In this study, the apparent binding constants and limiting mobilities of the multiply charged complexes of the Δ- and Λ-enantiomers of Ru(II)- and Fe(II)-polypyridyl associates ([Ru(2,2'-bipyridine)3 ]2+ , [Ru(1,10-phenanthroline)3 ]2+ , and [Fe(1,10-phenanthroline)3 ]2+ ) with single-isomer 2,3-diacetylated-6-sulfated-cyclodextrins (CDs) (12Ac-6S-α-CD, 14Ac-7S-β-CD, and 16Ac-8S-γ-CD) were determined by ACE using uncorrected and ionic strength corrected actual mobilities of the species involved. Two limiting models were tested for the ionic strength correction of the actual mobilities based on an empirical relation for the ionic strength correction of multivalent ionic species. In model 1, the nominal values of the charge numbers (zS,nom ) and analytical concentrations (cS,nom ) of the above CD selectors in the BGEs were applied for calculation of the BGE ionic strength, as usual. In model 2, the CD selectors were considered as singly charged species (zS = -1) with |zS,nom |-times higher concentrations in the BGE than their analytical concentrations (cS = |zS,nom | × cS,nom ) in the calculation of the BGE ionic strength. In all three cases-with uncorrected actual mobilities as well as with actual mobilities corrected according to the two limiting models-the measured effective mobilities of the above enantiomers fit well the theoretical curves of their mobility dependences on the CD selectors concentrations in the BGE, with high average coefficients of determination (R2 = 0.9890-0.9995). Nevertheless, the best physico-chemically meaningful values of the apparent binding constants and the limiting mobilities of the enantiomer-CDs complexes with low RSDs were obtained using the actual mobilities of the species involved corrected according to model 2.
Chiral ITP of the weak base methadone using inverse cationic configurations with H+ as leading component and multiple isomer sulfated β-CD (S-β-CD) as leading electrolyte (LE) additive, has been studied utilizing dynamic computer simulation, a calculation model based on steady-state values of the ITP zones, and capillary ITP. By varying the amount of acidic S-β-CD in the LE composed of 3-morpholino-2-hydroxypropanesulfonic acid and the chiral selector, and employing glycylglycine as terminating electrolyte (TE), inverse cationic ITP provides systems in which either both enantiomers, only the enantiomer with weaker complexation, or none of the two enantiomers form cationic ITP zones. For the configuration studied, the data reveal that only S-methadone migrates isotachophoretically when the S-β-CD concentration in the LE is between about 0.484 and 1.113 mM. Under these conditions, R-methadone migrates zone electrophoretically in the TE. An S-β-CD concentration between about 0.070 and 0.484 mM results in both S- and R-methadone forming ITP zones. With >1.113 mM and < about 0.050 mM of S-β-CD in the LE both enantiomers are migrating within the TE and LE, respectively. Chiral inverse cationic ITP with acidic S-β-CD in the LE is demonstrated to permit selective ITP trapping and concentration of the less interacting enantiomer of a weak base.
The aim of this study was to develop a method for the separation of oxaliplatin enantiomers at attomolar concentration levels. A combination of capillary electrophoresis and inductively coupled plasma mass spectrometry was chosen due to their unique characteristics, including fast and easy modification of separation selectivity, and significant limits of detection and linearity. In the first step, we optimized conditions for the separation of oxaliplatin enantiomers including background electrolyte composition and concentration, pH, and type and concentration of the chiral selector. Under optimal conditions, sodium borate buffer pH 9.5, ionic strength 40 mmol L-1, with 60 mg mL-1 sulfated β-cyclodextrin, separation was obtained with a resolution of 2.0. This electrolyte system was then used in the 'in-house' connection of capillary electrophoresis with inductively coupled plasma mass spectrometer. In this instance, separation lasted for 9.5 min. Calibrations were linear in the range of 0.1-500 μg mL-1 with R2 of 0.9999. LOD and LOQ values were of 64 ng mL-1 and 116 ng mL-1 of oxaliplatin, respectively. This represents detection of 49 fg or 125 attomol of oxaliplatin enantiomers in the capillary electrophoresis injected sample zone. Finally, the method was successfully applied for detection of oxaliplatin enantiomers in spiked urine samples.
The aim of this study was to focus on the reduction of chiral selector concentration, sulfated-β-cyclodextrin, in an attempt decrease the running costs associated with separating cetirizine enantiomers by capillary electrophoresis. The decrease in the concentration of chiral selector was achieved by adding D-glucose to the background electrolyte, which consisted of sodium borate. Optimal separation of cetirizine enantiomers was obtained in the electrolyte containing 500 mmol L-1 borate pH 9.5 with 1.0 mg mL-1 sulfated-β-cyclodextrin, and 1000 mmol L-1D-glucose. This means a 15-fold reduction in the concentration of sulfated-β-cyclodextrin. The mechanism of the separation in this electrolyte was investigated using direct injection mass spectrometry. The electrolyte of borate, D-glucose, and sulfated-β-cyclodextrin forms a dual selector system, in which one selector is represented by the sulfated-β-cyclodextrin and the second selector is represented by the D-glucose-borate complexes.
