Preparation of a Selective Receptor for Ephedrine for the Rapid Electrochemical Detection of Ephedrine in Human Urine Using Stabilized in Air Lipid Films with Incorporated Ephedrine Receptor

Abstract

AbstractThe present technique describes the preparation of a selective receptor for ephedrine and a technique for the rapid electrochemical detection of ephedrine in human urine using lipid films with incorporated receptor that are synthesized by a chemical reaction with a methacrylate polymer on a glass fiber filter. The selective receptor was synthesized using a resorcin[4]arene receptor and by transforming all the OH groups into methoxy groups. Injections of ephedrine were made into flowing streams of a carrier electrolyte solution and a transient current signal, with duration of seconds, appeared in less than two minutes after exposure of the lipid membranes to the compound. The magnitude of this signal was linearly related to the concentration of this stimulant, which could be determined at micromolar levels. The effect of potent interferences including a wide range of compounds usually found in human urine (i.e., ascorbic aid, glucose, leucine, glycine, tartrate, citrate, bicarbonate and caffeine) was examined. Also, the effect of proteins and lipids was investigated. The results showed that there were no interferences from all these constituents in concentration levels usually found in human urine samples. Dopamine was also investigated as a potent interferent. The results have shown that the transformation of the hydroxy to methoxy groups has increased the selectivity of the receptor towards ephedrine and decreased it towards dopamine which does not cause and interference at concentration levels lower than of 10−3 M. Urine samples provided similar results and allowed the development of a technique for the rapid electrochemical detection of this stimulant in human urine at the levels of 10−6 M concentrations. The reproducibility of the method was checked in about 100 samples.