同位素比值质谱与激光吸收光谱分析水中氢氧同位素方法的比较

Analysis of Hydrogen and Oxygen Isotope in Water Sample Using Isotope Ratio Mass Spectrometry and Laser Spectroscopy

氢氧稳定同位素在研究地球水循环过程中发挥着重要作用。本研究采用激光光谱法和高温热转换元素-同位素比值质谱法测定水样中氢同位素,采用激光光谱法和CO2-H2O平衡-同位素比值质谱法测定水样中氧同位素。结果表明:使用原理不同的两种方法测定地下水、海水和大气降水样品,测定的δ2 H和δ18 O值的精密度与准确度相当,激光光谱法以其快速高效、低成本、样品用量少占有优势;但使用这两种方法测定土壤抽提水样品时,激光光谱法测定δ18 O值与真值的偏差为0.34‰,而质谱法测定的偏差小于0.10‰;激光光谱法测定δ2 H值与真值的偏差为2.3‰,而质谱法测定的偏差小于0.6‰,说明质谱法的结果明显优于激光光谱法。

The stable isotopes of hydrogen and oxygen（δ2 H andδ18 O）are excellent tracers for studying on the natural water cycle.New analytical techniques for stable isotope ratio measurements have been rapidly developed over the past decade.These techniques include mass spectrometry with online or continuous flow apparatus for sample introduction,and laser spectroscopy.In this paper,theδ18 O value of water samples was determined by CO2-H2 O equilibration-isotope ratio mass spectrometry and laser spectroscopy,and theδ2 H value was determined by the laser spectroscopy and hightemperature conversion/elemental analysis-isotope ratio mass spectrometry（HTCIRMS）.The results show that the measurement accuracy and precision of two methods are almost same when determining theδ2 H andδ18 O value of the groundwater,seawaterand meteoric water samples.While,laser spectroscopy has the advantage of fast and efficient,low cost and few sample consumption.The two methods were also used to determine the extraction water from soil samples.Theδ18 O value deviation between the measurement and true value of laser spectroscopy technology is 0.34‰,and that of mass spectrometry is less than 0.10‰.Theδ2 H value deviation between the measurement and true value of laser spectroscopy technology is 2.3‰,and that of mass spectrometry is less than 0.6‰.The results indicate that mass spectrometry is much better than laser spectroscopy technology for the determination of water samples containing organic matter.