Chromatographic Elution Curves Research Articles

Primary structure, physicochemical properties, and digestive properties of four sequentially extracted polysaccharides from Tremella fuciformis

Polysaccharides from Tremella spp. are known to have various functions and applications. To fully understand the polysaccharide compositions of fruiting body of T. fuciformis, cold water extract (CWE), hot water extract (HWE), dilute alkaline extract (ALE), and dilute acid extract (ACE) were sequentially prepared and characterized. Their physicochemical properties, chemical composition, micromorphology, and functional properties were determined. Firstly, the four extracts showed significant difference in chemical compositions. Secondly, in the structural aspect, liquid chromatographic elution curves of the extracts had only one main peak except that CWE had two peaks. Fucose, galactose (or glucose), xylose, and mannose were detected in CWE and HWE. Differently, ALE had fucose, glucose, and xylose, and ACE had only galactose and glucose, which agreed with the information obtained from Fourier transform infrared spectra. Thirdly, in the physicochemical and nutritional aspects, the thermal stability of the four extracts decreased in the order of: ACE>HWE≈ALE>CWE. HWE and ALE had similar dynamic viscoelasticity, exhibiting viscous characteristics at low frequencies and elastic characteristics at higher vibration frequencies. The four extracts were digestive-resistant after in vitro mimic experiments. This study could provide some theoretical data support for the scientific research and its application in food, medicine, and cosmetics of tremella polysaccharides.

Establishment of Fuzzy Langmuir Adsorption Model and Prediction of Chromatographic Behavior

AbstractIn order to accurately predict the complex chromatographic behaviors of the components to be separated, the fuzzy Langmuir adsorption equations and the back propagation‐artificial neural network (BP‐ANN) are combined to establish fuzzy Langmuir adsorption models. Herein, the fuzzy Langmuir adsorption equations are deduced based on a series of different traditional adsorption equations such as with or without competition, one or two kinds of adsorbed sites, monomolecular or multimolecular adsorption, etc. The major adsorption parameter Ci (form concentration) is the function of the actual concentration ci, expressed in matrix form constructed by BP‐ANN and is obtained by solving the equilibrium dispersive chromatography model with the inverse method and genetic algorithm. Finally, the fuzzy Langmuir models are applied to study the chromatographic behaviors of m‐cresol and p‐cresol on MIL‐53 (Al) stationary phase. The results show that the models have excellent curve fitting ability, and can be used to determine the adsorption relationship and predict the chromatographic elution curves under complex or unknown adsorption mechanism.

Determination of Effective Components of Scutellaria indica from Different Habitats

A HPLC method for the determination of three effective components in Scutellaria indica from different habitats was established. Analysis was performed on Waters Spherisorb ODS2 (4.6 mm × 250 mm, 5 μ m) with gradient mobile phase of 0.5% glacial acetic acid aqueous solution-acetonitrile. The flow rate was 1 m L/min and the detection wavelength was set at 275 nm. The results showed that the chromatographic elution curves with good resolution and reproducibility were obtained. By comparing with the reference materials, three effective components were determined, namely, scutellarin, scutellarin and apigenin. The method is sensitive, accurate and repeatable, and can be used for the determination of three components in Scutellaria indica. The results also showed that there were significant differences in the chemical composition of Scutellaria indica from different areas. The quality differences of Scutellaria indica from different areas should be considered in the selection of Scutellaria indica.

Protein purification using chromatography: selection of type, modelling and optimization of operating conditions

To achieve a high level of purity in the purification of recombinant proteins for therapeutic or analytical application, it is necessary to use several chromatographic steps. There is a range of techniques available including anion and cation exchange, which can be carried out at different pHs, hydrophobic interaction chromatography, gel filtration and affinity chromatography. In the case of a complex mixture of partially unknown proteins or a clarified cell extract, there are many different routes one can take in order to choose the minimum and most efficient number of purification steps to achieve a desired level of purity (e.g. 98%, 99.5% or 99.9%). This review shows how an initial 'proteomic' characterization of the complex mixture of target protein and protein contaminants can be used to select the most efficient chromatographic separation steps in order to achieve a specific level of purity with a minimum number of steps. The chosen methodology was implemented in a computer- based Expert System. Two algorithms were developed, the first algorithm was used to select the most efficient purification method to separate a protein from its contaminants based on the physicochemical properties of the protein product and the protein contaminants and the second algorithm was used to predict the number and concentration of contaminants after each separation as well as protein product purity. The application of the Expert System approach was experimentally tested and validated with a mixture of four proteins and the experimental validation was also carried out with a supernatant of Bacillus subtilis producing a recombinant beta-1,3-glucanase. Once the type of chromatography is chosen, optimization of the operating conditions is essential. Chromatographic elution curves for a three-protein mixture (alpha-lactoalbumin, ovalbumin and beta-lactoglobulin), carried out under different flow rates and ionic strength conditions, were simulated using two different mathematical models. These models were the Plate Model and the more fundamentally based Rate Model. Simulated elution curves were compared with experimental data not used for parameter identification. Deviation between experimental data and the simulated curves using the Plate Model was less than 0.0189 (absorbance units); a slightly higher deviation [0.0252 (absorbance units)] was obtained when the Rate Model was used. In order to optimize operating conditions, a cost function was built that included the effect of the different production stages, namely fermentation, purification and concentration. This cost function was also successfully used for the determination of the fraction of product to be collected (peak cutting) in chromatography. It can be used for protein products with different characteristics and qualities, such as purity and yield, by choosing the appropriate parameters.

