碳酸盐晶格硫同位素分析前处理的影响

Sample Pretreatment Effects on Analytical Result of Carbonate Associated Sulfate Isotope

碳酸盐晶格硫可以记录地史时期海水的真实硫同位素组成,并已应用于早期生命演化和古环境等方面的相关研究之中。在硫酸盐晶格硫的同位素组成分析过程中,前处理过程中的化学条件对分析结果会产生一定的影响,但目前相关的系统研究较少。考察了盐酸用量、盐酸浓度、加入次氯酸钠溶液与否及其所选取浓度等对δ(34SCAS)的影响,结果表明:①盐酸不足量时可能生成铬酸钡等杂质沉淀影响硫同位素测定;②在盐酸足量的情况下δ(34SCAS)值变化不明显;③盐酸浓度与δ(34SCAS)值呈一定的负相关性,随着盐酸浓度的增大δ(34SCAS)值呈减小趋势;④不加入次氯酸钠时δ(34SCAS)值偏低,次氯酸钠浓度对δ(34SCAS)组成无明显影响。本研究为CAS硫同位素分析测定方法的确定提供了重要的参考。

Carbonate associated sulfate（CAS） records the information of the sulf ur isotope compositions of seawater.The sulfur isotope composition of CAS has b een applied in the research of the evolution of life and environment.The isotop ic values of CAS could be affected by the chemical conditions of pretreatment pr ocess,but a little systematic research has been reported on the related techniq ue.The effect of the dosage and concentration of hydrochloric acid and sodium h ypochlorite on the δ34SCAS has been studied in this paper.The results indicate d that：（1） When the dosage of HCl was not enough,BaCrO4 might be produced,whi ch influenced the determining of sulfur isotope.（2） When the HCl is adequate,t he excessive HCl has no influence on the δ34SCAS.（3） The δ34SCAS values decre ased with increasing of concentration of HCl.（4） The concentration of sodium h ypochlorite has no apparent effect on δ34SCAS values but it would be negatively skewed without sodium hypochlorite.The results of this research provided a ver y important reference to the method of CAS isotopic analysis.