied current of up to 30 μA. The enantioseparation behavior of the CDMPCZM columns was investigated by separating a set of 10 representative chiral compounds by varying the applied voltage and pH and organic composition of the aqueous organic mobile phases.

A Novel Biosynthetic Pathway of Archaetidyl-myo-inositol via Archaetidyl-myo-inositol Phosphate from CDP-archaeol and d-Glucose 6-Phosphate in Methanoarchaeon Methanothermobacter thermautotrophicus Cells

Ether-type inositol phospholipids are ubiquitously distributed in Archaea membranes. The present paper describes a novel biosynthetic pathway of the archaeal inositol phospholipid. To study the biosynthesis of archaetidylinositol in vitro, we prepared two possible substrates: CDP-archaeol, which was chemically synthesized, and myo-[(14)C]inositol 1-phosphate, which was enzymatically prepared from [(14)C]glucose 6-phosphate with the inositol 1-phosphate (IP) synthase of this organism. The complete structure of the IP synthase reaction product was determined to be 1l-myo-inositol 1-phosphate, based on gas liquid chromatography with a chiral column. When the two substrates were incubated with the Methanothermobacter thermautotrophicus membrane fraction, archaetidylinositol phosphate (AIP) was formed along with a small amount of archaetidylinositol (AI). The two products were identified by fast atom bombardment-mass spectrometry and chemical analyses. AI was formed from AIP by incubation with the membrane fraction, but AIP was not formed from AI. This finding indicates that archaeal AI was synthesized from CDP-archaeol and d-glucose 6-phosphate via myo-inositol 1-phosphate and AIP. Although the relevant enzymes were not isolated, three enzymes are implied: IP synthase, AIP synthase, and AIP phosphatase. AIP synthase was homologous to yeast phosphatidylinositol synthase, and we confirmed AIP synthase activity by cloning the encoding gene (MTH1691) and expressing it in Escherichia coli. AIP synthase is a newly found member of the enzyme superfamily CDP-alcohol phosphatidyltransferase, which includes a wide range of enzymes that attach polar head groups to ester- and ether-type phospholipids of bacterial and archaeal origin. This is the first report of the biosynthesis of ether-type inositol phospholipids in Archaea.

The covalently bonded cellulose tris(3,5-dimethylphenylcarbamate) on a silica monolithic capillary column for enantioseparation in capillary electrochromatography

A chiral capillary monolithic column for capillary electrochromatography (CEC) was prepared by covalent bonding of cellulose tris(3,5-dimethylphenylcarbamate) (CDMPC) on the silica monolithic matrix within the confine of a 50-μm i.d. bare fused silica capillary. Several pairs of enantiomers including neutral and basic analytes were baseline resolved on the newly prepared chiral capillary monolithic column in CEC with aqueous mobile phases. Fast enantioseparation was achieved due to the favorable dynamic properties of silica monolith. The covalent bonding of CDMPC as the chiral stationary phase for CEC also enabled the use of THF in mobile phase for enantioseparation of prazquantel by overcoming the incompatibility of THF and the physically coated CDMPC on a column.

Preparation and Evaluation of Capillary Electrophoresis Column Bonded with Carbosilane Dendrimers

A new chiral capillary electrophoresis column coated with carbosilane dendrimers with peripheral Si–Cl groups and β-cyclodextrin was prepared. The separation characteristics of stability and longevity of capillaries modified by coating carbosilane dendrimers and β-cyclodextrin ( β-CD) were satisfactory, and the variation of separation efficiency was less than 5% after continuous running for a month. The optimum conditions include a running voltage of 16 kV, a UV detector wavelength of 214 nm, sample injection time of 7 s, and a phosphate buffer solution concentration of 40 × 10 −3 M. Chlortrimeton, Hydrochloric Promethazine, and Benzedrine were selected as the separation model targets. The G2P modified column was especially effective in separating Chlortrimeton enantiomers. Under the specified conditions, the column efficiency was 2.5 × 10 5 Plates m −1 with a resolution ( R S) of 1.43 and baseline separation was obtained. The results were satisfactory.