Theoretical analysis of chromatographic peak asymmetry and sharpness by the moment method using two peptides

The analyses of peak shapes in chromatography are useful in operating chromatographic system. The asymmetry and sharpness of a chromatographic peak are estimated by the reversed-phase adsorption of two standard peptides (angiotensin II bradykinin) on C18. In this work, the average particle diameters of C18 were 5 and 15 μm, while the pore sizes were 100 and 300 A. The composition of the mobile phase was 50/50 vol. % of a binary mixture of acetonitrile and water with 0.1% TFA, and the particles were packed in a stainless column (4.6×150 mm). The third and the fourth central movement were calculated from the chromatographic elution curves by moment analysis. The peak asymmetry was determined by two theoretical calculations: the asymmetry factor by elution peak analysis and skewness with moment analysis. The sharpness was estimated by the fourth central moment. In this work, the most acceptable skewness was calculated when the pore size was 300 A. The large excess was observed on small pore size.

Determination of chromatographic peak parameters by non-linear curve fitting using statistical moments

There are many methods (manual, computer), which make possible the detailed analysis of chromatographic peak shape. Curve fitting seems to be one of the successful applications of the evaluation of chromatographic signals. In this case, a mathematical function is fitted to the digitized measuring points. Chromatographic elution curves are generally asymmetric, so it is necessary to find the best mathematical function, which corresponds perfectly to the signal form, and then to determine the parameters of the found equation. In this work a modified mathematical function is presented and used for curve fitting, in which the starting parameters are calculated from the statistical moments (retention time, variance, skewness, excess) of the peak shape. The fitting process gives a more accurate and rapid determination of peak shape characteristics, noise filtering and correction of baseline. The suggested modified Gaussian function, the simulated chromatographic peak shapes, the application of the function to the description of real signals and the parameters obtained by the fitting process will be demonstrated.

Parameter estimation of perillyl alcohol in RP-HPLC by moment analysis

Parameter estimations were made for the reversed-phase adsorption of perillyl alcohol (POH), a potent anti-cancer agent, on octadecylsilyl-silica gel (ODS). The average particle diame- ter of ODS was about 15 µm, and the particles were packed in the column (3.9 × 300 mm). The mobile phase used was a mixture of acetonitrile and water, in which the acetonitrile ranged be- tween 50 and 70 (v/v %). The first absolute moment and the second central moment were deter- mined from the chromatographic elution curves by moment analysis. Experiments were carried out using POH solutions within the linear adsorption range. The fluid-to-particle mass transfer coefficient was estimated using the Wilson-Geankoplis equation. The axial dispersion coefficient and the intraparticle diffusivity were determined from the slope and intercept of a plot of H vs 1/u0, respectively. The contributions of each mass-transfer step were axial dispersion, fluid-to- particle mass transfer, and intraparticle diffusion.

Linear chromatographic elution and breakthrough curves: quasi-lognormal distribution function and its derived equations

The quasi-lognormal distribution (Q-LND) probability density function and its integrating form (Q-LND approximation) were used to predict linear chromatographic elution curves and breakthrough curves, respectively. By comparing with the exact solution of the breakthrough curves, a general criterion for the applicability of the Q-LND probability density function and its integrating form was provided. The equations that include the first absolute moment and the second central moment were presented to calculate the chromatographic figures of merit for ideal and asymmetry peaks. Some problems such as the volume overloading in linear chromatography were discussed.

