High‐Performance Liquid Chromatographic Enantioseparation of Cyclic β‐Amino Acids on Zwitterionic Chiral Stationary Phases Based on Cinchona Alkaloids

Stereoselective high‐performance liquid chromatographic separations of eight sterically constrained cyclic β‐amino acid enantiomer pairs were carried out using the newly developed Cinchona alkaloid‐based zwitterionic chiral stationary phases Chiralpak ZWIX(+) and ZWIX(?). The effects of the mobile phase composition, the nature and concentrations of the acid and base additives, the counterions and temperature on the separations were investigated. The changes in standard enthalpy, Δ(ΔH°), entropy, Δ(ΔS°), and free energy, Δ(ΔG°), were calculated from the linear van't Hoff plots derived from the ln α vs. 1/T curves in the studied temperature range (10–50°C). The values of the thermodynamic parameters depended on the nature of the selectors and the structures of the analytes. Unusual temperature behavior was observed on the ZWIX(?) column: decreased retention times were accompanied by increased separation factors with increasing temperature. On the ZWIX(+) column only enthalpically, whereas on the ZWIX(?) column both enthalpically and entropically driven separations were observed. The elution sequence was determined in all cases and was observed to be the opposite on ZWIX(+) and on ZWIX(?). Chirality 27:563–570, 2015. © 2015 Wiley Periodicals, Inc.     

Enantiomeric Separation of Bicyclo[2.2.2]octane‐Based 2‐Amino‐3‐Carboxylic Acids on Macrocyclic Glycopeptide Chiral Stationary Phases

Direct high‐performance liquid chromatographic (HPLC) separation of four bicyclo[2.2.2]octane based 2‐amino‐3‐carboxylic acid enantiomers were developed on chiral stationary phases (CSPs) containing different macrocyclic glycopeptide antibiotic selectors. The analyses were performed under reversed‐phase, polar organic and polar ionic mode on macrocyclic‐glycopeptide‐based Chirobiotic T, T2, TAG, and R columns. The effects of the mobile phase composition including the acid and base modifier, the structure of the analytes, and the temperature on the separations were investigated. Experiments were achieved at constant mobile phase compositions on different stationary phases in the temperature range 5–40°C. Thermodynamic parameters were calculated from plots of ln k or ln α versus 1/T. It was recognized that the enantioseparations in reversed‐phase and polar organic mode were enthalpically driven, but under polar‐ionic conditions entropically driven enantioseparation was observed as well. Baseline separation and determination of elution sequence were achieved in all cases. Chirality 26:200–208, 2014. © 2014 Wiley Periodicals, Inc.     

Chromatographic profiles of tryptophan and kynurenine enantiomers derivatized with (S)‐4‐(3‐isothiocyanatopyrrolidin‐1‐yl)‐7‐(N,N‐dimethylaminosulfonyl)‐2,1,3‐benzoxadiazole using LC–MS/MS on a triazole‐bonded column

d ‐ and l ‐Tryptophan (Trp) and d ‐ and l ‐kynurenine (KYN) were derivatized with a chiral reagent, (S )‐4‐(3‐isothiocyanatopyrrolidin‐1‐yl)‐7‐(N,N‐dimethylaminosulfonyl)‐2,1,3‐benzoxadiazole (DBD‐PyNCS), and were separated enantiomerically by high‐performance liquid chromatography (HPLC) equipped with a triazole‐bonded column (Cosmosil HILIC) using tandem mass spectrometric (MS/MS) detection. Effects of column temperature, salt (HCO₂NH₄) concentration, and pH of the mobile phase in the enantiomeric separation, followed by MS detection of (S )‐DBD‐PyNCS‐d ,l ‐Trp and ‐d ,l ‐KYN, were investigated. The mobile phase consisting of CH₃CN/10 mM ammonium formate in H₂O (pH 5.0) (90/10) with a column temperature of 50–60 °C gave satisfactory resolution (R s) and mass‐spectrometric detection. The enantiomeric separation of d ,l ‐Trp and d ,l ‐KYN produced R s values of 2.22 and 2.13, and separation factors (α) of 1.08 and 1.08, for the Trp and KYN enantiomers, respectively. The proposed LC–MS/MS method provided excellent detection sensitivity of both enantiomers of Trp and KYN (5.1–19 nM).     

