An efficient and novel technology for the extraction of parasite genomic DNA from whole blood or culture

The aim of this study was to assess pathogen DNA extraction with a new spin column-based method (DNA-XT). DNA from either whole-blood samples spiked with Plasmodium falciparum or Leishmania donovani amastigote culture was extracted with DNA-XT and compared with that produced by a commercial extraction kit (DNeasy®). Eluates from large and small sample volumes were assessed by PCR and spectroscopy. Using a small volume (5 μl) of blood, the DNA-XT and DNeasy methods produced eluates with similar DNA concentrations (0.63 vs 1.06 ng/μl, respectively). The DNA-XT method produced DNA with lower PCR inhibition than DNeasy. The new technique was also twice as fast and required fewer plastics and manipulations but had reduced total recovered DNA compared with DNeasy

Use of cyclodextrins as chiral selectors for direct resolution of the enantiomers of fluoxetine and its metabolite norfluoxetine by HPLC

The goal of this work is to investigate the direct chromatographic separation of the enantiomers of fluoxetine and its active metabolite norfluoxetine. The liquid chromatographic retention behavior of these enantiomers on a β‐cyclodextrin bonded‐phase column was investigated with respect to mobile phase composition, pH, ionic strength, and solvent selectivity. Relationships were established between these factors and the three most important chromatographic parameters: retention time, resolution, and selectivity. Most of the evidence suggests that the unique selectivity of this column isdue to inclusion complex formation, which provides the physical basis for enantiomeric resolution. After these studies a set of optimum chromatographic conditions was chosen for the simultaneous separation/determination of a mixture of the four enantiomers using fluorescence detector. © 1993 Wiley‐Liss, Inc. Copyright © 1993 Wiley‐Liss, Inc

Evaluation of the chromatographic behaviour of fluoxetine and norfluoxetine using different cyclodextrins as mobile phase additives and fluorimetric detection

The principal goal of this work was to investigate the liquid chromatographic retention behaviour of fluoxetine and norfluoxetine using HPLC with respect to mobile phase composition, pH, flow rate and the amount of the native β-cyclodextrin (β-CD) or the β-hydroxypropyl-cyclodextrin (HP-β-CD), added to the mobile phase. Further, it was of interest to evaluate the effectiveness of β-CD and HP-β-CD to enhance fluorescence detection of these compounds. Another purpose of this study, was to calculate the formation constants of the inclusion complexes (K(f) of fluoxetine and norfluoxetine within the HP-β-CD, in different mobile phase compositions. Based on these findings, the log K(f) values of these two compounds referred to pure aqueous mobile phase (log K(fW), can be determined by extrapolation

Enantiomeric separation of zopiclone, its metabolites and products of degradation on a β-cyclodextrin bonded phase

In this paper the separation of zopiclone (ZP) enantiomers, its degradation products and chiral metabolites, has been investigated on a β-cyclodextrin bonded phase. The liquid chromatographic behavior of the enantiomers of zopiclone, zopiclone-N-oxide (OXZP) and N-desmethyl-zopiclone (DMZP) has been studied with respect to mobile-phase composition, pH, ionic strength and the nature of the organic modifier. Based on the results, conditions were chosen for the separation of the enantiomers of zopiclone, its chiral metabolites and its related degradation products. The separation selectivity of a β-cyclodextrin (β-CD) bonded-phase column was examined. Further, based on crystallographic data, a computer model of the ZP molecule has been designed by using the HyperChem program in order to estimate the possibility of the different groups to interact with the β-CD and to give a plausible explanation of the mechanism of chiral discrimination

Determination of selenium in human milk by electrothermal atomic absorption spectrometry and chemical modification

A method was developed for the determination of selenium in human milk using electrothermal atomic absorption spectrometry. The use of chemical modifiers as well as their implications during the pyrolysis step was examined. The chemical modifiers that were studied were Zr, Ir as well as the mixed modifier Zr-Ir. The Ir modifier stabilized selenium at 1000°C, Zr at 800°C, while the mixed modifier at 1200°C. The effect of modifier mass was studied and was found that better results are achieved with addition of 2 μg Zr and 2 μg Ir. The characteristic masses of selenium in the presence of Zr, Ir and the mixed modifier were found to be 73.3, 18.0 and 14.7 pg, respectively, while the corresponding limits of detection were found 2.0, 0.50 and 0.41 μg l-1. Consequently better results were obtained with the mixed modifier. The developed method was applied for the determination of selenium in human milk, which was digested with a HNO3 + H 2O2 mixture in a microwave oven. The limit of detection of the method was 1.37 μg l-1, the characteristic mass, m 0, was 48.8 pg and the repeatability was less than 5% as R.S.D.(%). Matrix matched calibration was used. Recoveries were estimated to be 93-105%. The method was applied to breast milk of Greek women (n = 9) and the Se content was found to be in the range 16.7-42.6 μg l-1 with mean value 27.4 ± 5.5 μg l-1. © 2005 Elsevier B.V. All rights reserved

