Liquid Chromatographic Separation Of Enantiomers Research Articles

Direct determination of tyrosine and tryptophane enantiomers in pumpkin (Cucurbita moschata) by HPLC-UV/Vis: Effect of cooking treatment on enantiomers profile

An analytical method to determine the content of tryptophan (Trp) and tyrosine (Tyr) enantiomers in pumpkin (Cucurbita moschata) is developed and validated. The method consists of a sample preparation procedure with a direct liquid chromatographic separation of enantiomers on a Whelk-O2 chiral stationary phase. The chromatographic separation was performed under gradient reversed-phase conditions in which the effect of pH and organic modifier were studied. A multivariate design of experiments was applied in the optimization of the extraction procedure. After optimization the complete analytical process was validated. Great accuracy was achieved with recovery between 92–109% with a relative standard deviation of less than 10%. Limits of detection obtained ranged between 0.04 and 0.07 mg L-1. The resulting analytical method is applied with success to dose the content of Trp and Tyr and their enantiomers in several pumpkin cultivars. The impact of several traditional cooking methods on the content of these amino acids was also studied. The obtained data showed that studied pumpkin is a good source of free Trp and Tyr, mainly L-Trp. The results confirm the natural presence of D-Trp in this vegetable. Finally, the results demonstrate that the levels of all analytes are modified during traditional cooking treatments.

Determination of Chemical and Enantiomeric Purity of α‐Amino Acids and their Methyl Esters as N‐Fluorenylmethoxycarbonyl Derivatives Using Amylose‐derived Chiral Stationary Phases

Liquid chromatographic enantiomer separation and simultaneous determination of chemical and enantiomeric purity of α‐amino acids and their methyl esters as N‐fluorenylmethoxycarbonyl (FMOC) derivatives was performed on three covalently bonded type chiral stationary phases (CSPs) derived from amylose derivatives. The enantiomer separation of α‐amino acid esters as N‐FMOC derivatives was better than that of the corresponding acids, especially for CSP 1 and 2. Chemical impurities as the corresponding racemic acids present in several commercially available racemic amino acid methyl esters were observed to be 0.49–17.50%. Enantiomeric impurities of several commercially available L‐amino acid methyl esters were found to be 0.03–0.58%, whereas chemical impurities as the corresponding racemic acids present in the same analytes were found to be 0.13–13.62%. This developed analytical method will be useful for the determination of chemical and enantiomeric purity of α‐amino acids and/or esters as N‐FMOC derivatives using amylose‐derived CSPs.

Liquid Chromatographic Enantiomeric Separation of Chiral Aliphatic Amines Using 2-Hydroxynaphthaldehyde as a Derivatizing Agent on Polysaccharide-Derived Chiral Stationary Phases

A new liquid chromatographic enantiomer separation of chiral amines as 2-hydroxynaphthaldimine derivatives on several coated and immobilized chiral stationary phases (CSPs) derived from polysaccharides is described. 2-Hydroxynaphthaldehyde was introduced as a derivatizing agent for the enantiomeric separation of chiral aliphatic amines under the normal phase conditions, and was found to both enhance detection sensitivity and provide suitable interaction sites for enantiodiscrimination. Cellulose-derived CSPs, in general, exhibited better enantiomeric separation than amylose-derived CSPs. Amongst the examined six covalently bonded and four coated-type CSPs, covalently bonded Chiralpak IC, which contains a cellulose-based chiral selector, showed the best enantioseparation. The method was applied to the determination of the enantiomeric purity of commercially available (R)- and (S)-leucinol. The enantiomeric impurities of the investigated analytes procured from two suppliers were found to be 0.06–1.20%. The developed analytical method was also validated in accordance with ICH guidelines and proved to be enantioselective, sensitive and effective for the enantiomeric separation of chiral aliphatic amines as 2-hydroxynaphthaldimine derivatives under ultraviolet detection.

Liquid chromatographic separation of the enantiomers of N-fluorenylmethoxycarbonyl α-amino acids on a covalently bonded type polysaccharide-derived chiral stationary phase under fluorescence detection

The liquid chromatographic enantiomer separation of N-fluorenylmethoxycarbonyl (FMOC) α-amino acids was performed using a covalently immobilized CSP (Chiralpak IB) with cellulose...

Liquid chromatographic separation and thermodynamic investigation of lorcaserin hydrochloride enantiomers on immobilized amylose-based chiral stationary phase.

