Le Centre de Compétence en Chimie et Toxicologie Analytiques. The Centre of Competence in Analytic Chemistry and Toxicology (CCCTA)

This article presents concisely activities, goals and members of the Centre of Competence in Analytical Chemistry and Toxicology which was created recently in the Lake Geneva region

What Type of Research Is Done in the Laboratory of Pharmaceutical Analytical Chemistry of the University of Geneva?

This article presents briefly the main research projects developed in the Laboratory of Pharmaceutical Analytical Chemistry at the University of Geneva. This laboratory is particularly concerned about enantiomeric separation of drugs and phytochemical analysis. In this context, techniques such as gas, liquid and supercritical fluid chromatography as well as capillary electrophoresis are studied. Furthermore, the development of new sample preparation techniques is investigated

Evaluation of an in-capillary approach for performing quantitative cytochrome P450 activity studies

An automated in-capillary assay requiring very small quantities of reagents was developed for performing in vitro cytochrome P450 (CYP450) drug metabolism studies. The approach is based on the following: (i) hydrodynamic introduction of nanoliter volumes of substrate and enzyme solutions in the sandwich mode, within a capillary; (ii) mixing the reagents by diffusion across the interfaces between the injected solutions; (iii) collection of the capillary content at the end of the in-capillary assay; and (iv) off-line analysis of the incubation mixture by ultrahigh pressure liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). After optimizing the injection sequence of the reagents, the in-capillary approach was applied to the quantitative determination of the kinetics of drug metabolism reactions catalyzed by three CYP450 isozymes involved in human drug metabolism: CYP1A2, CYP2D6, and CYP3A4. It was demonstrated that this in-capillary method was able to provide similar kinetic parameters for CYP450 activity (e.g., Michaelis constants and turnover values) as the classical in vitro method, with a drastic reduction of reagent consumption. Injection setups used for in-capillary CYP450 assay

Rapid analysis of fluoxetine and its metabolite in plasma by LC-MS with column-switching approach

Abstract.: A rapid and sensitive method was developed for the simultaneous determination of fluoxetine and its primary metabolite, norfluoxetine, in plasma. It was based on a column-switching approach with a precolumn packed with large size particles coupled with a liquid chromatography-electrospray ionisation-mass spectrometry (LC-ESI-MS). After a simple centrifugation, plasma samples were directly injected onto the precolumn. The endogenous material was excluded thanks to a high flow rate while analytes were retained by hydrophobic interactions. Afterwards, the target compounds were eluted in back flush mode to an octadecyl analytical column and detected by ESI-MS. The overall analysis time per sample, from plasma sample preparation to data acquisition, was achieved in less than 4min. Method performances were evaluated. The method showed good linearity in the range of 25-1000ngmL−1 with a determination coefficient higher than 0.99. Limits of quantification were estimated at 25ngmL−1 for fluoxetine and norfluoxetine. Moreover, method precision was better than 6% in the studied concentration range. These results demonstrated that the method could be used to quantify target compounds. Finally, the developed assay proved to be suitable for the simultaneous analysis of fluoxetine and its metabolite in real plasma sample

Evaluation of Solid-Phase Microextraction Desorption Parameters for Fast GC Analysis of Cocaine in Coca Leaves

By its simplicity and rapidity, solid-phase microextraction (SPME) appears as an interesting alternative for sample introduction in fast gas chromatography (fast GC). This combination depends on numerous parameters affecting the desorption step (i.e., the release of compounds from the SPME fiber coating to the GC column). In this study, different liner diameters, injection temperatures, and gas flow rates are evaluated to accelerate the thermal desorption process in the injection port. This process is followed with real-time direct coupling a split/splitless injector to a mass spectrometer by means of a short capillary. It is shown that an effective, quantitative, and rapid transfer of cocaine (COC) and cocaethylene (CE) is performed with a 0.75-mm i.d. liner, at 280°C and 4 mL/min gas flow rate. The 7-µm polydimethylsiloxane (PDMS) coating is selected for combination with fast GC because the 100- µm PDMS fiber presents some limitations caused by fiber bleeding. Finally, the developed SPME-fast GC method is applied to perform in less than 5 min, the quantitation of COC extracted from coca leaves by focused microwave-assisted extraction. An amount of 7.6 ± 0.5 mg of COC per gram of dry mass is found, which is in good agreement with previously published result

Comparative study of recent wide-pore materials of different stationary phase morphology, applied for the reversed-phase analysis of recombinant monoclonal antibodies

Various recent wide-pore reversed-phase stationary phases were studied for the analysis of intact monoclonal antibodies (mAbs) of 150kDa and their fragments possessing sizes between 25 and 50kDa. Different types of column technology were evaluated, namely, a prototype silica-based inorganic monolith containing mesopores of ∼250Å and macropores of ∼ 1.1μm, a column packed with 3.6μm wide-pore core-shell particles possessing a wide pore size distribution with an average around 200Å and a column packed with fully porous 1.7μm particles having pore size of ∼300Å. The performance of these wide-pore materials was compared with that of a poly(styrene-divinyl benzene) organic monolithic column, with a macropore size of approximately 1μm but without mesopores (stagnant pores). A systematic investigation was carried out using model IgG1 and IgG2 mAbs, namely rituximab, panitumumab, and bevacizumab. Firstly, the recoveries of intact and reduced mAbs were compared on the two monolithic phases, and it appeared that adsorption was less pronounced on the organic monolith, probably due to the difference in chemistry (C18 versus phenyl) and the absence of mesopores (stagnant zones). Secondly, the kinetic performance was investigated in gradient elution mode for all columns. For this purpose, peak capacities per meter as well as peak capacities per time unit and per pressure unit (PPT) were calculated at various flow rates, to compare performance of columns with different dimensions. In terms of peak capacity per meter, the core-shell 3.6μm and fully porous 1.7μm columns outperformed the two monolithic phases, at a temperature of 60°C. However, when considering the PPT values, the core-shell 3.6μm column remained the best phase while the prototype silica-based monoliths became very interesting, mostly due to a very high permeability compared with the organic monolith. Therefore, these core-shell and silica-based monolith provided the fastest achievable separation. Finally, at the maximal working temperature of each column, the core-shell 3.6μm column was far better than the other one, because it is the only one stable up to 90°C. Lastly, the loading capacity was also measured on these four different phases. It appeared that the organic monolith was the less interesting and rapidly overloaded, due to the absence of mesopores. On the other hand, the loading capacity of prototype silica-based monolith was indeed reasonabl