Benech H, Batel A, Pruvost A, Thomas J L, Grognet J M
CEA, Service de Pharmacologie et d'Immunologie, DSV/DRM, CEA/Saclay, Gif- sur-Yvette, France.
Magnes Res. 1998 Jun;11(2):91-102.
Pharmacokinetic studies using stable isotopes of magnesium as tracers need to determine the isotopic abundance in biological media by means of mass spectrometry. Of mass spectrometric techniques, electronic impact-mass spectrometry (EI-MS) and inductively coupled plasma-mass spectrometry (ICP-MS) can be used. We have measured the isotopic abundance in plasma and urinary samples and compared the precision and accuracy of these two methods. Graphical representations showed that mean differences were close to 0, there was no obvious relationship between the difference and the mean, and no systematic bias was evidenced at low or high isotopic abundance. This was shown for isotopic abundance of either 25 Mg and 26 Mg. EI-MS is able to measure magnesium isotopic abundance with an intra-day precision between 0.14 and 0.45 per cent and with an inter-day precision between 0.20 and 1.23 per cent. ICP-MS exhibited an intra-day precision between 0.01 and 0.06 per cent and an inter-day precision between 0.01 and 0.15 per cent. Our results showed that, despite the similar isotopic abundances in biological samples obtained with the two methods, a large difference in precision clearly favours ICP-MS in studies of magnesium behaviour using stable isotopes.
使用镁的稳定同位素作为示踪剂的药代动力学研究需要通过质谱法来测定生物介质中的同位素丰度。在质谱技术中，可以使用电子轰击质谱法（EI-MS）和电感耦合等离子体质谱法（ICP-MS）。我们测量了血浆和尿液样本中的同位素丰度，并比较了这两种方法的精密度和准确度。图形表示显示，平均差异接近0，差异与平均值之间没有明显关系，并且在低同位素丰度或高同位素丰度下均未发现系统偏差。这在25Mg和26Mg的同位素丰度中得到了体现。EI-MS能够测量镁的同位素丰度，日内精密度在0.14%至0.45%之间，日间精密度在0.20%至1.23%之间。ICP-MS的日内精密度在0.01%至0.06%之间，日间精密度在0.01%至0.15%之间。我们的结果表明，尽管用这两种方法获得的生物样品中的同位素丰度相似，但精密度上的巨大差异显然使ICP-MS在使用稳定同位素的镁行为研究中更具优势。