Polyacrylamide‐based monolithic capillary column with coating of cellulose tris(3,5‐dimethylphenyl‐carbamate) for enantiomer separation in capillary electrochromatography

A hydrophilic chiral capillary monolithic column for enantiomer separation in CEC was prepared by coating cellulose tris(3,5-dimethylphenyl-carbamate) (CDMPC) on porous hydrophilic poly(acrylamide-co-N,N'-methylene-bisacrylamide) (poly(AA-co-MBA)) monolithic matrix with confine of a fused-silica capillary. The coating conditions were optimized to obtain a stable and reproducible chiral stationary phase for CEC. The effect of organic modifier of ACN in aqueous mobile phase for the enantiomer separation by CEC was investigated, and the significant influence of ACN on the enantioresolution and electrochromatographic retention was observed. Twelve pairs of enantiomers including acidic, neutral, and basic analytes were tested and nine pairs of them were baseline-enantioresolved with acidic and basic aqueous mobile phases. A good within-column repeatability in retention time (RSD = 2.4%) and resolution (RSD = 3.2%) was obtained by consecutive injections of a neutral compound, benzoin, on a prepared chiral monolithic column, while the between-column repeatability in retention time (RSD = 6.4%) and resolution (RSD = 9.6%) was observed by column-to-column examination. The prepared monolithic stationary phase showed good stability in either acidic or basic mobile phase.

LC with a Teicoplanin Aglycone Chiral Sorbent for the Separation of the Enantiomers of Non-Steroidal Anti-Inflammatory Drugs: An Evaluation of Chiral Capillary Columns

A capillary column with a teicoplanin aglycone (TAG) stationary phase (CSP) was used for enantioselective separation of selected profen non-steroidal anti-inflammatory drugs in capillary liquid chromatography (cLC). The effect of variations in the mobile phase composition on the retention and enantioselective separation was examined. The best resolution was attained in the mobile phase composed of 40/60 (v/v) methanol/1.0% triethylamine acetate buffer, pH 4.0 or 4.5. Under the optimized separation conditions, five of the set of eight analytes were enantioresolved with resolution values better than 0.9. Only fenoprofen was not enantioseparated in any system tested. The optimized separation conditions were used for evaluation of three chiral capillary columns (all prepared in the same way in our laboratory) in terms of the repeatability and reproducibility of the results. The run-to-run repeatability was expressed in terms of the relative standard deviation (RSD) values, obtained from ten independent measurements, for the following parameters: the retention factor for the first eluted enantiomer (k1), the selectivity (α), the enantioresolution (R), the theoretical plate count per meter for the first eluted enantiomer (N1) and the elution curve asymmetry for the first eluted enantiomer (As1). None of the RSD values exceeded 8%. The column-to-column reproducibility of these parameters ranged between 1 and 9%. The results obtained with TAG based CSPs in cLC (a laboratory packed capillary column) were compared with those obtained by classical high-performance liquid chromatography (HPLC) with a commercially available column. The cLC procedure provided a better enantioresolution and the elution curves had a better symmetry.

Gas chromatographic analysis of amino acid enantiomers in Carbetocin peptide hydrolysates after fast derivatization with pentafluoropropyl chloroformate

A novel sample preparation protocol for gas chromatographic (GC) analysis of amino acid enantiomers in peptides was developed. It comprises traditional acid hydrolysis, a novel treatment of the analytes with a fluoroalkyl chloroformate and GC/FID separation of enantiomers on a chiral capillary column. The major improvements consist in that the derivatization step proceeds in organic-aqueous media within seconds and the amino acid derivatives are volatile enough to suit the temperature range of the chiral Chirasil-Val capillary column. The approach was found beneficial for chiral analysis of pharmaceutically important Carbetocin peptide.

Determination of 2,3-Butanediol and 2-Hydroxybutanone Stereoisomers in Batteries of Traditional Balsamic Vinegar

The absolute quantities and the stereoisomeric ratios of R, S-2-hydroxybutanone and R, R-, S, S-, R, S ( meso)-2,3-butanediol were determined in batteries of traditional balsamic vinegar (TBV) by gas chromatography-mass spectrometry (GC-MS), using a chiral capillary column, to evaluate if such parameters could be used to differentiate TBV differently aged and from different producers. Results showed that the initial amounts of 2-hydroxybutanone and 2,3-butanediol were quite variable, as a function of the producer of the vinegar; moreover, the 2-hydroxybutanone amount decreased during aging while 2,3-butanediol increased. Initially, the R-2-hydroxybutanone form prevails, and then the R/ S ratio decreased regularly during aging with some exceptions attributed to the addition of new barrels during the battery management. With regard to the 2,3-butanediol isomers, the most abundant was the R, R form, slowly transformed into the R, S and S, S isomers during aging. The GC-MS method used is easy and fast and could allow for a quick control of the maturation level of the vinegar.

