高效液相色谱法对二氢吡喃酮衍生物的手性拆分

介绍了利用手性chiralcel OD和chiralpak AD柱在高效液相色谱上对一系列二氢吡喃酮衍生物进行手性拆分，获得了良好的分离结果，考察了部分对映体在这两种柱上的色谱行为。实验表明手性化合物与手性柱之间存在着化学作用与空间作用，两者的共同作用决定了分离结果。     

Simultaneous enantioselective determination of six pesticides in aqueous environmental samples by chiral liquid chromatography with tandem mass spectrometry

A robust and sensitive method was developed for the enantiomeric analysis of six chiral pesticides (including metalaxyl, epoxiconazole, myclobutanil, hexaconazole, napropamide, and isocarbophos) in aquatic environmental samples. The optimized chromatographic conditions for the quantification of all the 12 enantiomers were performed with Chiralcel OD‐RH column using mobile phase consisting of 0.1% aqueous formic acid and acetonitrile operated under reversed‐phase conditions and then analyzed using liquid chromatography with tandem mass spectrometry. Twelve enantiomers were detected in multiple reaction monitoring mode. Solid‐phase extraction and dispersive liquid–liquid microextraction were employed in this study. Response surface methodology was applied to assist in the dispersive liquid–liquid microextraction optimization. Under the optimum conditions, recoveries of pesticides enantiomers varied from 83.0 to 103.2% at two spiked levels with relative standard deviation less than 11.5%. The concentration factors were up to 1000 times. Method detection and quantification limits varied from 0.11 to 0.48 ng/L and from 0.46 to 1.49 ng/L, respectively. Finally, this method was used to determination of the enantiomers composition of the six pesticides in environmental aqueous matrices, which will help better understand the behavior of individual enantiomer and make accurate risk assessment to ecosystems.     

Spectrophotometric Determination of Thyroxine Sodium with p-Benzoquinone

Abstract

A simple, sensitive and selective spectrophotometric method has been developed for the determination of thyroxine sodium. It is based on a reaction with excess of p-benzoquinone in ethanol (95%) whereby 1:1 (thyroxine sodium: quinone) coloured product is obtained, which has an apparent molar absorptivity of 2.911 × 10₃ 1mol_?1 and Beer's law is obeyed over the range of 40–200 μg.ml_?1. When applied to tablets labelled to contain 100 μg, the proposed method gave mean recoveries of 99,13 ± 0.36% for different amounts of added authentic drug.     

Computation of molecular parity violation using the coupled-cluster linear response approach

In memoriam, Nicholas C. Handy.

We report the implementation of a coupled-cluster linear response approach for the computation of molecular parity violation (in the framework of the PSI3 code, in particular). The approach is applied first to molecules such as hydrogen peroxide (HOOH), hydrogen disulfide (HSSH) and dichlorinedioxide (ClOOCl), which have been studied previously. The importance of including correlation is demonstrated for these examples, also including selected variations of geometry providing parity violation as a function of torsional angles. For the substituted allenes, 1,3 difluoroallene (CHF=C=CHF), 1,fluoro,3 chloroallene (CHF=C=CHCl) and 1,3 dichloroallene (CHCl=C=CHCl), we find that in particular the last molecule may be a suitable candidate for the experimental study of molecular parity violation.     

NMR study of localization and mobility of 1‐phenylethanol enantiomers in homochiral metal‐organic sorbent Zn2(bdc)(S‐lac)(dmf)

Structural features of localization of chiral isomers of 1‐phenylethanol (R‐PhEtOH and S‐PhEtOH) and their mobility activation in homochiral metal‐organic [Zn₂(bdc)(S‐lac)(dmf)] sorbent were studied with ¹H and ¹³C NMR methods. ¹³C NMR chemical shifts do not show obvious advantage of selective interaction of molecule guests. But activation molecular mobility of S‐PhEtOH and R‐PhEtOH clearly indicates that stabilization of [Zn₂(bdc)(S‐lac)(dmf)]·S‐PhEtOH structure is more preferable than stabilization of [Zn₂(bdc)(S‐lac)(dmf)]·R‐PhEtOH structure. Copyright © 2015 John Wiley & Sons, Ltd.     

A new example of reversal of the order of migration of enantiomers, as a function of cyclodextrin concentration and pH, by cyclodextrin-modified capillary zone electrophoresis: enantioseparation of 6,6′-dibromo-1,1′-binaphthyl-2,2′-diol

Enantioseparation of 6,6′-dibromo-1,1′-binaphthyl-2,2′-diol (DBBD) by cyclodextrin-modified capillary zone electrophoresis (CD-CZE) was studied using the three native α, β, and γ cyclodextrins, the three hydroxypropylated cyclodextrins (2-hydroxypropyl-α, β, and γ), heptakis-2,6-di-O-methyl-β-CD (DM-β-CD), and heptakis-2,3,6-tri-O-methyl-β-cyclodextrin (TM-β-CD). First, the acidity constants of DBBD were determined using capillary electrophoresis, before performing enantioseparation. The influence of the concentrations of the studied cyclodextrins on the enantioseparation was explored and the experimental optimal concentrations were determined and compared to the theoretical optimal concentrations. Moreover, the apparent complexation constants between each studied cyclodextrin and the two DBBD enantiomers were evaluated using a non-linear curve fitting method and three linear plotting methods (x-reciprocal, y-reciprocal and double reciprocal). For TM-β-CD, the order of migration of the enantiomers of DBBD reversed as a function of TM-β-CD concentration. The influence of the nature of methylated cyclodextrin derivatives (methyl-β-CD (M-β-CD) and DM-β-CD) was then studied. Inversion of the order of migration of the enantiomers of DBBD was observed for DM-β-CD, whereas the S enantiomer of DBBD always migrated first for M-β-CD.     

