Publications by authors named "Rudaz Serge"

A simple method using ultra performance LC (UPLC) coupled with UV detection was developed and validated for the determination of antituberculosis drugs in combined dosage form, i. e. isoniazid (ISN), pyrazinamide (PYR) and rifampicin (RIF).

View Article and Find Full Text PDF

Accurate determinations of lipophilicity indices benefit from recent advances in chromatographic sciences such as the launch of ultraperformance liquid chromatography (UPLC). The fast strategy presented here emerges as a powerful method suitable for high-throughput log P measurements of therapeutic compounds in isocratic and gradient modes. Because UPLC columns are highly stable in basic pH conditions, this approach allows a direct lipophilicity estimation of basic compounds in their neutral forms.

View Article and Find Full Text PDF

A LC-MS approach is presented for the isolation of minor key plant biomarkers, in view of their characterization by NMR at the microgram scale. Due to the complexity of plant extracts, the purification of metabolites present in low concentrations is critical. The strategy used relies on the optimization of the chromatographic analysis using ultra-performance liquid chromatography-time-of-flight mass spectrometry (UPLC-TOF-MS), thanks to modelling software.

View Article and Find Full Text PDF

CZE is an appropriate technique for separating charged species, but lacks selectivity for neutral compounds. Alternative approaches such as microemulsion electrokinetic chromatography (MEEKC) have been developed to broaden its range of applications. Hyphenation of MEEKC with MS is an attractive perspective since it can enhance sensitivity and selectivity.

View Article and Find Full Text PDF

In this study, ultra performance liquid chromatography (UPLC) using pressures up to 1,000 bar and columns packed with sub-2 microm particles has been combined with high temperature mobile phase conditions (up to 90 degrees C). By using high temperature ultra performance liquid chromatography (HT-UPLC), it is possible to drastically decrease the analysis time without loss in efficiency. The stability and chromatographic behavior of sub-2 microm particles were evaluated at high temperature and high pressure.

View Article and Find Full Text PDF

The use of CE coupled with MS (CE-MS) has evolved as a useful tool to analyze charged species in small sample volumes. Because of its sensitivity, versatility and ease of implementation, the ESI interface is currently the method of choice to hyphenate CE to MS. An alternative can be the atmospheric pressure photoionization (APPI) source, however, numerous parameters must be optimized for its coupling to CE.

View Article and Find Full Text PDF

Liquid chromatography (LC) is currently considered as the gold standard in pharmaceutical analysis. Today, there is an increasing need for fast and ultra-fast methods with good efficiency and resolution for achieving separations in a few minutes or even seconds. A previous article (i.

View Article and Find Full Text PDF

To study the stress-induced effects caused by wounding under a new perspective, a metabolomic strategy based on HPLC-MS has been devised for the model plant Arabidopsis thaliana. To detect induced metabolites and precisely localise these compounds among the numerous constitutive metabolites, HPLC-MS analyses were performed in a two-step strategy. In a first step, rapid direct TOF-MS measurements of the crude leaf extract were performed with a ballistic gradient on a short LC-column.

View Article and Find Full Text PDF

As a potential alternative to cyclosporine A (CsA) monitoring in whole blood, a sensitive and selective method was developed for quantifying this immunosuppressive drug in human peripheral blood mononuclear cells (PBMCs) by liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS). PBMCs were isolated from whole blood by density gradient centrifugation. After purification, cell counts were performed to express CsA amounts per single cell.

View Article and Find Full Text PDF

To study the influence of the particle size distribution (PSD), we measured the chromatographic performance of a series of sub-2 microm particle high performance liquid chromatography (HPLC) columns packed with four different particle mixtures having a purposely imposed different size distribution. Using the reduced kinetic plot representation by plotting the separation impedance (E(0)) versus the plate number ratio (N(opt)/N), the different columns could be classified according to their chromatographic performance without the need to specify a mean particle diameter or a molecular diffusion coefficient, as is needed in the classical reduced plate height and flow resistance analysis. The present analysis shows that it is not so much the width or span of the particle size distribution, but rather the presence of fines that greatly determines the chromatographic performance of particulate columns.

View Article and Find Full Text PDF

All analysts face the same situations as method validation is the process of proving that an analytical method is acceptable for its intended purpose. In order to resolve this problem, the analyst refers to regulatory or guidance documents, and therefore the validity of the analytical methods is dependent on the guidance, terminology and methodology, proposed in these documents. It is therefore of prime importance to have clear definitions of the different validation criteria used to assess this validity.

View Article and Find Full Text PDF

Liquid chromatography (LC) is considered to be the gold standard in pharmaceutical analysis. Today, there is a need for fast and ultra-fast methods with good efficiency and resolution for achieving separations in few minutes or even seconds. The present work describes a simple methodology for performing a successful method transfer from conventional LC to fast and ultra-fast LC.

View Article and Find Full Text PDF

A focused microwave-assisted extraction method was developed for the extraction of diosgenin from fenugreek (Trigonella foenum-graecum) seeds, air-dried and fresh leaves and air-dried roots. Several experimental parameters were studied, including extraction time, microwave power applied and percentage of 2-propanol in the extraction mixture as well as their interactions, in order to optimize the extraction efficiency. The two latter parameters were found to be the most important.

View Article and Find Full Text PDF

In order to reduce the analysis time and maintain good efficiency in liquid chromatography (LC), several solutions are currently being investigated. The focus of this study was to compare, both qualitatively and quantitatively, the chromatographic performance of a conventional LC with selected approaches, namely monolithic supports, high temperature LC (up to 90 degrees C), and sub-2 microm particles combined with high pressure (up to 1000 bar). This comparison was achieved from a qualitative point of view with a special attention paid to the analysis of time reduction, efficiency improvement, and pressure constraint.