A FAD-SMT Model of Large Scale Liquid Adsorption Chromatography

The paper proposes a FAD-SMT model of large-scale liquid chromatography by which a continuous equation of chromatographic separation is decomposed into a convection dispersion partial differential equation and a set of ordinary differential equations. The numerical method for the FAD-SMT model is established. The stability and the convergence condition of numerical solution, and the choice of time and space interval are discussed. The FAD-SMT model is used to simulate liquid adsorption chromatography and cycling adsorption chromatography. Results show that the elution curves calculated by FAD-SMT model are good agreement with the experimental elution curves of the separation of glucose and fructose, the separation of sucrose and reducing sugar and the separation of mannitol and sorbitol. The result of parameter sensitivity analysis shows that the chromatographic elution curves are more sensitive to the changes of the parameter ai in Langmuir isotherms than to the changes of other parameters in the studied system.

Diffusivity and Thermal Cracking Rate of Metalorganic Gases by Chromatography

Metalorganic gases such as trimethylaluminum (TMA), trimethylgallium (TMG), triethylaluminum (TEA), and triethylgallium (TEG) are often used as metal sources of chemical vapor deposition for producing epitaxial thin films of or . Film growth kinetics are governed by thermal cracking of those gases in a thermal boundary layer which is expected to develop on the heated substrate and also by diffusion of those gases from bulk stream into the boundary layer. Since there has been poor understanding on physicochemical properties of these gases, such as rate of thermal cracking reaction and molecular diffusion, the present work is aimed to determine these properties by means of a chromatographic technique (pulse‐response analysis) developed in the field of chemical engineering. Method of moment was used to analyze chromatographic elution curves and measurements at different temperature ranges provided diffusivities (293–428 K) and thermal cracking rate coefficients (454–580 K) of the four gases in hydrogen stream.

Diffusion coefficients from stopped-flow gas chromatography

Mutual diffusion coefficients of two gases A and B can be determined in an empty gas chromatographic column by letting component B enter at an intermediate position of the column and continuously flow through a part only of it, as a carrier gas. The other component A is injected in a small amount instantaneously at the closed end of the column with the detector placed at the other end. By repeatedly stopping and then restoring after a short time the flow of B, narrow extra peaks are produced on the chromatographic elution curve, owing to diffusion of A into B. An equation is derived giving the area under the curve of each stop-peak as a function of time of the corresponding stop. Plotting the experimental data according to this equation permits the determination of the diffusion coefficient of A into B. Some results obtained by this method show negligible variations with changes in the experimental parameters.

Influence of sorption on the shape of chromatographic elution curves

An expression for the chromatographic elution curve in the presence of the sorption effect and axial diffusion is obtained, and corresponding expressions for the first three statistical moments are derived. The shape of the chromatographic elution curve is considered for different values of the initial parameters, and the influence of non-linearity of the adsorption isotherm is also discussed.

Shape of the chromatographic elution curve derived from the normal distribution of sample in the column

The elution curve in linear chromatography has been derived from the assumption that the distribution of sample along the column is normal. From this normal distribution, the elution curve (the distribution of sample as a function of time) can easily be derived. This approach gives nearly the same result as other, mathematically more complex, derivations.

Moment analysis of nonlinear chromatographic elution curve

Moment analysis of nonlinear chromatographic elution curve

Versatile System for Partition Chromatography of Corticosteroids and Prediction of Their Elution Curves

The versatile solvent system of n-hexane-chloroform-dioxane-water in the ratio 90:10:40:5 was used for the partition chromatographic isolation of corticosteroids. The relative amounts of the components may be adjusted if necessary to give a convenient partition coefficient on a diatomaceous earth column. Data are presented for 17 steroids, showing the close agreement between partition coefficients predicted from chromatographic elution curve data and those calculated from solvent extraction data. A procedure for the experimental determination of column parameters is given, and the necessary equations are outlined. The prediction of peak elution volumes and solute bandwidths as a function of partition coefficients from the derived equations is demonstrated, and the quantitative effect of varying the stationary phase volume and column length is calculated. The effect of steroid side-chain structure and fluoride substitution on the partition coefficient was studied. The effect of the substituents can be estimated from their expected polarity.

The use of poorly resolved gas chromatographic curves for the analysis of binary mixtures of petroleum fractions

Blends of petroleum products are usually made from fractions which contain preponderantly the same compounds. Only the relative abundances vary. A calculation of the contribution of each blended fraction is theoretically possible with the aid of the gas Chromatographic elution curve even though resolution is uniformly poor in such complex systems. An elementary mathematical analysis is made to show what conditions must maintain. Experimental evidence is presented to indicate that the necessary conditions can be realized for petroleum blends. Binary mixtures of complex fractions may be analyzed with an accuracy of better than 10% and only normal attention to detail need be observed.