Β-cyclodextrin Phase Research Articles

Cyclodextrin-based Gas Chromatography and GC/MS methods for determination of chiral pair constituents in mint essential oils

ABSTRACT The genus Mentha has been known as culinary source of minty note. Besides, the essential oil imparts value to consumer products like confectionery, cosmetics, and pharmaceutical preparations. A simple and sensitive enantioselective gas chromatographic method is described for the quantitative analysis of terpenoid enantiomers in essential oils using different cyclodextrin coated stationary phases. Limonene, menthone, menthol, and menthyl acetate were identified as pure (-)-enantiomers whereas isomenthone, neomenthol, pulegone, and piperitone as pure (+)-enantiomers in menthol mint, and peppermint oils, respectively. The selectivity of each enantiomer was also demonstrated. A β-cyclodextrin phase with diethyl substitution provides baseline resolution for all target enantiomers with selectivity ranged from 1.004 to 1.050. Moreover, permethylated or diacetylated-β-cyclodextrin showed no selectivity for (+/-)-menthol enantiomers. The current study may facilitate the origin authentication studies of mint oils. Investigation of enantiomers involved in menthol biosynthesis revealed that only (-)-menthol is present in the essential oils of Mentha species.

Enantiomeric Separation of Chiral Amines and Amino Alcohols Using Acetylated β-Cyclodextrin Stationary Phase by High-Performance Liquid Chromatography

Enantiomeric separation ability on high-performance liquid chromatography (HPLC) was compared between native and acetylated β-cyclodextrin stationary phases. In the chiral stationary phases (CSP) used in this work, β-cyclodextrin is chemically bonded to aminopropyl silica gel via sugar chain spacer. The acetylated β-cyclodextrin phase (SUMICHIRALTM OA-7700) exhibits excellent performance for the separation of chiral amines and amino alcohols in reversed phase mode. Conventional phosphate buffer can be used in mobile phase without special modifier and the analytical method is easy to develop. OA-7700 is very useful practically for the determination of optical purity of many important chiral amines. It can separate enantiomers of 1-phenyl-2-(p-tolyl)ethylamine (PTE) which is used for industrial scale resolution of chrysanthemic acids and norephedrin (phenylpropanolamine) which is regulated as stimulant raw material.

Preparation of β-Cyclodextrin Capillary Column for Enantioseparation and Determination of Nicardipine and Manidipine by Capillary Electrochromatography

The separation and determination methods of calcium antagonists manidipine hydrochloride and nicardipine hydrochloride enantiomers were developed by open-tubular capillary electrochromatography( CEC),respectively. A new capillary column with p-nitrophenylcarbamation β-cyclodextrin was prepared by sol-gel method. The sol-gel modified with cyclodextrin derivative was characterized by infrared spectroscopy( IR) and scanning electron microscopy( SEM). In polar organic mode,the effect of the volume fraction and concentration of added triethylamine and glacial acetic acid,the content of organic solvents,the operating voltage,and temperature on the resolution( RS) were investigated. The optimized conditions were at 20 ℃,detection wavelength at 236 nm,and injection pressure at 3. 448 k Pa × 3 s. The compositions of mobile phases were V( Me OH) ∶ V( ACN) ∶ V( TEA) ∶ V( HOAc) = 57 ∶ 43 ∶ 0. 05 ∶ 0. 07 for manidipine hydrochloride and V( Me OH) ∶ V( ACN) ∶ V( TEA) ∶ V( HOAc) = 55 ∶ 45 ∶ 0. 05 ∶ 0. 08 for nicardipine hydrochloride. The resolution( Rs) of manidipine hydrochloride was 1. 39 at 25 k V. The resolution( Rs) of nicardipine hydrochloride was1. 30 at 20 k V. The RSDs of retention time and peak area were less than 1. 2% and 5. 6%( n = 5) for the drugs,respectively. It was indicated that new column has stable electrochromatography performance. The single run time were less than 5 min for manidipine hydrochloride and less than 7 min for nicardipine hydrochloride. Good linearity were observed in the concentration range of 5. 2 ~ 125. 0 mg / L with correlation coefficients 0. 9969 or more for both drug enantiomers. The limit of detection values were 1. 8 mg / L for manidipine and 2. 3 mg / L for nicardipine,respectively. The nitrophenyl carbamated β-cyclodextrin phase( NCDP) column were preliminarily used for determinations of manidipine hydrochloride and nicardipine hydrochloride tablet and capsule.