Structural Elucidation and Biological Activity of Acyl-homoserine Lactones from the Phytopathogen Pantoea ananatis Serrano 1928

In Gram-negative bacteria, the acyl-homoserine lactones (acyl-HSLs) are the main signaling substances employed in cell-to-cell communication systems. This paper describes the chemical characterization of acyl-HSLs produced by the worldwide-spread phytopathogen Pantoea ananatis (Serrano 1928) by using gas chromatography-electron impact mass spectrometry. The absolute configuration of the major identified substance, (S)-(--)-N-hexanoyl-HSL, was determined with gas chromatography-flame ionization detection with a chiral capillary column. Biological activities of extracts, fractions, and synthetic products were evaluated with the specific reporter Agrobacterium tumefaciensNTL4(pZLR4) in beta-galactosidase expression assays.

Enantiomeric separation of chiral polychlorinated biphenyls on β-cyclodextrin capillary columns by means of heart-cut multidimensional gas chromatography and comprehensive two-dimensional gas chromatography. Application to food samples

Three commercially available chiral capillary columns, Chirasil-Dex, BGB-176SE, and BGB-172, have been evaluated for the separation into enantiomers of the 19 chiral polychlorinated biphenyls (PCB) congeners stable at room temperature. The enantiomers of 15 chiral PCBs were, at least to some extent, separated using these beta-cyclodextrin based columns. Multidimensional techniques, such as heart-cut multi-dimensional gas chromatography (heart-cut MDGC) and comprehensive two-dimensional gas chromatography (GC x GC), were investigated for their ability to solve coelution problems with other PCBs present in commercial mixtures and real-life samples. Heart-cut MDGC improved the separation as compared to one-dimensional GC, and enantiomeric fractions of the investigated chiral PCBs could be determined free from interferences. However, limitations on the number of target compounds that can be transferred to the second column in a single run and, therefore, the time consumption, have led to the evaluation of GC x GC as an alternative for this type of analysis. With GC x GC, two column set-ups were tested, both having a chiral column as first-dimension column, and two different polar stationary phase columns in the second dimension. On using both column combinations, congeners 84, 91, 95, 132, 135, 136, 149, 174, and 176 could be determined free from coelutions with other PCBs. Results on the application of heart-cut MDGC to food samples such as milk and cheese are given, as well as the first results on the application of GC x GC to this type of samples.

β-CYCLODEXTRIN-MODIFIED MONOLITHIC STATIONARY PHASES FOR CAPILLARY ELECTROCHROMATOGRAPHY AND NANO-HPLC CHIRAL ANALYSIS OF EPHEDRINE AND IBUPROFEN

ABSTRACT Chiral monolithic capillary columns for reversed-phase capillary electrochromatography (CEC) and for nano-HPLC were prepared by linking β-cyclodextrin modifier into the acrylic monolithic phase. Columns with the physically and chemically bonded β-cyclodextrin derivatives were tested under CEC and nano-HPLC conditions; enatioselective separation of (−)-ephedrine/(+)-pseudoephedrine and (+/−)-ibuprofen was successfully performed. The separation efficiency of CEC and HPLC was examined and compared; resolution of (+/−) ibuprophen was 2.45 and 2.97 for CEC and HPLC respectively, number theoretical plates of thiourea were 41,600 N/m in CEC.

Stereoselective determination of the CYP2C19 probe drug mephenytoin in human urine by gas chromatography–mass spectrometry

A sensitive, specific and reproducible gas chromatographic assay utilizing mass-selective detection has been developed for the stereoselective determination of mephenytoin (MP) in human urine. Following extraction of urine samples using methyl tert.-butyl ether, separation of R- and S-MP was achieved with a chiral capillary column; detection and quantitation were accomplished by mass spectrometry in the single ion monitoring mode ( m/ z 104 and 189). Excellent linearity was observed for both enantiomers over the concentration range of 5–1000 ng/ml with corresponding correlation coefficients ( r)>0.99. The intra- and inter-day precision and accuracy were within ±5%. This method employs a simplified processing procedure, demonstrates improved extraction recovery, and provides at least 5-fold greater sensitivity than previously reported assays. This method is well suited for the phenotypic evaluation of CYP2C19 activity using mephenytoin.

