Metabolomics analysis II. Preparation of biological samples prior to detection

After discussing the significance of preliminary operations, such as selection or storage of biological samples, we critically review the other steps of the analytical process prior to metabolite detection. First comes interruption of metabolism or quenching, which is of crucial importance in the analysis of biological samples. Then, we consider quantitative extraction of metabolites (selective or total for targeted or global metabolomics analysis, respectively) as a function of sample characteristics: solid or liquid samples and cell culture. Finally, we comment on additional steps, such as preconcentration of metabolites, clean up of extracts and fractionation for metabolite separation, and discuss their inclusion in analytical methods.