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 | Mass spectrometry and Bioassay |
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| Mass spectrometry (MS) is an analytical technique based on fragmentation of molecules and the separation of the ionised fragments according to their mass and charge. The respective percentages of the various fragments from the mass spectrum which, under standard analytical conditions, corresponds to a genuine profile of the molecule. MS is used for the qualitative and quantitative analysis of natural elements and organic compounds in R & D laboratories. |
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| The structure of a molecule is determined by its mass spectrum after ionisation by one of the three (or more) following methods: Electron Impact (EI), the most energetic method which fractionates the molecule; Chemical Ionisation (CI+, CI-), a less energetic method which generally allows to obtain the molecu-lar ion of the compound; and FAB (Fast Atom Bombardment) which applies to fragile molecules like peptides or polysaccharides. The quantitative analysis of a molecule is achieved by measuring the abundance of one of the fragments obtained (SIM method: Single Ion Monitoring) after fragmentation. |
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| These various analytical methods are used by the teams associated with SPI-Bio to undertake three types of studies: |
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| Structure analysis: identification of metabolites and derivatives (chemical synthesis and degradation |
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| The identification, by MS, of metabolites in biological fluids, is the last stage of an assessment of the vari-ous metabolic routes of an active drug. Various ionisation techniques may be used after a gas or a liquid chromatography/mass spectrometry, in order to distinguish compounds which are chemically similar. Chemical ionisation is used to determine molecular mass and provide guidance on the chemical modifications which give rise to metabolites (e.g. hydroxyla-tion, demethylation). The fragments obtained by Chemical ionisation or electron Impact allow confirmation of hypotheses on the exact structure of the studied compound (parent substance or metabolite). |
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| Assay of active molecule after gas or liquid chromatography |
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| Combined gas or liquid chromatography/mass spec-trometry is used to analyse drugs in biological fluids. Sensitivity close to 10 pg/ml is currently obtained, al-lied to an optimal specificity. An automatic injector and data processing software allow analysis of large series of samples. |
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| Kinetics of a stable isotope of a natural element |
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| The bioavailability of natural elements with therapeutic interest in man may be calculated after administration of a stable isotope of the element. MS allows measurement of the isotopic ratio of this element in biological samples. It is therefore possible to deduce from this the concentration of the isotope added. H.B. |
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| Techniques available with SPI-Bio |
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- Ionisation: MS/ IE, CI+, CI-, FAB; MS/MS
- Coupling: CPG/MS; HPLC/MS; Direct introduction
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