- Publication type
- Journal Article MeSH
Head-column field-amplified sample stacking of cations from a low conductivity sample followed by enantiomeric separation using negatively charged chiral selectors was studied experimentally and with computer simulation. Aspects investigated include the direct electrokinetic injection of the analytes into the background electrolyte, the use of a selector free buffer plug, the contribution of complexation within the buffer plug and the application of an additional water plug between sample and buffer plug. Attention was paid for changes of ionic strength which is known to have a significant impact on complexation and thus effective mobility. Racemic methadone was selected as a model compound, randomly substituted sulfated β-cyclodextrin as chiral selector and phosphate buffers (pH 6.3) for the background electrolyte and the buffer plug. Results confirm that the buffer plug is providing a spacer between cationic analytes and the negatively charged selector during electrokinetic injection. Simulation predicts the required length and composition of the plug for a given injection time to avoid an interference with the selector. A short water plug added between the low conductivity sample and a high conductivity buffer plug is demonstrated to provide best conditions to achieve high sensitivity in enantioselective drug assays with sulfated cyclodextrins as selectors.
- MeSH
- beta-Cyclodextrins chemistry MeSH
- Electrophoresis, Capillary methods MeSH
- Cations chemistry MeSH
- Pharmaceutical Preparations analysis MeSH
- Methadone chemistry isolation & purification MeSH
- Computer Simulation MeSH
- Buffers MeSH
- Sulfates chemistry MeSH
- Stereoisomerism MeSH
- Water chemistry MeSH
- Publication type
- Journal Article MeSH
This contribution reports the synthesis, characterization and capillary electrophoretic application of heptakis-(6-O-sulfobutyl-ether)-β-cyclodextrin sodium salt, (6-(SB)7-β-CD). The compound was obtained through a five-steps synthesis and it represents the first example of single-isomer sulfobutylated cyclodextrin that carries the negatively charged functions exclusively on its primary side and it is unmodified on the lower rim. The purity of each intermediate was determined by appropriate liquid chromatographic methods, while the isomeric purity of the final product was established by an ad-hoc developed HPLC method based on a CD-Screen-IEC column. The structural identification of 6-(SB)7-β-CD was carried out by 1D, 2D NMR spectroscopy and ESI-MS. The chiral separation ability of 6-(SB)7-β-CD was studied by chiral capillary electrophoresis using the single-isomer host as a background electrolyte additive to separate the enantiomers of a representative set of pharmacologically significant model compounds such as verapamil, dapoxetine, ondansetron, propranolol, atenolol, metoprolol, carvedilol, terbutaline, amlodipine and tadalafil. The enantiomer migration order and the effects of the selector concentration on the enantiorecognition properties were investigated. NMR spectroscopy was applied to deepen and further confirm the host-guest interactions and in the case of the model compound dapoxetine a potential representation for the supramolecular assembly was developed based on the dataset collected by the extensive 2D NMR analysis. This single-isomer chiral selector offers a new alternative to the widely applied randomly sulfobutylated- and sulfated-beta-cylodextrins as well as to the single-isomer sulfated and carboxymethylated derivatives in chiral separations.
- MeSH
- beta-Cyclodextrins analysis chemical synthesis chemistry MeSH
- Electrophoresis, Capillary methods MeSH
- Electrolytes MeSH
- Spectrometry, Mass, Electrospray Ionization MeSH
- Hydrogen-Ion Concentration MeSH
- Magnetic Resonance Spectroscopy MeSH
- Stereoisomerism MeSH
- Chromatography, High Pressure Liquid MeSH
- Publication type
- Journal Article MeSH
Amino acids are crucial compounds involved in most biochemical processes essential for life. Since their dynamic turnover reflects the actual physiology of the cell/organism, a turnover assessment may provide valuable information related to multiple physiological and pathophysiological conditions. The sensitive determination of amino acids is predominantly associated with their derivatization which might be laborious, time-consuming and difficult to standardize. However, capillary electrophoresis offers the automatic injection and mixing of reactants, incubation of the reaction mixture, separation and detection of the reaction products in one on-capillary procedure. Among the on-capillary mixing strategies, electrophoretically mediated microanalysis (EMMA) is superior in terms of mixing efficiency. In this paper, we present an optimization of EMMA for the simultaneous derivatization of standard amino acids by naphthalene-2,3-dicarboxaldehyde/NaCN and its application to targeted human embryo metabolomics. For such a purpose, novel separation conditions were developed involving the background electrolyte, comprised of 73mM sodium dodecyl sulfate, 6.7 % (v/v) 1-propanol, 0.5mM (2-hydroxypropyl)-β-cyclodextrin and 135mM boric acid/sodium hydroxide buffer (pH 9.00). Finally, the optimized EMMA was compared to a fundamentally different mixing strategy, namely the transverse diffusion of laminar flow profiles, and proved to be also suitable for human plasma analysis.
