Determination of methylphenidate and its main metabolite in plasma by gas chromatography-chemical ionization mass spectrometry.
作者:KATSUYOSHI NAKAJIMA、HAJIME KOTAKI、YUKIYA SAITOH、FUJIO NAKAGAWA
DOI:10.1248/cpb.34.1701
日期:——
A method is described for the determination of methylphenidate and its main metabolite, ritalinic acid, in plasma from various species, based on gas chromatography-chemical ionization mass spectrometry using ethylphenidate as an internal standard. Methylphenidate in plasma is extracted with cyclohexane and converted to the pentafluoropropionyl (PFP) derivative. Ritalinic acid is extracted with 2-propanol from the salt-saturated remaining aqueous phase, converted to the parent drug by treatment with a mixture of methanol and sulfuric acid (2 : 1, v/v), and then converted to the PFP derivative. The protonated molecular ions at m/z 380 for the PFP derivative of methylphenidate and m/z 394 for that of the internal standard were used for selected ion monitoring analysis. The hydrolysis of methylphenidate in plasma before the addition of the internal standard could be prevented completely by holding the plasma sample at around 0°C. The limit of quantitation was 0.5 ng for methylphenidate and 2.5 ng for ritalinic acid using 0.5 ml of plasma. The present method is highly sensitive and reliable, and should be satisfactory for application to pharmacokinetic studies of methylphenidate in laboratory animals and man.
描述了一种通过气相色谱-化学电离质谱法,在不同物种的血浆中测定甲基苯丙胺及其主要代谢物瑞他林酸的方法,使用乙基苯丙胺作为内标。血浆中的甲基苯丙胺用环己烷提取,并转化为五氟丙酰(PFP)衍生物。瑞他林酸则从盐饱和后的剩余水相中用2-丙醇提取,通过与甲醇和硫酸的混合物(2:1,v/v)处理转化为母药物,随后转化为PFP衍生物。对于甲基苯丙胺的PFP衍生物,其质荷比(m/z)为380,内标的质荷比为394,用于选择性离子监测分析。通过将血浆样本保持在约0°C,可以完全防止在添加内标之前甲基苯丙胺在血浆中的水解。使用0.5毫升血浆,可量化的最低限度为甲基苯丙胺0.5 ng,瑞他林酸2.5 ng。该方法具有高灵敏度和可靠性,适用于实验动物和人类中甲基苯丙胺药代动力学研究。