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Chromatographic Data (chromatographic + data)
Selected AbstractsEnantiomeric separation by HPLC of 1,4-dihydropyridines with vancomycin as chiral selectorCHIRALITY, Issue 6 2003Gianpiero Boatto Abstract The macrocyclic antibiotics represent a relatively new class of chiral selectors in CE, HPLC, and TLC. We have examined the use of the macrocyclic antibiotic vancomycin as a chiral selector in HPLC for the separation of 1,4-dihydropyridines (DHPs) calcium antagonists (CAs). Chromatographic data of six 1,4-dihydropyridine calcium channel blockers obtained on the vancomycin chiral stationary phase (Chirobiotic V) were compared with those obtained on an ,1 -acid glycoprotein (AGP) HPLC stationary phase. Optimization of pH and organic modifier was carried out in order to modulate the retention properties of each system. All chiral neutral DHPs were resolved on the AGP column, whereas on Chirobiotic V only basic DHPs showed a split peak. The analytical chromatographic procedure on Chirobiotic V proved suitable for semipreparative separation, since the separation factor on the analytical column was high enough to obtain pure enantiomers with high yields. Chirality 15:494,497, 2003. © 2003 Wiley-Liss, Inc. [source] Development and application of a fatty acid based microbial community structure similarity indexENVIRONMETRICS, Issue 4 2002Alan Werker Abstract This article presents an index of similarity that has application in monitoring relative changes of complex microbial communities for the purpose of understanding the impact of community instability in biological wastewater treatment systems. Gas chromatographic data quantifying microbial fatty acid esters extracted from biosolids samples can be used to infer the occurrence of changes in mixed culture community structure. One approach to rapidly assess the relative dissimilarity between samples is to calculate a similarity index scaled between 0 and 1. The many arbitrary scales that are associated with the available calculation methods for similarity indices limits the extent of application. Therefore, a specialized index of similarity was derived from consideration of the measurement errors associated with the chromatographic data. The resultant calculation method provides a clear mechanism for calibrating the sensitivity of the similarity index, such that inherent measurement variability is accommodated and standardization of scaling is achieved. The similarity index sensitivity was calibrated with respect to an effective gas chromatographic peak coefficient of variation, and this calibration was particularly important for facilitating comparisons made between different systems or experiments. The proposed index of similarity was tested with data acquired from a recently completed study of contaminant removal from pulp mill wastewater. The results suggest that this index can be used as a screening tool to rapidly process microbial fatty acid (MFA) compositional data, with the objective of making preliminary identification of underlying trends in (MFA) community structure, over time or between experimental conditions. Copyright © 2002 John Wiley & Sons, Ltd. [source] Protein profile study of breast-tissue homogenates by HPLC-LIFJOURNAL OF BIOPHOTONICS, Issue 5 2009K. Kalyan Kumar Abstract Proteomics is a promising approach for molecular understanding of neoplastic processes including response to treatment. Widely used 2D-gel electrophoresis/Liquid chromatography coupled with mass spectrometry (LC-MS) are time consuming and not cost effective. We have developed a high-sensitivity (femto/subfemtomoles of protein/20 ,l) High Performance Liquid Chromatography-Laser Induced Fluorescence HPLC-LIF instrument for studying protein profiles of biological samples. In this study, we have explored the feasibility of classifying breast tissues by multivariate analysis of chromatographic data. We have analyzed 13 normal, 17 malignant, 5 benign and 4 post-treatment breast-tissue homogenates. Data was analyzed by Principal Component Analysis PCA in both unsupervised and supervised modes on derivative and baseline-corrected chromatograms. Our findings suggest that PCA of derivative chromatograms gives better classification. Thus, the HPLC-LIF instrument is not only suitable for generation of chromatographic data using femto/subfemto moles of proteins but the data can also be used for objective diagnosis via multivariate analysis. Prospectively, identified fractions can be collected and analyzed by biochemical and/or MS methods. