High-efficiency Chromatography Research Articles

Negatively Charged Composite Nanofibrous Hydrogel Membranes for High-Performance Protein Adsorption.

Nanofibrous materials are considered as promising candidates for fabricating high-efficiency chromatography media, which are urgently needed in protein pharmaceuticals purification and biological research, yet still face several bottlenecks. Herein, novel negatively charged composite nanofibrous hydrogel membranes (NHMs) are obtained by a facile combination of electrospinning and surface coating modification. The resulting NHMs exhibit controllable morphologies and chemical structures. Benefitting from the combined effect of the stable framework of silicon dioxide (SiO2) nanofiber and the function layer of negatively charged hydrogel, as well as good pore connectivity among nanofibers, NHMs exhibit a high protein adsorption capacity of around 1000 mg g−1, and are superior to the commercial cellulose fibrous adsorbent (Sartobind®) and the reported nanofibrous membranous adsorbents. Moreover, due to their relatively stable physicochemical and mechanical properties, NHMs possess comprehensive adsorption performance, favorable resistance to acid and solvents, good selectivity, and excellent regenerability. The designed NHMs composite adsorbents are expected to supply a new protein chromatography platform for effective protein purification in biopharmaceuticals and biochemical reagents.

Electrochemical Transformation of 4-Chlorophenol for the Determination of Chloride in Advanced Oxidation Processes

Water is necessary natural resources for life on the planet, however in the last decades it has become evident the contamination of this by the diverse anthropogenic activities that generated a wide range of chemical species that are hardly removed by conventional treatments, therefore, other feasible alternatives have been sought to obtain a better efficiency for the removal of said pollutants. When the degradation of the organic matter of the effluents is carried out by applying different physicochemical processes, it is possible to form less toxic chemical species. One of the techniques for the removal of contaminants are the advanced oxidation processes (POA), these processes have been used for the degradation or mineralization of organic compounds of refractory and toxic effluents, where the hydroxyl radical is generated in situ (•OH) that due to its chemical properties has the ability to degrade or mineralize the refractory matter, resulting in less toxic byproducts and halogen oxyanions, which improve the efficiency of the treatment.There are different types of POA, however advanced electro-oxidation processes (PEOA) have shown great efficiency in the oxidation of organic matter by changing the electrolyte and the electrode system with some variation to improve the process. It is worth mentioning that the degradation of organic matter in these processes is of the utmost importance, since it is mostly used for the elimination of certain organic molecules that are found in the aqueous medium and that are toxic.In recent years, different studies have been carried out in which it is shown that chlorophenolic molecules, such as 4-chlorophenol (4- (CPh)) is degraded by advanced electro-oxidation processes. The 4-CPh is degraded by applying an electrochemical process through the •OH and releases the Cl that is in the molecule and is transformed as Cl- which reacts with the different radial in the medium with the possibility of generating oxidizing agents as oxyanions. However, the Cl- species can not only be obtained from the molecule, but it can also be present in the supporting electrolyte or by the nature of the sample.The degradation of the chlorophenolic molecules will allow the formation of chemical species that will depend on the pH in which the reaction is found, considering that in recent studies that at higher pH values it is very probable that there is the formation of chlorates. However, in the majority of the investigations, only reference is made to the fact that the formation of chlorates does not predominate at acid pHFor the identification of organic matter degradation, different analytical techniques are used to monitor degraded species. The most used techniques for the identification of these species are high efficiency chromatography (HPLC), UV-VIS spectrophotometry for organic species, however for the anionic species the use of ion chromatography (IC) is made. Figure 1

Exploring the complexity of oil sands process-affected water by high efficiency supercritical fluid chromatography/orbitrap mass spectrometry.

Approximately 1 billion m(3) of oil sands process-affected water (OSPW) is currently stored in tailings ponds in Northern Alberta, Canada. The dissolved organic compounds in OSPW have been termed a supercomplex mixture of bitumen-derived substances and continuing efforts to understand its underlying chemical composition are important for evaluating its environmental hazards. Packed column supercritical fluid chromatography (SFC) was applied to OSPW analysis for the first time. By combining four columns in series (each 25 cm × 4.6 mm I.D., 5.0 µm bare silica) approximately 80,000 plates were achieved on a 1 m column. Using a simple fixed restrictor, the SFC eluent was coupled directly to ultrahigh-resolution orbitrap mass spectrometry (SFC/Orbitrap-MS). SFC/Orbitrap-MS, with positive and negative atmospheric pressure chemical ionization (APCI +/-), revealed the partial or full chromatographic separation of isomers for a wide array of chemical species, including naphthenic acids (Cn H2n + Z O2 ) and unknown sulfur- and nitrogen-containing molecules. For smaller compounds (e.g. naphthenic acids where n ≤10), or for larger structurally constrained compounds (e.g. C16 naphthenic acid with 9 double-bond equivalents), apparent baseline resolution of many isomers was possible. Isomer-specific MS/MS experiments furthermore allowed characterization of functional groups in novel species. For example, in APCI+ mode, up to 16 isomers of C6 H11 ON were revealed to have amide and amino functionalities. This combination of high efficiency chromatography and ultra-high mass resolution detection resulted in a powerful method with capabilities for characterizing or 'fingerprinting' unknown species with little interference. The method has great promise for environmental monitoring and forensics in the oil sands region, as well as for further studies on the composition of dissolved organic compounds in OSPW.

