Are the solvent effects critical in the modeling of polyoxoanions?

DFT calculations were driven for a set of differently charged polyoxoanions in the gas phase and in solution. We have calculated and analyzed their geometries and orbital energies to trace simple rules of behavior regarding the modeling of anions in isolated form. We discuss the quality of the results depending on the molecular charge, q, and the size of the cluster in terms of the number of metal centers, m. When the q/m ratio reaches a value of approximately 0.8, DFT calculations for the isolated anion fail to describe the gap between the band of occupied oxo orbitals and the set of unoccupied orbitals delocalized among the metal atoms. In these cases the incorporation of the stabilizing external fields generated by the solvent through continuum models improves the geometries and orbital energies.     

Relevance and use of capillary coatings in capillary electrophoresis–mass spectrometry

Over the last two decades, coupled capillary electrophoresis (CE)–mass spectrometry (MS) has developed into a generally accepted technique with a wide applicability. A growing number of CE-MS applications make use of capillaries where the internal wall is modified with surface coating agents. In CE-MS, capillary coatings are used to prevent analyte adsorption and to provide appropriate conditions for CE-MS interfacing. This paper gives an overview of the various capillary coating strategies used in CE-MS. The main attention is devoted to the way coatings can contribute to a proper CE-MS operation. The foremost capillary coating methods are discussed with emphasis on their compatibility with MS detection. The role of capillary coatings in the control of the electroosmotic flow and the consequences for CE-MS coupling are treated. Subsequently, an overview of reported applications of CE-MS employing different coating principles is presented. Selected examples are given to illustrate the usefulness of the coatings and the overall applicability of the CE-MS systems. It is concluded that capillary coatings can enhance the performance and stability of CE-MS systems, yielding a highly valuable and reproducible analytical tool.     

Why not using capillary electrophoresis in drug analysis?

CE and related methods are well-established techniques in the analysis of biomolecules, such as DNA and proteins. Even though CE is a rather good alternative to HPLC for the evaluation of the impurity profile and the enantiomeric purity of a drug, it is rarely applied. This might be due to the reservation of national licensing authorities and the pharmacopoeia commissions for several reasons. In this review containing some experimental data we report on several drug examples which demonstrate the superiority of CE over HPLC in special cases, i.e., in the analysis of antibiotics, amino acids and peptides, and the determination of enantiomeric purity. However, in order to make the CE techniques more suitable for pharmacopoeial purposes the general methods describing separation methods have to be complemented with the adjustment of the electrophoretic conditions being necessary to satisfy the system suitability criteria without fundamentally modifying the methods. Taken together CE should be more often applied in drug quality control.     

Thermodynamics of the solubility of sulfamethoxydiazine in organic solvents in the range 293.15–323.15 K

The solubilities of sulfamethoxydiazine in methanol, ethanol, 1-propanol, 2-propanol, acetone, and chloroform have been determined in the range 293.15–323.15 K by a static equilibrium method. The calculated results show that the correlation of the Apelblat equation for measured systems has less deviation than that of the λh equation. The positive Δ_sol H and Δ_sol S for each system revealed that sulfamethoxydiazine being dissolved in each solvent was an entropy-driven process.     

Are deep eutectic solvents a real alternative to ionic liquids in metal-catalysed reactions?

This microreview tries to answer the question: Are Deep Eutectic Solvents a real alternative to Ionic Liquids in metal-catalysed reactions? We have gathered the outstanding results of the use of DES in metal-catalysed processes and we have compared them to the ones with ILs. The huge possibilities of combinations of the components of the DES provide a vast number of different solvents with tunable properties. These DES have been successfully applied to different reactions such as, couplings or hydrogenations, among others. But additional work is still be necessary to explore the use of DES in other reactions and to go in depth in the study of the influence of the nature of the DES. Finally, we also present the rise in a new family of solvents, bio-based ionic liquids, complementary to the use of DES in order to fully substitute traditional ILs.     

