Complex formation and enantioselectivity studies of triazole fungicide and organophosphorus pesticide enantiomers using capillary electrophoresis

Several cyclodextrin modified-micellar electrokinetic chromatography (CDMEKC) methods were developed for the successful triazole fungicides separation. In the first part, an efficient method was developed for the simultaneous enantioseparation of cyproconazole (4 stereoisomer), bromuconazole (4 stereoisomer) and diniconazole (2 stereisomer) enantiomers using CD-MEKC with a dual mixture of neutral cyclodextrins as chiral selector. The best simultaneous separation of cyproconazole, bromuconazole, and diniconazole enantiomers was achieved with a mixture of 27 mM HP-β-CD and 3 mM HP-γ-CD in 25 mM phosphate buffer (pH 3.0) containing 40 mM sodium dodecyl sulfate (SDS) and 15% iso-propanol as organic modifier. Complete separation of 10 stereoisomer of triazole fungicides were obtained in a single run with good resolution (Rs 1.74“26.31) and high peak efficiency (N > 400 000). In the second part of the study, enantioseparation of hexaconazole, penconazole, myclobutanil, and triadimefon was investigated. Simultaneous enantioseparation of penconazole, myclobutanil, and triadimefon was achieved under acidic condition (pH 3.0) using 25 mM phosphate buffer, 50 mM SDS, and 30 mM HP-γ-CD, with Rs greater than 0.9 whereas, simultaneous enantioseparation of hexaconazole, penconazole, and myclobutanil was successfully achieved under neutral condition (pH 7.0) using 25 mM phosphate buffer, 40 mM SDS, and 40 mM HP-γ-CD, with Rs greater than1.6. In order to improve detection sensitivity, on-line preconcentration technique was investigated. It was found that sweeping technique as an on-line preconcentration technique improved the detection sensitivity of the enantioseparation of cyproconazole, bromuconazole, and diniconazole by 30 to 60-fold, with good repeatabilities in the migration time, peak area and peak height were obtained with RSDs in the range of 0.08“0.32%, 0.03“ 2.44%, and 2.13“8.44% respectively. Furthermore, sweeping technique improved the detection sensitivity of the enantioseparation of hexaconazole, penconazole and myclobutanil by 62- to 67-fold. Good repeatabilities in the migration time, peak area and peak height were obtained with RSDs in the range of 2.39“3.90%, 1.96€“6.15%, and 2.80“6.64% respectively. Finally, the formation constant of diniconazole enantiomers with HP-γ-CD under neutral and acidic condition was investigated using CD-MEKC

Photografted methacrylate-based monolithic columns coated with cellulose tris(3,5-dimethylphenylcarbamate) for chiral separation in CEC

A chiral capillary monolithic column for enantiomer separation in capillary electrochromatography was prepared by coating cellulose tris(3,5-dimethylphenylcarbamate) on porous glycidyl methacrylate-co-ethylene dimethacrylate monolith in capillary format grafted with chains of [2(methacryloyloxy)ethyl] trimethylammonium chloride. The surface modification of the monolith by the photografting of [2(methacryloyloxy)ethyl] trimethylammonium chloride monomer as well as the coating conditions of cellulose tris(3,5-dimethylphenylcarbamate) onto the grafted monolithic scaffold were optimized to obtain a stable and reproducible chiral stationary phase for capillary electrochromatography. The effect of organic modifier (acetonitrile) in aqueous mobile phase for the enantiomer separation by capillary electrochromatography was also investigated. Several pairs of enantiomers including acidic, neutral, and basic analytes were tested and most of them were partially or completely resolved under aqueous mobile phases. The prepared monolithic chiral stationary phases exhibited a good stability, repeatability, and column-to-column reproducibility, with relative standard deviations below 11% in the studied electrochromatographic parameters.Fil: Echevarria, Romina Noel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Exactas; ArgentinaFil: Carrasco Correa, Enrique Javier. Universidad de Valencia; EspañaFil: Keunchkarian, Sonia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Exactas; ArgentinaFil: Reta, Mario Roberto. Universidad Nacional de La Plata. Facultad de Ciencias Exactas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Herrero Martinez, José Manuel. Universidad de Valencia; Españ

The way to ultrafast, high-throughput enantioseparations of bioactive compounds in liquid and supercritical fluid chromatography

Until less than 10 years ago, chiral separations were carried out with columns packed with 5 or 3 μm fully porous particles (FPPs). Times to resolve enantiomeric mixtures were easily larger than 30 min, or so. Pushed especially by stringent requirements from medicinal and pharmaceutical industries, during the last years the field of chiral separations by liquid chromatography has undergone what can be defined a “true revolution”. With the purpose of developing ever faster and efficient method of separations, indeed, very efficient particle formats, such as superficially porous particles (SPPs) or sub-2 μm FPPs, have been functionalized with chiral selectors and employed in ultrafast applications. Thanks to the use of short column (1–2 cm long), packed with these extremely efficient chiral stationary phases (CSPs), operated at very high flow rates (5–8 mL/min), resolution of racemates could be accomplished in very short time, in many cases less than 1 s in normal-, reversed-phase and HILIC conditions. These CSPs have been found to be particularly promising also to carry out high-throughput separations under supercritical fluid chromatography (SFC) conditions. The most important results that have been recently achieved in terms of ultrafast, high-throughput enantioseparations both in liquid and supercritical fluid chromatography with particular attention to the very important field of bioactive chiral compounds will be reviewed in this manuscript. Attention will be focused not only on the latest introduced CSPs and their applications, but also on instrumental modifications which are required in some cases in order to fully exploit the intrinsic potential of new generation chiral columns

Towards an expert system for enantioseparations: induction of rules using machine learning