- MeSH
- Amino Acids chemistry isolation & purification MeSH
- beta-Cyclodextrins MeSH
- Chromatography, Micellar Electrokinetic Capillary instrumentation methods MeSH
- Fluorescence MeSH
- 2-Hydroxypropyl-beta-cyclodextrin MeSH
- Plasma chemistry MeSH
- Humans MeSH
- Check Tag
- Humans MeSH
- Publication type
- Journal Article MeSH
- Evaluation Study MeSH
The enantioselectivity of neutral single-isomer synthetic precursors of sulfated-β-cyclodextrins was studied. Four neutral single-isomer cyclodextrins substituted on the secondary side with acetyl and/or methyl functional groups, heptakis(2-O-methyl-3,6-dihydroxy)-β-cyclodextrin (HM-β-CD), heptakis(2,3-di-O-acetyl-6-hydroxy)-β-cyclodextrin (HDA-β-CD), heptakis(2,3-di-O-methyl-6-hydroxy)-β-cyclodextrin (HDM-β-CD), heptakis(2-O-methyl-3-O-acetyl-6-hydroxy)-β-cyclodextrin (HMA-β-CD), and their sulfated analogs the negatively charged heptakis(2,3-di-O-methyl-6-sulfato)-β-cyclodextrin (HDMS-β-CD) and heptakis(2,3-di-O-acetyl-6-sulfato)-β-cyclodextrin (HDAS-β-CD) were investigated by non-aqueous capillary electrophoresis in the view of enantiodiscrimination for various drugs and related pharmaceutical compounds. The focus of the present work was on the chiral selectivity studies of the neutral derivatives, which are the synthesis intermediates of the sulfated products. The chiral recognition experiments proved that among the neutral compounds the HMA-β-CD shows remarkable enantioselectivity towards chiral guests in non-aqueous capillary electrophoresis, while HM-β-CD, HDA-β-CD and HDM-β-CD failed to resolve any of the 25 studied racemates under the applied experimental conditions. In order to get deeper insight into the molecular interactions between the studied single-isomer cyclodextrin and chiral fluoroquinolones (ofloxacin, gatifloxacin and lomefloxacin) and β-blockers (propranolol), (1)H and ROESY NMR experiments were performed. The 2-O-methylation in combination with the 3-O-acetylation of the host was evidenced to exclusively carry the essential spatial arrangement for chiral recognition.
- MeSH
- Acetylation MeSH
- beta-Cyclodextrins chemical synthesis MeSH
- Electrophoresis, Capillary * MeSH
- Fluoroquinolones chemistry MeSH
- Indicators and Reagents MeSH
- Magnetic Resonance Spectroscopy MeSH
- Propranolol chemistry MeSH
- Stereoisomerism MeSH
- Publication type
- Journal Article MeSH
- Comparative Study MeSH
The chiral recognition of the centrally acting analgesic agent tapentadol and its isomers with various cyclodextrins (CDs) was studied by capillary electrophoresis, focusing on the migration order of four stereoisomers. In the case of non-charged hydroxypropylated CDs (2-hydroxypropyl-β-CD, 2-hydroxypropyl-γ-CD) the beta derivative was able to discriminate the S,R- and R,S-isomers in acidic background electrolyte, whereas the gamma allowed the separation of S,S- and R,R-tapentadol, respectively. Dual CD system containing both hosts was used to separate all of four isomers. Negatively charged sulfated-α-CD at 1.0% (w/v) concentration in 100mM sodium borate buffer (pH 9.5) was capable of separating the isomers with favorable enantiomer migration order and the optimized method was able to determine 0.15% of chiral impurities of tapentadol in the presence of the last migrating clinically important R,R-isomer.
A neutral marker of the EOF can gain a nonzero effective mobility because of its possible interaction with a charged complexing agent, such as a chiral selector in CE. We determined effective mobilities of four compounds often used as EOF markers (dimethyl sulfoxide, mesityl oxide, nitromethane, and thiourea) in the BGE-containing sulfated β-CD (60 g/L). All the compounds studied were measurably mobilized by their interaction with the selector. The highest effective mobility (-3.0·10(-9) m(2) s(-1) V(-1)) was observed for thiourea and the lowest (-1.5·10(-9) m(2) s(-1) V(-1)) for dimethyl sulfoxide and nitromethane. The mobilities were determined by a new two-detector pressure mobilization method (2d method), which we propose, and the results were confirmed by standard CE measurements. In the 2d method, one marker zone is situated in the BGE containing the charged selector, while the second marker zone is surrounded with a selector-free BGE, which prevents its complexation. The initial distance between the two marker zones equals the capillary length from the inlet to the first detector. After a brief voltage application, the final distance between the marker zones is determined based on known capillary length from the first to the second detector. The difference between these two distances determines the effective mobility.
- MeSH
- Acetone chemistry MeSH
- beta-Cyclodextrins chemistry MeSH
- Models, Chemical * MeSH
- Dimethyl Sulfoxide chemistry MeSH
- Electrophoresis, Capillary methods MeSH
- Electrolytes chemistry MeSH
- Electroosmosis methods MeSH
- Hexanones chemistry MeSH
- Methane analogs & derivatives chemistry MeSH
- Nitroparaffins chemistry MeSH
- Thiourea chemistry MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