A novel liquid chromatographic method was developed for enantiomeric separation of lorcaserin hydrochloride on Chiralpak IA column containing chiral stationary phase immobilized with amylose tris (3.5-dimethylphenylcarbamate) as chiral selector. Baseline separation with resolution greater than 4 was achieved using mobile phase containing mixture of n-hexane/ethanol/methanol/diethylamine (95:2.5:2.5:0.1, v/v/v/v) at a flow rate of 1.2mL/min. The limit of detection and limit of quantification of the S-enantiomer were found to be 0.45 and 1.5μg/mL, respectively; the developed method was validated as per ICH guideline. The influence of column oven temperatures studied in the range of 20°C to 50°C on separation was studied; from this, retention, separation, and resolution were investigated. The thermodynamic parameters ΔH°, ΔS°, and ΔG° were evaluated from van't Hoff plots,(Ink' versus 1/T) and used to explain the strength of interaction between enantiomers and immobilized amylose-based chiral stationary phase.

Homochiral metal-organic frameworks based on amino acid ligands for HPLC separation of enantiomers.

Natural amino acids are well known to form coordination polymers with transition metal ions. In this study, six homochiral metal-organic frameworks constructed from Zn2+ or Co2+ ions and various enantiopure amino acid (L-tyrosine, L-histidine, L-tryptophan and L-glutamic acid), namely [Zn(L-tyr)]n (L-tyrZn), [Zn4 (btc)2 (Hbtc)(L-His)2 (H2 O)4 ]·1.5H2 O, {[Zn2 (L-trp)2 (bpe)2 (H2 O)2 ]·2H2 O·2NO3 }n , [Co2 (L-Trp)(INT)2 (H2 O)2 (ClO4 )], [Co2 (sdba)((L-Trp)2 ] and [Co(L-Glu)(H2 O)·H2 O]∞ , were synthesized according to the methods previously reported in the literature. The six homochiral MOFs were explored as the chiral stationary phases for high-performance liquid chromatographic separation of enantiomers using hexane/isopropanol or hexane/dichloromethane as mobile phase. Various types of enantiomers such as alcohols, amines, ketones, ethers, organic acids, etc. can be resolved on these homochiral MOF columns. The results revealed that the enantioseletivities of homochiral MOFs based on amino acids as chiral bridging ligands used as stationary phases are practical in HPLC.

Liquid chromatographic enantiomer separation of 1-naphthylamides of chiral acids using several amylose- and cellulose-derived chiral stationary phases.

The liquid chromatographic enantiomer separation of various chiral acids as 1-naphthylamides was performed using several chiral stationary phases (CSPs). The CSPs used in this study were six covalently bonded and four coated type CSPs derived from amylose and cellulose derivatives as chiral selectors. The degree of enantioseparation is affected by the structure of chiral acids and the CSPs used, which have different chiral selectors and types of immobilization. For the enantiomer resolution of chiral acids as 1-naphthylamide derivatives, the performance of the coated type Lux Cellulose-1 was superior to those of the other CSPs, except for 2-aryloxypropionic acid derivatives. Owing to the strong ultraviolet absorbance of the 1-naphthyl group, the convenient analytical method developed and validated in this study could be expected to be very useful for the enantiomer separation of various chiral acids as 1-naphthylamide derivatives using polysaccharide-derived CSPs.

고성능 액체 크로마토그래피에서 아미노산과 이들 에스테르의 플루오레닐메톡시카르보닐 유도체의 자외선과 형광 검출에서의 동시 광학분리

Liquid chromatographic enantiomer separation of α-amino acids and their methyl and ethyl esters as fluorenylmethoxycarbonyl (FMOC) derivatives was performed using a recently developed chiral column (Chiralpak IE) based on polysaccharide derivative under simultaneous UV detection and fluorescence detection. The degree of enantiomer separation of α-amino acid esters as FMOC derivatives is generally higher than that of the corresponding α-amino acids. Especially, α-amino acid methyl esters showed the greatest enantioseparation. As this method developed in this study can be applied to determine the chemical and optical purity of α-amino acids and esters, it is expected to be quite useful for their chiral separation using Chiralpak IE.

