An LC–MS–MS method for quantitation of four new phenethylamines (BOX series) in plasma: in vivo application

The appearance of new “designer drugs” in the illicit market poses a serious health risk because they have unknown safety profiles, have a high potential for abuse, high potency, and can lead to devastating health consequences. For this reason, it is desirable to develop validated and reliable analytical screening tests that allow detection of amphetamines and related designer drugs in biological samples. We report a method for separation and quantitation of four new phenethylamines, 4-bromo-2,5-beta-trimethoxyphenethylamine (BOB), 4-methyl-2,5-beta-trimethoxyphenethylamine (BOD), 3,4-methylenedioxy-beta-methoxyphenethylamine (BOH), and 4-methyl-2,5-dimethoxy-beta-hydroxyphenethylamine (BOHD), in plasma. Quantitation was achieved via liquid chromatography–tandem mass spectrometry (LC–MS–MS) in the multiple reaction monitoring mode, using 2,3-dimethoxyphenethylamine- d 3 as internal standard. The method was validated according to international guidelines. The parameters determined were selectivity, sensitivity, matrix effect, linearity, precision, recovery, and stability. All parameters were satisfactory. To remove matrix interference, solid-phase extraction was introduced in the method as clean-up step. The same method was applied in a pharmacokinetic study to monitor the target compounds in rat plasma after a single oral administration. The developed and validated LC–MS–MS method is the first available for quantitation of BOB, BOH, BOD, and BOHD in a biological matrix. This method is recommended for use in forensic and clinical toxicology, because of its sensitivity, selectivity, and simplicity. An important extension of this method could involve its application to other complex matrices.