A Carbon-13 Isotope Analyzer Based on CO Emission Spectroscopy

碳同位素分析为研究代谢途径和追踪环境中的碳转化提供了宝贵的工具。国际和平研究所建议开发一种光学技术，方便地测量碳同位素(13C/12C)比值。该仪器将使用线性光电二极管阵列来成像由含碳分子的等离子体发射产生的光谱。算法将被用来消除光谱干扰，并校正由于样品压力和功率耦合的变化而引起的同位素比值漂移。初步工作表明，发射系统可用于测定二氧化碳样品中的13C/12C比值，相对精度可达2.5%，可提高6倍。还对数据处理的数学方法进行了评估。第二阶段建议的后续研究将涉及调整排放方法，以确定来自气相色谱仪的二氧化碳洗脱液的13C/12C比率。对系统进行改进，包括设计和测试适合在大气压下取样的进样系统，可能会产生一个自动样品处理系统，该系统将与碳-氮分析仪相连，用于在线测定13C和15N的同位素比。第二阶段目标的成功实现将导致开发一种廉价、可靠的质谱学替代品，用于从同一样品中测定13C和最终的15N和18O的同位素比率。该仪器可方便地用于示踪剂研究，如果进一步改进，可能有助于医学和环境领域的自然丰度分析，从而使更多的研究人员更容易获得同位素测量。

Isotopic carbon analysis provides a valuable tool for studies of metabolic pathways and for tracing carbon transformations in the environment. The PI proposes to develop an optical technique for the convenient measurement of carbon isotopic (13C/12C) ratios. The instrument will use a linear photodiode array to image the spectra arising from plasm-emission of carbon-containing molecules. Algorithms will be applied to remove spectral interferences and to correct for isotopic ration shifts due to variations in sample pressure and power coupling. Initial work demonstrated that an emission system could be used to determine the 13C/12C ratio in CO2 samples up to a relative precision of 2.5% which could be improved by a factor of 6. Mathematical methods were also evaluated for data processing. Follow-on studies proposed in phase II will involve adapting the emission method for determining 13C/12C ratios for CO2 eluant from a gas chromatograph. System refinements, including the design and testing of an inlet system suitable for sampling at atmospheric pressure, may lead to an automated sample processing system which will be coupled to a carbon-nitrogen analyzer for on-line isotope ratio determinations of both 13C and 15N. Successful accomplishment of the objectives of phase II should result in the development of an inexpensive, reliable alternative to mass spectrometry for the determination of the isotopic ratios of 13C and eventually 15N, and 18O from the same sample. The instrument could be readily used for tracer studies, and with further refinements may be useful for natural abundance analyses, in both medical and environmental fields thereby making isotopic measurements more accessible to a broader range of researchers.