Quinine‐Based Zwitterionic Chiral Stationary Phase as a Complementary Tool for Peptide Analysis: Mobile Phase Effects on Enantio‐ and Stereoselectivity of Underivatized Oligopeptides

Peptide stereoisomer analysis is of importance for quality control of therapeutic peptides, the analysis of stereochemical integrity of bioactive peptides in food, and the elucidation of the stereochemistry of peptides from a natural chiral pool which often contains one or more D‐amino acid residues. In this work, a series of model peptide stereoisomers (enantiomers and diastereomers) were analyzed on a zwitterionic ion‐exchanger chiral stationary phase (Chiralpak ZWIX(+) 5 µm), in order to investigate the retention and separation performance for such compounds on this chiral stationary phase and elucidate its utility for this purpose. The goal of the study focused on 1) investigations of the effects of the sample matrix used to dissolve the peptide samples; 2) optimization of the mobile phase (enabling deriving information on factors of relevance for retention and separation); and 3) derivation of structure–selectivity relationships. It turned out that small di‐ and tripeptides can be well resolved under optimized conditions, typically with resolutions larger than 1.5. The optimized mobile phase often consisted of methanol–tetrahydrofuran–water (49:49:2; v/v/v) with 25 mM formic acid and 12.5 mM diethylamine. This work proposes some guidance on which mobile phases can be most efficiently used for peptide stereoisomer separations on Chiralpak ZWIX. Chirality 28:5–16, 2016. © 2015 Wiley Periodicals, Inc.     

Identification of N‐octylnortadalafil and its Stereoisomers in Dietary Supplements with Chiral Liquid Chromatography–Circular Dichroism

A direct chiral liquid chromatography–circular dichroism (LC‐CD) method was developed for the simple and rapid identification of N‐octylnortadalafil [(6R, 12aR)‐6‐(1,3‐benzodioxol‐5‐yl)‐2‐octyl‐2,3,6,7,12,12a‐hexahydropyrazino[1’,2’:1,6]pyrido[3,4‐b]indole‐1,4‐dione; RR‐OTDF] and its stereoisomers in dietary supplements. Samples were extracted with methanol. Compounds were then separated by chiral LC‐CD using Chiralcel OD‐RH (4.6 × 1 50 mm, 5 µm) with 5 mM ammonium formate (pH 3)/0.1% formic acid in acetonitrile (95:5, v/v) mixture solution (mobile phase A) and 0.1% formic acid in acetonitrile (mobile phase B). The isocratic elution used was mobile phase A / mobile phase B (3:7, v/v) at a flow rate of 1 ml/min. The column temperature was held at 30°C. RR‐OTDF and its stereoisomers were separated within 20 min with the resolution factors being over 2.0. Using this method, RR‐OTDF and (6R, 12aS)‐6‐(1,3‐benzodioxol‐5‐yl)‐2‐octyl‐2,3,6,7,12,12a‐hexahydropyrazino[1’,2’:1,6]pyrido[3,4‐b]indole‐1,4‐dione were detected in a dietary supplement. Chirality 28:204–208, 2016. © 2016 Wiley Periodicals, Inc.     

Liquid and subcritical fluid chromatographic enantioseparation of Nα‐Fmoc proteinogenic amino acids on Quinidine‐based zwitterionic and anion‐exchanger type chiral stationary phases. A comparative study

Stereoselective high‐performance liquid chromatographic and subcritical fluid chromatographic separations of 19 N^α‐Fmoc proteinogenic amino acid enantiomers were carried out by using Quinidine ‐based zwitterionic and anion‐exchanger‐type chiral stationary phases Chiralpak ZWIX(−) and QD‐AX. For optimization of retention and enantioselectivity, the ratio of bulk solvent components (MeOH/MeCN, H₂O/MeOH, or CO₂/MeOH) and the nature and concentration of the acid and base additives (counter‐ and co‐ions) were systematically varied. The effect of column temperature on the enantioseparation was investigated and thermodynamic parameters were calculated from the van't Hoff plots ln α vs. 1/T. The thermodynamic parameters revealed that the enantioseparations were enthalpy‐driven. The elution sequence was determined in all cases and with the exception of Fmoc‐Cys(Trt)‐OH, it was identical on both chiral stationary phases whereby the L‐enantiomers eluted before the D‐enantiomers.     

