Application of sol-gel based molecularly imprinted xerogel for on-line capillary microextraction of fentanyl from urine and plasma samples

A molecularly imprinted xerogel (MIX) for fentanyl was successfully prepared on the inner surface of a copper tube by sol-gel technology. Primarily, the tube was treated by self-assembly monolayers of 3-(mercaptopropyl) trimethoxysilane and then [3-(2,3-epoxypropoxy)-propyl]-trimethoxysilane was employed as a precursor for imprinting the template molecule in acidic conditions. During the sol-gel process influential parameters including volume and concentration of fentanyl were carefully investigated to obtain the most efficient and appropriate xerogel. In parallel, a non-imprinted xerogel (NIX) was synthesized in the absence of fentanyl. The extraction efficiencies achieved from MIX and NIX, showed some degree of selectivity for the MIX coating. Donepezil was used to estimate the selectivity of the imprinted xerogel with respect to the template molecule. The ratio of MIX/ NIX, as a criterion of selectivity, was about 2.5 and 1.1 for fentanyl and donepezil, respectively. The linearity of the analyte was in the range of 5-5000 mu g L-1. LOD was found to be 3 mu g L-1 and the inter-and intra-day RSD% of 5.5 and 6.5 (n = 5) were obtained. The developed method was conveniently applied to plasma and urine samples spiked with the analyte, while the relative recovery percentages for the spiked samples were up to 85%.