Enantiomeric Separation in Comprehensive Two‐dimensional Gas Chromatography with Accurate Mass Analysis

Chiral comprehensive two-dimensional gas chromatography (eGC×GC) coupled to quadrupole-accurate mass time-of-flight mass spectrometry (QTOFMS) was evaluated for its capability to report the chiral composition of several monoterpenes, namely, α-pinene, β-pinene, and limonene in cardamom oil. Enantiomers in a standard mixture were fully resolved by direct enantiomeric-GC analysis with a 2,3-di-O-methyl-6-t-butylsilyl derivatized β-cyclodextrin phase; however, the (+)-(R)-limonene enantiomer in cardamom oil was overlapped with other background components including cymene and cineole. Verification of (+)-(R)-limonene components based on characteristic ions at m/z 136, 121, and 107 acquired by chiral single-dimension GC-QTOFMS in the alternate MS/MSMS mode of operation was unsuccessful due to similar parent/daughter ions generated by interfering or co-eluting cymene and cineole. Column phases SUPELCOWAX, SLB-IL111, HP-88, and SLB-IL59, were incorporated as the second dimension column ((2)D) in chiral GC×GC analysis; the SLB-IL59 offered the best resolution for the tested monoterpene enantiomers from the matrix background. Enantiomeric ratios for α-pinene, β-pinene, and limonene were determined to be 1.325, 2.703, and 1.040, respectively, in the cardamom oil sample based on relative peak area data.

β-Cyclodextrin as a stationary phase for the group separation of polycyclic aromatic compounds in normal-phase liquid chromatography

The separation of highly alkylated polycyclic aromatic compounds according to the size of their aromatic system is investigated using the polycyclic aromatic sulfur heterocycles in vacuum gas oil. A large number of reference compounds containing several parent ring systems and different alkylation patterns were first investigated to characterize the retention of polycyclic aromatic compounds likely to occur in high-boiling petroleum samples. A β-cyclodextrin phase, Merck ChiraDex, was found to be more suitable than chemically bonded aminopropanosilane and tetrachlorophthalimide in normal-phase HPLC with respect to a combination of selectivity towards the number of aromatic double bonds and degree of influence of the alkyl groups of the aromatic compounds. Finally the preseparated polycyclic aromatic sulfur heterocycles from a vacuum gas oil were fractionated according to the number of condensed aromatic rings on the ChiraDex phase and were characterized by Fourier transform ion cyclotron resonance mass spectrometry.

The HPLC Enantioresolution of Phenyl Isocyanated Amino Acids, Peptides and Amino Alcohols on Cyclodextrin Bonded Phases Using the Acetonitrile-Based Mobile Phase

A variety of amino acids (primary and secondary), peptides and amino alcohols are pre-column phenyl isocyanated in alkaline medium and enantioresolved on the naphthylethylcarbamated β-cyclodextrin (i.e., RN- and SN-β-CD) bonded chiral phases (CSPs) using the acetonitrile-based mobile phase and on a native β-cyclodextrin (β-CD) phase for comparison. The resolution is believed to be a result of the hydrogen bonding between the secondary hydroxyl groups of cyclodextrin and the functional groups of analyte and is enhanced as the amino and the carboxyl groups are attached to the stereogenic center of analyte. Also, the enhancement is observed if the steric hindrance between the side-chain group of amino acid and the chiral selector exists. However, the resolution is deteriorated in the case that the side-chain group close to the stereogenic center of amino acid becomes bulky or is capable of forming hydrogen bonding with chiral selector. The aromatic moiety of the tagging reagent not only contributes the retention, but also benefits the resolution in some cases on the RN- and SN-β-CD phases through π-π interaction. The resolution is either not observed or unsatisfactory in the reversed-phase mode.

Determination of RS, E/Z-tocotrienols by HPLC

Synthetic α-tocotrienol was separated into four geometrical E/Z side chain isomers by preparative HPLC (permethylated β-cyclodextrin phase). The isolated isomers were resolved in ethylene glycol dimethyl ether, converted into the corresponding methyl ether using dimethyl sulfate, and the tocotrienol methyl ethers were extracted with n-hexane. A subsequent HPLC separation on a chiral phase (adsorbent cellulose derivated with 3,5-dimethyl phenyl carbamate) discriminates between the enantiomers of each E/Z side chain isomer, achieving the complete resolution of the eight occurring synthetic RS, E/Z-α-tocotrienols. The method can be shortened by omitting the preparative separation of the E/Z tocotrienol isomers prior to the chromatography on the chiral dimethyl phenyl carbamate phase. The simplified method achieved the following separation: RS, E/Z-α-tocotrienol separated into five peaks, RS, E/Z-β-tocotrienol into eight, RS, E/Z-γ-tocotrienol into six and RS, E/Z-δ-tocotrienol into eight peaks. The naturally occurring R, E-E-tocotrienol isomer could be identified within the synthetic RS, E/Z-isomers by co-chromatography with tocotrienol methyl ethers derived from natural sources, respectively.

