Dummy molecularly imprinted solid phase extraction in a nylon membrane filter for analysis of vardenafil in health care products

Abstract

A novel dummy molecularly imprinted polymer (MIP) was prepared for highly specific recognition of vardenafil. Sildenafil was used as the template, and Fe-based metal-organic gel was in situ formed and acted as structural modulator and porogenic agent. The obtained MIP was demonstrated to have stronger binding affinity and higher binding capacity towards vardenafil than non-imprinted polymer (NIP). Adsorption processes of vardenafil on MIP and NIP were fitted well by Freundlich isotherm model. Combined with LC-MS analysis, a miniaturized solid phase extraction (SPE) method using MIP as the adsorbent and using a syringe connected with a nylon membrane filter as the adsorbent container was developed. Under the optimal extraction parameters, trace vardenafil has been extracted by the developed method from the spiked water sample with satisfied recovery of 104%, and the intra- and inter-day relative standard deviations (RSDs) were below 7.3%. The linear range was 10–1000 ng mL−1 (R2 = 0.9996), and the limit of detection (LOD, S/N = 3) and limit of quantification (LOQ, S/N = 10) were 1.8 and 6.0 μg L−1, respectively. Finally, the proposed MIP-SPE-LC/MS method was applied to discover vardenafil from health care products (HCPs) using standard addition method. The repeatability for both HCPs was below 6.3% (RSD values). Analysis results implied that the developed MIP-SPE-LC/MS method is green, convenient and useful to monitor the illegal additives in HCPs.