4. Screening and sample analysis

First of all, the analyst is faced with specific difficulties, such as having the right samples and equipment for the job, keeping abreast of new molecules in circulation, finding bibliography relating to the subject, and above all having the molecules and their metabolites referenced in his laboratory.

Once all these parameters have been taken into account, the analysis can be carried out under optimum conditions. Analytical procedures are often composed of immunochemical screening, ELISA (Enzyme-Linked immunosorbent assay) or RIA (RadioImmunoAssay), followed by chromatographic confirmation, or directly by chromatographic analysis. Immunological methods are used for screening to verify the presence of molecules in a non-specific, non-quantitative way.

The two possible chromatographic methods are gas chromatography and liquid chromatography....