Extracción y cuantificación del alcaloide esteroidal solasodina, de los frutos del Solanum wrightii Benth y el Solanum pseudocapsicum L

Se recolectaron frutos del Solanum wrightii Benth y el Solanum pseudocapsicum L con el fin de implementar un proceso para la extracción, purificación, identificación y cuantificación de la solasodina presente en ellos. El proceso inicial se basó en la publicación de Sanabria (1980), con un proceso de secado, molienda y desengrase, seguido de una extracción sólido-líquido con etanol al 95%, en reflujo. Se continuó con el procedimiento descrito por Mola, de Araujo y de Magalhães (1997); los extractos recuperados se concentraron a presión reducida, obteniendo una pasta semisólida que fue disuelta en una solución de HCL 0.5 M, seguido de una precipitación de los glucoalcaloides mediante la adición de solución de NaOH 6.0 M; estos se sometieron a hidrólisis ácida en una mezcla de etanol al 95% y HCl 3.0 M, durante cuatro horas. Se precipitó un sólido grisáceo que se separó por centrifugación y se purificó en cromatografía de columna (CC), según el procedimiento descrito por Pinell, Sauvain y Cuevas (1998); se logró separar un compuesto con punto de fusión de 202°C, que corresponde al de la solasodina estándar. Para confirmar el compuesto se realizaron pruebas de identificación de alcaloides, cromatografía de capa fina (CCF), cromatografía liquida de alta eficiencia (HPLC) e identificación por espectroscopia infrarroja. La cuantificación de la solasodina se realizó por HPLC, por el método de patrón externo mediante una curva de calibración con patrones desde 15 ppm hasta 50 ppm. La solasodina obtenida presentó una coloración amarilla y un rendimiento de 0.074% en base seca. El procedimiento se repitió para los frutos del S. pseudocapsicum L. Sin embargo, en la etapa de purificación por CC no se logró una separación óptima de los compuestos alcaloidales presentes y no fue posible obtener solasodina.

Influence of cardiopulmonary bypass on cefuroxime plasma concentration and pharmacokinetics in patients undergoing coronary surgery

The aims of this study were to evaluate the influence of cardiopulmonary bypass (CPB) on the plasma concentrations and pharmacokinetics of cefuroxime and to assess whether the cefuroxime dose regimen (a 1.5 g dose, followed by 750 mg every 6 h for 24 h) is adequate for cardiac surgery antibiotic prophylaxis. A prospective, controlled, observational study compared patients undergoing coronary surgery with CPB (CPB group, n = 10) or off-pump surgery (off-pump group, n = 9). After each cefuroxime dose, blood samples were sequentially collected and analysed using high-efficiency chromatography. For demographic data and pharmacokinetic parameters, the authors used Fisher's exact test for nominal variables and Student's t-test and the Mann-Whitney U-test for parametric and non-parametric variables, respectively. Plasma concentrations were compared using ANOVA, and the percentage of patients with a remaining plasma concentration of >16 mg/l within 6 h after each bolus was quantified in tabular form. After each cefuroxime bolus was administered, both groups presented a significant decrease in plasma concentration over time (P < 0.001), without differences between the groups. The mean CPB time of 59.7 ± 21.1 min did not change cefuroxime plasma concentrations or pharmacokinetics. The mean clearance ± SD (ml/kg/min) and median elimination half-life (h) of the CPB group versus the off-pump group were 1.7 ± 0.7 versus 1.6 ± 0.6 (P = 0.67), respectively, and 2.2 versus 2.3 (P = 0.49), respectively. Up to 3 h following the first bolus of 1.5 g, but not after 6 h, all patients had plasma concentrations >16 mg/l (CPB group = 20% and off-pump group = 44%). However, after all 750 mg boluses were administered, concentrations <16 mg/dl were reached within 3 h. CPB does not influence cefuroxime plasma concentrations. The dosing regimen is adequate for the intraoperative period, but in the immediate postoperative period, it requires further review.

