Rapid Separation on Activated Charcoal of High Oligosaccharides in Honey

A novel, simple and rapid stability-indicating high-performance liquid chromatographic (HPLC) method for pravastatin sodium (PRA) was successfully developed and validated for the assay of in tablets. Chromatographic separation was achieved isocratically on a C₁₈ column (150 mm × 4.6 mm) utilizing a mobile phase of methanol-phosphate buffer (pH 7; 0.02 M) (57:43, v/v) at a flow rate of 1.0 mL min⁻¹ with UV detection at 238 nm. A linear response (r = 0.9999) was observed in the range of 1–5 μg mL⁻¹. The method showed good recoveries (100.50%) and the relative standard deviation of intra and inter-day were 1.40%. The method can be used for both quality control assay of pravastatin in tablets and for stability studies as the method separates pravastatin from its degradation products and tablet excipients.An erratum to this article can be found at     

Separation of metal complexes by on-line coupled LC-GC

The on-line coupled LC-GC technique was applied to the analysis of several metal chelates of N,N-diethyldithiocarbamic acid. A 10-port valve interface was used to couple the LC and GC instruments. Conditions during sample transfer into the GC gave fully concurrent solvent evaporation. The chelates investigated were separated with a short apolar fused silica column. LC preseparation was made with cyano or amino phases using a hexane/dichloromethane mixture as eluent. On-line LC-GC combination seems to be very suitable for the separation of the metal chelates studied.     

Countercurrent Chromatography for the Measurement of the Hydrophobicity of Sulfonamide Amphoteric Compounds

Octanol-water partition coefficients (P _o/w ) of 17 sulfonamides (SAs) were determined by countercurrent chromatography (CCC). The measured P _o/w values were in the 0.002–46 range (–2.65 < log P _o/w < 1.7). The lipophility of these compounds depends on the pH showing a maximum for intermediate values. The apparent P _o/w coefficients of SAs were obtained at 5 pH values: 2, 3, 5, 7 and 11, using 0.01 M ammonium phosphate octanol saturated buffers. A theoretical model linking these values with pH for amphoteric compounds was checked and verified. Often the P _o/w coefficients of the molecular forms obtained with the CCC method differ significantly from literature values obtained using softwares and/or from experimental values calculated with extrapolation. The CCC method allows also the determination of the P _o/w coefficients of the ionic forms of the SAs, cationic forms at low pH values and anionic forms at elevated pHs. The acidity constants were also estimated using the theoretical model. Relationships between SA retention factors obtained by RPLC and hydrophobicity were also discussed.     

Facile extraction of berberine from different plants,separation, and identification by thin-layer chromatography,high-performance liquid chromatography,and biological evaluation against Leishmaniosis

The extraction of berberine was carried out from Berberis vulgaris, Berberis aquifolium, and Hydrastis canadensis plants using ethanol and water (70:30, v/v). The extracted berberine was characterized by ultraviolet-visible and Fourier-transform infrared spectroscopy. The purity of berberine was ascertained by thin-layer chromatography using n-propanol-formic acid-water (95:1:4) and (90:1:9) solvents. hR_f values were in the range of 44–49 with compact spots (diameter 0.2–0.4 cm). HPLC was carried out using ammonium acetate buffer and acetonitrile in gradient mode with Zodiac (4.6 × 150 mm, 3 μm) column. The flow rate was 1.0 mL/min and detection was at 220 nm. The values of separation and resolution factors of the standard and the extracted berberine were in the range of 1.13–1.16 and 1.40–1.71, respectively. A comparison has shown that both thin-layer chromatography and high-performance liquid chromatography (HPLC) methods found applications in different situations and requirements. The extracted berberine samples were used to treat Leishmaniosis and the results showed better activity of berberine in comparison to the standard drug Amphotericin B. Briefly, the reported research is a novel and may be used to extract berberine from plants, separation and identification of berberine by thin layer chromatography and HPLC and to treat Leishmaniosis.     

Chiral Resolution of the Enantiomers of New Aromatase Inhibitors by Liquid Chromatography on Amylose Stationary Phases

Analytical HPLC methods for derivatized amylose chiral stationary phases were developed for the direct enantioseparation of substituted [1-(imidazo-1-yl)-1-phenylmethyl)] benzothiazolinone and benzoxazolinone derivatives with one stereogenic center. These analogues of fadrozole constitute new potent nonsteroidal inhibitors of aromatase (P450 arom.). The separations were made using normal phase methodology with mobile phase consisting of n-hexane-alcohol (ethanol, 1-propanol or 2-propanol) in various proportions, and a silica-based amylose tris-3,5-dimethylphenylcarbamate (Chiralpak AD), or tris-(S)-1-phenylethylcarbamate (Chiralpak AS). The effects of concentration of various aliphatic alcohols in the mobile phase were studied. Baseline separation (R_s > 1.5) was easily obtained in all cases, ethanol being often the more interesting modifier. The effects of structural features of the solutes along with the temperature of the column on the discrimination between the enantiomers were examined for different mobile phase compositions.     