Laccase-mediated oxidation of the steroid hormone 17β-estradiol in organic solvents

Laccase-mediated oxidation of the steroid hormone 17β-estradiol 1 in organic solvents or in a biphasic system allowed the isolation of the C–C and C–O dimers 1a–d. Concerning the C–C dimers, the relative ratio of the symmetric 4-4′ 1c and asymmetric 4-2′ 1d products was influenced by the catalyst used. Both 1c and 1d were formed as an equimolar mixture of diastereomeric atropisomers.     

Separation of metal ions by capillary electrophoresis – diversity, advantages, and drawbacks of detection methods

Capillary electrophoresis (CE) has been applied to metal-ion analysis during the last 10 years. To improve sensitivity and selectivity different modes of detection have been adapted or developed. The selection of commercially available detection systems for metal-ion analysis is still primarily limited to UV–Vis detection, although other commercial systems, e.g. fluorescence, conductivity, or interfaces for coupling to mass spectrometry (MS) or inductively coupled plasma mass spectrometry (ICP–MS) are becoming available. High demands are made on any detector used in CE, because the analytical signal has to be extracted from less than 1 nL of sample, which corresponds to a total amount of ≤ 10^–12 to 10^–15 mol analyte. This paper compares currently available and recently developed detection methods for CE as applied to the analysis of metal ions. Commercially available techniques, for example UV– Vis, fluorescence, or mass spectrometry, and other new detection methods including electrochemistry, radioactivity, and XRF, are discussed and future trends are anticipated.     

Determination of tetramethrin in water by liquid microextraction–capillary electrophoresis

1. Download : Download full-size image

     

Mechanism of the reaction of 1,1′-diethylferrocene and decamethylferrocene with peroxides in organic solvents

Kinetic relationships of oxidation of 1,1′-diethylferrocene and decamethylferrocene with peroxides ROOR (R = H, t-C₄H₉) in organic solvents were studied and the composition of oxidation products was established. It is shown that reactivity of (C₅H₄C₂H₅)₂Fe is significantly lower than that of Cp*₂Fe [Cp* = η⁵-C₅(CH₃)₅] which is seen from the ability of the first metal complex to undergo oxidation with a notable rate only in the presence of Brønsted acids, whereas the second substance is oxidized both in the presence and in the absence of these acids. Two possible mechanisms of oxidation of metal complexes in the presence of strong acids are discussed. One of them is based on the ability of ferrocene to fast and equilibrium protonation with the formation of Cp₂Fe⁺—H structure. Another one considers the ability of metal complexes to coordinate peroxides with the formation of weakly bound charge transfer complexes of the composition Cp₂Fe^δ+·ROOR^δ-. The possibility of their formation is confirmed by the oxidation of Cp₂Fe with hydroperoxides in the absence of acids.     

Impact of substituent position in monosubstituted α-cyclodextrins on enantioselectivity in capillary electrophoresis

In this study, our three recently synthesized regiospecifically monosubstituted carboxymethyl-α-cyclodextrins (CMACDs) were successfully applied for the enantiomeric separation of several biologically important low-molecular weight compounds by capillary electrophoresis. The enantioselectivity of the individual monosubstituted CMACDs added into the background electrolyte (BGE) was studied and compared with the mixture of three monosubstituted CMACDs and with native α-cyclodextrin at pH of the BGE ranging from 2.5 to 11. Our experiments revealed a significant influence of the position of the carboxymethyl group on the α-cyclodextrin skeleton on the enantioselectivity for all the studied analytes. Interestingly, the least common 3(I)-O regioisomer was revealed as the most effective chiral selector.     

