Separation Of Various Classes Research Articles

Extraction Kinetics of Pyridine, Quinoline, and Indole from the Organic Phase with Natural Deep Eutectic Solvents and Separation Study Using a Centrifugal Extractor

In this study, the kinetics of extracting pyridine, quinoline, and indole from model fuels using natural deep eutectic solvents (NaDES) composed of carboxylic acids, xylitol, and water were investigated under static conditions. This research marks the first examination of extraction kinetics in this context. The key kinetic parameters of the extraction process were identified. Notably, it was observed that the mass transfer coefficient for indole was in the range of 3.4 × 10−6 to 1.2 × 10−6, depending on NaDES. That is significantly lower, by an order of magnitude, than for pyridine and quinoline under identical experimental conditions. The study revealed that, under specific conditions, where thermodynamic equilibrium for indole cannot be reached, it becomes possible to achieve kinetic separation of the components. The presented experimental data obtained on a centrifugal extractor showed a decrease in the degree of indole extraction with increasing flow: Extraction efficiency decreased from 63% at a flow rate of 0.05 L/h to 18% at 0.8 L/h. Moreover, the research indicated that, during indole extraction, the mass transfer coefficient in a centrifugal extractor was 1.3 × 10−4, which is two orders of magnitude higher than under static conditions. The study underscores the potential utility of the proposed extraction systems based on environmentally friendly NaDES, comprised of carboxylic acids and xylitol, for the kinetic separation of various classes of heterocyclic compounds. Overall, the research provides valuable insights into the kinetics of extraction and the potential applications of ‘green’ NaDES in the separation of heterocyclic compounds from organic liquids.

Medium Fluorous Separation Using Hydrofluoroether and Weakly Polar Solvents for Environmentally Friendly Recycling of Catalysts

As a novel approach to the separation of polyfluorinated compounds, we disclosed that HFE 7100 (methyl perfluorobutyl ether) forms with alkanes or chlorinated solvents two-layer systems between −51 and 30 °C depending on the nonfluorinated solvent. Similarly, more fluorinated HFE 7500 (ethyl perfluoroisoheptan-3-yl ether) forms the corresponding two-layer systems between −42 and 79 °C. While fluorinated compounds bearing 40–60% of fluorine were exclusively dissolved in the hydrofluoroether layer, nonfluorinated compounds strongly prevailed in the nonfluorinated solvent. The noncoordinating and aprotic character of the solvents used, as well as their low boiling points, enabled efficient isolation and recycling of sensitive polyfluoroalkylated Hoveyda–Grubbs second-generation precatalyst analogues. This medium fluorous method was further extended to the separation of various classes of polyfluorinated compounds including reaction intermediates, ligands, and ionic liquids. The key components of the medium f...

SFC-MS/MS as an orthogonal technique for improved screening of polar analytes in anti-doping control

HPLC is considered the method of choice for the separation of various classes of drugs. However, some analytes are still challenging as HPLC shows limited resolution capabilities for highly polar analytes as they interact insufficiently on conventional reversed-phase (RP) columns. Especially in combination with mass spectrometric detection, limitations apply for alterations of stationary phases. Some highly polar sympathomimetic drugs and their metabolites showed almost no retention on different RP columns. Their retention remains poor even on phenylhexyl phases that show different selectivity due to π-π interactions. Supercritical fluid chromatography (SFC) as an orthogonal separation technique to HPLC may help to overcome these issues. Selected polar drugs and metabolites were analyzed utilizing SFC separation. All compounds showed sharp peaks and good retention even for the very polar analytes, such as sulfoconjugates. Retention times and elution orders in SFC are different to both RP and HILIC separations as a result of the orthogonality. Short cycle times could be realized. As temperature and pressure strongly influence the polarity of supercritical fluids, precise regulation of temperature and backpressure is required for the stability of the retention times. As CO2 is the main constituent of the mobile phase in SFC, solvent consumption and solvent waste are considerably reduced. Graphical Abstract SFC-MS/MS vs. LC-MS/MS.

Stereo-specific LC and LC-MS bioassays of antidepressants and psychotics.

Stereochemistry in drug action is gaining importance because the enantiomers often differ in their biological activity and pharmacokinetic profiles. The use of racemic drugs may contribute to adverse effects owing to the presence of either inactive or toxic enantiomers. Most of the drugs currently used to treat psychiatric disorders, including depression, contain one or more chiral centers and are mostly sold as racemates. Single-enantiomer drugs provide greater selectivity for their biological targets, improved therapeutic indices and better pharmacokinetics compared with racemates. Therefore it is of great importance to monitor body fluid/tissue levels of drugs used to treat depression and psychiatric disorders. The present manuscript gives an overview of liquid chromatographic and mass spectrometric techniques reported during 2000-2013 for enantiomeric separation of various classes of antidepressants, viz. selective serotonin reuptake inhibitors, serotonin and norepinephrine reuptake inhibitors, noradrenergic and specific serotonergic antidepressants, norepinephrine reuptake inhibitors, norepinephrine-dopamine reuptake inhibitors, nonamphetamine central nervous system stimulants, serotonin and dopamine inhibitors and γ-aminobutyric acid receptor agonists in biological matrices. Techniques used for extraction, separation and quantification are discussed.