Preparation of affinity carriers for the study of binding properties of aspartic proteinases

We have chosen aromatic amino acids and their derivatives as ligands for the affinity chromatography of aspartic proteinases (pepsins and pepsinogens). The following ligands were used: L‐tyrosine, L‐phenylalanine, tyramine, and N‐acetyl‐L‐phenylalanine, and their iodinated derivatives (mono‐ and di‐substituted) with free or blocked amino group. Two types of reactions were used for coupling ligands to Sepharose activated with divinyl sulfone (DVS): via amino group or via carboxyl group. Ligands with free amino group were directly coupled to the activated matrix (L‐tyrosine, 3‐iodo‐L‐tyrosine, 3,5‐diiodo‐L‐tyrosine, L‐phenylalanine, 4‐iodo‐L‐phenylalanine, tyramine); ligands with blocked amino group (N‐acetyl‐L‐phenylalanine, BOC‐L‐tyrosine, BOC‐3,5‐diiodo‐L‐tyrosine; BOC: tert‐butoxy carbonyl) were coupled to Sepharose containing linked ethylenediamine using the carbodiimide reaction. Alternatively, ethylenediamine was bound to free carboxyl croup using the same reaction and these ligand derivatives reacted with divinyl sulfone activated Sepharose. The prepared affinity carriers were used to study the binding properties of porcine pepsin and pepsinogen.     

Enantiomeric Separation of Underivatized Aliphatic β-Amino Alcohols by Ligand-exchange Chromatography using N-n-Dodecyl-(1R,2S)-norephedrine as a Coating Reagent for Reversed-phase Column

Underivatized aliphatic β-amino alcohols with a primary or secondary alcohol moiety were separated into enantiomers by high performance liquid chromatography using octadecylsilanized silica coated with N-n-dodecyl-(1R,2S)-norephedrine as the stationary phase and an aqueous solution containing copper(II) and barbital as the mobile phase.     

Rapid isolation,reliable characterization,and water solubility improvement of polymethoxyflavones from cold‐pressed mandarin essential oil

Polymethoxyflavones possess many biological properties, as lipid‐lowering, hypoglycaemic, anti‐inflammatory, antioxidant, and anticancer activities, therefore, they may be employed as nutraceuticals or therapeutic agents. The scarcity of pure polymethoxyflavones on the market as well as their low water solubility limited in vivo studies and the use of polymethoxyflavones as food or pharmaceutical supplements. Since mandarin peels are a rich source of polymethoxyflavones, tangeretin, nobiletin, sinensetin, tetra‐O‐methyl scutellarein, and heptamethoxyflavone were purified from a nonvolatile residue of a cold‐pressed mandarin essential oil using a multidimensional preparative liquid chromatographic system coupled with a photodiode array detector and a single quadrupole mass spectrometer. A new prototype, consisting of a nano‐liquid chromatography system coupled with an electron ionization mass spectrometer, was used for the characterization of the pure isolated molecules. Finally, due to the collection of highly pure nobiletin and tangeretin, the ability of 2‐hydroxypropyl‐β‐cyclodextrin to enhance the water solubility of both polymethoxyflavones was evaluated by phase solubility studies and Job's plot method.     

Determination of Polyvinyl Alcohol Using Gel Filtration Liquid Chromatography

Gel filtration chromatography using a TSKgel G2000 SW column coupled with differential refractive index detection was used to analyse five grades of polyvinyl alcohol. Limits of detection and quantification for the assay were 0.14 mg mL^–1, 0.47 mg mL^–1 respectively. The inter and intra-day co-efficient of variance were both <7%. There was a significant difference (p<0.05, n=5) between the calibration curves across the five grades of PVA due to a refractive index range of 13.0790 –1.3181 (n=3). The assay accuracy was 98.99% ± 8.97% (n=5) and 90.60% ± 7.87% (n=5) of a spiked PVA sample was recovered from a commercial formulation.     

Diastereomeric and enantiomeric resolution of methoxytetrahydronaphthalene derivatives, melatonin ligand receptors, by HPLC on amylose chiral stationary phases

Summary Five methoxytetrahydronaphthalene derivatives, new agonist and antagonist ligands for melatonin receptors, were resolved into their diastereomers by analytical HPLC methods using derivatized amylose, chiral stationary phases. Separation was by using normal phase methodology with a mobile phase ofn-hexane-alcohol (ethanol or 2-propanol) and a silica-based amylose tris-(S)-1-phenylethylcarbamate (Chiralpak AS), or tris-3,5-dimethylphenylcarbamate (Chiralpak AD). The effects of structural variation in the solutes were noted. Baseline separation was easily obtained in many cases.     

