摘要
对于红外激光系统和紫外激光系统 ,由于它们加热样品的反应机理完全不同 ,决定了它们在稳定同位素地球化学分析中的不同使用范围。根据对CO2 激光系统分析地球化学样品的实践 ,发现对结果产生干扰的因素有 :(1)石英的粒径效应 ;(2 )微量样品接收电压过低 ;(3)分子筛的吸附能力 ;(4 )系统中的吸附水 ;(5 ) 14 N19F+ 对δ17O值的影响。由于石英的粒径效应而导致细粒石英 (粒径<2 5 0 μm)的δ18O值偏低 ,可以采用不聚焦激光的快速加热法来解决。由于样品量太少而决定了样品气体接收电压过低 ,导致δ18O值出现系统偏高或偏低 ,可以利用校正曲线对结果进行校正。分子筛吸附性能的下降会产生氧同位素的分馏 ,因此确定分子筛的使用寿命非常重要。系统中的吸附水利用氟化物试剂预氟化来去除 ,重要的是应避免在预氟化的过程中产生大量的HF腐蚀激光系统的BaF2 窗口玻璃并与部分矿物样品发生反应。
There are significant differences in the nature of fluorination and the mechanisms of laser sample coupling between IR and UV lasers. Their applications to oxygen isotope analysis are also different. The accuracy and precision of CO 2 laser fluorination analysis are influenced by the following factors: the grain size, the volume of sample gas, the efficiency of adsorption of molecule sieve, the adsorbing water in laser system, and the δ 17 O values affected by 14 N 19 F +. The δ 18 O values of fine grain quartz are lower than its true values because of the grain size effect. The CO 2 laser fluorination technique, using rapid heating and defocused beam, allows both high accuracy and high precision determination of oxygen isotope ratios for quartz, feldspar and whole rock. The inaccurate results that are caused by micro volume sample gas can be calibrated by an empirical curve. The declining of molecule sieve's adsorption can also produce oxygen isotope fractionation. Therefore, it is important to determine the life time of molecule sieve. Failure to make pre fluorination can result in the production of significant amounts of HF, which frosts the BaF 2 window and even reacts with some minerals.
出处
《地学前缘》
EI
CAS
CSCD
2003年第2期279-286,共8页
Earth Science Frontiers
基金
国家自然科学基金项目 ( 4 0 0 3 3 0 10 )
中国科学院知识创新工程项目 (KZCX2 10 7)
