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The metabolome is characterized by a large number of molecules exhibiting a high diversity of chemical structures and abundances, requiring complementary analytical platforms for extensive coverage. Of these analytical platforms, atmospheric pressure ionization Fourier transform mass spectrometry (FT/MS) instruments are popular because they provide accurate mass measurements with ppm and even sub-ppm errors, and also high and ultra-high resolving power. In this article, we evaluate the improvements provided for metabolomics by different types of FT/MS instruments, together with the ability of these platforms to cover the various analytical requirements: global metabolite profiling, absolute quantification and also structural characterization, of metabolomics. The specificities of FT/MS in terms of data pre-processing and the input of accurate mass measurements for biological interpretation and for highlighting metabolic networks are also addressed.

The insulin-like-growth-factor-I (IGF-I) peptide is known to be a marker for growth hormone administration. The development of a quantification method by electrospray ionization mass spectrometry (ESI-MS) coupled with high-performance liquid chromatography (HPLC) is required. This paper describes a method to quantify IGF-I using the internal standard R3 IGF-I in its oxidized forms. A deconvolution software was used to quantify the set of multi-charged molecules recorded on an ESI ion trap mass spectrometer. The results (i.e., linearity, reproducibility and concentration range) were obtained on standard samples and the described LC-ESI-MS method should be applicable to biological samples.

A threshold concentration for cortisol in equine urine was fixed at 1.0 microgram ml-1 by the racing authorities in 1994. In some circumstances, interlaboratory discrepancies were observed and structural cortisol modification was revealed. In order to elucidate the degradation process and to prevent it, an identification study of the produced compound was carried out. The modified substrate was characterised by the same molecular weight as cortisol and a shorter retention time under the conditions used for the cortisol quantification (M.A. Popot, PhD Thesis, King's College, London, 1996). To identify this isomer, HPLC-APCI-MS and MS-MS methods were applied to the cortisol post-administration extract diluted in the mobile phase which was either a mixture of methanol-water or labelled methanol-water (CH3OD-D2O). Stereochemical effects were studied under these conditions. Deuterium-hydrogen exchange was also monitored by HPLC-APCI-MS. Considering MS and MS-MS data, the hypothesis of isomerisation at C11 giving the 11 alpha-cortisol was rejected. Isotopic labelling has allowed determination of the number of labile hydrogen atoms of the modified cortisol. Cortisol and modified cortisol have the same number of mobile hydrogens. Therefore, the hypothesis of a reduction at C20 along with an oxidation at C11 has also been rejected. Deuterium-hydrogen exchanges could be a useful tool to elucidate the structure of compounds analysed by HPLC-APCI-MS in a complex matrix such as horse urine extract.