Biomedical subjects

Davy Guillarme

Publications and source records attributed to Davy Guillarme.

6 recordsLinked to original sources

PubMed2006

Recent developments in liquid chromatography--impact on qualitative and quantitative performance.

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. For this purpose, the different approaches were discussed using Knox curves and other kinetic plots. It appeared that columns packed with sub-2 microm particles under high-pressure conditions (UPLC) were well adapted and this option represents an attractive alternative to conventional LC; however, the other alternative approaches should not be neglected. The quantitative evaluation of these techniques was performed on the basis of the validation of results of a pharmaceutical formulation (Rapidocaïne), following SFSTP 2003 guidelines. Fast-LC approaches demonstrated equivalent performance to conventional LC in terms of trueness, precision, and accuracy profile, with a significant time reduction (up to 8x) according to the selected methodology.

Chromatography, Liquid↗

PubMed2006

Chromatographic behaviour and comparison of column packed with sub-2 microm stationary phases in liquid chromatography.

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. For this purpose, different parameters were discussed namely: separation impedance (E), Knox curves (h,v), and number of plates by time unit (N/t0). Kinetic plots were also drawn. It appeared that sub-2 microm supports were well adapted to improve chromatographic performance and to reduce the analysis time. Furthermore, it was also demonstrated that the best chromatographic performances were reached with high pressure systems (up to 1000 bar).

Chromatography, Liquid↗

PubMed2006

Practical constraints in the kinetic plot representation of chromatographic performance data: theory and application to experimental data.

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. The method, for example, allows one to account for the fact that the advantageous solutions displayed by the silica monolith and 5 microm particle columns in the large plate number range of the free kinetic plot are no longer accessible if applying a maximal column length constraint of Lmax = 30 cm. In the plate number range that remains accessible, the investigated sub-2 mum particle columns in any case perform (at least for the presently considered parabene separation) better than the 3.5 mum particle columns or silica monolith, especially if considering the use of system pressures exceeding 400 bar. The constrained kinetic plot method can also be used to select the best-suited column length from an available product gamma to perform a separation with a preset number of plates. One of the optimization results that is obtained in this case is that sometimes a significant gain in analysis time can be obtained by selecting a longer column, yielding the desired plate number at a larger velocity than that for a shorter column.

Algorithms↗

PubMed2006

Enhanced method performances for conventional and chiral CE-ESI/MS analyses in plasma.

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. CE-ESI/MS analyses of pharmaceutical compounds and amphetamine derivatives were developed. Detection limits of 1 ppm were reached with PP and HD injection whereas 1 ppb was detected when samples were prepared with LLE and injected by EK. Same experiments were performed for stereoselective determinations in partial-filling mode and detection limits achieved were equivalent to conventional analysis (0.5 ppb per enantiomer). When complex matrices are analyzed, MS signal suppression or enhancement effects are generally not reproducible and could compromise results with ESI. Therefore, matrix effect was investigated in CE-ESI/MS with a commercially available coaxial sheath-liquid ESI interface used as postcapillary infusion system to determine MS signal alterations. Matrix effects were differentially evidenced according to the selected sample preparation. With PP, signal suppression was observed out of the analyses migration window, while for LLE no relevant matrix effect occurred in all experiments.

Amphetamines↗

PubMed2006

Fast analysis in liquid chromatography using small particle size and high pressure.

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. Advantages of small particles working at high pressure will be discussed in terms of sensitivity, efficiency, resolution, and analysis time. Potential problems encountered with high pressure in terms of frictional heating and solvent compressibility will also be discussed even if systems working at a maximum pressure of 1000 bar are not influenced by these parameters and give reliable and reproducible results. Several applications will highlight the potential and interest of this new technology.

Chromatography, Liquid↗

PubMed2005

Some advantages of high temperature for the separation of pharmaceutical compounds with mass spectrometry detection.

The beneficial effects of high temperature on separation and detection of basic compounds, the detection being performed by MS via ESI, are investigated. The influence of various parameters on both separation and detection performances is studied. These parameters include the mobile phase pH, the temperature, and the type of stationary phase. Experiments are performed under gradient elution conditions. The results obtained with four different supports, silica-, zirconia-, carbon-, and polymer-based columns, are compared by means of different criteria including the elution composition, the peak asymmetry, and the S/N. High temperature liquid chromatography at high pH with volatile buffers suitable for MS detection was shown to be an interesting choice for solutes with basic sites.

Chromatography, Liquid↗