Jackson Sarah J, Waterhouse John S, Bluck Leslie J C
MRC Human Nutrition Research, Elsie Widdowson Laboratory, Fulbourn Road, Cambridge CB1 9NL, UK.
Rapid Commun Mass Spectrom. 2007;21(18):3123-8. doi: 10.1002/rcm.3195.
The incorporation of stable isotopes improves the assessment of glucose metabolism and, with some researchers using two tracers, (2)H-glucose assessed by gas chromatography/mass spectrometry (GC/MS) and (13)C-glucose by gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS), a common derivative for both is advantageous. The most commonly used derivatives for GC/MS are inappropriate for GC/C/IRMS as additional functional groups dilute the label. We therefore considered the suitability of six derivatives for both GC/MS and GC/C/IRMS. Glucose alkylboronates were prepared by adding the appropriate alkylboronic acid (butyl- or methylboronic acid) in pyridine to desiccated glucose. The derivatisation was completed by reacting this with either (a) acetic anhydride or trifluoroacetic anhydride (acetate derivatives) or (b) bis(trimethylsilyl)trifluoroacetamide BSTFA (TMS derivatives). All six derivatives were assessed using GC/MS and (13)C GC/C/IRMS. Neither TMS derivative exhibited any signal intensity in the molecular ion, although a M-15 ion showed good agreement between experimental and theoretical data and, whilst still low in intensity, could be suitable for isotope work. Similarly, none of the acetate derivatives showed any intensity at the molecular ion although three key fragmentation series were identified. The most attractive sequence, initiated by the loss of 1,2 cyclic boronate, resulted in the main fragment ion of interest, m/z 240, corresponding to the fluorinated methylboronate derivate. Minimal carbon and hydrogen atoms are added to this derivative making it an excellent choice for stable isotope work, while proving suitable for analysis by both GC/MS and GC/C/IRMS.
稳定同位素的引入改善了葡萄糖代谢的评估，并且由于一些研究人员使用两种示踪剂，即通过气相色谱/质谱法（GC/MS）评估的（2）H-葡萄糖和通过气相色谱/燃烧/同位素比质谱法（GC/C/IRMS）评估的（13）C-葡萄糖，一种对两者通用的衍生物是有利的。GC/MS最常用的衍生物不适用于GC/C/IRMS，因为额外的官能团会稀释标记。因此，我们考虑了六种衍生物对GC/MS和GC/C/IRMS的适用性。葡萄糖烷基硼酸酯是通过在吡啶中向干燥的葡萄糖中加入适当的烷基硼酸（丁基硼酸或甲基硼酸）制备的。通过将其与（a）乙酸酐或三氟乙酸酐（乙酸酯衍生物）或（b）双（三甲基硅基）三氟乙酰胺BSTFA（TMS衍生物）反应来完成衍生化。使用GC/MS和（13）C GC/C/IRMS对所有六种衍生物进行了评估。两种TMS衍生物在分子离子中均未表现出任何信号强度，尽管M-15离子在实验数据和理论数据之间显示出良好的一致性，并且尽管强度仍然较低，但可能适用于同位素研究。同样，乙酸酯衍生物在分子离子处均未显示任何强度，尽管鉴定出了三个关键的碎片系列。最具吸引力的序列是由1,2环状硼酸酯的损失引发的，产生了感兴趣的主要碎片离子，m/z 240，对应于氟化甲基硼酸酯衍生物。向该衍生物中添加的碳和氢原子最少，这使其成为稳定同位素研究的极佳选择，同时证明适用于GC/MS和GC/C/IRMS分析。