Electrostatic interaction mechanism on the separation of phenols by non-aqueous capillary electrophoresis

The electrostatic interaction between additive and analyte is of great importance to non-aqueous cap- illary electrophoresis(NACE)separation.Three tetraalkylammonium bromides and acetonitrile were applied as additives and running solvent respectively.The effect of alkyl chain length and concentra- tion of additive on electrostatic interactions was investigated by the separation of phenols.The sepa- ration ability was found to increase with decreasing alkyl chain length of the additive,and the resolu- tion values were increased with increasing additive concentration.The separation was seriously dete- riorated after a little amount of water was added in the running solution.Furthermore,the electrostatic interaction is strong under the conditions of low electron cloud density,weak steric hindrance and multi-interaction sites.Thus,the separation result can be predicted by theoretical analysis,which is helpful for the separation of other substances in NACE based on electrostatic interaction.     

Separation of chiral basic drugs with sulfobutyl-β-cyclodextrin in capillary electrophoresis

Summary Separation of the enantiomers of 22 chiral basic drugs not previously separated with sulfobutyl-β-cyclodextrin (SBE-β-CD) as a chiral selector has been investigated by capillary zone electrophoresis. By dissolving the drug in Britton-Robinson buffer then optimization of selector concentration, pH, and amount injected, the enantiomers of 19 drugs were successfully separated, two for the first time.     

Frequency characteristic of series piezoelectric sensor and application to the determination of water in organic solvents

Theoretical consideration was proposed for the frequency response of a series piezoelectric sensor to the properties of liquid and verified experimentally. This kind of sensor has sensitive and selective frequency response to the permittivity and specific conductivity of solution with excellent stability, and was applied to the determination of micro-content of water in organic solvents. The detection limit is 0.01 g/L in dioxane.     

Recombinant drugs-on-a-chip: The usage of capillary electrophoresis and trends in miniaturized systems – A review

We present here a critical review covering conventional analytical tools of recombinant drug analysis and discuss their evolution towards miniaturized systems foreseeing a possible unique recombinant drug-on-a-chip device. Recombinant protein drugs and/or pro-drug analysis require sensitive and reproducible analytical techniques for quality control to ensure safety and efficacy of drugs according to regulatory agencies. The versatility of miniaturized systems combined with their low-cost could become a major trend in recombinant drugs and bioprocess analysis. Miniaturized systems are capable of performing conventional analytical and proteomic tasks, allowing for interfaces with other powerful techniques, such as mass spectrometry. Microdevices can be applied during the different stages of recombinant drug processing, such as gene isolation, DNA amplification, cell culture, protein expression, protein separation, and analysis. In addition, organs-on-chips have appeared as a viable alternative to testing biodrug pharmacokinetics and pharmacodynamics, demonstrating the capabilities of the miniaturized systems. The integration of individual established microfluidic operations and analytical tools in a single device is a challenge to be overcome to achieve a unique recombinant drug-on-a-chip device.     

Development of ion chromatography and capillary electrophoresis methods for the determination of Li in Li–Al alloy

Two methods were developed for determination Li content in Li–Al alloy by employing ion chromatography (IC) and capillary electrophoresis (CE) without any prior separation of Al matrix. In absence of suitable certified reference material the two methods were used to validate each other. Using a high capacity column and a weaker eluent methane sulphonic acid, it was possible to separate Li in IC without eluting strongly retained Al. The method showed good precision and sensitivity and was extended for analysis of routine samples. In the case of CE using imidazole as co-ion, Li was detected in CE by indirect detection. In view of no interference from Al, samples were analyzed without any matrix separation. The CE method was used successfully for sample analysis and results were compared with IC results.     

Solubility of benzilic acid in select organic solvents at 298.15 K

Experimental solubilities are reported for benzilic acid dissolved in ethanol, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, 1-heptanol, 2-propanol, 2-butanol, 2-methyl-1-propanol, diethyl ether and methyl tert-butyl ether at 298.15?K. Results of these measurements reveal that the observed solubilities in the nine alcohol solvents fall within a fairly narrow mole fraction range of each other. Benzilic acid is also very soluble in the two ether solvents studied.     

