Determination of nitecapone and ( 13 C 6 )nitecapone in human plasma by gas chromatography/mass spectrometry

A gas chromatographic/mass spectrometric method is developed and validated for simultaneous determination of nitecapone and its 13 C 6 ‐labelled analogue in human plasma using ( 2 H 6 , 13 C 6 )nitecapone as internal standard. The method involves extraction of the analytes from plasma to ethyl acetate‐hexane mixture (20:80) and conversion to bis(trimethylsilyl) ethers prior to determination by gas chromatography/mass spectrometry using selected ion monitoring. The quantification range is 0.5–2000 ng ml −1 . Precision ranges from 11.3% (coefficient of variation) at low levels to 2.4% at high levels. Recovery is about 50% in the whole range. The method is applied to a pharmacokinetic study where nitecapone diluted with 14 C‐labelled nitecapone is given intravenously concomitantly with an oral dose of ( 13 C 6 )nitecapone.