Capillary electrophoresis and column chromatography in biomedical chiral amino acid analysis

Free amino acids are typically quantified as the sum of their enantiomers, because in terrestrial organisms they mainly exist in the left-handed form. However, with increasing understanding of the biological significance of right-handed amino acids interest in enantioselective quantification of amino acids has steadily increased. Initially, electrophoretic and chromatographic methods using chiral (pseudo)-stationary phases or chiral eluents were applied to the separation of amino acid enantiomers. Later, derivatization of amino acids prior to chromatography with chiral reagents gained in popularity, because the diastereomers formed can be resolved on conventional reversed-phase columns. Novel multi-interaction chiral columns turned attention back to direct chiral chromatographic methods. Hyphenation to mass spectrometry has increasingly replaced optical detection because of superior selectivity, although this has not obviated the need for baseline resolution of amino acid enantiomers. Despite the progress made, enantioselective separation and quantification of amino acids remains an analytical challenge owing to frequently incomplete resolution of all naturally occurring enantiomers and insufficient sensitivity for the determination of the trace amounts of d-amino acids typically found in biological fluids and tissues. Chiral GC-MS analysis of heptafluorobutanol/pentafluoropropionanhydride amino acid derivatives on an Rt-gDEXsa column     

Analysis of enantiomers in biological matrices by charged cyclodextrin-mediated capillary zone electrophoresis in column-coupling arrangement with capillary isotachophoresis

The possibility to apply charged chiral selector as buffer additive in capillary zone electrophoresis (CZE) on-line coupled with capillary isotachophoresis (CITP) was studied. Enantioseparations and determinations of trace (ng/ml) antihistaminic drugs [pheniramine (PHM), dimethindene (DIM), dioxopromethazine (DIO)] present in samples of complex ionic matrices (urine) served as model examples. A negatively charged carboxyethyl-β-cyclodextrin (CE-β-CD) was used as a chiral selector in analytical CZE stage following upon a sample pretreatment by CITP (preconcentration of the analytes from 5 to 20-times diluted urine samples, partial sample clean up removing macroconstituents from the sample matrices). A high recognition capability of the oppositely charged CE-β-CD was demonstrated by enantioselective retardation of the drugs in presence of micro-and semi-macroconstituents migrating in CZE stage and detectable by UV detector. In this way, enantiomers of the drugs could be easily separated and determined. Due to lack of interferences between the drugs and sample-matrix constituents in presence of charged CE-β-CD, demands on both spacers in CITP step and multiple column-switching were minimized. CITP-CZE method with charged selector appeared to be a useful analytical approach for the trace enantiomers in complex ionic matrices as it combined enhanced separation selectivity and sample loadabitlity with high separation efficiency and provided favorable performance parameters including sensitivity, linearity, precision, accuracy/recovery and robustness with minimal demands on sample preparation. Analysis of urine sample taken from a patient treated by PHM, showing concentration profile of PHM enantiomers and their metabolites, illustrated potentialities of the method in clinical research.     

Simultaneous separation of five fluoroquinolone antibiotics by capillary zone electrophoresis

A chiral separation method for glycidol enantiomers determination by normal-phase high-performance liquid chromatography coupled to atmospheric pressure chemical ionization mass spectrometry was developed. Two chiral stationary phases, amylose tris-(3,5-dimethylphenylcarbamate) (Chiralpak AD-H) and (S)-indoline-2-carboxylic acid and (R)-1-(α-naphthyl) ethylamine (SUMICHIRAL OA-4900) have been investigated. The effects of the mobile phase composition, elution program and column temperature were also studied. Under the best conditions: Chiralpak AD-H column, mobile phase composition n-hexane:ethanol (70:30, v/v), flow rate of 0.8 mL/min and 40 °C column temperature, a good resolution (Rs = 1.6) for both enantiomers has been achieved with an analysis time of 16 min. The method was found to be linear in the range from 100 to 500 ppm for both glycidol enantiomers with a good determination coefficient (r² higher than 0.99) and good precision. Limits of detection of 31 and 50 ppm for (R)-(+)-glycidol and (S)-(−)-glycidol, respectively, were obtained. The method was applied to the determination of the enantiomeric excess and yield obtained in a asymmetric epoxidation process of allyl alcohol with a chiral titanium-tartrate complex as catalyst.     

茚虫威对映体分离及手性拆分热力学研究

在纤维素-三-(3,5-二甲基苯基氨基甲酸酯)(Chiralcel OD-H)手性柱上对茚虫威对映体的分离进行了研究。考察了流动相中改性剂种类和浓度、流速及柱温对分离效果的影响,并对茚虫威对映体与固定相之间保留和分离的热力学机理进行了讨论。结果表明,以正己烷-异丙醇(85∶15)为流动相,柱温为25℃,流速1.0 mL.min-1时,茚虫威对映体能获得基线分离,分离因子(α)和分离度(Rs)分别为1.50和3.49;分别以5种体积分数均为15%的醇改性正己烷,分离因子的变化顺序为:异丁醇异丙醇乙醇正丁醇正丙醇,正丙醇的分离因子为1.67,证明醇的极性和空间位阻同时影响拆分效果;在0.4~1.1 mL.min-1的流速范围内,分离度(Rs)随着流速的增大而逐渐减小;当柱温为15~35℃时,分离因子随着温度的升高呈降低趋势,两对映体的lnα与1/T呈良好的线性关系,手性拆分过程受焓的控制。