Fig. 1

HPLC chromatograms of (a) drug-free urine extract; (b) urine sample spiked with spironolactone (10 μg/mL; RT: 8.56 min), canrenone (10 μg/mL; RT: 11.11 min) and n-propylbenzene (10 μg/mL; IS, RT: 5.61 min); and (c) urine extract after the administration of spironolactone for 12–16 h (20 mg/kg, p.o.). 1: n-propylbenzene; 2: spironolactone; 3: canrenone