INDIRECT DETERMINATION OF EPHEDRINE IN URINE BY DIFFERENTIAL-PULSE POLAROGRAPHY

The nitrosation of ephedrine and the electrochemical reduction of N-ni trosoephedrine were investigated by differential pulse polarography an d have been optimized in order to attain the optimum analytical signal . Reduction of the N-nitrosoephedrine was carried out in one irreversi ble, diffusion-controlled step using potassium chloride-hydrochloric a cid. In 0.1 M hydrochloric acid the N-nitrosoephedrine shows a well-de fined reduction peak at -0.77 V (vs. Ag/AgCl/3 M KCl). An indirect dif ferential-pulse polarographic method is described for the determinatio n of ephedrine at levels higher than 2.5 mu g per mL of urine. An extr action procedure with C-18 cartridge and a fast and easy nitrosation r eaction with sodium nitrite in 0.2 M phthalate potassium hydrogen is a lso described. Determination of 5 mu g/mL of N-nitrosoephedrine in uri ne samples of 4 mL was possible using the standard addition method, wi th a relative error of -4.0% and relative standard deviations no highe r than 2.1%.