Preparation of a selective receptor for ephedrine for the development of an optical spot test for the detection of ephedrine in human urine using stabilized in air lipid films with incorporated receptor.

The present technique describes the preparation of a selective receptor for ephedrine and a simple sensitive spot optical test for the rapid one-shot detection of ephedrine in human urine using lipid films with an 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. The lipid films without this receptor provided fluorescence under a UV lamp. The use of the receptor in these films quenched this fluorescence, and the color became similar to that of the filters without the lipid films. A drop of aqueous solution of ephedrine provided a "switching on" of the fluorescence, which allows the rapid detection of this stimulant in human urine at the levels of 10(-8) M concentrations. The effect of potent interferences (i.e., proteins, lipids, ascorbic aid, glucose, leucine, glycine, tartrate, citrate, bicarbonate, and caffeine) was examined. The results showed no interferences from these compounds in concentration levels usually found in human urine samples. Dopamine was also investigated as a potent interfering agent, and the results have shown that the transformation of the hydroxy to methoxy groups has altered the selectivity of the receptor. This species does not cause interference at concentration levels lower than 10(-6) M. A drop of urine containing ephedrine provided also a "switching on" of the fluorescence, which allows the rapid detection of this stimulant in human urine at the levels of 10(-8) M concentrations. The reproducibility of the method was checked in approximately 100 samples, and all of them were found to provide similar results. Note that the colors of the filters remain stable for periods of more than 2 months.