Development and validation of a liquid chromatography-tandem mass spectrometric method for the determination of alpha-methyltyrosine in human plasma.
A sensitive and selective LC-MS-MS method for the isolation and quantification of alpha-methyltyrosine (AMT) from human plasma is described. The method employs a simple protein precipitation using zinc sulfate and sodium hydroxide. This precipitation procedure produced samples with high aqueous content that could be directly injected into a LC-MS-MS system without compromising reverse-phase chromatographic performance. Chromatographic separation was performed on a MetaChem MonoChrom C(18) column (2.0 mm x 50 mm; 5 microm) at a flow rate of 1 mL/min. Compounds were eluted using a gradient mixture of water-acetic acid (100:0.1, v/v) and acetonitrile-acetic acid (100:0.1, v/v). The structural analog alpha-hydroxymethyltyrosine was used as the internal standard. Mass spectrometric detection was carried out with a triple quadrupole mass spectrometer. The method was validated and used to determine human plasma AMT concentrations, and has been implemented to derive pharmacokinetic parameters.
Humphries
David
D
Department of Drug Disposition, Eli Lilly and Company, Lilly Corporate Center, Indianapolis, IN 46285, USA. humphries_david_j@lilly.com
Ruterbories
Kenneth
K
Chan
Clark
C
Narayanan
Rangaraj
R
D019540:Area Under Curve; D002138:Calibration; D002851:Chromatography, High Pressure Liquid; D004791:Enzyme Inhibitors / Q000097:blood* / Q000493:pharmacokinetics; D006207:Half-Life; D006801:Humans; D007202:Indicators and Reagents; D008297:Male; D013058:Mass Spectrometry; D011786:Quality Control; D015203:Reproducibility of Results; D012997:Solvents; D013048:Specimen Handling; D019805:alpha-Methyltyrosine / Q000097:blood* / Q000493:pharmacokinetics
D004791:Enzyme Inhibitors; D007202:Indicators and Reagents; D012997:Solvents; D019805:alpha-Methyltyrosine