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Correlation optimized warping and dynamic time warping as preprocessing methods for chromatographic dataJOURNAL OF CHEMOMETRICS, Issue 5 2004Giorgio Tomasi Abstract Two different algorithms for time-alignment as a preprocessing step in linear factor models are studied. Correlation optimized warping and dynamic time warping are both presented in the literature as methods that can eliminate shift-related artifacts from measurements by correcting a sample vector towards a reference. In this study both the theoretical properties and the practical implications of using signal warping as preprocessing for chromatographic data are investigated. The connection between the two algorithms is also discussed. The findings are illustrated by means of a case study of principal component analysis on a real data set, including manifest retention time artifacts, of extracts from coffee samples stored under different packaging conditions for varying storage times. We concluded that for the data presented here dynamic time warping with rigid slope constraints and correlation optimized warping are superior to unconstrained dynamic time warping; both considerably simplify interpretation of the factor model results. Unconstrained dynamic time warping was found to be too flexible for this chromatographic data set, resulting in an overcompensation of the observed shifts and suggesting the unsuitability of this preprocessing method for this type of signals. Copyright © 2004 John Wiley & Sons, Ltd. [source] Shifted factor analysis,Part III: N -way generalization and applicationJOURNAL OF CHEMOMETRICS, Issue 7 2003Sungjin Hong Abstract The ,quasi-ALS' algorithm for shifted factor estimation is generalized to three-way and n -way models. We consider the case in which mode A is the only shifted sequential mode, mode B determines shifts, and modes above B simply reweight the factors. The algorithm is studied using error-free and fallible synthetic data. In addition, a four-way chromatographic data set previously analyzed by Bro et al. (J. Chemometrics 1999; 13: 295,309) is reanalyzed and (two or) three out of four factors are recovered. The reason for the incomplete success may be factor shape changes combined with the lack of distinct shift patterns for two of the factors. The shifted factor model is compared with Parafac2 from both theoretical and practical points of view. Copyright © 2003 John Wiley & Sons, Ltd. [source] Equations to predict precipitation onset and bubblepoint pressures of asphaltenic reservoir fluidsAICHE JOURNAL, Issue 7 2009J. M. del Rio Abstract A set of algebraic equations to predict upper onset-of-precipitation and bubble-point pressures of asphaltene-containing reservoir fluids in wide temperature ranges are proposed. In developing the equations, laboratory data of 11 Mexican and 12 more live oils have been analyzed, and a correlation of these data with temperature has been found. A modified least-squares regression method has been used to develop two versions of the proposed equations. In one version, a single pressure/temperature data point is required to predict the entire onset/bubble-point curves at any temperature. For oils with no experimental precipitation data available at all, a second version of the proposed expressions employs standard chromatographic data of the reservoir fluid to provide a reasonable prediction. The average absolute deviations in calculated onset and bubble-point pressures by the proposed equations are 2.53 and 0.45MPa by the one-point correlations, respectively, and 3.96 and 1.62 MPa by the compositionally-based correlations, respectively. The developed expressions are simple and can be used to provide reasonable predictions of upper onset and bubble-point pressures of asphaltenic live oils in cases where laboratory data are scarce. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Predictions of peptides' retention times in reversed-phase liquid chromatography as a new supportive tool to improve protein identification in proteomicsPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 4 2009Tomasz B, czek Dr. Abstract One of the initial steps of proteomic analysis is peptide separation. However, little information from RP-HPLC, employed for peptides separation, is utilized in proteomics. Meanwhile, prediction of the retention time for a given peptide, combined with routine MS/MS data analysis, could help to improve the confidence of peptide identifications. Recently, a number of models has been proposed to characterize quantitatively the structure of a peptide and to predict its gradient RP-HPLC retention at given separation conditions. The chromatographic behavior of peptides has usually been related to their amino acid composition. However, different values of retention coefficients of the same amino acid in different peptides at different neighborhoods were commonly observed. Therefore, specific retention coefficients were derived by regression analysis or by artificial neural networks (ANNs) with the use of a set of peptides retention. In the