Enantioseparation of chiral pharmaceuticals by vancomycin‐bonded stationary phase and analysis of chiral recognition mechanism

The drug chirality is attracting increasing attention because of different biological activities, metabolic pathways, and toxicities of chiral enantiomers. The chiral separation has been a great challenge. Optimized high‐performance liquid chromatography (HPLC) methods based on vancomycin chiral stationary phase (CSP) were developed for the enantioseparation of propranolol, atenolol, metoprolol, venlafaxine, fluoxetine, and amlodipine. The retention and enantioseparation properties of these analytes were investigated in the variety of mobile phase additives, flow rate, and column temperature. As a result, the optimal chromatographic condition was achieved using methanol as a main mobile phase with triethylamine (TEA) and glacial acetic acid (HOAc) added as modifiers in a volume ratio of 0.01% at a flow rate of 0.3 mL/minute and at a column temperature of 5°C. The thermodynamic parameters (eg, ΔH, ΔΔH, and ΔΔS) from linear van 't Hoff plots revealed that the retention of investigated pharmaceuticals on vancomycin CSP was an exothermic process. The nonlinear behavior of lnk′ against 1/T for propranolol, atenolol, and metoprolol suggested the presence of multiple binding mechanisms for these analytes on CSP with variation of temperature. The simulated interaction processes between vancomycin and pharmaceutical enantiomers using molecular docking technique and binding energy calculations indicated that the calculated magnitudes of steady combination energy (ΔG) coincided with experimental elution order for most of these enantiomers.     

Chiral separation of aliphatic primary amino alcohols as o‐phthaldialdehyde/mercaptoethanol derivatives on polysaccharide‐based chiral stationary phases

A sensitive chiral high performance liquid chromatography (HPLC) method for the determination of aliphatic primary amino alcohol isomers with o‐phthaldialdehyde/mercaptoethanol precolumn derivatization has been developed and validated. Seven chiral columns were tested in a reversed phase mode. Excellent enantioseparation with the resolution more than 2.0 was achieved on Chiralcel OJ‐3R. The effect of various chromatographic conditions including column temperature, acetonitrile content in the mobile phase, buffer pH, buffer concentration, and buffer type in the mobile phase on the retention and the selectivity was investigated. The final mobile phase consisted of binary mixture of 20mM ammonium formate solution with acetonitrile (75:25; v/v). The analyses were performed at mobile phase flow rate of 1.0 mL/min and the column temperature of 40°C. The fluorescence detection was performed at excitation wavelength of 345 nm and emission wavelength of 450 nm. The developed method was fully validated in terms of linearity, sensitivity, accuracy, precision, intermediate precision, and selectivity according to International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use guidelines using internal normalization procedure. The proposed chiral method was proved to be highly sensitive, simple, and rapid and was successfully applied to the determination of D‐Valinol content in commercially available samples of L‐Valinol.     

Chiral HPLC Separation and Modeling of Four Stereomers of DL‐Leucine‐DL‐Tryptophan Dipeptide on Amylose Chiral Column

Chiral high‐performance liquid chromatography (HPLC) separation and modeling of four stereomers of DL‐leucine‐tryptophan DL‐dipeptide on AmyCoat‐RP column are described. The mobile phase applied was ammonium acetate (10 mM)‐methanol‐acetonitrile (50:5:45, v/v). The flow rate of the mobile phases was 0.8 mL/min with UV detection at 230 nm. The values of retention factors for LL‐, DD‐, DL‐, and LD‐ stereomers were 2.25, 3.60, 5.00, and 6.50, respectively. The values of separation and resolution factors were 1.60, 1.39, and 1.30 and 7.76, 8.05, and 7.19. The limits of detection and quantitation were ranging from 1.0–2.3 and 5.6–14.0 μg/mL. The simulation studies established the elution orders and the mechanism of chiral recognition. It was seen that π–π connections and hydrogen bondings were the main forces for enantiomeric resolution. The reported chiral HPLC method may be applied for the enantiomeric separation of DL‐leucine‐DL‐tryptophan in unknown matrices. Chirality 28:642–648, 2016. © 2016 Wiley Periodicals, Inc.     

