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首页> 外文期刊>Journal of mass spectrometry: JMS >Liquid and gas chromatography coupled to isotope ratio mass spectrometry for the determination of C-13-valine isotopic ratios in complex biological samples
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Liquid and gas chromatography coupled to isotope ratio mass spectrometry for the determination of C-13-valine isotopic ratios in complex biological samples

机译：液相色谱和气相色谱-同位素比质谱法测定复杂生物样品中的C-13-缬氨酸同位素比

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摘要

On-line gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) is commonly used to measure isotopic ratios at natural abundance as well as for tracer studies in nutritional and medical research. However, high-precision C-13 isotopic enrichment can also be measured by liquid chromatography-isotope ratio mass spectrometry (LC-IRMS). Indeed, LC-IRMS can be used, as shown by the new method reported here, to obtain a baseline separation and to measure C-13 isotopic enrichment of underivatised amino acids (Asp, Thr-Ser, Glu, Pro, Gly, Ala, Cys and Val). In case of Val, at natural abundance, the SD(delta C-13) reported with this method was found to be below M. Another key feature of the new LC-IRMS method reported in this paper is the comparison of the LC-IRMS approach with the conventional GC-C-IRMS determination. To perform this comparative study, isotopic enrichments were measured from underivatised Val and its N(O, S)-ethoxycarbonyl ethyl ester derivative. Between 0.0 and 1.0 molar percent excess (MPE) (delta C-13 = -12.3 to 150.8 parts per thousand), the calculated root-mean-square (rms) of SD was 0.38 and 0.46 parts per thousand and the calculated rms of accuracy was 0.023 and 0.005 MPE, respectively, for GC-C-IRMS and LC-IRMS. Both systems measured accurately low isotopic enrichments (0.002 atom percent excess (APE)) with an SD (APE) of 0.0004. To correlate the relative (delta C-13) and absolute (atom%, APE and MPE) isotopic enrichment of Val measured by the GC-C-IRMS and LC-IRMS devices, mathematical equations showing the slope and intercept of the curves were established and validated with experimental data between 0.0 to 2.3 MPE. Finally, both GC-C-IRMS and LC-IRMS instruments were also used to assess isotopic enrichment of protein-bound C-13-Val in tibial epiphysis in a tracer study performed in rats. Isotopic enrichments measured by LC-IRMS and GC-C-IRMS were not statistically different (p > 0.05). The results of this work indicate that the LC-IRMS was successful for high-precision C-13 isotopic measurements in tracer studies giving C-13 isotopic enrichment similar to the GC-C-IRMS but without the step of CC derivatisation. Therefore, for clinical studies requiring high-precision isotopic measurement, the LC-IRMS is the method of choice to measure the isotopic ratio.
机译：在线气相色谱-燃烧-同位素比率质谱法（GC-C-IRMS）通常用于测量自然丰度下的同位素比率以及营养和医学研究中的示踪剂研究。但是，也可以通过液相色谱-同位素比质谱（LC-IRMS）来测量高精度的C-13同位素富集。实际上，如此处报道的新方法所示，可以使用LC-IRMS来获得基线分离并测量未衍生氨基酸（Asp，Thr-Ser，Glu，Pro，Gly，Ala，半胱氨酸和瓦尔）。如果是Val，在自然丰度下，发现用此方法报告的SD（δC-13）低于M。本文报道的新LC-IRMS方法的另一个关键特征是LC-IRMS的比较常规GC-C-IRMS测定的方法。为了进行这项比较研究，从未衍生的Val及其N（O，S）-乙氧基羰基乙基酯衍生物中测定了同位素富集。在0.0和1.0摩尔百分比过量（MPE）之间（δC-13 = -12.3至150.8千分之几），计算得出的SD均方根（rms）为0.38和0.46千分之几以及计算出的rms精度GC-C-IRMS和LC-IRMS的MPE分别为0.023和0.005 MPE。两种系统均能准确测量出低同位素富集度（过量0.002原子百分数（APE）），而SD（APE）为0.0004。为了关联通过GC-C-IRMS和LC-IRMS设备测得的Val的相对（δC-13）和绝对（原子％，APE和MPE）同位素富集，建立了显示曲线的斜率和截距的数学方程式并用0.0到2.3 MPE之间的实验数据进行了验证。最后，在大鼠进行的示踪研究中，GC-C-IRMS和LC-IRMS仪器还用于评估胫骨骨physi中蛋白质结合的C-13-Val的同位素富集。通过LC-IRMS和GC-C-IRMS测量的同位素富集无统计学差异（p> 0.05）。这项工作的结果表明，LC-IRMS在示踪剂研究中成功用于高精度C-13同位素测量，其C-13同位素富集类似于GC-C-IRMS，但没有CC衍生化步骤。因此，对于需要高精度同位素测量的临床研究，LC-IRMS是测量同位素比的首选方法。

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