Development of a screening method for the detection of analogues of sildenafil and vardenafil by the use of liquid chromatograph coupled with triple quadrupole linear ion trap mass spectrometer

Abstract

Sildenafil and vardenafil are western drugs used in the treatment of male erectile dysfunction (ED). Prescription is required to use these drugs in many countries including Hong Kong. Recently, health supplements and Chinese herbal drugs claiming to have improvement in male potency were found to be adulterated with these drugs. Even worse, some of these products were found to contain analogues of ED drugs. For regulatory purposes, drug enforcement agencies often use analytical techniques such as HPLC-UV or LC-MS/MS in scheduled multiple reaction monitoring (MRM) mode for routine screening of western drug ingredients. However, drug analogues are expected to have different elution profiles and the ions produced by drug analogues would be different, making them transparent in scheduled MRM conditions. To tackle the problem, an acquisition method that combined precursor ion scan (PIS) with information dependent acquisition (IDA) followed by enhanced product ion (EPI) scan was developed. Results suggested that such an approach could provide a very powerful tool in the detection of analogues of sildenafil and vardenafil.