The rôle of some organic solvents in flame photometry

Summary The influence of acetone, methanol andn-propylalcohol, in various concentrations, on the Na-emission and the temperature in an air-acetylene flame has been investigated at various gas/air ratios and at various heights in the flame. A sprayer with spray-chamber and a Meker burner have been used. The experiments indicate that the gain in Na-emission upon adding organics to the analyzed solution cannot be related simply to a single property of the organic-water mixture only. The experiments on the flame temperature, measured by line-reversal, show that spraying organic liquids into the flame may result in an increase or a decrease of flame temperature, according as the gas-air mixture is lean or rich. The effect of these organic liquids on the flame temperature and so on the excitation of Na appears to be small when compared to their effect on the spray-yield. The measured temperature effect appears to agree with quantitative calculations.

---

Zusammenfassung Der Einfluß verschiedener Konzentrationen von Aceton, Methanol und n-Propylalkohol auf die Na-Emission und Temperatur einer Acetylen-Luftflamme wurde untersucht, wobei sowohl die Höhe der Meßstelle in der Flamme wie auch das Gas/Luft-Mischungsverhältnis variiert wurden. Ein Indirektzerstäuber und Mekerbrenner wurden dabei benutzt. Die Zunahme der Na-Emission hängt nicht in einfacher Weise von nur einer einzigen Eigenschaft des Lösungsmittels ab. Die Messungen der Flammentemperatur wurden mit Hilfe der Liniemimkehrmethode durchgeführt und zeigten, daß bei Zugabe der organischen Substanzen eine Erhöhung oder eine Erniedrigung der Temperatur auftreten kann, je nachdem, wie gerade das Gas/Luft-Mischungsverhältnis eingestellt wird. Der Einfluß der organischen Lösungsmittel auf die Flammentemperatur und dadurch auf die Anregung der Na-Atome ist gering im Vergleich mit deren Effekt auf die Zerstäuberwirkung. Die gemessene Temperaturbeeinflussung stimmt mit dem berechneten Wert überein.

---

Résumé En changeant les mélanges d'acétylène/air et l'hauteur de la région mesurée dans la flamme, on a étudié l'influence des différentes concentrations d'acétone, méthanol et n-propylalcool sur la température de la flamme et sur l'émission du Na. Un pulvérisateur indirect et un brûleur de Meker ont été utilisés. Les expériences montrent que l'accroissement de l'émission du Na, causé par la substance organique, n'est pas liée simplement à une seule propriété de la mélange organo-aqueuse. En mesurants la température de la flamme par la méthode d'inversement de raye nous avons montré que l'addition de substance organique donne aussi un accroissement, qu'un abaissement de la température, selon que la mélange gaz/air est faible ou riche. L'effet de la substance organique sur la température (et par la sur l'excitation du Na) se montre plus faible que l'effet sur le rendement du pulvérisateur. L'effet sur la température mesuré est en concordance avec l'effet calculé.

---

---

On leave from Israel Atomic Energy Commission Hakyria, Tel Aviv.     

What is the future of electrophoresis in large-scale genomic sequencing?

Although a finished human genome reference sequence is now available, the ability to sequence large, complex genomes remains critically important for researchers in the biological sciences, and in particular, continued human genomic sequence determination will ultimately help to realize the promise of medical care tailored to an individual's unique genetic identity. Many new technologies are being developed to decrease the costs and to dramatically increase the data acquisition rate of such sequencing projects. These new sequencing approaches include Sanger reaction-based technologies that have electrophoresis as the final separation step as well as those that use completely novel, nonelectrophoretic methods to generate sequence data. In this review, we discuss the various advances in sequencing technologies and evaluate the current limitations of novel methods that currently preclude their complete acceptance in large-scale sequencing projects. Our primary goal is to analyze and predict the continuing role of electrophoresis in large-scale DNA sequencing, both in the near and longer term.