Liquid Chromatographic Enantiomer Separation of α-Amino Acid Esters as Nitrobenzoxadiazole Derivatives Using Polysaccharide-Derived Chiral Stationary Phases

Liquid chromatographic enantiomer separation of -amino acid esters as nitrobenzoxadiazole (NBD) derivatives was performed using several chiral stationary phases (CSPs) based on polysaccharide derivatives under fluorescence detection. For enantiomer separation by normal HPLC, the non-aqueous derivatization method of -amino acid esters for NBD analytes was introduced. Among the six CSPs used in this study, the performance of Chiralpak IA was superior for enantiomer resolution of NBD derivatives of several -amino acid methyl esters. Also the convenient analytical method using polysaccharide-derived CSPs developed in this study was applied to determine the optical purity of -amino acids esters. It was investigated that the enantiomeric impurity levels of 0.02-1.73% were found after determination of enantiomeric purities of several commercially available L-amino acid methyl esters. It is expected to be quite useful for enantiomer separation of other -amino acid esters as NBD derivatives by normal HPLC.

Structural and temperature effects on enantiomer separations of bicyclo[2.2.2]octane-based 3-amino-2-carboxylic acids on cinchona alkaloid-based zwitterionic chiral stationary phases

Procedures for the direct high-performance liquid chromatographic enantiomer separation of four bicyclo[2.2.2]octane-based 3-amino-2-carboxylic acids were developed in polar-ionic mode on zwitterionic chiral stationary phases (CSPs) based on cinchonane alkaloide quinine, quinidine and chiral sulfonic acid motifs. The effects of the mobile phase composition including the type of acid and base additives, the structures of the analytes and temperature were investigated.Experiments were performed at constant mobile phase compositions in the temperature range 10–50°C in order to study the effects of temperature, and thermodynamic parameters were calculated from plots of ln k or ln α vs. 1/T. Some mechanistic aspects of the chiral recognition process are discussed with respect to the structures of the analytes. It was found that the enantiomeric separations were in most cases enthalpically driven, but entropically driven separation was also observed. The sequence of elution of the enantiomers on the pseudo-enantiomerically behaving CSPs was determined in all cases.

ENANTIOMER SEPARATION OF N-t-BOC AND N-CBZ α-AMINO ACIDS AND THEIR ESTERS ON POLYSACCHARIDE DERIVED CHIRAL STATIONARY PHASES

Liquid chromatographic enantiomer separation of N-t-BOC and N-CBZ α-amino acid, methyl ester, and ethyl ester derivatives was performed on chiral stationary phases (CSPs) based on polysaccharide derivatives. Good resolution of N-t-BOC and N-CBZ α-amino acid derivatives was achieved on Chiralcel OD, Chiralcel OF, and Chiralpak AD, respectively. Enantioselectivites of N-CBZ protected derivatives were found better than those of N-t-BOC protected derivatives. Moreover, the results of liquid chromatography and computational chemistry suggest that L-form is more retained in the case of carboxylic group of enantiomer locating toward to the inside of grooves, on the other hand, D-form is more retained in the case of alkyl group of α-position of N-protected α-amino acid derivatives locating toward to the inside of grooves.

고성능 액체 크로마토그래피에서 키랄 크라운 에테르로부터 유도된 키랄 고정상을 이용한 광학분리의 비교

Comparative liquid chromatographic enantiomer separation of α-amino acids, their esters and primary amino compounds was performed using two chiral stationary phases (CSPs) prepared by covalently bonding (+)-(18-crown-6)- 2,3,11,12-tetracarboxylic acid (18-C-6-TA) of the same chiral selector. In general, the separation factors and resolution factors for these analytes on CSP 1 were greater than on CSP 2, while these capacity factors on CSP 2 were quite greater than on CSP 1. Except for leucine methyl ester and phenylalanine methyl ester, the elution orders of all analytes including α- amino α-alkyl acids and phenylglycine alkyl esters on CSP 1 are identical to those on CSP 2. This study showed that different connecting structures for these two CSPs might influence their ability to resolve the analytes depending on their structures related to the chiral recognition mechanism.

아미노산 에스테르의 벤조피논 이민 유도체의 액체 크로마토그래피의 광학분리

A convenient liquid chromatographic enantiomer separation of several <TEX>${\alpha}$</TEX>-amino acid esters as benzophenone Schiff base derivatives on covalently immobilized chiral stationary phases (CSPs) derived from polysaccharide derivatives was developed. The benzophenone imine derivatives of <TEX>${\alpha}$</TEX>-amino acid esters were readily prepared by stirring benzophenone imine and the <TEX>${\alpha}$</TEX>-amino acid ester hydrochloride salts in 2-propanol. The chromatographic conditions used on all CSPs were 0.5% or 5% 2-propanol/hexane (V/V) as the mobile phases at 1 mL/min of flow rate and UV 254 nm detection. The performance of Chiralpak IC among all CSPs was superior to that of the other CSPs for resolution of benzophenone imine derivatives of <TEX>${\alpha}$</TEX>-amino acid esters. It is expected that the developed analytical method will be useful for enantiomer resolution of other <TEX>${\alpha}$</TEX>-amino acid esters as benzophenone Schiff base derivatives.