Cis/trans isomers of tocotrienols - occurrence and bioavailability

In nature tocotrienols (compounds of vitamin E) have only been found in the 2R,3′trans,7′trans (R, trans-trans) configuration whereas synthetic tocotrienols often represent a mixture of cis and trans side chain isomers. In this study tocotrienols were isolated from samples (egg yolk, palm oil, and ewe's milk) by extraction of the unsaponifiable matter and subsequent semi-preparative high-performance liquid chromatography (HPLC). A recently developed HPLC method [two series-connected columns ET 200/4 NUCLEODEX β-PM (200×4 mm ID, permethylated β-cyclodextrin phase; Macherey-Nagel, Duren, Germany), acetonitrile/water eluent (58 : 42 by vol.), fluorescence detection at an emission wavelength of 330 nm (excitation wavelength = 295 nm)] was used to separate the isolated tocotrienols into the four potential cis/trans side chain isomers. Commercially available, synthetic α-tocotrienol was orally administered to a laying hen. In the egg yolk all four α-tocotrienol geometrical isomers could be determined, thus demonstrating the bioavailability. Furthermore, no cis/trans isomers of γ-tocotrienol from hardened palm oil (melting point 46 °C) could be detected, i.e. the hydrogenation process during oil hardening evidently caused no isomerization of γ-tocotrienol. Finally, it is shown that ewe's milk does not contain a detectable amount of cis/transα-tocotrienol isomers, which might derive from biohydrogenation during microbial metabolism in the rumen.

Separation and characterization of cis - trans isomers of α-tocotrienol by HPLC using a permethylated β-cyclodextrin phase

The behaviour of α-, β-, γ- and δ-tocotrienols (structurally related to tocopherols with naturally trans-configurated double bonds in the side-chain) during HPLC on a permethylated β-cyclodextrin phase was studied. A newly developed isocratic HPLC method is described with an acetonitrile/water (58:42 by vol.) eluent and fluorescence detection at an emission wavelength of 330 nm (excitation wavelength = 295 nm). Each of the separately injected tocotrienols exhibited four peaks. The four separated components of α-tocotrienol were identified by spectroscopy (MS, 1H-NMR, FTIR) to be structural side-chain isomers. The order of retention times was determined to be all-cis-α-tocotrienol followed by cis-trans-/trans-cis-α-tocotrienol (differentiation between the two compounds was not possible) with all-trans-α-tocotrienol as the last eluting isomer.

Enantiomeric composition of monoterpene hydrocarbons inn-hexane extracts ofAngelica archangelica L. roots and seeds

Roots and seeds of Angelica archangelica L. were collected from different localities in western, eastern and northern Finnish Lapland. Two root samples and 33 seed samples were extracted with n-hexane and analysed by GC–MS using a chiral β-cyclodextrin phase. Major compounds in the root oils were (−)-α-pinene (19–42%) and (+)-sabinene (21–28%). One of the oils contained 22% (+)-3-carene but the other one had none at all. The seed oils were dominated by (−)-β-phellandrene (>60%). Other major compounds were (+)-sabinene, (+)-α-pinene, myrcene, (−)-α-phellandrene, (−)-α-pinene and (−)-limonene. Some statistically significant differences between seed samples from different localities could also be found. © 1997 John Wiley & Sons, Ltd.

Enantiomeric composition of monoterpene hydrocarbons in n-hexane extracts of Angelica archangelica L. roots and seeds

Roots and seeds of Angelica archangelica L. were collected from different localities in western, eastern and northern Finnish Lapland. Two root samples and 33 seed samples were extracted with n-hexane and analysed by GC–MS using a chiral β-cyclodextrin phase. Major compounds in the root oils were (−)-α-pinene (19–42%) and (+)-sabinene (21–28%). One of the oils contained 22% (+)-3-carene but the other one had none at all. The seed oils were dominated by (−)-β-phellandrene (>60%). Other major compounds were (+)-sabinene, (+)-α-pinene, myrcene, (−)-α-phellandrene, (−)-α-pinene and (−)-limonene. Some statistically significant differences between seed samples from different localities could also be found. © 1997 John Wiley & Sons, Ltd.