Systematic approach to treatment of enantiomeric separations in capillary electrophoresis and liquid chromatography II. A study of the enantiomeric separation of fluoxetine and norfluoxetine

A systematic approach to enantiomeric separations in capillary electrophoresis (CE) and liquid chromatography (LC) with chiral mobile phase additives (MPA) or a chiral stationary phase (CSP) is used in the study of fluoxetine and norfluoxetine with cyclodextrins as chiral selectors. Binding constants and selectivities are determined under the same experimental conditions (mobile phase, buffer composition). Good agreement is found between results from the three techniques. The role of the buffer salt is investigated by comparison of binding constants obtained with triethylammonium and sodium acetate buffers. Investigation of the effects of derivatisation of the selector in CE and LC with MPA demonstrates the appropriate choice of cyclodextrin type for use in LC. By studying the influence of organic modifier content on separation parameters, CE can predict a useful solvent working range for a CSP. © 1995

Liquid chromatographic retention behaviour and separation of promethazine and isopromethazine on a β-cyclodextrin bonded-phase column

A liquid chromatographic method for the separation of promethazine (PR) and its positional isomer isopromethazine (IPR) is described.PR is an N-substituted phenothiazine with the actions and the uses of the antihistamines (H1-receptor antagonists). IPR is an impurity in the pharmaceutical preparations of PR and must be controlled at a level below 1%. The liquid chromatographic behaviour of PR and IPR on a hydrolytically stable β-cyclodextrin (β-CD) column with respect to mobile phase composition, pH, ionic strength and the nature of the organic modifier was also investigated. Based on the results, conditions were chosen for the isocratic separation of the two isomers. The proposed separation method is simple and rapid and permits the simultaneous determination of PR and IPR. The separation selectivity of a cyclodextrin bonded-phase column was examined. Special attention was devoted to modelling the inclusion complexes of PR and IPR with β-CD in order to predict their optimum orientation within the β-CD cavity. © 1994

Solvent selectivity in chiral chromatography using a β‐cyclodextrin‐bonded phase

A β‐cyclodextrin‐bonded phase has been used to investigate the separation of the enantiomers of atenolol, oxprenolol, celiprolol, tertatolol, terbutaline, fluoxetine, norfluoxetine, and zopiclone, focusing on the importance of solvent selectivity. With cyclodextrin (CD)‐bonded phases, chiral discrimination occurs because the two enantiomers of a racemate form inclusion complexes of different strengths within the CD cavity. The organic modifier molecules tend to compete with solutes for a definite number of adsorption sites on the stationary phase. Moreover, the ternary complex formation may play an important role in chiral recognition. In this study, it was of interest to estimate the influence of mobile phase modifiers with respect to solvent type (i.e., ACN, MeOH, EtOH, THF, i‐PrOH, PrOH and t‐BuOH), size and shape, and concentration. Solvent selectivity has been investigated by using different organic modifiers in mobile phases with the same polarity, and relationships were established between the logarithm of solvent partition coefficient (log Ps) and the three most important chromatographic parameters: retention time (t), resolution (R), and enantioselectivity (α). Thus, it seems that the hydrophobicity of the organic modifier becomes one of the dominant factors affecting the inclusion process phenomena. Further, the apparent partition coefficients of the compounds under study have been determined and a comparison has been attempted regarding the degree of their enantiomeric resolution. © 1995 Wiley‐Liss, Inc. Copyright © 1995 Wiley‐Liss, Inc

Prediction of distribution coefficients from structure. Comparison of calculated and experimental data for various drugs

The efficiency of the program PrologD to predict distribution coefficients (D) at any pH and pairing ion concentration has been tested using experimental logD values for various drugs measured under standard conditions of buffers and ionic strength. Clonidine derivatives, fluoroquinolones and β-blockers were included as particular pharmacological classes within the testing data set. Calculations were performed using the three logP estimation options implemented in the program. PrologD proved to be very efficient and can be of great advantage in drug research. Prediction patterns and correlations between experimental and calculated data indicate acceptable results for more than 80 of the data. In addition, comparable studies using the different options permitted suggestions for the more suitable logP estimation method in respect of the particular classes of compounds