Analytical Discrimination of the Cold-Pressed Oils of Mandarins and their Hybrids

Volatile compositions of the cold-pressed peel oils of a Satsuma mandarin cultivar, from Japan, and four other cultivars of mandarin hybrids such as Temple, Orlando, Kara and Minneola obtained from Ethiopia and Kenya were analyzed by capillary GC and GC/MS, without prior separation. Satsuma mandarin and Temple were characterized by high concentrations of (E,E)-α-farnesene and linalool, respectively. The enantiomeric distribution of α-pinene, β-pinene, sabinene, limonene, linalool, citronellal and α-terpineol was studied by simple and reliable enantioselective GC methods involving either a chiral capillary column or an on-line coupling of non-chiral and chiral capillary columns. The (+)-enantiomers of most of the components in all of the analyzed oils were present in excess, except for linalool and citronellal in the oils of Satsuma mandarin and Temple, respectively. Cold-pressed oils of Satsuma mandarin were found to contain about 75% enantiomeric excess of (3R)-(-)-linalool instead of (3S)-(+)-linalool excess, as was found in the oils of other mandarin cultivars and hybrids.

The Aroma of Brazilian Ambarella Fruit (Spondias cytherea Sonnerat)

From the static cryogenic headspace of ambarella fruit, six impact aroma compounds were characterized by aroma extract dilution analysis. By multidimensional GC/MS using chiral capillary column, these substances were identified as ethyl (S)(+) 2-methyl butyrate (fruity), ethyl isovalerate (fruity and cheese-like), ethyl propionate (fruity), ethyl butyrate (fruity and refreshing), (R)(-)-linalool (floral) and trans-pinocarveol (herbaceous). Trapping those substances by the use of a GC-sniffing port allowed a very typical fruity ambarella essence.

Role of solid-phase microextraction in the identification of highly volatile pheromones of two Rhinoceros beetles Scapanes australis and Strategus aloeus (Coleoptera, Scarabaeidae, Dynastinae)

Solid-phase microextraction (SPME) samplings from live insects or natural secretion allowed one to identify the aggregation pheromones of the pest beetles Scapanes australis and Strategus aloeus by efficient and rapid isolation of their highly volatile (72< M r<116) components. S. australis male pheromone was identified as a 84:12:4 (w/w) mixture of 2-butanol [67:33 ( R)-(−):( S)-(+) ratio], 3-hydroxy-2-butanone and 2,3-butanediol [43:17:40 ( R, R)-(−):( S, S)-(+): meso ratio], and S. aloeus pheromone as a 95.5:4.0:0.5 (w/w) mixture of 2-butanone, 3-pentanone and sec.-butyl acetate by GC–MS using conventional and chiral capillary columns. This is the first report of Scarabaeidae pheromones based on such small and common molecules.

Evaluation of monoterpenic biogenic volatile organic compounds in ambient air around Eucalyptus globulus, Pinus halepensis and Cedrus atlantica trees growing in Algiers city area by chiral and achiral capillary gas chromatography

The monoterpenic biogenic volatile organic compounds (BVOCs) in ambient air around either Eucalyptus globulus, Cedrus atlantica and Pinus halepensis trees from El- Hamma Botanical Garden (Algiers) or from Pinus halepensis trees field located in Bab-Ezzouar (suburb of Algiers) was qualitatively and semi-quantitatively evaluated. The sampling was carried out in ambient air by adsorption through an activated charcoal cartridge followed by the carbon disulfide extraction. The solution was subjected to high-resolution gas chromatography (HRGC) analysis in programmed temperature. The identification of the components was established by the means of retention Kovàts indexes. The use of a β-cyclodextrin chiral capillary column allowed a good separation of monoterpenic enantiomers released in the atmosphere. The enantiomeric ratio provided a good insight into the enantiomeric compound preferentially emitted by plants.

Enantiomer separation of polychlorinated biphenyl atropisomers and polychlorinated biphenyl retention behavior on modified cyclodextrin capillary gas chromatography columns

Seven commercially-available chiral capillary gas chromatography columns containing modified cyclodextrins were evaluated for their ability to separate enantiomers of the 19 stable chiral polychlorinated biphenyl (PCB) atropisomers, and for their ability to separate these enantiomers from achiral congeners, necessary for trace environmental analysis of chiral PCBs. The enantiomers of each of the 19 chiral PCBs were at least partially separated on one or more of these columns. Enantiomeric ratios of eleven atropisomers could also be quantified on six columns as they did not coelute with any other congener containing the same number of chlorine atoms, so could be quantified using gas chromatography–mass spectrometry. Analysis of a lake sediment heavily contaminated with PCBs showed enantioselective occurrence of PCB 91, proof positive of enantioselective in situ reductive dechlorination at the sampling site.