Dietary supplements are currently popular because of their natural origin, especially male enhancement products. However, some of these products have been found to contain erectile dysfunction drugs that inhibit the enzyme phosphodiesterase-5 (PDE-5), leading to adverse effects on human health. In this study, capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-C4D) was used to determine four PDE-5 inhibitors (including acetyl vardenafil, homosildenafil, hydroxy acetildenafil and mirodenafil) in dietary supplement samples. The optimum analytical conditions included electrolyte solution of 20 mM arginine (Arg)/acetic acid (Ace)/acetonitrile (ACN) 20% pH 6.5, silica capillary 50 μm inner diameter with effective length of 50 cm, separation voltage of 20kV, siphoning hydrodynamic injection at a height of 25 cm for 30 s. At the optimum analytical conditions, the limits of detection of acetyl vardenafil, homosildenafil, hydroxy acetildenafil, and mirodenafil were 2.1, 1.6, 2.3, and 1.3 mg/L, respectively. The analysis of four PDE-5 inhibitors by CE-C4D also showed good repeatability (< 5 %) and recovery (> 97 %). This method was further applied to simultaneously determine the amount of acetyl vardenafil, homosildenafil, hydroxy acetildenafil, and mirodenafil in three functional products. All four PDE-5 inhibitors were not detected in these samples. To demonstrate the utility of this method, the mixture of four PDE-5 inhibitors standard solutions was added to three samples. The recovery was between 98.8 % and 100.6%, illustrating the potential applicability of the method of determining PDE-5 inhibitors in dietary supplement samples.
PDE-5, CE-C4D, acetyl vardenafil, homosildenafil, hydroxy acetildenafil, mirodenafil.
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