Maximizing Gaussianity using kurtosis measurement in the kernel space for kernel linear discriminant analysis

Kernel-linear discriminant analysis (K-LDA) is the notable breakthrough among the dimensionality reduction techniques for supervised classification. The parameter used in the kernel function is usually tuned using k-fold cross-validation. Recently, a technique is proposed to optimize the bandwidth parameter of the Gaussian kernel by simultaneously maximizing the homoscedasticity (identical co-variance matrices) and the separation of various classes in the higher dimensional space ( HDS ). In this technique, it is assumed that the individual classes are Gaussian distributed in the HDS , which are not usually true in practical applications. In this paper, we propose a technique that maximizes the Guassianity of the individual classes and the separation of various classes in the HDS using “kernel-trick”. This is determined by the tuning parameters used in the kernel function. The steepest-descent algorithm is used to obtain the optimal value of the tuning parameters. The experiments are performed with the synthetic datasets and real datasets to demonstrate the improved results obtained using the proposed technique. The proposed technique can also be adopted for other kernel functions used in K-LDA.

ChemInform Abstract: Separation, Identification, and Quantification of Carotenoids in Fruits, Vegetables, and Human Plasma by High Performance Liquid Chromatography

Separation, identification, and quantitation by high performance liquid chromatography of prominent carotenoids and carotenol fatty acid esters in various fruits and vegetables are reviewed. Examples of transformations of carotenoids as a result of food preparation are discussed. Recent developments in separation and identification of several carotenoids in human plasma are presented. The micronutrients considered in this text will be largely limited to carotenoids, but the analysis of vitamin A and two forms of vitamin E (y- and a-tocopherol) in human plasma will be briefly discussed. Carotenoids are among the most abundant naturally occumng pigments that are found in plants and plant foods. The present number of naturally occumng carotenoids isolated from various sources is in excess of 560 (ref. 6). Current food composition tables (ref. 7 & 8) lack detailed analytical information in that they only provide data on vitamin A activity which is largely contributed by about four carotenoids in plant foods (ref. 9). In the past decade, with the implementation of high performance liquid chromatography (HF'LC), more attention has been focused on the separation of all the carotenoid constituents of foods. In the following section, the separation of various classes of carotenoids by HPLC is described.

Ionic liquids as background electrolyte additives and coating materials in capillary electrophoresis; 187–198

Now that many scientific investigations focus on ionic liquids (IL) to establish their potential in different chemical processes, their application for the separation of various classes of compounds in capillary electrophoresis has also been recognized. ILs have been used as background electrolytes in aqueous and non-aqueous capillary electrophoresis for the separation of a number of different analyte types providing both control of the electroosmotic flow and the charging of analytes. Besides this ILs are used as micelle-forming compounds and capillary wall modifiers, as well as separation media additives in NACE for contactless conductivity detection.

Review of applications of high-field asymmetric waveform ion mobility spectrometry (FAIMS) and differential mobility spectrometry (DMS)

High-Field Asymmetric Waveform Ion Mobility Spectrometry (FAIMS) and Differential Mobility Spectrometry (DMS) harness differences in ion mobility in low and high electric fields to achieve a gas-phase separation of ions at atmospheric pressure. This separation is orthogonal to either chromatographic or mass spectrometric separation, thereby increasing the selectivity and specificity of analysis. The orthogonality of separation, which in some cases may obviate chromatographic separation, can be used to differentiate isomers, to reduce background, to resolve isobaric species, and to improve signal-to-noise ratios by selective ion transmission. This review will focus on the applications of these techniques to the separation of various classes of analytes, including chemical weapons, explosives, biologically active molecules, pharmaceuticals and pollutants. These papers cover the period up to January 2007.

Separation, identification, and quantification of carotenoids in fruits, vegetables and human plasma by high performance liquid chromatography

Abstract

Studies of chromatographic packings consisting of porous polymers : II. Separation properties of a porous styrene polymer cross-linked by di(methacryloyloxymethyl)naphthalenes

A cross-linked porous styrene polymer has been used for chromatographic separation of various classes of organic compounds and its properties have been compared with those of Chromosorb 101 and Porapak Q. This polymer shows higher initial decomposition temperatures than Chromosorb 101 and Porapak Q. Its usefulness as a column packing for gas chromatography has been estimated from polarities, numbers of theoretical plates, resolutions and retention times for various organic mixtures. Besides hydrocarbons, alcohols, carboxylic acids and ketones, the new column packing could be used for separation of amines.

Application of droplet counter-current chromatography to the isolation of natural products

Droplet counter-current chromatography (DCC), a recently developed all-liquid separation technique, has been applied to the preparative separation of various classes of natural products. From a crude extract of Ajuga pyramidalis (Labiatae), several hundred milligrams of pure iridoid glycosides could be obtained within 8 h. The volume of mobile phase used for the elution was less than 150 ml. Another example dealilng with iridoid glycosides is given bythe isolation of several consittuents of a Castilleja species (Scrophulariaceae). DCC has also been used to separate xanthone-O-glycosides from a North-American Gentiana species (Gentianaceae) and the main alkaloids of an opium extract. Thin-layer chromatography (TLC) was found to be an ideal and quick method for the selectionof solvent systems.

The Analytical Separation of Various Classes of Sugars

The Analytical Separation of Various Classes of Sugars