Determination of synthetic phosphodiesterase-5 inhibitors by LC-MS2 in waters and human urine submitted to dispersive liquid -liquid microextraction

High-performance liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS2) with a triple quadrupole is proposed for determining the synthetic phosphodiesterase-5 inhibitors, sildenafil, tadalafil and vardenafil, and the active metabolite N-desmethyl sildenafil. The method was successfully applied to the analysis of waters of different origins and human urine samples. Dispersive liquid-liquid microextraction (DLLME) was applied in the classical way for water analysis, whereas a previous extraction into an organic solvent was necessary for urine samples, the acetonitrile extract being used as dispersant solvent in the DLLME step. The analytes were determined by LC-ESI-MS2 in the multiple reaction monitoring mode. Detection limits were in the 5-50 and 15-250 ng L-1 ranges for water and urine samples, respectively. The repeatability was calculated using the relative standard deviation, obtaining values of between 3.6% and 10.1%. The enrichment factors were between 75 and 81. Accuracy of the procedure was calculated through recovery assays and average recoveries +/- SD (n = 48) of 93.6 +/- 3.5 and 91.1 +/- 3.5 were obtained for water and urine samples, respectively. None of the samples analyzed contained the target compounds, at least above the corresponding detection limits.