Preparation of urine samples prior to targeted or untargeted metabolomics mass-spectrometry analysis

Steps preceding introduction of the analytical sample into individual separation equipment and/or mass-spectrometry (MS) detectors for targeted or untargeted metabolomics studies have not generally received the required attention, but particularly in dealing with urine samples. These steps have been classified into urine sample-pretreatment steps (i.e. those encompassing from sampling to storage) and urine sample-preparation steps (i.e. from thawing to insertion into the separation device and/or detector). We first discuss the steps constituting the former group (sampling time and collection, quenching, preservative addition, volume correction, pH adjustment, deproteinization by centrifugation, normal filtration, ultrafiltration, ultrasound-assisted filtration and freezing/thawing cycles), and of those forming the latter group (dilution, enzymatic hydrolysis, sample clean-up and preconcentration by solid-phase extraction, liquid liquid extraction, evaporation, and lyophilization). We then reach conclusions that open a door to future, necessary research to improve the field of metabolomics on urine samples. Crown Copyright (C) 2012 Published by Elsevier Ltd. All rights reserved.