Qualitative analysis of illegally adulterated sildenafil and related compounds in dietary supplements by ultra-high performance liquid chromatography-quadrupole-time-of-flight mass spectrometry

Abstract

The presence of illegally adulterated sildenafil and related compounds in dietary supplements was qualitatively analyzed by employing ultra-high performance liquid chromatography-quadrupole-time-of-flight mass spectrometry (UPLC-Q-TOF-MS). Samples were extracted by ultrasonic method using methanol. The analysis was performed on an Agilent Poroshell 120 SB-C18 column (75 mm×3.0 mm, 2.7 μm) using gradient elution with a mixture of aqueous formic acid solution (0.1%, v/v) and acetonitrile as the mobile phase at a flow rate of 0.4 mL/min. Q-TOF-MS equipped with ESI ion source was operated in a positive ionization mode. Qualitative analysis was based on the retention time and the accurate relative molecular mass of elemental compositions of the precursor ion and product ions. The limits of detection (LODs) of sildenafil and other 99 compounds were found to be 0.1-50 mg/kg or 0.1~50 mg/L in 10 different matrices. In this manuscript, the fragmentation behavior of 98 phosphodiesterase-5 inhibitors are categorically summarized, which can provide information for referencing and identification of suspicious compounds. The method was successfully applied to the analysis of actual samples, of which 19 compounds combated the illegal adulteration behavior effectively.