Sensitive determination of oxybutynin and desethyloxybutynin in dog plasma by LC–ESI/MS/MS

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• 作者：Kim ; Hohyun ; Han ; Sang Beom
• 关键词：Tandem mass spectrometry ; Liquid chromatography ; Multiple reaction monitoring ; Oxybutynin ; Desethyloxybutynin ; Diazepam
• 刊名：Journal of Pharmaceutical and Biomedical Analysis
• 出版年：2003
• 出版时间：February 26, 2003
• 年：2003
• 卷：31
• 期：2
• 页码：341-349
• 全文大小：206 K

文摘

A sensitive and selective liquid chromatographic method coupled with tandem mass spectrometry (LC–MS/MS) was developed for the quantification of oxybutynin and desethyloxybutynin in dog plasma. Diazepam was used as internal standard, with plasma sample extracted using n-hexane and back-extracted using hydrochloric acid. A centrifuged lower layer (aqueous layer) was injected into a C₁₈ XTerra MS column (2.1×30 mm²) with 3.5 μm particle size. The analytical column lasted for at least 500 injections. The mobile phase was composed of 90 % methanol, with flow rate at 200 μl/min. The mass spectrometer was operated in positive ion mode using electrospray ionization. Nitrogen was used as the nebulizer gas and argon was used as the collision gas. Using MS/MS with multiple reaction monitoring (MRM) mode, oxybutynin and desethyloxybutynin were detected without severe interferences from plasma matrix. Oxybutynin produced a protonated precursor ion ([M+H]⁺) at m/z 358 and a corresponding product ion at m/z 142. Desethyloxybutynin produced a protonated precursor ion ([M+H]⁺) at m/z 330 and a corresponding product ion at m/z 96. And internal standard (diazepam) produced a protonated precursor ion ([M+H]⁺) at m/z 285 and a corresponding product ion at m/z 193. Detection of oxybutynin and desethyloxybutynin in dog plasma were accurate and precise, with detection limit at 0.1 ng/ml. This method has been successfully applied to a study of oxybutynin and desethyloxybutynin in dog plasma.