A. UPLC-AMS analysis of the 6–12 hour urine pool, not treated with β-glucuronidase, from a representative volunteer. Non-β-glucuronidase treated urine contains few retained metabolites and a low [14C] signal. B. UPLC-AMS analysis of urine from the same pool, treated with β-glucuronidase, contained several metabolites that were free to be extracted, separated, and detected.