Approaches for The Rapid Identification of Drug Metabolites in Early Clinical Studies

Understanding the metabolism of a novel drug candidate in drug discovery and drug development is as important today as it was 30 years ago. What has changed in this period is the technology available for proficient metabolite characterization from complex biological sources. High-efficiency chromatography, sensitive MS and information-rich NMR spectroscopy are approaches that are now commonplace in the modern laboratory. These advancements in analytical technology have led to unequivocal metabolite identification often being performed at the earliest opportunity, following the first dose to man. For this reason an alternative approach is to shift from predicting and extrapolating possible human metabolism from in silico and nonclinical sources, to actual characterization at steady state within early clinical trials. This review provides an overview of modern approaches for characterizing drug metabolites in these early clinical studies. Since much of this progress has come from technology development over the years, the review is concluded with a forward-looking perspective on how this progression may continue into the next decade.

Surface diffusion in reversed-phase liquid chromatography

More than 40 years ago, Giddings pointed out in "Dynamics of Chromatography" that surface diffusion should become an important research topic in the kinetics of chromatographic phenomena. However, few studies on surface diffusion in adsorbents used in chromatography were published since then. Most scientists use ordinary rate equations to study mass transfer kinetics in chromatography. They take no account of surface diffusion and overlook the significant contributions of this mass transfer process to chromatographic behavior and to column efficiency at high mobile phase flow rate. Only recently did the significance of surface diffusion in separation processes begin to be recognized in connection with the development of new techniques of fast flow, high efficiency chromatography. In this review, we revisit the reports on experimental data on surface diffusion and introduce a surface-restricted molecular diffusion model, derived as a first approximation for the mechanism of surface diffusion, on the basis of the absolute rate theory. We also explain how this model accounts for many intrinsic characteristics of surface diffusion that cannot properly be explained by the conventional models of surface diffusion.

Laser beam deflection sensor as a detector for high-efficiency chromatography

Laser beam deflection sensor as a detector for high-efficiency chromatography

High speed—high efficiency chromatography

Les progres en chromatographie passent par la chromatographie a grande vitesse et rendement eleve

Direct coupling of packed fused-silica liquid chromatographic columns to a magnetic sector mass spectrometer and application to polar thermolabile compounds

Fused-silica columns of 0.22 mm I.D. packed with normal small-particle high-performance liquid chromatography packing material were studied. The shape of the column end allows direct connection to a combined electron impact—chemical ionization (EI—CI) ion source. To inject small volumes a syringe-loaded micro-sample injector is used with the time splitting technique. Mass spectra obtained from easily vaporized compounds are similar to, but display less thermal decomposition than, normal EI spectra. Mass spectra of underivatized native mono- and disaccharides give useful structural information. Results from the analysis of cardiac glucosides are also shown. The system provides high-efficiency chromatography with a universal detector, suitable for the analysis of non-volatile and labile compounds.

Isolation and characterization of the opioid peptides from rat pituitary: beta-lipotropin.

Rat beta-lipotropin was isolated from 40 anterior pituitaries using high efficiency chromatography columns and sensitive fluorometric methods. The beta-lipotropin was characterized as to molecular weight, amino acid composition, and generation of opioid activity by trypsinization. Other opioid peptides, as well as a precursor to opioid peptides with a molecular weight larger than that of beta-lipotropin, were observed in this tissue.

Two-component solvent systems in adsorption chromatography on silica gels with different specific surface areas

In adsorption flat-bed and column liquid chromatography, multicomponent solutions are most frequently used as mobile phases as they enable the range of combinations of chromatographic systems to be increased. Flat-bed chromatography frequently gives a preliminary determination of the optimal conditions for the chromatographic separation of mixtures in liquid column and high-efficiency chromatography. Therefore, the development of the possibilities of separating a mixture of substances on the basis of the data for the adsorption of the pure components on solid adsorbents is very important. The relationship between theoretical and experimental R m 1,2 values and the composition of the conformal system carbon tetrachloride-chloroform used as the mobile phase was studied, using silica gels with different specific surface areas as adsorbent. The results showed good agreement between theoretical functions R M 1,2 = f(ϕ 1) and the experimental functions, where ϕ 1 is the volume fraction of component 1 in the mobile phase. It was found that the value of a particular function depended on the specific surface area of the adsorbent. Some deviations from the observed regularities were found to be caused by the large interaction energies of the adsorbents with large specific surface areas on the separated substances and molecules of the mobile phase.