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 1.2 mL/min. The limit of detection and limit of quantification of the S‐enantiomer were found to be 0.45 and 1.5 μg/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     

Enantiospecific Analysis of 8‐Prenylnaringenin in Biological Fluids by Liquid‐Chromatography‐Electrospray Ionization Mass Spectrometry: Application to Preclinical Pharmacokinetic Investigations

8‐Prenylnaringenin (8PN) is a naturally occurring bioactive chiral prenylflavonoid found most commonly in the female flowers of hops (Humulus lupulus L.). A stereospecific method of analysis for 8PN in biological fluids is necessary to study the pharmacokinetic disposition of each enantiomer. A novel and simple liquid chromatographic‐electrospray ionization‐mass spectrometry (LC‐ESI‐MS) method was developed for the simultaneous determination of R‐ and S‐8PN in rat serum and urine. Carbamazepine was used as the internal standard (IS). Enantiomeric resolution of 8PN was achieved on a Chiralpak^® AD‐RH column with an isocratic mobile phase consisting of 2‐propanol and 10 mM ammonium formate (pH 8.5) (40:60, v/v) and a flow rate of 0.7 mL/min. Detection was achieved using negative selective ion monitoring (SIM) of 8PN at m/z 339.15 for both enantiomers and positive SIM m/z at 237.15 for the IS. The calibration curves for urine were linear over a range of 0.01–75 µg/mL and 0.05–75 µg/mL for serum with a limit of quantification of 0.05 µg/mL in serum and 0.01 µg/mL in urine. The method was successfully validated showing that it was sensitive, reproducible, and accurate for enantiospecific quantification of 8PN in biological matrices. The assay was successfully applied to a preliminary study of 8PN enantiomers in rat. Chirality 26:419–426, 2014. © 2014 Wiley Periodicals, Inc.     

Liquid chromatographic direct resolution of flecainide and its analogs on a chiral stationary phase based on (+)‐(18‐crown‐6)‐2,3,11,12‐tetracarboxylic acid

Flecainide, an antiarrythmic agent, and its analogs were resolved on a high performance liquid chromatographic chiral stationary phase (CSP) based on (+)‐(18‐crown‐6)‐2,3,11,12‐tetracarboxylic acid with the use of a mobile phase consisting of methanol‐acetonitrile‐trifluoroacetic acid‐triethylamine (80/20/0.1/0.3, v/v/v/v). The chiral resolution was quite successful, the separation factors (α) and the resolutions (R_S) for 20 analytes including flecainide being in the range of 1.19–1.82 and 1.73–6.80, respectively. The ortho‐substituent of the benzoyl group of analytes was found to cause decrease in the retention times of analytes probably because of the conformational deformation of analytes originated from the steric hindrance exerted by the ortho‐substituent. Chirality, 2010. © 2009 Wiley‐Liss, Inc.     

Enantiomeric separation of type I and type II pyrethroid insecticides with different chiral stationary phases by reversed‐phase high‐performance liquid chromatography

The enantiomeric separation of type I (bifenthrin, BF) and type II (lambda‐cyhalothrin, LCT) pyrethroid insecticides on Lux Cellulose‐1, Lux Cellulose‐3, and Chiralpak IC chiral columns was investigated by reversed‐phase high‐performance liquid chromatography. Methanol/water or acetonitrile/water was used as mobile phase at a flow rate of 0.8 mL/min. The effects of chiral stationary phase, mobile phase composition, column temperature, and thermodynamic parameters on enantiomer separation were carefully studied. Bifenthrin got a partial separation on Lux Cellulose‐1 column and baseline separation on Lux Cellulose‐3 column, while LCT enantiomers could be completely separated on both Lux Cellulose‐1 and Lux Cellulose‐3 columns. Chiralpak IC provided no separation ability for both BF and LCT. Retention factor (k) and selectivity factor (α) decreased with the column temperature increasing from 10°C to 40°C for both BF and LCT enantiomers. Thermodynamic parameters including ?H and ?S were also calculated, and the maximum R_s were not always obtained at lowest temperature. Furthermore, the quantitative analysis methods for BF and LCT enantiomers in soil and water were also established. Such results provide a new approach for pyrethroid separation under reversed‐phase condition and contribute to environmental risk assessment of pyrethroids at enantiomer level.     