Comparative high-performance liquid chromatography enantioseparations on polysaccharide based chiral stationary phases prepared by coating totally porous and core–shell silica particles

This article reports comparative high-performance liquid chromatographic separations of enantiomers with chiral stationary phases (CSPs) prepared by coating cellulose tris(4-chloro-3-methylphenylcarbamate) on totally porous and on core–shell type silica of comparable particle diameter. Several interesting observations were made: (1) the selectivity of separation was higher on core–shell type CSP compared to totally porous CSP at comparable content of chiral selector (polysaccharide derivative); (2) much flatter dependence of plate height on the mobile phase flow rate was observed for columns packet with CSP prepared with core–shell silica compared to the ones packed with CSPs prepared with totally porous particles; (3) at low mobile phase flow rates core–shell CSP provided lower resolving ability compared to a commercially available CSP having four times higher content of chiral selector along with higher retention of chiral analytes. However, at high flow rates core–shell type CSP performed similarly or better than the commercial column in regards of plate count (N) and peak resolution (Rs) per column length and within a given total analysis time. The advantage of CSP prepared with core–shell silica is obvious from the viewpoint of plate numbers and resolution calculated per unit time (i.e. speed of analysis).

고성능 액체 크로마토그래피에 의한 다당 유도체를 기초로 한 흡착되거나 공유결합된 키랄 고정상에서 키랄 아미노 알코올의 안트르알디민 유도체의 광학분리

The convenient derivatization method of chiral amino alcohols as 9-anthraldimine Schiff base derivatives for chiral resolution was developed and the liquid chromatographic enantiomer separation of chiral amino alcohols as 9-anthraldimine derivatives was investigated on several coated and covalently bonded polysaccharide-derived chiral stationary phases (CSPs). In general, the performance of Chiralcel OD-H (or Chiralcel OD) (α = 1.24-2.89), the coated CSP derived from cellulose derivative was superior to the other CSPs for resolution of 9-anthraldimine derivatives of several amino alcohols. The results of enantioseparation depending on the structure of 9-anthraldimine analytes like the steric bulky group and the polar moiety etc were discussed. The analytical method was applied to measure the enantiomeric purity of commercially available chiral amino alcohols. It is expected that the convenient analytical method will be very efficient for determination of enantiomeric purity of amino alcohols as 9-anthraldimine Schiff base derivatives with strong UV absorption.

Enantiomer separation of α-amino acid methyl esters and some aliphatic amines as 9-anthraldimine derivatives by high performance liquid chromatography

The liquid chromatographic enantiomer separation of several alpha-amino acid methyl esters as 9-anthraldehyde Schiff base derivatives on five polysaccharide-derived chiral stationary phases (CSPs) was described. The 9-anthraldehyde imine derivatives of a-amino acid esters were prepared by stirring 9-anthraldehyde with the alpha-amino acid ester hydrochloride salts. The chromatographic conditions were 3%-10% (v/v) 2-propanol-n-hexane as the mobile phases at the flow rate of 1.0 mL/min and detected at UV 254 nm. The performance of Chiralcel OD (or Chiralcel OD-H) among the five CSPs was superior to those of the other CSPs for the resolution of 9-anthraldimine derivatives of alpha-amino acid methyl esters. The enantiomers of all a-amino acid methyl esters as the 9-anthraldimine derivatives were base-line resolved on Chiralcel OD or Chiralcel OD-H (alpha = 1.24-5.47, Rs = 2.56-13.90). The L-enantiomers of all analytes were strongerly restrained than the respective D-enantiomers on the Chiralcel OD (or Chiralcel OD-H) CSPs. The method was also used for the enantiomer separation of aliphatic amines and good separation was obtained. It is expected that the analytical method will be useful for the enantiomer resolution of other alpha-amino acid esters and amine compounds as 9-anthraldimine derivatives.

