Chen Zhensheng, Griffin Ian J, Kriseman Yana L, Liang Lily K, Abrams Steven A
US Department of Agriculture/Agricultural Research Service Children's Nutrition Research Center, Houston, TX 77030, USA.
Clin Chem. 2003 Dec;49(12):2050-5. doi: 10.1373/clinchem.2003.025692.
Analytical methods for measuring the calcium isotope distribution in enriched human serum samples that use low blood volumes, simple preparation methods, and rapid analysis are important in clinical studies of calcium kinetics. Previously, sample preparation by oxalate precipitation typically required 500 micro L of serum. This method was time-consuming, and the blood volume required was limiting in circumstances when only a small amount of serum could be obtained.
Serum was collected from humans who were administered (42)Ca, and 20 micro L of serum was mixed with 2 mL of 0.22-0.67 mol/L HNO(3) at room temperature for between 1 min and 16 h. The (42)Ca/(43)Ca ratio in the supernatant was measured by a magnetic sector inductively coupled plasma mass spectrometer (ICP-MS). Calcium isotope ratios from these equilibration solutions were compared with data from oxalate-precipitated serum samples to determine the optimum equilibrium time and the effect of acid concentration on equilibrium.
Various amounts of aggregated particles developed in different acid-serum mixtures. These affected the time required for isotope equilibration in the mixture. The shortest equilibrium time needed for the calcium isotopes varied from 1 to 6 h for samples acidified with 0.22-0.45 mol/L HNO(3). Data obtained from these solutions were consistent with data from oxalate-precipitated calcium. The precision of (42)Ca/(43)Ca ratio measurements was better than 0.5%.
We have developed a simple, rapid sample preparation technique for ICP-MS analysis in which 20 micro L of serum can be used for accurate measurement of the calcium isotope distribution in a sample with good precision and a rapid analysis time.
在钙动力学的临床研究中，采用少量血液、简单制备方法和快速分析来测量富集人血清样本中钙同位素分布的分析方法很重要。以前，通过草酸盐沉淀进行样本制备通常需要500微升血清。该方法耗时，并且在只能获得少量血清的情况下所需的血量是有限的。
收集接受（42）Ca的人的血清，将20微升血清在室温下与2毫升0.22 - 0.67摩尔/升HNO（3）混合1分钟至16小时。通过磁扇形电感耦合等离子体质谱仪（ICP - MS）测量上清液中的（42）Ca/（43）Ca比率。将这些平衡溶液中的钙同位素比率与草酸盐沉淀血清样本的数据进行比较，以确定最佳平衡时间和酸浓度对平衡的影响。
在不同的酸 - 血清混合物中形成了不同数量的聚集颗粒。这些影响了混合物中同位素平衡所需的时间。用0.22 - 0.45摩尔/升HNO（3）酸化的样本中，钙同位素所需的最短平衡时间为1至6小时。从这些溶液中获得的数据与草酸盐沉淀钙的数据一致。（42）Ca/（43）Ca比率测量的精密度优于0.5％。
我们开发了一种用于ICP - MS分析的简单、快速的样本制备技术，其中20微升血清可用于精确测量样本中的钙同位素分布，具有良好的精密度和快速的分析时间。