View Article and Find Full Text PDF

Matrix effects on mass spectrometry (MS) response were investigated with three atmospheric pressure ionization (API) sources after on-line solid-phase extraction (SPE) of human plasma. On-line SPE was evaluated with one restricted access material (RAM), two large particle supports (LPS) and one monolith. A sample protein precipitation (PP) with acetonitrile (2:1) and a direct injection were tested.

View Article and Find Full Text PDF

In order to enhance chromatographic performances in terms of efficiency and rapidity, LC has recently evolved in the development of short columns packed with small particles (sub-2 microm) working at high pressures (> 400 bar). This approach has been described 30 years ago according to the fundamental chromatographic equations. However, systems and columns compatible with such high pressures have been introduced in the market in 2004 only.

View Article and Find Full Text PDF

The chromatographic performance of several base-deactivated stationary phases was evaluated with a specific chromatographic test. Seven basic test compounds, possessing different physico-chemical properties were injected on different supports with two mobile phases: one at pH 7.0 (acetonitrile-phosphate buffer, 40:60, v/v), and the other at pH 3.

View Article and Find Full Text PDF

In order to reduce the analysis time and maintain good efficiency in liquid chromatography, it is advisable to simultaneously decrease the column length and the particle size of the chromatographic support. Therefore, several manufacturers have developed and commercialized short columns filled with particles that have a diameter smaller than 2 microm. The focus of this work was to check the chromatographic performance of such columns and compare possibilities offered by sub-2 microm supports with conventional columns in terms of analysis time reduction and efficiency improvements.

View Article and Find Full Text PDF

Analyses of statistical variance were applied to evaluate the precision and practicality of a CD-based NACE assay for R-timolol after enantiomeric separation of R- and S-timolol. Data were collected in an interlaboratory study by 11 participating laboratories located in Europe and North America. General qualitative method performance was examined using suitability descriptors (i.

View Article and Find Full Text PDF

Nonaqueous capillary electrophoresis (NACE) was successfully applied to the enantiomeric purity determination of S-timolol maleate using heptakis(2,3-di-O-methyl-6-O-sulfo)-beta-cyclodextrin (HDMS-beta-CD) as chiral selector. With a background electrolyte made up of a methanolic solution of 0.75 M formic acid, 30 mM potassium camphorsulfonate and containing 30 mM HDMS-beta-CD, the determination of 0.

View Article and Find Full Text PDF

It is demonstrated that the kinetic plot representation of experimental plate height data can also account for practical constraints on the column length, the peak width, the viscous heating, and the mobile-phase velocity without needing any iterative solution routine. This implies that the best possible kinetic performance to be expected from a given tested support under any possible set of practical optimization constraints can always be found using a directly responding calculation spreadsheet template. To show how the resulting constrained kinetic plots can be used as a powerful design and selection tool, the method has been applied to a series of plate height measurements performed on a number of different commercial columns for the same component (butyl-parabene) and mobile-phase composition.

View Article and Find Full Text PDF

Due to its high efficiency, selectivity, and sensitivity, CE-ESI/MS has evolved as an efficient technique for the drugs and metabolites analysis in biological matrices. However, a sample preparation is mandatory prior to CE-ESI/MS analysis. To achieve fast and simplified sample preparation of plasma samples, protein precipitation (PP) and liquid-liquid extraction (LLE) were used with two injection techniques: hydrodynamic (HD) and electrokinetic (EK) injection.

View Article and Find Full Text PDF

A simple and fast procedure was developed for the simultaneous determination of eight benzodiazepines (BZDs) in whole blood using liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry (LC-APCI-MS). Sample pretreatment was carried out using a simple liquid-liquid extraction (LLE) with n-butylchloride, and chromatographic separation was performed using a monolithic silica column to speed up the analytical process. APCI and electrospray ionization (ESI) were compared.

View Article and Find Full Text PDF

An RPLC was developed to rapidly determine lipophilicity of neutral and basic compounds using three base deactivated RPLC stationary phases particularly designed for the analysis of basic compounds, namely, Supelcosil ABZ(+)Plus, Discovery RP Amide C16, and Zorbax Extend C18. The work consisted of three sets of experiments. In the first log kw values of neutral compounds were extrapolated using hydroorganic mobile phases at different compositions.

View Article and Find Full Text PDF

A headspace solid-phase microextraction combined with GC-MS method was developed for the extraction and analysis of cannabinoids from Cannabis samples. Different commercially available fibres were evaluated; polydimethylsiloxane 100 microm was selected as the most efficient one. In order to enhance sensitivity and reduce analysis time, the sampling temperature was studied and it showed that extraction should be performed at a high temperature (150 degrees C).

View Article and Find Full Text PDF

A PHP Error was encountered

Severity: Warning

Message: fopen(/var/lib/php/sessions/ci_sessiondd66p8eb8uijunsqhevlpspnoseiia2q): Failed to open stream: No space left on device

Filename: drivers/Session_files_driver.php

Line Number: 177

Backtrace:

File: /var/www/html/index.php
Line: 316
Function: require_once

A PHP Error was encountered

Severity: Warning

Message: session_start(): Failed to read session data: user (path: /var/lib/php/sessions)

Filename: Session/Session.php

Line Number: 137

Backtrace:

File: /var/www/html/index.php
Line: 316
Function: require_once