Gas Bench II-IRMS磷酸法在线测定水中溶解无机碳碳同位素分析条件及影响因素

采用Gas Bench II-IRMS 对水中溶解无机碳碳同位素在线测定影响因素进行研究，确立了分析方法。通过对影响因素的研究确定了水中溶解无机碳碳同位素测试的最佳平衡时间；样品水中溶解无机碳浓度与样品测试的信号强度呈明显正相关；测试过程中色谱柱温度的高低不仅会影响样品峰的出峰时间，还会影响样品峰宽、峰高及峰积分面积等，影响最终测试结果。为了确保水中溶解无机碳碳同位素测试方法的准确性与可行性，进行了方法试验验证，水中溶解无机碳碳同位素比值（δ13C）的测定值与验证单位给出的δ13C测定值相一致，此测试方法具有可行性。在线测试的高效率和小样量与传统方法比较有显著优势，这为拓展同位素分析技术的应用领域提供了一种快速、高效的手段。本测试分析方法适用于地下水、地表水、大气降水的溶解无机碳碳同位素组成的在线测定。 

A study on the test conditions and influence factors in online-phosphoric acid method for carbon isotopes of dissolved inorganic carbon compounds in water samples by Gas Bench II-IRMS

The objects of this paper is to determine the test conditions and influencing factors in online-phosphoric acid method by using Gas Bench II-IRMS for carbon isotopes of dissolved inorganic carbon compounds in water samples. The equilibrium time, chromatographic column, sample condition, sample volume and the reaction temperature were analyzed comprehensively. The conclusions were as follows, (1) The best equilibrium time of the dissolved inorganic carbon isotope in the water sample was identified. (2)There is obviously positive correlation between inorganic carbon concentration and the sample test signal intensity. (3) In the process of sample testing, the temperature of chromatographic column can not only affect the appearance time of sample peak, but also affect the peak width ,peak height and the peak area, leading to different degrees of isotope fractionation. The samples should be kept under 25 ℃ in the reaction process, meanwhile, ±1 ℃ difference in temperature between room temperature and constant temperature sample plate is required .If the temperature difference is too large, there will be water vapor in the sample vial, which will not only lead to the isotope fraction of the sample, but also affect the service life of taking gas needle even lead to serious gas needle blocking. This method can be used to analyze the δ13C values of dissolved inorganic carbon in groundwater, surface water and meteoric water.