Determination of trimethylamine‐N‐oxide in combination with l‐carnitine and γ‐butyrobetaine in human plasma by UPLC/MS/MS

An ultra‐high‐performance liquid chromatography–mass spectrometry (UPLC/MS/MS) method was developed and validated for the quantification of trimethylamine‐N‐oxide (TMAO) simultaneously with TMAO‐related molecules l ‐carnitine and γ‐butyrobetaine (GBB) in human blood plasma. The separation of analytes was achieved using a Hydrophilic interaction liquid chromatography (HILIC)‐type column with ammonium acetate–acetonitrile as the mobile phase. TMAO determination was validated according to valid US Food and Drug Administration guidelines. The developed method was successfully applied to plasma samples from healthy volunteers. Copyright © 2015 John Wiley & Sons, Ltd.     

Quantitative analysis of phenibut in rat brain tissue extracts by liquid chromatography–tandem mass spectrometry

Phenibut (3-phenyl-4-aminobutyric acid) is a γ-aminobutyric acid mimetic drug, which is used clinically as a mood elevator and tranquilizer. In the present work, a rapid, selective and sensitive liquid chromatography–tandem mass spectrometry method for quantification of phenibut in biological matrices has been developed. The method is based on protein precipitation with acidic acetonitrile followed by isocratic chromatographic separation using acetonitrile–formic acid (0.1% in water; 8:92, v/v) mobile phase on a reversed-phase column. Detection of the analyte was performed by electrospray ionization mass spectrometry in multiple reaction monitoring mode with the precursor-to-product ion transition m/z 180.3 → m/z 117.2. The calibration curve was linear over the concentration range 50–2000 ng/mL. The lower limit of quantification for phenibut in rat brain extracts was 50 ng/mL. Acceptable precision and accuracy were obtained over the whole concentration range. The validated method was successfully applied in a pharmacological study to analyze phenibut concentration in rat brain tissue extract samples. Copyright © 2008 John Wiley & Sons, Ltd.