HPLC‐PDA‐ORD Bioassay of S‐(+) and R‐(−) Clopidogrel on Rat Dried Blood Spots

A simple and rapid chiral high‐performance liquid chromatography (HPLC) method was developed and validated for bioanalysis of clopidogrel enantiomers on rat dried blood spots (DBS). Clopidogrel enantiomers were extracted from DBS using ethanol: methanol (80:20, v/v) and separated on a Chiralcel OJ‐H column containing cellulose tris (4‐methly benzoate) as a polysaccharide stationary phase using n‐hexane–ethanol‐diethylamine (70:30, 0.1 v/v) as a mobile phase at a flow rate of 1.0 mL/min. The detection was carried out at 220 nm using a photodiode array (PDA) detector while the elution order of the enantiomers was determined by a polarimeter connected to PDA in series. The effect of hematocrit on extraction of clopidogrel enantiomers from DBS was evaluated and no interference from endogenous substances was noticed. The overall accuracy of (R) and (S) enantiomers of clopidogrel from DBS were 91.6 and 89.2%, respectively. The calibration curves were linear over the concentration range of 1–500 µg/mL for both enantiomers. The results show that the method is specific, precise, and reproducible (intra‐ and interday precision relative standard deviations (RSDs) <10.0%). The stability of racemic clopidogrel was performed under all storage conditions and the results were found to be well within the acceptance limits. Chirality 26:102–107, 2014.© 2014 Wiley Periodicals, Inc.     

Enantiomeric separation of triazole fungicides with 3-μm and 5-μml particle chiral columns by reverse-phase high-performance liquid chromatography

This study used chiral columns packed with 3‐μm and 5‐μm particles to comparatively separate enantiomers of 9 triazole fungicides, and Lux Cellulose‐1 columns with chiral stationary phase of cellulose‐tris‐(3,5‐dimethylphenylcarbamate) were used on reverse‐phase high‐performance liquid chromatography with flow rates of 0.3 and 1.0 mL min⁻¹ for 3‐μm and 5‐μm columns, respectively. The (+)‐enantiomers of hexaconazole ( 1 ) , tetraconazole ( 4 ) , myclobutanil ( 7 ) , fenbuconazole ( 8 ) and the (−)‐enantiomers of flutriafol ( 2 ) diniconazole ( 3 ) , epoxiconazole ( 5 ) , penconazole ( 6 ) , triadimefon ( 9 ) were firstly eluted from both columns, the elution orders identified with an optical rotation detector didn't change with variety of column particles and mobile phases (acetronitrile/water and methanol/water). The plots of natural logarithms of the selectivity factors (ln α) for all fungicides except penconazole ( 6 ) versus the inverse of temperature (1/T) were linear in range of 5–40°C. The thermodynamic parameters (ΔH°, ΔS°, ΔΔH° and ΔΔS°) were calculated using Van't Hoff equations to understand the thermosynamic driving forces for enantioseparation. This work will be very helpful to obtain good enantiomeric separation and establish more efficient analytical method for triazole fungicides. Chirality, 2011. © 2011 Wiley‐Liss, Inc.     

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

The liquid chromatographic separation of permethrin enantiomers on chiral β‐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), α (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. Chirality 2010. © 2009 Wiley‐Liss, Inc.     

A validated enantiospecific method for determination and purity assay of clopridogrel

A new and accurate HPLC method using β‐cyclodextrin chemically bonded to spherical silica particles as chiral stationary phase (CSP) was developed and validated for determination of S‐clopidogrel and its impurities R‐enantiomer and S‐acid as a hydrolytic product. The effects of acetonitrile and methanol content in the mobile phase and temperature on the resolution and retention of enantiomers were investigated. A satisfactory resolution of S‐clopidogrel active form and its impurities was achieved on ChiraDex® column (5 μm, 4 × 250 mm) at a flow rate of 1.0 ml/min and 17°C using acetonitrile, methanol and 0.01 M potassium dihydrogen phosphate solution (15:5:80 v/v/v) as mobile phase. The detection wavelength was set at 220 nm. The method was validated in terms of accuracy, precision, linearity, and robustness. The limit of detection for R‐enantiomer and S‐acid were 0.75 and 0.09 μg/ml, respectively, injection volume being 20 μl. Finally, the molecular modeling of the inclusion complexes between the analytes and β‐cyclodextrin was performed to investigate the mechanism of the enantiorecognition and to study the quantitative structure–retention relationships. Chirality, 2009. © 2008 Wiley‐Liss, Inc.     

