Determination of ephedrine alkaloids in human urine and plasma by liquid chromatography/tandem mass spectrometry: collaborative study.

A collaborative study was conducted to evaluate the accuracy and precision of a method for ephedrine-type alkaloids (i.e., norephedrine, norpseudoephedrine, ephedrine, pseudoephedrine, methylephedrine, and methylpseudoephedrine) in human urine and plasma. The amount of ephedrine-type alkaloids present was determined using liquid chromatography (LC) with tandem mass selective detection. The test samples were diluted to reflect a concentration of 5.00-100 ng/mL for each alkaloid. An internal standard was added and the alkaloids were separated using a 5 microm phenyl LC column with an ammonium acetate, glacial acetic acid, acetonitrile, and water mobile phase. Eight blind duplicates of human urine and eight blind duplicates of human plasma were analyzed by 10 collaborators. In addition to negative controls, test portions of urine and plasma were fortified at 3 different levels with each of the 6 ephedrine-type alkaloids at approximately 1, 2, and 5 microg/mL for urine and 100, 200, and 500 ng/mL for plasma. On the basis of the accuracy and precision results for this collaborative study, it is recommended that this method be adopted Official First Action for the determination of 6 different ephedrine-type alkaloids in human urine and plasma.