LIQUID CHROMATOGRAPHIC ENANTIOMER SEPARATION OF AMINO ACID ESTERS AS 9-ANTHRALDIMINE SCHIFF BASES USING POLYSACCHARIDE-DERIVED CHIRAL STATIONARY PHASES

The liquid chromatographic enantiomer separation of several amino acid methyl esters as 9-anthraldehyde Schiff base derivatives on coating and covalently bonded polysaccharide-derived chiral stationary phases (CSPs) is described. The 9-anthraldehyde imine derivatives of amino acid esters were readily prepared by stirring 9-anthraldehyde with the amino acid ester hydrochloride salts. The performance of Chiralcel OD among all examined CSPs was superior to that of the other CSPs for resolution of 9-anthraldimine derivatives of amino acid methyl esters. The enantiomers of all examined amino acid methyl esters as the 9-anthraldimine derivatives were base-line resolved on Chiralcel OD. The L-enantiomers of all analytes are preferentially retained on Chiralcel OD. The chromatographic methods developed in this study were applied in the determination of enantiomeric purity of some commercially available D- or L-amino acid methyl esters.

Development of liquid chromatographic enantiomer separation methods and validation for the estimation of ( R)-enantiomer in eslicarbazepine acetate

Chiral separation method development was carried out for eslicarbazepine acetate and its ( R)-enantiomer on diverse chiral stationary phases. Better chiral selectivity was observed on cellulose tris-(3,5-dichlorophenylcarbamate) immobilized column (Chiralpak IC-3). Under polar organic mode (POM), with 100% acetonitrile as mobile phase and 0.5 ml/min flow, a resolution close to three was achieved. With normal phase (NP) mobile phase consisting dichloromethane:ethanol (90:10, v/v) and 1.0 ml/min flow, a resolution close to six was achieved. Detection was done by UV at 220 and 240 nm respectively. Both the methods were found to be robust and were validated with respect to robustness, precision, linearity, limit of detection, limit of quantification and accuracy. The proposed methods are suitable for the accurate estimation of ( R)-enantiomer in bulk drug samples up to 0.1% when a 1 mg/ml analyte test solution is chromatographed.

HPLC‐method for determination of permethrin enantiomers using chiral β‐cyclodextrin‐based stationary phase

The liquid chromatographic separation of permethrin enantiomers on chiral beta-cyclodextrin-based stationary phase has been investigated. All four enantiomers are obtained by using simple methanol and water mobile phase, under gradient mode. The method was optimized and validated. The relationship between temperature and chromatographic parameters: k' (capacity factor), alpha (separation factor) and Rs (resolution factor) was studied. Van't Hoff's curves for each enantiomer were plotted for temperature range 288-318 K. It was noticed that the response factor ratio of permethrin isomers differ and calculated value is found to be 1.66 (cis/trans, for n = 5). This method has been used for determining permethrin enantiomer ratio for a few samples of working standards and one formulation.

다당유도체로 공유결합된 카이랄 칼럼에서 이동상과 분석물질의 용매가 거울상 이성질체의 광학분할에 미치는 영향

공유결합된 다당유도체에서 유도된 카이랄 칼럼인 Chiralpak IC을 사용하여 N-BOC <TEX>$\alpha$</TEX>-amino acid와 그들의 ethyl ester 유도체의 액체크로마토그래피 거울상 이성질체의 분리를 수행하였다. 다양 한 이동상에서 공유결합된 카이랄 칼럼인 Chiralpak IC에서 거울상 이성질체가 분리된 실험결과를 나 타내었으며, 광학분할의 선택성과 분리인자가 이동상에 따라 크게 영향을 받았다. 또한 동일한 이동 상에서 분석물질의 녹이는 용매에 따라 거울상 이성질체의 분리에 미치는 영향과 분석용 컬럼에서 거울상 이성질체의 분리의 여러 예를 나타내었다. Liquid chromatographic enantiomer separation of N-tert-butoxycarbonyl (BOC) <TEX>$\alpha$</TEX>-amino acids and their ethyl esters was performed on covalently immobilized chiral column (Chiralpak IC) derived from polysaccharide derivative. The solvent versatility of the covalently immobilized Chiralpak IC in enantiomer separation of N-BOC <TEX>$\alpha$</TEX>-amino acid ethyl ester derivatives was shown and the chromatographic parameters of their enantioselectivities and resolution factors were greatly influenced by the nature of the mobile phase. Also the effect on the dissolving solvent for these analytes on the enantiomer separation using the same mobile phase and the examples of preparative enantiomer separation on analytical column were shown.