review, various approaches for peptide elution time prediction in RP-HPLC are presented and critically discussed. The contribution of sequence dependent parameters (e.g., amphipathicity or peptide sequence) and peptide physicochemical descriptors (e.g., hydrophobicity or peptide length) that have been shown to affect the peptide retention time in LC are considered and analyzed. The predictive capability of the retention time prediction models based on quantitative structure,retention relationships (QSRRs) are discussed in details. Advantages and limitations of various retention prediction strategies are identified. It is concluded that proper processing of chromatographic data by statistical learning techniques can result in information of direct use for proteomics, which is otherwise wasted. [source] Retention data from reverse-phase high-performance thin-layer chromatography in characterization of some bis-salicylic acid derivativesBIOMEDICAL CHROMATOGRAPHY, Issue 8 2009-Sekuli, Tatjana Djakovi Abstract The chromatographic behaviour of salicylic acid derivatives was investigated using reversed-phase high performance thin-layer chromatography (RP HPTLC) with methanol,water and dioxane,water binary mixtures as mobile phase in order to establish relationships between chromatographic data and selected physico-chemical parameters that are related to ADME (absorption, distribution, metabolism and elimination). Some of the investigated compounds were screened for antioxidant activity. Examination of chromatographic behaviour revealed a linear correlation between RM values and the volume fraction of mobile phase modifier. Obtained RM0 values were correlated with lipophilicity, solubility, human intestinal absorption, plasma-protein binding, and blood,brain barrier data. The comparison among chromatographic data obtained by two mobile phase was performed with a statistical technique, principle component analysis. Copyright © 2009 John Wiley & Sons, Ltd. [source] Ef,ciency of antidepressant drugs as monoamine reuptake inhibitors: analysis of the hydrophobicity in,uence using biopartitioning micellar chromatographic dataBIOMEDICAL CHROMATOGRAPHY, Issue 7 2004C. Quiñones-Torrelo Abstract The reuptake blockade of biogenic amines by antidepressants is related not only to their therapeutics effects, but also to their side effects and potential drug,drug interactions. As an alternative to classical quantitative structure,activity relationships studies, in this work we propose different quantitative retention,activity relationships (QRAR) models that are able to describe the monoamine reuptake inhibition by antidepressants. The retention of compounds is measured using a biopartitioning micellar chromatography (BMC) system that can simulate the same hydrophobic, electronic and steric molecular interactions as those that condition drug activity. Since all the compounds considered in this work are structurally related because all of them share the same molecular features as the corresponding basic pharmacophore, the results obtained show that there is a retention range in which antidepressants present the highest monoamine reuptake inhibitor potency. Copyright © 2003 John Wiley & Sons, Ltd. [source] Quantifying Process Tradeoffs in the Operation of Chromatographic SequencesBIOTECHNOLOGY PROGRESS, Issue 4 2003Sheau-Huey Ngiam A method for the rapid representation of key process tradeoffs that need to be made during the analysis of chromatographic sequences has been proposed. It involves the construction of fractionation and maximum purification factor versus yield diagrams, which can be completed easily on the basis of chromatographic data. The output of the framework developed reflects the degree of tradeoff between levels of yield and purity and provides a fast and precise prediction of the sample fraction collection strategy needed to meet a desired process specification. The usefulness of this approach for the purposes of product purification and contaminant removal in a single chromatographic step has been successfully demonstrated in an earlier paper and it is now extended by application to a chromatographic sequence: the separation of a hypothetical three-component protein system by hydrophobic interaction chromatography (HIC) followed by size exclusion chromatography (SEC). The HIC operation has a strong impact upon the subsequent SEC step. The studies show how the analysis of performance in such a chromatographic sequence can be carried out easily and in a straightforward fashion using the fractionation diagram approach. The methodology proposed serves as a useful tool for identifying the process tradeoffs that must be made during operation of a sequence of chromatographic steps and indicates the impact on further processing of the cut-point decisions that are made. [source] | ||||||||||