Enantiomeric Recognition of Racemic 4‐Aryl‐1,4‐dihydropyridine Derivatives via Chiralpak AD‐H Stationary Phases

The chromatographic chiral resolution of two new series of racemic 4‐substituted‐1,4‐dihydropyridine derivatives was studied on a commercial Chiralpak AD‐H column. Analytes without 5,5‐dimethyl substituents ( 1–15 ) are more efficiently resolved than analytes with 5,5‐dimethyl groups ( 16–30 ). The AD‐H column discriminated between enantiomers through both hydrogen bonding attractions and π–π interactions. This interpretation is in accord with plots of the logarithm of separation factors, log(α), versus σ (Hammett–Swain substituent parameter) and σ⁺ (Brown substituent constant) plots. By elucidating the effects of the remote substituents on these chiral separations, it was shown that the influence of π–π interaction forces increase when steric bulk effects act to decrease the hydrogen bonding attractive forces on the AD‐H column. Chirality 24:854–859, 2012. © 2012 Wiley Periodicals, Inc.     

Direct Enantioseparation of Nitrogen‐heterocyclic Pesticides on Amylose‐tris‐(5‐chloro‐2‐methylphenylcarbamate) by Reversed‐Phase High‐Performance Liquid Chromatography

In this study, 11 nitrogen‐heterocyclic pesticides were stereoselectively separated on amylose‐tris‐(5‐chloro‐2‐methylphenylcarbamate) chiral stationary phase, using reversed‐phase high‐performance liquid chromatography with diode array detector and optical rotation detector at 426 nm. The effects of mobile phase composition and column temperature (5–40 °C) on separation were investigated. When acetonitrile and water were used as mobile phase, satisfactory separations were obtained on amylose‐tris‐(5‐chloro‐2‐methylphenylcarbamate) for four pesticides with elution orders of (+)/(?)‐simeconazole (1) , (?)/(+)‐nuarimol (3) , (?)/(+)‐carfentrazone‐ethyl (4) , and (?)/(+)/(?)/(+)‐bromuconazole (9) and part separations for three with elution orders of (?)/(+)‐famoxadone (6) , (+)/(?)‐fenbuconazole (10) , and (?)/(+)‐triapenthenol (11) . Only two chromatographic peaks on diode array detector were obtained for diclobutrazol (2) , cyproconazole (5) , etaconazole (7) , and metconazole (8) , although they should have four stereoisomers in theory because of presences of two chiral centers in molecules. The stereoisomeric optical signals of all pesticides did not reverse with temperature changes but would reverse with different solvent types for some pesticides. These results will be useful to prepare and analyze individual enantiomers of chiral pesticides. Chirality 24:1031–1036, 2012. © 2012 Wiley Periodicals, Inc.     

A 3D Homochiral MOF [Cd2(d‐cam)3]•2Hdma•4dma for HPLC Chromatographic Enantioseparation

Up to now, some chiral metal‐organic frameworks (MOFs) have been reported for enantioseparation in liquid chromatography. Here we report a homochiral MOF, [Cd2(d‐cam)3]·2Hdma·4dma, used as a new chiral stationary phase for high‐performance liquid chromatographic enantioseparation. Nine racemates of alcohol, naphthol, ketone, and base compounds were used as analytes for evaluating the separation properties of the chiral MOF packed column. Moreover, some effects such as mobile phase composition, column temperature, and analytes mass for separations on this chiral column also were investigated. The relative standard deviations for the resolution values of run‐to‐run and column‐to‐column were less than 2.1% and 3.2%, respectively. The experimental results indicate that the homochiral MOF offered good recognition ability, which promotes the application of chiral MOFs use as stationary phase for enantioseparation. Chirality 28:340–346, 2016. © 2016 Wiley Periodicals, Inc.