Variation and inheritance of monoterpenes inLarix species

The terpene composition of the hydrodistilled leaf oil of Larix decidua Mill., L. sibirica Lebed., L. leptolepis (Sieb. et Zucc.) Gord., L. sibirica×leptolepis, L. leptolepis×sibirica, L. decidua×leptolepis, L. leptolepis×decidua, L. sibirica×decidua and L. laricina×decidua was examined by GC–MS using a β-cyclodextrin phase. Altogether 38 components were identified, which represented more than 95% of the total oil composition. The qualitative composition of the volatile oil was very similar in all the Larix species studied. The relative amounts of the monoterpene hydrocarbons varied considerably both within and between species. The major components of the Larix leaf oils studied were (−)- and (+)-α-pinene, (−)-β-pinene, myrcene and (+)-3-carene. © 1997 John Wiley & Sons, Ltd.

Studies on the enantioselectivity in the lipase-catalyzed synthesis of monoacylglycerols from isopropylidene glycerol

The regioselective lipase-catalyzed acylation of isopropylidene glycerol using different vinyl esters as acyl donors in toluene was studied. Reaction progress and enantioselectivity were monitored by gas chromatography using a permethylated β-cyclodextrin phase. All vinyl esters were completely converted after 20 to 24 h and it was found that the S-enantiomer reacted faster. Lower enantiomeric excess were found using e. g. vinyl palmitate (18 %ee) compared to e. g. vinyl butyrate (42 %ee) with crude lipase from Pseudomonas cepacia. Immobilization using the sol-gel method resulted in higher remaining activities (up to 69%) and increased enantioselectivity E (up to 8.5).

Chiral separations of β-blocking drug substances using chiral stationary phases

Three chiral stationary phases were evaluated for their usefulness in determinations of optical purity and separations of β-blocking drug substances. The phases were a modified cellulose phase (Chiralcel OD), an immobilized protein (AGP) and a β-cyclodextrin phase (Cyclobond I). These phases were evaluated concerning their practical analytical use for the determination of the enantiomeric purity of non-racemic β-blocking substances. The best phase proved to be Chiralcel OD, which provided excellent separations of almost all β-blocking substances tested and rugged determinations performed with satisfactorily low detection limits. Similar results could be obtained with AGP, but this did not seem to be sufficiently rugged for routine analysis. The β-cyclodextrin phase resulted in poor chiral separations of most β-blocking substances and the usefulness of this phase for analytical purposes seems limited.

Isoarborinol through geological times: Evidence for its presence in the Permian and Triassic

Optical rotation measurements and HPLC chiral separations using a β-cyclodextrin phase, performed on aromatic hydrocarbons isolated from diverse geological sources, and belonging to the arborane or fernane triterpenoid series, have shown that isoarborinol, one of the possible biological precursors, was abundantly present at the time of deposition of Permian and Triassic sediments. This fact considerably reinforces the hypothesis that arborane derivatives in sediments, often found in abundance in lacustrine or lagoonal environments, must originate from microorganisms such as aerobic bacteria or algae rather than from angiosperms, a group of higher plants whose evolution dates from the Cretaceous and currently believed to be the principal source of isoarborinol.

Comparison of liquid chromatographic selectivity for polycyclic aromatic hydrocarbons on cyclodextrin and C18 bonded phases

Selectivity towards polycyclic aromatic hydrocarbons (PAHs) was studied on cyclodextrin bonded phases and compared to selectivity observed on C18 phases. The study included the separation of eleven five-ring PAH isomers on each of three phase types; monomeric C18, polymeric C18 and cyclodextrin. Retention of PAHs ranging in size from three to six condensed rings was also investigated. Retention on the cyclodextrin phase is based on inclusion complexing between the solute and cyclodextrin cavity, resulting in a strong shape dependence. However, the shape selectivity exhibited by the cyclodextrin phase is different from that exhibited by either the monomeric or polymeric C18 phases; retention on the cyclodextrin phase is strongly dependent on the shape and shows very little molecular weight dependence. Calculations of solute molecular widths were performed to predict the isomers' ability to enter the cyclodextrin cavity. The effect of sample solvent and injection volume was also investigated for the cyclodextrin phase. A retention model based on the solute shape is proposed for PAH isomers on β-cyclodextrin phase.

Separation of Cyclodextrins Using Cyclodextrin Bonded Phases

Abstract Two different cyclodextrin bonded phases (α and β) were used for the separation of α-, β-and γ-cyclodextrins. The β-cyclodextrin phase was found to be, in general, more effective at resolving the cyclodextrins than the α-cyclodextrin bonded phase. Acetonitrile/water mixtures were used as mobile phases. The effect of mobile phase composition on retention and resolution is examined. The elution order was found to be size dependent. The results are discussed in terms of the overall retention mechanism.