To establish an analytical method for detecting of de-N-ethyl derivative of vardenafil drug in foods by high-resolution mass spectrometry “diagnostic ion” coupled with nuclear magnetic resonance spectroscopy.

The samples to be tested were dissolved in methanol/H₂O, extracted by ultrasound and injected into high-resolution mass spectrometry to analyze and determine the nafil-type of the unknown compound. After extraction, enrichment, purification and concentration of the targeted analyte in the positive sample, it was identified through nuclear magnetic resonance spectroscopy analysis. A quantitative method for detecting of vardenafil derivative in foodstuffs was developed by ultra performance liquid chromatography-coupled triple quadrupole mass spectrometry (UPLC-MS/MS).

The unknown compound was characterized as de-N-ethyl derivative of vardenafil drug. UPLC-MS/MS analysis showed that the mass spectrometric response of de-N-ethyl derivative of vardenafil drug in 4 kinds of food matrix were well linear in the mass concentration range of 2–100 ng/mL. The spiking average recovery rate in 4 kinds of food matrix were ranged from 74.07%–110.05% with relative standard deviations of 0.36%–5.09% in 4 different concentrations. The limits of detection (S/N=3) and limits of quantitation (S/N=10) was 0.05 mg/kg and 0.10 mg/kg, respectively. This method was developed and employed to screen 50 batches of samples and de-N-ethyl derivative of vardenafil drug was detected in 5 batches of samples along with a content between 722 mg/kg to 1548 mg/kg.

The established detection method does not require complex sample pretreatment, and has high sensitivity and good accuracy, which can meet the requirements for detecting de-N-ethyl derivative of vardenafil drug in food in routine laboratory tests after being re-examined by 6 inspection and testing institutions.