A commercially available machine induction tool was used in an attempt to automate the acquisition of the knowledge needed for an expert system for enantioseparations by High Performance Liquid Chromatography using Pirkle-type chiral stationary phases (CSPs). Various rule-sets were induced that recommended particular CSP chiral selectors based on the structural features of an enantiomer pair. The results suggest that the accuracy of the optimal rule-set is 63% + or - 3% which is more than ten times greater than the accuracy that would have resulted from a random choice

Determination of Enantiomeric Compositions of Analytes Using Novel Fluorescent Chiral Molecular Micelles and Steady State Fluorescence Measurements

Novel fluorescent chiral molecular micelles (FCMMs) were synthesized, characterized, and employed as chiral selectors for enantiomeric recognition of non-fluorescent chiral molecules using steady state fluorescence spectroscopy. The sensitivity of the fluorescence technique allowed for investigation of low concentrations of chiral selector (3.0 x 10(-5) M) and analyte (5.0 x 10(-6) M) to be used in these studies. The chiral interactions of glucose, tartaric acid, and serine in the presence of FCMMs poly(sodium N-undecanoyl-L-tryptophanate) [poly-L-SUW], poly(sodium N-undecanoyl-L-tyrosinate) [poly-L-SUY], and poly(sodium N-undecanoyl-L-phenylalininate) [poly-SUF] were based on diastereomeric complex formation. Poly-L-SUW had a significant fluorescence emission spectral difference as compared to poly-L-SUY and poly-L-SUF for the enantiomeric recognition of glucose, tartaric acid, and serine. Studies with the hydrophobic molecule alpha-pinene suggested that poly-L-SUY and poly-L-SUF had better chiral discrimination ability for hydrophobic analytes as compared to hydrophilic analytes. Partial-least-squares regression modeling (PLS-1) was used to correlate changes in the fluorescence emission spectra of poly-L-SUW due to varying enantiomeric compositions of glucose, tartaric acid, and serine for a set of calibration samples. Validation of the calibration regression models was determined by use of a set of independently prepared samples of the same concentration of chiral selector and analyte with varying enantiomeric composition. Prediction ability was evaluated by use of the root-mean-square percent relative error (RMS%RE) and was found to range from 2.04 to 4.06%

Development of an in-capillary derivatization method by CE for the determination of chiral amino acids in dietary supplements and wines

A fast in-capillary derivatization method by CE with 6-aminoquinolyl-N-hydroxysuccinimidyl\ud carbamate was developed for the first time for the determination of\ud amino acid enantiomers (arginine, lysine, and ornithine) in dietary supplements and\ud wines. Because of the initial current problems due to the formation of precipitates into\ud the capillary during the derivatization reaction, a washing step with an organic solvent as\ud DMSO between injections was necessary. Different approaches were also investigated to\ud enhance the sensitivity of detection. A derivatization procedure, where plugs of ACN,\ud derivatizing agent (10mM 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate), and\ud sample in borate (1:1 v/v) were injected in tandem (2, 3, and 6 s, respectively, at 50 mbar),\ud was selected because it enabled to obtain the most sensitive and reproducible results.\ud Appropriate analytical characteristics (linearity, LOD and LOQ, precision, absence of\ud matrix interferences, and accuracy) were obtained for this method. Finally, the optimized\ud method was successfully applied to the determination of the enantiomers of arginine,\ud lysine, and ornithine in food samples of different complexities (dietary supplements and\ud wines).The authors thank the Ministry of Education and Science (Spain) and the Comunidad Autónoma de Madrid (Spain) for research projects CTQ2006-03849/BQU and S-0505/AGR- 0312, respectively. Carmen Garcı´a-Ruiz thanks the Ministry of Science and Technology (Spain) for the Ramon y Cajal program (RYC-2003-001). A.B.M.-G. thanks the University of Alcala for her pre-doctoral contract

Aminosavak és peptidek folyadékkromatográfiája. Királis elválasztások. = Chromatography of amino acids and peptides. Chiral separations.

Munkánk során nagyhatékonyságú folyadékkromatográfiás és kapilláris elektroforetikus módszereket fejlesztettünk különböző biológiai és gyógyszeripari szempontból fontos vegyületek (elsősorban ?-, ß- és ?-aminosavak, ß-laktámok, naftol analógok és opioid peptidek) sztereoizomerjeinek elválasztására. Vizsgáltuk a mozgófázis összetételének és hőmérsékletének, illetve különféle királis szelektorok hatását a kromatográfiás viselkedésre. Tanulmányoztuk különböző új fejlesztésű királis kolonnák elválasztóképességét, illetve vizsgáltuk a különféle királis szelektorok és a modellmolekulák közötti kölcsönhatásokat. A hőmérsékletfüggésből nyert termodinamikai adatok és a kémiai szerkezettől való függés alapján következtetést vontunk le az elválasztás mechanizmusára vonatkozóan. Feltérképeztük a molekulaszerkezet és kromatográfiás viselkedés között fennálló kapcsolatokat. Eredményeinket rangos nemzetközi folyóiratokban publikáltuk. | The goal of the present project was to develop new chromatographic and electrophoretic methods for the analysis of the stereoisomers of biologically and/or pharmaceutically important compounds (e.g. ?-, ß- and ?-amino acids, ß-lactams, naphthol analogs and opioid peptides). The effects of the mobile phase composition, temperature, and different chiral selectors on the retention have been studied. The separation efficiency of newly developed chiral stationary phases and interactions between chiral selectors and model compounds have been investigated. By variation of the chromatographic parameters, the separation of the stereoisomers has been optimized. Mechanistic aspects of the chiral recognition process have been studied with respect to the structures of the analytes. Based on variable-temperature studies it could be concluded that the enantioseparations were in most cases enthalpy-driven but entropy-driven separation was also observed. Results have been published in international journals and conferences