Extracted ion chromatograms of urine extract with mass selection at m/z 465.3 (a), mass selection and mobility selection between TG (b), mass selection and mobility selection for ETG (c), tandem mass selection for the product ions m/z 109.1 and 97.1 (d), tandem mass selection and mobility selection for TG (e), and tandem mass selected and mobility selected for ETG (f). The mobility selection was found to decrease the presence of noise and spurious signals. Reproduced with permission from Kaur-Atwal et al. [4], copyright 2011 Royal Society of Chemistry.