Retention behaviour of model solutes on mixed silica-magnesia adsorbents by TLC. Comparison with the adsorption properties of Florisil

Summary The retention behaviour of positional isomers (phenols, aniline derivatives, quinoline bases) and polyaromatic hydrocarbons on mixed silica-magnesia layers is examined using various binary eluents (ethyl acetate, dioxane or 2-propanol in n-heptane). The influence of magnesia content in mixed adsorbents and concentration of polar modifier in the eluent on retention were investigated. Results obtained in chosen systems were compared with retention of solutes on Florisil layers using the same eluents by theR _{M Florisil} vsR _{M mix} correlations. Analysis of the structural effects of solutes and the position of points onR _{M Florisil} vsR _{M mix} diagrams enables comparison of chemical character and distribution of active centers on Florisil and mixed adsorbent surfaces.     

High performance liquid chromatography on the chiral stationary phase (R,R)-DACH-DNB using carbon dioxide-based eluents

Fast and efficient separations of chiral stereolabile compounds were obtained at very low temperature on a π-acid chiral stationary phase (R,R-DACH-DNB) using carbon dioxide-based mobile phases containing alcoholic polar modifiers. Furthermore, efficient separations of the newly discovered spherical carbon cluster buckminsterfullerene (C₆₀) and the related higher fullerenes (C₇₀, etc.) have been performed on the same stationary phase using eluents based on either n-hexane or carbon dioxide.     

Separation and characterisation of products of the reaction between propionamide and formaldehyde

Summary Propionamide-formaldehyde reaction products have been characterised using micellar electrokinetic chromatography (MEKC), HPLC-electrospray-MS (HPLC-ES-MS) and time-of-flight-MS (TOF-MS). HPLC-MS-MS was used to distinguish between isomeric species. The MEKC separation of all reaction products was obtained with good resolution and efficiency. Comparison of water-micelle distribution constants (P _MEKC) for propionamide-formaldehyde with those for caprolactam-formaldehyde reaction products suggests that the concentration of sodium dodecyl sulfate appropriate for use in MEKC is inversely related toP _MEKC. Quantification of all species containing one or two amide units was achieved using standard calibration, mass balance and the assumption of identical absorption coefficients for the same functional groups in monomers and dimers.     

Activity ranking of synthetic analogs targeting vascular endothelial growth factor receptor 2 by an integrated cell membrane chromatography system

Evaluating the biological activities of small molecules represents an important part of the drug discovery process. Cell membrane chromatography (CMC) is a well‐developed biological chromatographic technique. In this study, we have developed combined SMMC‐7721/CMC and HepG2/CMC with high‐performance liquid chromatography and time‐of‐flight mass spectrometry to establish an integrated screening platform. These systems was subsequently validated and used for evaluating the activity of quinazoline compounds, which were designed and synthesized to target vascular endothelial growth factor receptor 2. The inhibitory activities of these compounds towards this receptor were also tested using a classical caliper mobility shift assay. The results revealed a significant correlation between these two methods (R² = 0.9565 or 0.9420) for evaluating the activities of these compounds. Compared with traditional methods of evaluating the activities analogous compounds, this integrated cell membrane chromatography screening system took less time and was more cost effective, indicating that it could be used as a practical method in drug discovery.     

Free release static coating of glass capillary columns; rapid coating at lower temperatures and elevated pressures

The coating speed upon static coating of glass capillary columans was evaluated in terms of inner diameter and length of the column, viscosity and pressure of solvent vapor, etc. From the equation obtained it can be shown that a smaller diameter of a microbore column restricts solvent vapor transfer to the orifice of the column drastically. To compensate for this restriction, a higher pressure at the meniscus is needed. As an alternative to using a higher coating temperature, application of more volatile solvents such as n-butane and isobutane is proposed. Several glass capillary columns (130 μm i.d.) were coated with SE-54 dissolved inpentane-acetone mixed with n-butane or isobutane and the column performances were evaluated. Selection of these solvents permitted free release static coating of ca. 100 μm columns at lower or even ambient temperatures and they were equally suitable as commonly applied solvents (e.g. pentane) to coat highly efficient columns.     

Development and validation of an ultra‐performance convergence chromatography method for the quality control of Angelica gigas Nakai

Ultra‐performance convergence chromatography, which integrates the advantages of supercritical fluid chromatography and ultra high performance liquid chromatography technologies, is an environmentally friendly analytical method that uses dramatically reduced amounts of organic solvents. An ultra‐performance convergence chromatography method was developed and validated for the quantification of decursinol angelate and decursin in Angelica gigas using a CSH Fluoro‐Phenyl column (2.1 mm × 150 mm, 1.7 μm) with a run time of 4 min. The method had an improved resolution and a shorter analysis time in comparison to the conventional high‐performance liquid chromatography method. This method was validated in terms of linearity, precision, and accuracy. The limits of detection were 0.005 and 0.004 μg/mL for decursinol angelate and decursin, respectively, while the limits of quantitation were 0.014 and 0.012 μg/mL, respectively. The two components showed good regression (correlation coefficient (r²) > 0.999), excellent precision (RSD < 2.28%), and acceptable recoveries (99.75–102.62%). The proposed method can be used to efficiently separate, characterize, and quantify decursinol angelate and decursin in Angelica gigas and its related medicinal materials or preparations, with the advantages of a shorter analysis time, greater sensitivity, and better environmental compatibility.     

Phenomenon of dual‐ and single‐retention behaviors of solutes and its validation by computational simulation in linear programmed temperature gas chromatography

The current theory of programmed temperature gas chromatography considers that solutes are focused by the stationary phase at the column head completely and does not explicitly recognize the different effects of initial temperature (T_o) and heating rate (r_T) on the retention time or temperature of a homologue series. In the present study, n‐alkanes, 1‐alkenes, 1‐alkyl alcohols, alkyl benzenes, and fatty acid methyl esters standards were used as model chemicals and were separated on two nonpolar columns, one moderately polar column and one polar column. Effects of T_o and r_T on the retention of nonstationary phase focusing solutes can be explicitly described with isothermal and cubic equation models, respectively. When the solutes were in the stationary phase focusing status, the single‐retention behavior of solutes was observed. It is simple, dependent upon r_T only and can be well described by the cubic equation model that was visualized through four sequential slope analyses. These observed dual‐ and single‐retention behaviors of solutes were validated by various experimental data, physical properties, and computational simulation.     

Simple thin layer chromatography–ultraviolet spectrophotometric method for quality assessment of binary fixed‐dose‐combinations of lamivudine/tenofovir disoproxil fumarate and lamivudine/zidovudine in tablet formulations

Antiretroviral fixed‐dose‐combination drugs are best assayed with high‐performance liquid chromatography, or liquid chromatography–tandem mass spectrometry. However, most scientists in developing nations have no access to these expensive instruments. A more affordable quantitative technique is the use of ultraviolet–visible spectroscopy—where often the absorption spectra of these antiretrovirals are overlapping; thus complex derivative methodologies are required for quantification. A simple, rapid, and accurate thin layer chromatography–ultraviolet spectrophotometric method for the quantification of binary mixtures of lamivudine, zidovudine, and tenofovir–disoproxil–fumarate in tablet formulations was developed. Lamivudine/tenofovir–disoproxil–fumarate and lamivudine/zidovudine were extracted and separated on glass thin‐layer chromatography plates. Drugs were identified in ultraviolet light at 254 nm and quantified in acidic medium using ultraviolet spectrophotometry. The retardation factors were 0.43, 0.79, and 0.81 for lamivudine, tenofovir–disoproxil–fumarate, and zidovudine, respectively, with corresponding absorption maxima at 270, 260, and 265 nm. Linearity ranged from 1 to 40 µg/mL for all drugs (R = 0.9998–0.9999), while recovery studies were 95.10–102.11% and amount in formulations ranged from 97.99 ± 0.63 to 101.47 ± 2.39%. The paired t‐test (n = 5) indicated no significant difference between the proposed and high‐performance liquid chromatography methods, hence comparable and can be used as an alternative method in routine quality determination of antiretroviral medicines.     

HPLC-MS and MECC analysis of coumarins

Summary MECC separation of 11 coumarins has been achieved by use of a running electrolyte at pH 10.4 prepared from 50 mM boric acid, 10 mM sodium tetraborate and 100 mM sodium hydroxide. The buffer solution contained 50 mM SDS and, as organic modifier 1%n-propanol. The applied voltage was 25 kV and the temperature of the capillary was kept constant at 20°C. HPLC baseline separation of the coumarin mixture was obtained by use of a reversed-phase column and an acetonitrile-water solvent gradient. UV detection was performed at 205 nm. Peak assignment and purity control were achieved by HPLC-mass spectrometry with either an electrospray interface or an atmospheric-pressure chemical-ionization interface. Compounds were detected in either negative- or positive-ion modes. These MECC and HPLC-MS methods are suitable for ‘fingerprint’ analysis of a number of coumarin-containing plants, e.g. Fr.Ammi visnagae, Rd.Scopoliae and Rd.Imperatoriae.